Paper 47 Reoperation and Failure Rate at Six Years Following Revision ACL Reconstruction: A MARS Cohort Study Mars Group. Washington University St. Louis, St Louis, MO Objectives: Revision anterior cruciate ligament (ACL) reconstruction remains a challenge for orthopaedic surgeons, as results are persistently inferior to those of primary reconstructions. There is very limited data regarding outcomes at 6 years following revision ACL surgery. The purpose of this study was to report the rate of reoperation, further revision, and conversion to total knee arthroplasty (TKA) in a large cohort of revision ACL reconstructions Methods: Patients undergoing revision ACL reconstructions were identified and prospectively enrolled between 2006 and 2011. Data collected included baseline demographics, intraoperative surgical technique, and a series of validated patient-reported outcome instruments. Patients were followed up by questionnaire and telephone at 6 years following index revision surgery and asked if they had undergone any further surgical procedures to either knee. If a patient reported having undergone subsequent surgery, operative reports detailing the subsequent procedure(s) were obtained and categorized. Results: Six-year follow-up subsequent surgical data was available for 951/1234 patients (77%). In this available cohort, 556 (58%) were male, mean age was 28 years (range 12-61 years) and mean BMI was 26.1 (range 17.1-47.5). Allograft was used in 510 (54%) cases, BTB autograft in 234 (25%), soft tissue autograft in 174 (18%) and other grafts were used in the remaining 33 (3%). Their index surgery was their first revision ACL reconstruction in 822 (86.4%), in 108 (11.4%) it was their second, and in 21 (2.2%) it was their third or greater. This revision procedure was a mean of 5.7 years (range 0.1-26 years) from their prior ACL reconstruction. At six years following the index revision procedure, 16.2% of the cohort underwent at least 1 subsequent surgical procedure on their index knee. Of the reoperations, 29% were meniscal procedures (71% meniscectomy, 18% repair), 21% were articular cartilage procedures (79% chondroplasty, 15% microfracture, 3% OATS, 3% ACI), 11% were for arthrofibrosis, 9% for hardware removal, and 6% were for a subsequent revision ACL reconstruction. Surprisingly, only 5% reported having undergone a subsequent TKA on their ipsilateral knee. During this same 6-year follow-up period, 6% of the cohort (n=53 patients) underwent a subsequent surgery on their contralateral knee, of which 36 were ACL reconstructions. Conclusion: Our data shows that there is a reoperation rate of greater than 15% following ACL revision, which is an important point of discussion between surgeons and their patients. Of particular interest is that there was a 6% rate of recurrent ACL failure and 5% rate of subsequent TKA in this young cohort 6 years following a revision ACL reconstruction.

Paper 48 Blood Flow Restriction Training Does Not Improve Quadriceps Strength After Anterior Cruciate Ligament Reconstruction Michael Curran1, Asheesh Bedi, MD1, Christopher Mendias2, Edward M. Wojtys, MD3, Megan Kujawa1, Riann Palmieri-Smith, PhD, ATC1. 1University of Michigan, Ann Arbor, MI, 2Hospital for Special Surgery, New York, NY, 3MedSport - Univ of Michigan, Ann Arbor, MI Objectives: Blood flow restriction training (BFRT) involves obstruction of venous outflow of working muscles during exercise and may lead to more substantial recovery of quadriceps strength after anterior cruciate ligament (ACL) reconstruction. The purpose of this study is to examine the effects of BFRT in ACL reconstruction patients before and after exposure to BFRT. Methods: This study was a randomized controlled trial in which 36 patients who had torn their ACL and were scheduled to undergo ACL reconstructive surgery (ACLR) with an autograft were randomized to receive exercise with BFRT (N=18) or exercise without BFRT (N=18). Participants in both groups performed the same exercise, but either did or did not have blood flow restricted. The exercise component of the intervention consisted of all subjects performing a single-leg isokinetic leg press, at an intensity of 70% of the subjects’ one-repetition maximum, for four sets of ten repetitions two times per week for 8 weeks beginning at 8 weeks post-operatively. Patients randomized to the BFRT group performed the leg-press exercise with a blood flow restriction cuff applied to the thigh and set to a limb occlusion pressure of 80 percent. All participants were concurrently undergoing standard ACL rehabilitation at the same physical therapy clinic. Bilateral isometric (recorded at a knee angle of 90°) and isokinetic (60°/second) quadriceps strength were recorded using a Biodex dynamometer (System 4, Shirley, NY) prior to ACLR and after the conclusion of the 8-week intervention. Peak isometric and isokinetic quadriceps strength were utilized to generate isometric and isokinetic quadriceps symmetry indices ((ACLR limb strength/Healthy limb strength) x100). Change from baseline symmetry scores were then generated using the following equation: (post-intervention symmetry - pre-intervention symmetry)/pre-intervention symmetry in order to account for possible differences in strength between groups prior to intervention delivery. Change from baseline isometric and isokinetic quadriceps symmetry scores were then compared between groups (exercise with BFRT, exercise without BFRT) using one-way analysis of variance tests with an a priori α set to P≤ 0.05. Effect sizes (Cohen’s d) and 95% confidence intervals were also computed. Results: No significant differences were found for change from baseline isokinetic quadriceps symmetry index (P=0.39, BFRT mean=-0.05, Control mean=-0.19) or change from baseline isometric quadriceps symmetry index (P=0.62, BFRT mean=-0.04, control mean=-0.10). The effect sizes for isokinetic quadriceps symmetry index (d=0.28, 95% CI= -0.37, 0.93) and isometric quadriceps symmetry (d=0.16, 95% CI= -0.49, 0.80) were small with confidence intervals that crossed zero.

Conclusion: An 8-week blood flow resistance training + exercise intervention did not increase quadriceps muscle strength in patients who had undergone ACL reconstruction. Based on our findings, application of blood flow restriction training in ACL reconstruction patients to improve quadriceps strength may not be warranted. Future studies may benefit from a longer follow-up and larger sample size.

Paper 49 Quadriceps Tendon Autografts Have A Lower Early Graft Failure Rate Than Hamstring Tendon Autografts When Performing Transphyseal Acl Reconstructions Andrew T. Pennock, MD1, Kristina Parvanta Johnson, ATC, OPA-C1, Henry G. Chambers, MD1, Tracey P. Bastrom, MA1, Raghav Badrinath, MD1, Robby Turk, BA1, M. Morgan Dennis1, Eric W. Edmonds, MD2. 1Rady Children's Hospital, San Diego, CA, 2Rady Children's Specialists San Diego, San Diego, CA Objectives: It is unclear what the optimal graft choice is for performing a transphyseal ACL reconstruction in a skeletally immature patient. The purpose of the current study was to evaluate outcomes and complications of skeletally immature patients undergoing an ACL reconstruction with hamstring tendon autograft versus quadriceps tendon autograft. Methods: Between 2012 and 2016, 104 skeletally immature patients from a single institution underwent a primary transphyseal ACL reconstruction with either quadriceps tendon autograft or hamstring tendon autograft based on surgeon preference. Patient demographic, injury, radiographic, and surgical variables were documented. Outcome measures included Lysholm score, SANE score, pain score, satisfaction, return to sport, and complications such as graft tears and physeal abnormalities. Results: Ninety patients (87%) including 62 hamstring tendon reconstructions and 28 quadriceps tendon reconstructions were available for a minimum follow-up of 2 years. The mean age of the patients was 14.8±1.3 years. No differences in chronologic age, bone age, gender, patient size, or mechanism of injury were noted between patient groups. There were no differences in surgical variables except the quadriceps tendon grafts were larger than the hamstring tendon grafts (9.6 mm vs 7.8 mm; p<0.001). Patient outcomes at a mean follow-up of 2.8 years revealed no differences based graft type with a mean Lysholm score, SANE score, pain score, satisfaction, and Tegner score were 95, 91, 0.8, 9.3, and 6.9 respectively. While there were no physeal complications in either group, patients undergoing a hamstring tendon autograft reconstruction were more likely to tear their graft (19% vs 0%; p= 0.01). Conclusion: Skeletally immature patients undergoing an ACL reconstruction can be successfully managed with either a quadriceps tendon autograft or a hamstring tendon autograft with good short-term outcomes, relatively high rates of return to sport, and low rates of physeal abnormalities. The primary differences between grafts were that the quadriceps tendon grafts were larger and were associated with a lower retear rate. Although a relatively new graft source for skeletally immature ACL reconstructions, the quadriceps tendon is not only a viable graft option, but it may be superior to the hamstrings tendon when it comes to early graft failures.

Paper 50 Lateral Extra-Articular Tenodesis Does Not Affect Rotatory Knee Instability in Anatomic ACL Reconstruction Andrew J. Sheean, MD1, Jayson Lian2, Sean J. Meredith, MD3, Robert Tisherman4, Andrew D. Lynch, PhD, PT3, Volker Musahl, MD4, Bryson P. Lesniak, MD4. 1San Antonio Military Medical Center, San Antonio, TX, 2University of Pittsburgh Medical Center, Warren, NJ, 3University of Pittsburgh/UPMC Medical Education Program, Pittsburgh, PA, 4University of Pittsburgh Medical Center, Pittsburgh, PA Objectives: Single-bundle, anatomic anterior cruciate ligament reconstruction (ACLR) may not fully restore rotatory knee stability, and the addition of a lateral extra-articular tenodesis (LET) has been proposed as means for reducing residual rotatory knee instability. However, the magnitude of the in vivo, time zero effects of these procedures on rotatory knee instability remain poorly defined. The pivot shift test is used to assess for rotatory knee instability; however, it is a subjective grading system with limited generalizability and ability to predict clinical outcomes. Consequently, a quantified pivot shift (QPS) test software application, PIVOT iPad, has been developed and validated to measure the magnitude of rotatory knee laxity. The objective of this study was use intraoperative QPS (iQPS) to assess for differences in residual rotatory knee instability after ACLR versus ACLR augmented with lateral extra-articular tenodesis (ACLR + LET.) Methods: During examination under anesthesia (EUA), QPS was performed on both the operative and non-operative knees prior to ACLR (Figure 1A) Three, yellow ¾ inch markers were attached to skin overlying bony landmarks: lateral epicondyle, Gerdy’s tubercle and 3 cm posterior to Gerdy’s tubercle. The PIVOT software application was used to measure lateral compartment translation (Figure 1B) ACLR were randomly augmented with a LET if the lateral compartment translation measured during QPS was greater than or equal to double the amount of lateral compartment translation measured for the unaffected knee. iQPS measurements were subsequently performed after either ACLR or ACLR + LET with sterile markers (Figure 1C) iQPS data were recorded and compared to both the preoperative QPS measurements of the affected and unaffected knees. Based upon normative QPS data established from a database of >150 previously performed ACLR at our institution, it was determined that 8 patients in each group would be required to achieve 80% power with an effect size of 1.2mm and an alpha level of 0.05. Post-procedure iQPS data were compared to preoperative QPS measurements with paired samples t-tests. Results: iQPS measurements were performed in 20 ACLR (10 ACLR and 10 ACLR + LET). The mean age in the cohort was 17.3 years old (range: 17-24 years old.). Both ACLR and ACLR + LET resulted in significant decreases in rotatory knee instability when compared to preoperative QPS measurements (pre-ACLR: 4.7 ± 1.9 v. post-ACLR: 1.3 ± 0.70, P < 0.001; pre-ACLR +LET: 3.6 ± 1.8 v. post-ACLR + LET: 0.9 ± 0.5, P < 0.001.) When comparing isolated ACLR to ACLR + LET, no significant differences were observed in the magnitude of change in iQPS between the pre and post-intervention states (ACLR: - 3.5 ± 1.6 mm v.

ACLR + LET: -1.5 ± 3.1 mm, P = N.S.) Furthermore, there were no significant differences in lateral compartment translation between the operative knees and non-operative knees (ACLR: -0.1 ± 0.9 mm v. ACLR + LET: -0.5 ± 1.0 mm, P = N.S.), suggesting that neither ACLR nor ACLR + LET led to over-constrained kinematics. Conclusion: In this randomized control study, both ACLR and ACLR + LET resulted in significant decreases in rotatory knee instability. However, there were no significant differences in time-zero, rotatory knee instability detected between isolated ACLR versus ACLR combined with LET in patients. The utility of combining a LET with ACLR remains unclear, and future research is necessary to refine the indications for LET in patients with high-grade rotatory knee instability.

Paper 51 Static Lateral Tibial Plateau Subluxation Predicts the Grade of Rotatory Knee Laxity in ACL-Deficient Knees Jayson Lian, BA1, João V. Novaretti, MD2, Andrew J. Sheean, MD3, Neel K. Patel, MD2, Adam Popchak, DPT, PhD, SCS2, Volker Musahl, MD2. 1Albert Einstein College of Medicine, Bronx, NY, 2University of Pittsburgh Medical Center, Pittsburgh, PA, 3San Antonio Military Medical Center, San Antonio, TX Objectives: In anterior cruciate ligament-deficient (ACL-D) knees, injury pattern and bony morphology have been shown to influence both static anterior tibial subluxation relative to the femur and dynamic rotatory knee laxity. Therefore, the relationship between static anterior tibial subluxation and dynamic rotatory knee laxity was investigated. The goal of this study was to determine if static tibial subluxation as measured on magnetic resonance imaging (MRI) was associated with the grade of rotatory knee laxity in ACL-D knees. Methods: Two-hundred and fifty-eight knees underwent preoperative, image-guided assessment of lateral knee compartment translation during quantitative pivot shift (QPS). Subluxations of the medial and lateral tibial plateaus were measured on preoperative MRI in a subset of primary ACL-D knees meeting criteria for high-grade (QPS > 5.2 mm) and low-grade (QPS < 2.4 mm) rotatory laxity. Tibial subluxations on MRI were compared between patients with high- and low-grade rotatory laxity using pairwise t-test, and analyzed using uni- and multivariate logistic regression. Significance was set at p<0.05.

Results: On MRI, greater anterior subluxation of the lateral tibial plateau was observed in patients with high-grade compared to low-grade rotatory knee laxity (4.5 mm vs. 2.3 mm; p<0.05). No similar relationship was observed for the medial tibial plateau (-0.9 mm vs. -0.4 mm; p>0.05). Univariate logistic regression demonstrated that static subluxation of the lateral tibial plateau was associated with high-

grade rotatory knee laxity (Odds ratio [OR] 1.2; p<0.05). An optimal cut-off of 2.95 mm of static lateral tibial subluxation was associated with high-grade rotatory knee laxity (sensitivity: 75%; specificity: 63%). Lateral meniscus injury was the first variable to enter a multivariate regression analysis and proved to be most associated with high-grade rotatory knee laxity ([OR] 6.8; p < 0.05). When lateral meniscus injury was excluded from multivariate regression analysis, static anterior subluxation of the lateral tibial plateau alone was associated with high-grade rotatory knee laxity ([OR] 1.2; p<0.05).

Conclusion: Data from this MRI study of two distinct rotatory knee laxity groups showed that static anterior subluxation of the lateral tibial plateau of 2.95 mm or greater was associated with high-grade rotatory knee laxity, and each millimeter increase of lateral tibial plateau subluxation was associated with a 1.2-fold odds of high-grade rotatory knee laxity. Anterior subluxation of the lateral tibial plateau on MRI was not independently associated with high-grade rotatory knee laxity in the presence of concomitant lateral meniscus injury. Static measurements made pre-operatively may aid in predicting high-grade rotatory knee laxity and refining the indications for individualized knee surgery.

Paper 52 Failure and Reoperation Rates Following Arthroscopic Primary Repair Versus Reconstruction of the Anterior Cruciate Ligament Jelle P. van der List1, Anne Jonkergouw2, Gregory S. DiFelice, MD2. 1Spaarne Gasthuis, Amsterdam, Netherlands, 2Hospital for Special Surgery, New York, NY Objectives: To compare the failure and reoperation rates of arthroscopic primary repair versus reconstruction of the anterior cruciate ligament (ACL). Methods: This study retrospectively reviewed all patients with ACL injury operatively treated between April 2008 and May 2016 by one surgeon. All patients with proximal tears were treated with primary repair using suture anchors, or otherwise underwent standard reconstruction. Patients were included if minimum two-year follow-up was present, and were excluded for multiligamentous injuries. Charts were reviewed and patients were contacted to assess failure (instability, graft rupture or revision), reoperation (other than revision), complications and contralateral failure. Results: 154 patients were included of which 56 underwent primary repair (36.4%). Mean age was 30 years (range 14-57), 70% was male and mean follow-up was 3 years (range 2-9). Patients undergoing ACL reconstruction were younger (28 vs. 33, p=0.002) and were more often male (77% vs. 59%, p=0.02). Failure rates were lower following primary repair (10.7%) than ACL reconstruction (12.2%) but this was not statistically significant (p=0.776). Also, no clinical relevant or statistical significant differences were found between repair and reconstruction in reoperations (7.1% each group), complications (1.8% vs. 3.1%, respectively) and contralateral failures (3.6% vs. 4.1%, respectively) (all p>0.99). With revision surgery, no complications were noted following primary repair revision (primary reconstruction; 0%) but 25% of revision reconstructions failed and 1 needed reoperation (8%). Conclusion: This study is the first study to compare the failure and reoperation rates following arthroscopic primary repair versus reconstruction in a large cohort of patients. With the treatment algorithm of primary repair for proximal avulsion tears and reconstruction of midsubstance tears, equivalent outcomes were noted between both treatments. Arthroscopic primary repair is a safe and good treatment for ACL injuries and has similar failure and reoperation rates when compared to the gold standard of ACL reconstruction.

Paper 53 The Effect of Tibial Slope on Anterior Cruciate Ligament Reconstruction: A Matched Case-Control Study Including 317 Revisions Joseph D. Cooper, MD1, Wei Wang, PhD,2, Heather A. Prentice, PhD3, Tadashi Ted Funahashi, MD4, Gregory B. Maletis, MD5 1Keck School of Medicine University of Southern California, Los Angeles, CA, 2Surgical Outcomes and Analysis, Kaiser Permanente, San Diego, CA, 3Kaiser Permanente, San Diego, CA, 4Kaiser Permanente, Irvine, CA, 5Kaiser Permanente Hospital, Baldwin Park, CA Objectives: There is evidence the slope of the tibial plateau may play a role in need for revision following ACL reconstruction (ACLR), however, previous studies are limited by small sample sizes, radiographic measurement, single surgeon experience, lateral tibial posterior slope (LTPS) only, or a lack of confounder adjustment. Further, the role of the medial posterior tibial slope (MTPS) on revision risk has yet to be evaluated. We sought to (1) determine the relationship of revision status following ACLR and LTPS, (2) determine the relationship of revision status and MTPS, and (3) determine the relationship of revision status and the difference between MTPS and LTPS. Methods: We conducted a nested case-control study of 317 matched pairs using an integrated U.S. healthcare system’s ACLR registry (2006- 2014). Cases were defined as patients who underwent a revision following primary unilateral ACLR; controls were defined from the same cohort as non-revised patients during the same time frame. Controls were matched to cases according to age, gender, body mass index, race, graft type, femoral fixation device, and follow-up time. Magnetic resonance imaging (MRI) images were used by a single blinded reviewer to measure tibial slopes. Wilcoxon signed rank test was applied to compare the slopes between revised and non-revised groups continuously and McNemar test to compare slopes of ≥12° between groups. Results: No difference was observed between revised and non-revised patients in LTPS (mean: 6.1 vs. 6.1, p=0.972) or MTPS (mean: 4.6 vs. 4.9, p=0.281) measurement. When comparing revised ACLR to non-revised ACLR, a greater proportion of revised ACLR had a LTPS of ≥12° (7.6% vs. 3.8%, P=0.034), while no difference was found in the proportion of ACLR with a MTPS ≥12° (1.6% vs. 2.5%, P=0.405). No difference was found when evaluating the medial-to-lateral slope difference (-1.5 vs. -1.2, p=0.289). Conclusion: In our nested case-control study of over 300 revised ACLR patients matched to non-revised patients, we did not find an association between the slope of the lateral and medial tibial plateaus and revision.

Paper 54 Early Versus Delayed Surgery Results In Similar Outcomes Following Multiligament Knee Injury; A Prospective Cohort Daniel B. Whelan, MD, MSc1, Ryan M. Khan, BSc1, Matthew Rubacha, MD2, Graeme Hoit, MD1. 1St. Michael's Hospital, Toronto, ON, Canada, 2Methodist Hospital (Houston) Program, Houston, TX Objectives: Multiligament knee injuries (MLKI’s) are rare, but life-altering injuries that have significant implications on patients’ functional status, quality of life and return to work and sport. While the treatment of these injuries is far from standardized, there exists good evidence to support operative intervention. Unfortunately there are no guidelines to indicate the ideal timing of surgery after injury to optimize clinical outcomes and patient satisfaction. With that in mind, the aim of this study was to assess injury specific functional outcomes following surgery for MKLIs and identify advantages to early versus delayed surgery. Methods: Between 2006-2017, adults with MLKIs were identified at an academic level 1-trauma center. Patients were enrolled in prospective data collection and followed routinely after surgery. Study participants were stratified into early (<45 days from injury) and delayed surgical intervention (>45 days from injury). The primary analysis was patient reported outcomes in the form of a specific and validated score (MLQOL) to compare early vs delayed surgical intervention. We secondarily analyzed associations between age, gender, BMI, injury severity (Schenck classification), associated nerve injuries, and reoperation rates to our primary outcome measure. Results: : A total of 152 patients were identified, with 85 patients in the early group and 67 in the delayed. The mean time to surgery was 16.7 ± 7.9 days in the early group versus 253 ± 132.6 days in the delayed. Average follow-up was 46.7 months. There was no significant difference between groups with respect to age, gender distribution, BMI, injury mechanism, nor severity. The early surgery group was found to include more patients with lateral sided injuries (p=0.010) as well as nerve injuries at initial presentation (p=0.002). The delayed group was found to have more patients with PCL involvement compared to early surgery (P=0.003). We did not identify a significant difference in pain, stiffness, or instability patient reported outcome scores between the early and delayed surgical groups. 49 of the 152 patients underwent a repeat operation (32%) including manipulation under anesthesia, arthroscopic debridement, removal of hardware, revision and/or conversion to total knee arthroplasty. No significant difference was found in reoperation rates between the two groups. In our primary outcome, we did not identify any relationship between early or late surgery and MLQOL scores. In our secondary analysis, using a linear regression model, we determined older age to be independently predictive of poor outcomes with respect to pain (p=0.018), stiffness (p=0.048) and instability (p=0.004) as assessed through MLQOL questionnaire. Conclusion: In our analysis, stratifying patients to early vs delayed surgery had no effect patient reported outcomes following MLKI reconstruction. In the secondary outcome measures, we identified

that regardless of time from injury to surgical intervention, older age was independently predictive of poor pain, stiffness, and instability scores in the MLQOL questionnaire. To our knowledge this is the largest prospectively collected dataset of injury specific outcomes in MLKIs. This analysis will allow for an evidence based approach to guide discussion, manage expectations, and predict outcomes of MLKI patients as well as provide the framework for how surgeons manage these significant injuries.

Paper 55 Delay in Surgical Management of Multiligament Knee Injuries is Associated with Cartilage and Meniscus Injury Alan G. Shamrock, MD, James Hall, BS, Christina Hajewski, MD, Qiang An, PhD, Kyle R. Duchman, MD. University of Iowa Hospitals and Clinics, Iowa City, IA Objectives: Multiligament knee injuries (MLKIs) are potentially devastating injuries and can lead to significant functional impairment. Long-term outcomes and reconstructive options for MLKIs have been well described, however limited data exists on meniscus and chondral injuries in the setting of a multiligament deficient knee. The purpose of this study was to describe the pattern of meniscus and cartilage pathology in operative MLKIs and determine the relationship between surgical timing and degree of intra-articular injury. Methods: Consecutive patients with surgically treated MLKIs involving two or more ligaments (ACL, PCL, MCL, or PLC) over a 15-year period at a single large academic institution were retrospectively reviewed. Subjects were grouped based on their ligament injury pattern and the presence or absence of meniscus and chondral injury were recorded. Surgical intervention within 6 weeks of injury was deemed acute, while surgery occurring more than 6 weeks from injury was classified as delayed. Chi square and logistic regression were utilized for statistical analysis, with significance set at p<0.05. Results: In the 15-year study period, 207 patients with MLKIs (age: 28.4 +/- 12.1 years; 74.9% male) were surgically treated at our institution. There were 104 meniscal (50.2%) and 70 chondral (33.8%) injuries in the cohort. The most common ligamentous injury pattern was ACL/MCL (n=47, 22.7%) and ACL/PCL (n=47, 22.7%), followed by ACL/PCL/MCL (n=35, 16.9%) [Table 1]. Meniscectomy (n=52, 50.0%) was the most frequently performed procedure for meniscus injuries followed by meniscus repair (n=32, 30.8%). Compared to acutely managed patients, the delayed intervention group had significantly more meniscus pathology (57.1% vs 42.1%, p=0.03) and were more likely to undergo meniscectomy compared to repair (p=0.002). Of the 70 cartilage injuries, 11 (15.7%) required surgical debridement. Chondral pathology was more frequently present in the delayed intervention group compared to the acutely managed group (p=0.003). Meniscus injury rates in MLKIs sustained during sporting activity did not differ from non-sporting injuries (p=0.59) however, the non-sporting group had significantly more cartilage injuries (42.0% vs 18.1%, p<0.001). Conclusion: Surgical reconstruction of MLKIs delayed for more than 6 weeks was associated with increased meniscus and cartilage pathology. This may be the result of the severity of the initial injury, which may warrant surgical delay in more severe cases, or persistent knee instability placing the meniscus and chondral surface at risk for injury.

Paper 56 Decreased Posterior Tibial Slope Does Not Impact Postoperative Posterior Knee Laxity after Double-Bundle Posterior Cruciate Ligament Reconstruction Nicholas N. DePhillipo, MS, ATC, OTC1, Andrew S. Bernhardson, MD2, Zachary S. Aman, BA3, Mitchell Kennedy, BS3, Grant Dornan, MSc4, Robert F. LaPrade, MD, PhD1 1The Steadman Clinic, Vail, CO, 2Steadman Philippon Research Institute Program, Vail, CO, 3The Steadman Philippon Research Institute, Vail, CO, 4Steadman Philippon Research Institute, Vail, CO Objectives: Recent clinical studies have identified sagittal plane posterior tibial slope as a risk factor for increased postoperative laxity after single-bundle (SB) posterior cruciate ligament reconstruction (PCLR). However, the effect of tibial slope and its role in graft laxity following double-bundle (DB) PCLR has not been investigated clinically. Therefore, the purpose of this study was to retrospectively compare the degree of posterior tibial slope and its impact on posterior tibial translation (PTT) after DB PCLR. It was hypothesized that preoperative tibial slope would not be associated with graft laxity following DB PCLR. Methods: Patients who underwent primary DB PCLR without ACL injury between 2010 and 2017 by a single surgeon were retrospectively analyzed. Measurements of posterior tibial slope were performed using the lateral radiograph and PTT was measured using kneeling PCL stress radiographs, preoperatively and at a minimum of 1-year postoperatively. Linear regression was used to assess the relationship between native posterior tibial slope and postoperative graft laxity, determined by PCL stress radiographs. Results: One hundred three patients with PCL tears and subsequent DB PCL reconstructions were included. Ninety (87.4%) patients reported a contact mechanism at time of injury, while 13 (12.6%) patients reported a noncontact injury mechanism. Sixty-four (62.1%) patients had combined extra-articular ligament injuries that were concurrently reconstructed with the PCL tear, while isolated PCL tears were identified in 39 (37.9%) patients. Forty-nine (47.6%) patients had an acute (less than 6 weeks) injury, 54 (52.4%) patients had a chronic (greater than 6 weeks) injury at time of imaging and evaluation. Four (4%) patients demonstrated failed PCLRs, as defined by SSD in PTT greater than 8 mm on PCL stress radiographs. The mean posterior tibial slope for all PCL injured patients was 5.9 degrees &#177; 2.2 degrees. There was a significant reduction in the amount of mean SSD in PTT between preoperative (10.6 &#177; .7 mm) and postoperative (1.5 &#177; 2.6 mm) PCL stress radiographs following DB PCLR (95% CI [8.4, 9.8], p &lt; 0.001). Linear regression analysis revealed no significant correlation between preoperative posterior tibial slope and the amount of SSD in PTT on postoperative stress radiographs obtained at a mean 18.5 months postoperatively (R = -0.115, p = 0.249). Similarly, when adjusting for combined ligamentous injury, injury chronicity, mechanism of injury, BMI, and age at surgery via multiple linear regression, preoperative tibial slope was not a significant independent predictor of postoperative SSD in PTT (beta = -0.079, 95% CI [-0.308, 0.150], p = 0.496). Combined injury (beta = -1.01, 95% CI [-2.00, -0.01], p = 0.047) was a significant independent predictor of decreased

postoperative SSD in PTT on posterior stress radiographs. Conclusion: Graft laxity, determined by PTT in posterior kneeling stress radiographs, was not influenced by decreased posterior tibial slope in patients following DB PCLRs. Combined PCL injury was a significant independent predictor of decreased postoperative SSD in PTT on posterior stress radiographs. Additionally, the majority of patients (96%) demonstrated improved objective posterior knee stability following DB PCLR. Thus, DB PCLR can be recommended as a surgical treatment option for patients with grade III isolated and combined PCL injuries, irrespective of native posterior tibial slope.

.

Multiple linear regression model for postoperative residual posterior tibial translation (PTT).

Beta 95% Confidence Interval

Standard Error

t-value

p-value

(Intercept) 1.303 [-3.173, 5.778] 2.25 0.58 0.565

Tibial Slope -0.079 [-0.308, 0.15] 0.12 -0.68 0.496

Combined Injury -1.01 [-2, -0.01] 0.50 -2.01 0.047 Chronic Injury (greater than 6 weeks) -0.69 [-1.65, 0.27] 0.48 -1.42 0.158

Contact Mechanism of Injury 0.76 [-0.75, 2.27] 0.76 1 0.322 Follow-Up Time (months) 0.062 [0.03, 0.094] 0.02 3.81 0.001

Body Mass Index -0.056 [-0.192, 0.081] 0.07 -0.81 0.421

Age At Surgery 0.031 [-0.008, 0.07] 0.02 1.59 0.115

Paper 57 Comparing the Efficacy of Kneeling Stress Radiographs and Weighted Gravity Stress Radiographs to Assess Posterior Cruciate Ligament Insufficiency Charles L. Holliday, BS1, Ryan Martin, MD, FRCSC2, John A. Grant, MD, PhD, FRCSC1. 1MedSport, Dept. of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, 2University of Calgary, Calgary, AB, Canada Objectives: Kneeling stress radiographs are commonly used to evaluate posterior cruciate ligament (PCL) laxity. Patients, however, report significant pain, and reproducibility is challenged due to its dependence on patient body weight distribution to produce posterior tibial displacement (PTD). Weighted gravity stress radiographs may offer better reproducibility and comfort than the kneeling technique, but its efficacy has not been studied. Hypothesis: weighted gravity radiographs will be more comfortable and produce similar PTD measurements when compared to the kneeling technique. Methods: Patients 18-70 years old with non-operatively or >6 months post-operatively treated PCL injuries (isolated or multi-ligamentous) were recruited from two academic level one trauma centers to undergo bilateral PCL stress radiographs. Exclusions: open/bilateral injuries, fractures. Patients underwent PCL stress radiographs by two randomly ordered methods. Kneeling stress views: patients knelt on padded scales (separate for each knee) with the padding distal to the tibial tubercle. Patients were verbally encouraged to place equal weight on both knees (scale outputs not visible to the patient). A digital radiography plate was placed between the legs to acquire bilateral lateral radiographs. Weighted gravity stress views: Patients lay supine with their hip and knee at 90°with the heel supported. A 20lb weight was placed on the anterior tibia just distal to the tibial tubercle. A lateral radiograph was taken and then repeated on the contralateral leg. Images were anonymized and uploaded to PACS for measurement. Outcomes: side to side difference (SSD) in translation of the posterior tibial condyles relative to the posterior femoral condyles (primary outcome); patient-reported VAS knee pain (100mm) during the radiographs; time required to acquire the images; patient preference for technique. Statistics: sample size = 31 patients to detect a 2mm difference (α=0.05, power 80%, SD = 2.8mm [Jung, 2006]). Paired t-tests were used to compare the SSD between the kneeling and weighted gravity methods, VAS pain, and time to complete the radiographs. Results: 40 patients (77.5% male, 34.5 ± 12.8yrs old, 65% left knee) were recruited. 42.5% had undergone PCL reconstruction. There was no difference between the two radiographic methods in the mean SSD (kneeling = 6.29 ± 4.58mm, gravity = 6.82 ± 4.60mm, p= 0.61). There was no difference in the total time required to perform the radiographs (kneeling = 307.3s ± 140.5s, gravity = 318.7s ± 151.1s, p= 0.73) or the number of radiographs taken to obtain acceptable images (kneeling = 3.6 ± 1.6, gravity = 3.7 ± 1.7, p= 0.73). The amount of weight placed on each knee during the kneeling views differed slightly but was not significant (affected = 21.5 ± 11.3kg, unaffected = 26.1 ± 12.1kg, p= 0.09). There was significantly less knee pain reported for the gravity views (kneeling = 31.8 ± 26.6, gravity = 4.0 ± 12.0, p < 0.0001). 94.6% of patients preferred the gravity method.

Conclusion: Weighted gravity PCL stress radiographs should be considered for use in clinical practice as they produce similar posterior tibial translation values to the kneeling technique, do not rely on patient weightbearing, and provide significantly better patient comfort.

Paper 58 Non-traumatic Fatalities in Football: Over-conditioning Kills Barry P. Boden, MD1, Ilan Breit2, Scott Anderson, ATC3. 1The Orthopaedic Center, Rockville, MD, 2Baltimore, MD, 3Norman, OK Objectives: Football is associated with the highest number of fatalities of any high school (HS) or college sport. In contrast to the annual number of traumatic fatalities in football, which has declined 4-fold since the 1960’s, the annual number of non-traumatic fatalities has stayed constant with current rates that are 2 to 3 times higher than traumatic fatalities. The purpose of this study was to describe the epidemiology and causes of non-traumatic fatalities in HS and college football players, to determine the effectiveness of the NCAA policies to reduce heat and sickle cell trait (SCT) fatalities, and to provide prevention strategies. Methods: We retrospectively reviewed non-traumatic football fatalities identified over a 20 year period from July 1998 through June 2018. Information was obtained from extensive internet searches, as well as depositions, investigative, autopsy, media, and freedom of information reports. Heat and SCT fatality rates were compared pre and post implementation of the NCAA football acclimatization model (2003) and SCT screening (2010) policies, respectively. Results: There were 187 (150 H.S., 37 college) non-traumatic fatalities (avg. 9/yr.). The most common causes of fatalities were cardiac (98, 52%), heat (44, 24%), SCT (23, 12%), and asthma (10, 5%). The majority of fatalities (127, 68%) occurred outside of the regular season months of September through December with the most common month for fatalities being August (61, 33%). Most (163, 87%) of the fatalities occurred during a practice or conditioning session (heat=100%, SCT=100%, asthma=90%, cardiac=77%). Hallmarks of exertion-related fatalities were: 1. conditioning sessions supervised by the football coach or strength and conditioning coach, 2. irrationally intense workouts and/or punishment drills, and 3. an inadequate medical response. The average annual rate of heat-related fatalities remained unchanged at the collegiate level pre (0.4) and post (0.4) implementation of the NCAA football acclimatization model in 2003. The average annual number of SCT deaths in collegiate football declined 58% (0.83 to 0.25) after the 2010 NCAA SCT screening policies were implemented. At the HS level, where there are no SCT guidelines, the number of SCT fatalities increased 400% (0.25/yr. to 1.0/yr.) since 2010. Conclusion: Most non-traumatic fatalities in HS and college football athletes do not occur while playing the game of football, but rather during conditioning sessions which are often associated with overexertion and/or punishment drills by coaches, especially strength and conditioning coaches. The football acclimatization model implemented by the NCAA in 2003 has failed at reducing exertional heat-related fatalities at the collegiate level. SCT screening policies adopted by the NCAA in 2010 have been effective at reducing fatalities in college athletes and similar guidelines should be mandated at the HS level. Conditioning related fatalities are preventable by establishing standards in workout design,

holding coaches and strength and conditioning coaches accountable, ensuring compliance with current policies, and allowing athletic health care providers complete authority over medical decisions.

Paper 59 Trends in US High School Football Concussion Reporting, 2012-2017 Scott O. Burkhart, PsyD, Dustin M. Loveland, MD, Troy M. Smurawa, M.D., John Polousky, MD. Children's Health Andrews Institute, Plano, TX Objectives: Football has been a sport with high concussion rates when examined independently

(Rosenthal et al., 2014). Accurately describing injury trends in high school sports is necessary to identify student-athletes at the greatest risk of injury and where potential injury reduction interventions should be focused. With increased reported high school concussion injuries and associated state legislative requirements, increased incidence rates are needed. The purpose of this study was to provide updated high-school football concussion incidence rates. Methods: Data Source and Study Period This study used data from the Rank One Health Injury Surveillance Database (ROH ISD). Data for the current study were analyzed across 6 calendar years (2012 through 2017) from 1,999 high schools. Data from the current study examined high school football concussion data in males ages 14 to 18. The ROH ISD consists of a convenience sample of participating schools from 2012 to 2017. Exposure and injury data represent a convenience sample of US high schools. For the current study, only data provided across all 1,999 high schools were included. All 1,999 high schools included in the current study logged practice and game participation events for each individual athlete participating in football at the respective high school and athletic exposures (AEs) are an accurate representation of rostered athletes participating in either practices or games by age and calendar year. The ROH ISD was deemed Category 4 IRB exempt. Statistical Analysis Injury counts, practice exposures, game exposures, and distributions by event type (practice or game), age, and injury mechanism were examined. Injury rates per 1,000 AEs and injury rate ratios (IRRs) were calculated by event type. Injury proportion ratios (IPRs) were used to examine differences by calendar year. Risk ratios (RRs) were calculated to compare event type by calendar year. All 95% confidence intervals (CIs) not containing 1.0 were considered statistically significant. Results: 997,308 male student-athletes participated in high school football. ATs recorded a total of 14,103 concussions in high school football from a total of 235,134 total injuries across all high school sports. High school football concussions accounted for 6% of all injuries in high school sports from 2012-2017. More concussions occurred in games (51.8%) than practices (48.2%). Decreases were found in annual injury rates for practices in high school football student-athletes from 2012 to 2016 with an increase in 2017. Decreases were found in annual injury rates for games from 2012 to 2016 with an increase in 2017. IPR decreased by year from 2012 to 2016 (with an increase in 2017. IRR and RR comparisons for games versus practices were significant from 2012 to 2017 (Table 1).

Conclusion: This study marks the largest epidemiological high school football concussion incidence investigation to date. The findings from this study provide updated high school football concussion incidence rates and provide further evidence of differences in injury rates when comparing practices and games. The higher rates of concussions occurring in games relative to practices emphasize prior trends of injury risk relative to the level of competition. Overall, results highlight a decline in injury rates over time and lower rates of injury compared to prior high school football epidemiological concussion studies.

Paper 60 Trochleoplasty is a Viable Option for Patellar Instability in Patients with Severe Trochlear Dysplasia: a Minimum 1-year Follow-Up Prospective Study S. Evan Carstensen, MD, Matthew Tyrrell Burrus, MD, Scott Feeley, Jourdan M. Cancienne, MD, David R. Diduch, MD University of Virginia, Charlottesville, VA Objectives: Patellar instability caused by trochlear dysplasia may be addressed by sulcus-deepening trochleoplasty. A paucity of data exists from the United States regarding this procedure and no long term follow up. The purpose of this study was to evaluate the outcome data of patients undergoing sulcus-deepening trochleoplasty for high-grade trochlear dysplasia at our institution. Methods: Sixty-four patients (71 knees) with severe trochlear dysplasia were prospectively enrolled and underwent sulcus-deepening trochleoplasty using the Dejour method from 2011-2018. Thirty-six of 71 knees (50.6%) had prior surgery and failed prior surgical management for patellar instability. Concomitant procedures during trochleoplasty were performed at varying rates. Radiographic analysis, physical examination, and clinical follow-up were obtained for all patients. At enrollment, patients completed preoperative visual analog scores (VAS), international knee documentation committee (IKDC) and Kujala scores, which were repeated at their 6 month, 1 year, 2 year, 3 year, and 4 year follow-up visits. Preoperatively, the patellotrochlear index (PTI), trochlear spur height, and trochlear depth were all measured. The patient’s sulcus angle was measured preoperatively and postoperatively on sunrise (merchant) view xray. Of the entire cohort, 43 patients (49 knees) had at least one year complete follow-up including xrays, physical exam, and patient-reported outcome measures and were included in the study. Results: The majority of patients were female (81.6%) with a mean age of 19.6 (+/- 6.8y). Follow-up ranged from 12 months to 78.4 months (mean 27.7 +/- 15.4). At the time of enrollment, mean BMI was 27.1 kg/m2 (+/-6.3) with one current smoker and one diabetic patient. Mean duration of symptoms prior to surgery was 75.2 months (+/- 72.5; r: 4-370mos). All knees were either Dejour B (81.3%) or D (18.8%) with a mean Caton-Deschamps index (CDI) of 1.20 (+/-0.2). Mean spur height preoperatively was 7.41mm (+/1.84mm) with a mean trochlear depth -0.18 (+/-2.71). Mean patellotrochlear index (PTI) was 0.41 (+/0.41). There were zero episodes of recurrent instability. All patients reported clinically significant improvements compared with baseline preoperative outcome scores. The mean preoperative IKDC score was 49.99, which improved to 79.86 (p&lt0.001), and the mean preoperative Kujala score was 55.88, which improved to 85.80 (p&lt0.001). Patients reported high satisfaction rates (9.5 +/-1.6 out of 10). All but 1 patient (96.9%) returned to work while 88.2% of patients were able to return to sport. Ten knees (20.4%) developed arthrofibrosis and required manipulation under anesthesia while eight of which underwent simultaneous arthroscopic lysis of adhesions. At the latest follow-up, mean knee range of motion was 132.4 +/- 13.2 degrees. Preoperative VAS was 3.31 (right) and 4.16 (left) while postoperative was 1.31 (right) and 1.76 (left) (p=0.007 R, 0.002 L). Radiographic analysis of the sulcus

angle demonstrated a significant decrease from 148.86 degrees (+/-11.42) preoperatively to 135.11 degrees (+/-8.85) postoperatively (p&lt0.001). Conclusion: In the setting of severe trochlear dysplasia, sulcus-deepening trochleoplasty can provide a reliable and successful surgical solution to recurrent patellar instability. At a minimum of one year follow-up, the majority of patients were satisfied with their outcome corroborated by their subjective, validated outcome measures.

Paper 61 Distalization Of Tibial Tubercle for Patella Stabilization: Does Length Of Distalization Or Residual Patella Alta Effect Outcome? Andrew Schmiesing, MD1, Marta Engelking2, Julie Agel, MA, ATC2, Elizabeth A. Arendt, MD1. 1University of Minnesota, Minneapolis, MN, 2UMn, Minneapolis, MN Objectives: Distalization of the tibial tubercle (DTT) is a surgical procedure to help stabilize the patella when patella alta is present. The purpose of this study is to: 1) evaluate the accuracy of our operative intervention (i.e. how often is patella height normalization achieved). 2) correlate post-operative (residual) patella alta with recurrent patellar instability 3) correlate the mm of distal displacement with negative outcomes Methods: Data was collected retrospectively on consecutive patients who underwent DTT as part of their surgical procedure for recurrent lateral patella dislocation. All patients had concurrent medial patella ligament reconstruction (MPFLR), performed by a single surgeon between 2009-2015. Data collected included demographics, pre-and post-operative imaging measurements related to patella alta and trochlear dysplasia on MRI and plain radiographs, recurrent lateral patella dislocations, and complications including fracture and knee arthrofibrosis. Surgical planning including the assessment of the Caton-Deschamps index (CD) on sagittal radiographic imaging. The surgical goal was to have a final CD between 1.0-1.2, or a maximum distance moved of 15 mm in cases of severe patella alta. When CD was within normal limits due to patellar anatomy, we used as a proxy the patellar-trochlear index (PTI), aiming for a PTI of 25% judged intra-operatively. Results: 89 patients underwent DTT over a 7-year period. There were 21 (24%) males/68 (76%) females. Mean (range): age 21 (13-45), BMI 25.8 (17-44.6). Pre-op imaging measurements were: IS ratio 1.5 (1.18-2.06), CD ratio 1.4 (1.05-1.93), lateral patella tilt 24.7º (1º-53º), TT-TG 18.6 mm (8-28), sulcus angle 158º (123-180), PTI 29% (5-70). Post-operative mean CD was 1.09 (0.92-1.67). The amount of distalization averaged 9.8 (range 4 to 15). 13 patients had residual patella alta (CD>1.2). One patient with residual patella alta re-dislocated (CD=1.25). The most extreme residual patella alta (1.67) had a pre-op CD of 1.97 and was distalized 15mm. There was no patellar baja. 6 patients (6%) had frank recurrent patellar dislocation; postoperative patella height in this group averaged 1.11 (1.02 -1.25), indicating that re-dislocation was not due to residual patella alta. Tibia fracture (4%) was not related to mm of distalization; mean (10) /range 8-15mm. Arthrofibrosis requiring manipulation was needed in 11 patients (13%) whose mean distalization was 11.8 mm (9-15mm). This distance was significantly different (p=0.009) from those not requiring manipulation.

Conclusion: Distalization of TT leads to a high rate of normalization of patellar height measurements, with 94% patella stabilization. Residual patella alta was not associated with an increased risk of recurrence (p=0.57). Distalizing the tibial tubercle up to 15mm did not increase fracture risk, however there was an increase in arthrofibrosis requiring manipulation.

Paper 62 Medial Patellofemoral Ligament Reconstruction with and without Tibial Tubercle Osteotomy Seth L. Sherman, MD, John W. Welsh, Joseph M. Rund, BS, Lasun O. Oladeji, MD, John R. Worley, Taylor Ray. University of Missouri, Columbia, MO Objectives: The medial patellofemoral ligament (MPFL) is the primary soft-tissue restraint against lateral patellar displacement. Surgery to address MPFL incompetence is the current gold standard for recurrent patellofemoral instability. The role of tibial tubercle osteotomy (TTO) as an adjunct to MPFL reconstruction remains controversial. Our purpose was to evaluate a cohort of patella instability patients undergoing surgical soft tissue stabilization with or without concomitant TTO. Our hypothesis was that there would be no difference between cohorts in baseline values, subjective outcome scores at final follow-up, or complication profile. Methods: Following IRB approval, retrospective review of prospectively collected data identified a consecutive cohort of patients undergoing soft tissue stabilization for recurrent patella instability, with or without concomitant TTO. Indications for TTO were at the surgeon’s discretion, including elevated TT-TG, Caton-Deschamps ratio, and/or unloading chondral lesion(s). Surgery was performed by a single sports fellowship trained surgeon. Pre-surgical and post-surgical patient reported outcomes were collected including KOOS domains, PROMIS (global health, mental health, physical function, pain interference), IKDC, SANE, and Marx scores. Complications requiring re-operation (infection, stiffness, recurrent instability) were recorded. Results were analyzed statistically. Results: The cohort was comprised of 87 patients (95 knees), with 25 males (28.7%) and 62 females (71.3%). The MPFL-TTO cohort had 32 patients (38 knees) and the MPFL-Iso had 55 patients (57 knees). The average age of the MPFL-TTO cohort was 28.3 (range 19.5-44.6) and the average age of the MPFL-Iso group was 29.8 (18.7-55.3). There was no significant difference in pre-operation outcome scores between groups (p>.05). Significant improvements were seen for all KOOS domains in both patient cohorts with no significant differences detected between groups. SANE, IKDC, and PROMIS scores improved significantly with no differences detected between groups. Marx activity score at 6 months post-operatively was significantly different between the groups favoring the isolate MPFL reconstruction cohort. (MPFL-TTO 0.79 +/- 2.15 vs. 4.61 +/- 5.44 in the MPFL-Iso group (p=0.01)). In terms of complications, 4 knees in the MPFL-TTO group required further surgery (2 for stiffness, 1 for infection, and 1 for fracture) and 6 knees in the MPFL-Iso cohort required surgery (4 for stiffness, 1 for infection, and 1 for recurrent instability). Neither the overall complication rate of 4 vs. 6 (p=1) nor the recurrent instability rate of 0 vs. 1 (p=0.41) was significant. Conclusion: In a cohort of patients undergoing MPFL reconstruction, the addition of an appropriately indicated TTO appears to be both safe and effective. Both MPFL-TTO and MPFL-Iso groups demonstrated significant improvement in the majority of subjective outcome scores without major

difference between groups. Marx activity scores were higher for the isolated MPFL reconstruction cohort at relatively short term follow-up. The surgical complication profile was similar between groups. Further work is needed to clearly define the role of TTO as an adjunct procedure to MPFL reconstruction.

Paper 63 Partial Patellar Tendon Tears in Athletes: When Is Surgery Required? Mikhail Golman, MS1, Margaret L. Wright, MD1, Tony Wong2, Thomas Sean Lynch, MD1, Christopher S. Ahmad, MD1, Stavros Thomopoulos, PhD1, Charles A. Popkin, MD1. 1Columbia University, New York, NY, 2New York, NY Objectives: Partial patellar tendon tears (PPTTs) can be a frustrating injury for athletes and physicians. Determining the location and size of the PPTT are fundamental in understanding prognosis and selecting the most effective treatment. With recent enhancements in MRI quality, the size and dimensions of the tear can be more easily and accurately estimated. While some PPTTs respond to therapy, medication, bracing, biologic injections, and/or ultrasound procedures, other PPTTs in do not respond and require surgical intervention. The goal of this study is to correlate PPTT size and location to clinical outcomes, in order to create a classification system to help guide treatment decisions for athletes with PPTT. Methods: 112 athletic patients (range: 15-45 y/o, mean 23.9+7.2 y/o) who underwent knee MRI were included in this study. 85 of those patients (mean 24.9+8.1 y/o) presented with history and physical examination concerning for recalcitrant patellar tendonitis or suspicion of a partial patellar tendon tear. The other 27 athletic patients (mean 25.6+6.3 y/o) underwent MRI for other pathology and were included as age-matched controls. MR scans were evaluated for patellar tendon tear size, thickness, and location with respect to the entire patellar tendon. Descriptive statistics were used to evaluate tendon size and tear distributions. Pearson correlation, univariate regressions, and logistic regression were performed to correlate tendon geometry and tear sizes. Tear geometry variables were compared to patient outcome measures (return to previous activity level, surgical treatment) using t-tests. Results: 56 out of 85 symptomatic patients had partial patellar tendon tears. 91% of PPTTs involved the posterior and posteromedial region of the proximal patellar tendon (Figure 1). On axial MRI imaging, patients with PPTT had mean tendon thickness of 10 mm compared to 5.9 mm for athletes with no PPTT, including healthy controls (p<.0001). There was a significant correlation between patellar tendon thickness and PPTT size (R=0.85, p<0.0001). Logistic regression analysis showed that athletes with patellar tendon thickness above 7.45 mm are likely to have PPTTs (100% sensitivity). Tear distributions according to MRI grading are shown in Table 1. 11 out of 56 patients underwent surgery for PPTT. All 11 of these patients had tear sizes on axial images > 50% of tendon thickness (mean thickness of tear 6.3mm). Logistic regression showed that patellar tendon thickness > 8.8 mm, and/or tear size > 55 % correlated with surgical intervention. Five of the surgical patients did not make a return to sport at the same level. No patient in this series had surgery for tear thickness less than 4.5mm. Basketball, track and field and soccer were the most common sports involved in the study. Conclusion: PPTTs are located posterior/posteromedially in the proximal patellar tendon. The most sensitive metric for PPTTs are patellar tendon thickness (anterior to posterior), where thickness more than 8.8 mm is strongly predictive of having a partial tear in the tendon. Athletes with greater than a 55

% tear thickness on axial MRI imaging or with a tear measuring more than 4.5mm on axial cuts are less likely to respond to non-operative treatment. Tracking thickness changes on axial views, specifically in the posterior/posteromedial region, may predict effectiveness of non-operative therapy.

Distribution of PPTTs according to MRI based grading

- Criteria [tear % in thickness]

Thickness [mm] (A->P)

Tear Thickness[mm] (A->P)

Repair Surgeries [patients]

Did NOT return to previous activity [patients]

Grade 1 No tears 6.15 +/- 1.86 0 0 2

Grade 2 Tears <25 % 8.71 +/- 1.65 1.8 +/- 0.6 0 1

Grade 3 25 % < 50 % 10.03 +/- 2.37 3.8 +/- 1.4 0 3

Grade 4 above 50% > 10.27 +/- 2.22 6.3 +/- 1.5 11 5

Total - - - 11 11

Paper 64 Athletic Hip Injuries in Major League Baseball Pitchers Associated with UCL Pathology David Eric Kantrowitz1, David P. Trofa, MD2, Denzel R. Woode1, Christopher S. Ahmad, MD1, Thomas Sean Lynch, MD1 1Columbia University, New York, NY, 2OrthoCarolina Sports Medicine, Shoulder & Elbow Program, Charlotte, NC Objectives: Ulnar collateral ligament (UCL) reconstruction is a reliable treatment for elite overhand throwers with UCL pathology. In recent years, this operation has become increasingly common among Major League Baseball (MLB) pitchers. Predisposing factors and associated comorbidities, however, have not been well elucidated in the literature. The purpose of this investigation is to determine if professional baseball pitchers who underwent UCL reconstruction had an increased incidence of hip or groin injuries 4 years prior to or following their surgery. We hypothesized that MLB pitchers who sustained hip or groin injuries may have been more likely to develop UCL pathology due to kinetic chain alterations and overcompensation at the distal upper extremity during overhand throwing. Methods: This case controlled study utilized a comprehensive list of all 247 MLB players who underwent UCL reconstruction between 2005 and 2017, through aggregation of online publicly accessible data. Application of inclusion criteria yielded a final sample size of 145. These athletes’ injury histories were identified using systematic online searches and cross referenced with the official MLB disabled list. Age, playing time, and ERA-matched controls were generated for comparison of results. Results: Of the 145 MLB pitchers who underwent UCL reconstruction between 2005 and 2017, 40 (27.6%) endured a proximal lower extremity injury within 4 years of their surgery. Specifically, 16 pitchers sustained hip injuries, 13 suffered hamstring injuries, and 14 experienced groin injuries. A significantly lower rate of hip and groin related injuries, 18%, was identified in matched controls during a similar timeframe (p = 0.049). This represents an odds ratio of 1.74, indicating that players who underwent a UCL reconstruction were 74% more likely to have sustained a hip, groin or hamstring injury within an eight-year timeframe compared to matched controls. Hip injuries, specifically, were independently associated with UCL reconstruction compared to matched controls (p = 0.027). Conclusion: The results of this study demonstrate that MLB pitchers who required UCL reconstruction sustained a higher frequency of hip injuries both before and after surgery compared to matched controls. This association is significant as treatment of antecedent hip pathology, as well as emphasis on hip and core muscle mobility and strengthening, may help reduce the UCL injury burden in MLB pitchers.

Paper 65 Incidence Of Elbow Ulnar Collateral Ligament Surgery In Collegiate Baseball Players Marcus A. Rothermich, MD1, Stan A. Conte, PT, DPT, ATC2, Glenn S. Fleisig, PhD3, E. Lyle Cain, MD4, Jeffrey R. Dugas, MD4 1South Florida Orthopaedics & Sports Medicine, Stuart, FL, 2Conte Injury Analytics, Santa Clara, CA, 3American Sports Medicine Institute, Birmingham, AL, 4Andrews Sports Medicine & Orthopaedic Center, Birmingham, AL Objectives: Recent studies in the literature have highlighted the progressive increase in the incidence of ulnar collateral ligament (UCL) injuries to the elbow in baseball players of all levels. However, knowledge of the incidence and other epidemiological factors regarding UCL injuries, specifically in college baseball players, is currently lacking. In 2016, we launched a prospective, multi-year study to evaluate the incidence of UCL injuries requiring surgery in National Collegiate Athletic Association (NCAA) Division I baseball programs. Methods: We invited 157 Division I collegiate baseball programs after the 2017 season, and 155 agreed to participate in the study. After the 2018 season, all 297 programs were invited and 294 participated. At the conclusion of the 2017 and 2018 collegiate baseball seasons, the athletic trainer for each program entered anonymous, detailed information on injured players through an electronic survey into a secured database. Results: We obtained a 100% completion rate in the first two years of this ongoing study (155/155 respondents in the first year, 294/294 in the second year). Of the 5,364 collegiate baseball players tracked in Year 1 (2016-2017), 134 underwent surgery for an injured UCL, resulting in a team surgery rate of 0.86 per program. In Year 2 (2017-2018), there were 230 surgeries reported from 10,019 players tracked, resulting in a team surgery rate of 0.78 per program. A majority of schools experienced at least one surgery during both years (56.8% in Year 1, 50.7% in Year 2). Pitchers experience a vast majority of the surgical injuries (85.8% in Year 1, 84.3% in Year 2). Underclassmen made up 65.7% of surgeries in Year 1, which fell slightly to 56.1% in Year 2. Nearly half of the surgeries occurred during an ongoing baseball season in Year 1 (48.5%), but this fell in Year 2 to 41.3%. In both years, a non-significant majority of players were from warm-weather states (65.4% in Year 1, 52.9% in Year 2). Revision surgical rates remained nearly constant with 3.0% revision surgeries in Year 1 compared with 2.6% revisions in Year 2. Interestingly, the percentage of UCL repairs with internal brace augmentation rose from 9.5% in Year 1 to 19.9% of all procedures in Year 2. Conclusion: The incidence of UCL surgeries in NCAA Division I collegiate baseball players represents substantial morbidity to this young athletic population. This multi-year prospective study has been established to assess the incidence of surgical UCL injuries in collegiate baseball. Also, importantly, with multiple years of data we will identify trends in the demographics of players undergoing surgery and in

surgical details over time. Awareness of these factors should be considered in injury prevention programs in the future.

Paper 66 Outcomes of Non-Operatively Treated Elbow Ulnar Collateral Ligament Injuries in Professional Baseball Players by Magnetic Resonance Imaging Tear Grade and Location Aakash Chauhan, MD, MBA1, Peter Nissen Chalmers, MD2, Peter Douglas McQueen, MD3, Christopher L. Camp, MD4, Hollis G. Potter, MD5, Michael G. Ciccotti, MD6, John D'Angelo7, Heinz R. Hoenecke, MD8, Brandon J. Erickson, MD9, Stephen Fealy, MD5, Jan Fronek, MD10 1Dupage Medical Group, Naperville, IL, 2University of Utah Health, Salt Lake, UT, 3Romano Orthopedics, Chicago, IL, 4Hospital for Special Surgery, Rochester, MN, 5Hospital for Special Surgery, New York, NY, 6Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA, 7Major League Baseball, New York, NY, 8Scripps Clinic, La Jolla, CA, 9Rothman Institute, New York, NY, 10Scripps Clinic Medical Group, La Jolla, CA Objectives: Evaluate the relationship of 1) MRI tear grade and 2) injury location with outcomes for non-operatively treated elbow ulnar collateral ligament (UCL) injuries in professional baseball players. Methods: 544 professional baseball players were identified from the MLB Health and Injury Tracking System (HITS) that were treated non-operatively for their UCL injuries from 2011-2015. Of these players, 237 MRI’s were directly available for review by an independent, expert musculoskeletal radiologist who evaluated the grade (Grade I -edema, II-partial tear, III-complete tear) and location of the tears (humeral, ulnar, both-sided). Player demographics and outcomes including return to throwing (RTT), return to play (RTP), failed non-operative treatment leading to UCL reconstruction (UCLR), and Kaplan-Meier survivorship analysis of the native UCL to re-injury or surgery based on MRI grade and tear location was measured. A multivariate analysis adjusting for age, MRI grade, tear location, and level of play (Major = MLB; Minor = MiLB) was also performed. Results: The average age of all players was 22.5 years, 90% played at the MiLB level, and 84% were pitchers. The radiologist’s MRI injury grade was distributed as follows: Grade I (36%), Grade II (49%), and Grade III (15%) injuries. The tear locations were distributed as follows: humeral (65%), ulnar (13%), and both-sided (22%). There were no statistically significant differences in RTT, RTP, and UCLR by grade or tear location. However, objectively, ulnar-sided tears had the lowest RTT (81%) and RTP (42%). The ulnar (58%) and both-sided (60%) tears also had an objectively higher rate of UCLR compared to humeral sided tears (51%, p=0.441). The survivorship analysis showed a consistent decline over time with increasing MRI grade. By location, humeral tears had the highest survivorship (1 yr = 51%; 2 yr = 44%). However, there was no statistically significant differences in survivorship for either grade or location. Multivariate analysis measured the likelihood of not returning to play as 3 times higher [95% CI: 1-9.3; p=0.044] for older players (>25) compared to younger players. The likelihood of having re-injury or UCLR after non-operative treatment failed was almost 6 times higher [95% CI: 1.5-21.7; p=0.012] for MLB players as opposed to MiLB players. MRI grade and tear location were not significantly predictive of returning to play, re-injury, or surgery.

Conclusion: This is the largest study to evaluate the prognostic relationship of MRI injury grade and tear location with outcomes for non-operatively treated elbow UCL tears in professional baseball players. Lower MRI grade and humeral location were objectively associated with a higher RTT, higher RTP, lower UCLR, and higher survival compared to higher grade, and ulnar or both-sided tears. Older age (>25) had a significantly higher likelihood of not returning to play after non-operative treatment. Competing at the MLB level had a higher likelihood of re-injury or having UCLR. Based on this study, non-operative treatment of UCL injuries will likely be more successful in younger players, lower grade tears, and humeral-sided injuries.

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Paper 67 Major League Baseball Pitching Performance after Tommy John Surgery and the effect of Tear Characteristics, Technique, and Graft Type Nathan E. Marshall, MD1, Robert A. Keller, MD1, Orr Limpisvasti, MD2, Brian M. Schulz, MD3, Neal S. ElAttrache, MD4. 1Ascension Providence Rochester, Rochester, MI, 2Kerlan-Jobe Orthopaedic Clinic, Los Angeles, CA, 3Kerlan Jobe Orthopedic Clinic, Los Angeles, CA, 4Kerlan-Jobe Orthopaedic Clinic Program, Los Angeles, CA Objectives: Return to play and player satisfaction has been quite high after ulnar collateral ligament reconstruction (UCLR), however, there has been little reported on how outcomes are affected by surgical technique, graft type and tear characteristics. The purpose was to evaluate surgical techniques, graft type and tear characteristics on MLB performance after UCLR. Methods: MLB pitchers that underwent primary UCLR at a single institution were included. Tear characteristics included tear location, tear grade and acuity. Surgical technique and graft type was also collected. Pitching performance statistics, including earned run average (ERA), Walks hits per innings pitched (WHIP), innings pitched, and fastball velocity were evaluated 3 years pre- and post-UCLR. Results: 46 MLB pitchers were identified having primary UCLR. Return to play was 96%, with 82% returning to MLB play. Technique performed showed no difference in performance. Pitchers with palmaris grafts were younger (p=0.043), played longer after surgery (p=0.007), and returned to play at 100% (35/35) vs. 82% (9/11) of gracilis grafts (p=0.011). Pitchers with distal tears pitched at higher velocity (93.0 vs. 90.6 mph)(p=0.023) and had better performance (ERA, p=0.003; WHIP, p=0.003) prior to surgery, with proximal tears improving to match this performance and velocity after reconstructionhigher . Pitchers with complete tears played longer after surgery (5.9 vs. 4.0 years)(p=0.033), had better ERA (p=0.041) prior to injury and better WHIP (p=0.037) and strikeouts/9 innings (p=0.025) after reconstruction vs. partial tears. Chronic tears had a significant improvement in ERA from 4.49 to 3.80 (p=0.040) postoperatively. Conclusion: Technique performed and graft type used did not affect performance, however, palmaris grafts returned at a higher rate than gracilis grafts. Distal tears occurred in pitchers with greater velocity and better performance prior to injury with proximal tears matching this performance after reconstruction. Pitchers with complete tears played longer after reconstruction. Pitchers who had partial tears had worse performance prior to injury and after reconstruction and chronic tears saw a significant improvement in ERA with reconstruction.

Paper 68 Clinical Utility Of An MRI Based Classification For Operative Versus Non-operative Management Of UCL Tears: Two-year Follow Up Prem N. Ramkumar, MD, MBA1, Heather S. Haeberle, BS2, Sergio M. Navarro, BS3, Salvatore Joseph Frangiamore, MD4, Lutul D. Farrow, MD5, Mark S. Schickendantz, MD6. 1Cleveland Clinic, Cleveland, OH, 2Baylor College of Medicine, Houston, TX, 3Said Business School, Oxford, United Kingdom, 4Summa Health Orthopaedics and Sports Medicine, Akron, OH, 5The Cleveland Clinic Sports Health Center, Garfield Heights, OH, 6Cleveland Clinic Sports Health, Cleveland, OH Objectives: A recently introduced classification of medial ulnar collateral ligament (UCL) tears accounting for location and severity has demonstrated high interobserver and intraobserver reliability, but little is known about its clinical utility. The purpose of this study was to assess the relationship of the MRI-based classification system in predicting which athletes succeeded non-operative versus operative treatment after completing a standardized rehabilitative program. Secondary objectives included sub-analysis of baseball players, including return-to-play (RTP) and return-to-prior performance (RPP). Methods: After a priori power analysis, 58 consecutive patients with UCL tears and a minimum of two-year follow-up were retrospectively classified into those succeeding operative versus non-operative treatments. The MRI-based classification system accounting for UCL tear location and severity were correlated with non-operative and operative cohorts. Sub-analyses for baseball players, including RTP and RPP, were performed. Results: A total of 58 patients (40 baseball players, 34 pitchers) met inclusion criteria. A total of 35 patients (32 baseball players, 27 pitchers) underwent surgery, and 23 patients (8 baseball players, 7 pitchers) completed non-operative management. No patients in the non-operative arm crossed over to surgery after completing the rehabilitative program. Patients with distal (OR: 48.0, p=0.0004) and complete (OR: 5.4, p=0.004) tears were more likely to undergo surgery. Baseball players, regardless of position, were confounding determinants of operative management, although there was no difference in RTP and RPP between treatment arms. Conclusion: A six-stage MRI-based classification addressing UCL tear grade and location may confer early decision-making as patients likely to fail non-operative treatment have complete, distal tears whereas those with proximal, partial tears may be more amenable to non-operative modalities.

Summary of eligible baseball players with UCL tears stratified by MRI-based classification Non-operative Operative Total

1A (Partial Proximal) 6 0 6 1B (Complete Proximal) 0 4 4 2A (Partial Midsubstance) 0 1 1

2B (Complete Midsubstance) 2 5 7 3A (Partial Distal) 0 9 9 3B (Complete Distal) 0 13 13

Paper 69 Osseous Healing with Non-Rigid Suture Fixation Offers a Compelling Alternative to Conventional Latarjet Procedure Vivek Kalia, MD, MPH, MS1, Emily G. Pacheco, MS2, Michael T. Freehill, MD2. 1University of Michigan Orthopaedic Sports Medicine and Shoulder Surgery, Ann Arbor, MI, 2University of Michigan, Ann Arbor, MI Objectives: The Latarjet procedure, both open and arthroscopically, is a popular means to surgically address anterior glenohumeral (GH) joint instability. Though the arthroscopic approach to the Latarjet is becoming increasingly common, challenges persist: (1) technical difficulty positioning the bone block flush with the glenoid and the screws parallel to the glenoid surface (2) postoperative complications secondary to the two bicortical fixation screws, and (3) considerable risk of neurological injury. Recently, a novel surgical technique has been described which uses a guided surgical approach for graft positioning with non-rigid fixation via a suture suspensory system. The objective of our retrospective study was to evaluate healing rates and long-term stability of shoulders who underwent this new technique of anterior glenoid augmentation. The specific aims of our study were to assess (1) if this non-rigid suture fixation system is stable enough to allow the autograft bone to heal onto the native glenoid appropriately and (2) if the autograft bone could be reliably placed without migration of the graft. Methods: In this retrospective study, we gathered anonymized DICOM computed tomography (CT) datasets from a total of 107 patients who underwent non-rigid suture fixation with a cortical button fixation device in lieu of the traditional bicortical screws during arthroscopic Latarjet procedure. Of the 107 patients, only 75 patients had at least two CT scans performed at two different time periods which could be compared in terms of osseous healing and potential migration. The first CT scan for each patient was 2 weeks postoperative. Each patient’s CT scans were compared side-by-side by the same fellowship-trained musculoskeletal radiologist on a diagnostic workstation. Data recorded included the age, gender, date of each scan, initial graft position on the glenoid, presence and degree of graft migration on delayed follow-up scan (minimum 3 months), and the percentage of osseous healing (as assessed by osseous bridging) on the delayed follow-up scan. A minority of patients had several delayed timepoint scans (several years out), and those were evaluated as well. Descriptive statistics were calculated evaluating the average migration and average percent healing at both timepoints. Results: Our population (n=75) consisted of 61 men (81.3%) and 14 women (18.7%). The mean age of was 27.3 ± 1.1 years. The mean time period between initial CT scan (2 weeks postoperative) and follow-up CT scan to assess for healing and migration was 27 ± 2 weeks. At delayed follow-up scan, the average percent healing on follow-up scan was 78% ± 4%. A total of 61 out of 75 (81%) patients had greater than 75% healing on follow-up scan. The average migration of the coracoid graft in our study was 1.45 ± 0.23 mm, ranging from 0 mm to 8.75 mm. A total of 37/75 (49.3%) of the patients had no migration at all on follow-up scan, and 63/75 (84%) had migration of < 2 mm.

Conclusion: Based on these findings, non-rigid suture fixation with a cortical button device offers a safe alternative to traditional screw fixation for the Latarjet procedure. Though a non-rigid fixation system, osseous healing with minimal migration of the graft can be predicted.

Paper 70 Management of The Failed Latarjet Procedure: Outcomes of Revision Surgery With Fresh Distal Tibial Allograft Andrew S. Bernhardson, MD1, Liam A. Peebles, B.A.2, Colin P. Murphy, B.A.2, Anthony Sanchez, B.S,2, Robert F. LaPrade, MD, PhD1, Matthew T. Provencher, MD1 1The Steadman Clinic, Vail, CO, 2The Steadman Philippon Research Institute, Vail, CO Objectives: A patient with recurrent instability after a failed Latarjet procedure remains a challenge to address. The vast majority of these result in large amounts of bone loss, resorption, and issues with retained hardware, and there is minimal literature that assesses outcomes of revision surgery following a failed Latarjet. The objective of this study was to determine the outcomes of patients who underwent revision surgery for a recurrent shoulder instability after a failed Latarjet procedure. Methods: All consecutive patients who presented with recurrent anterior shoulder instability after a Latarjet procedure were prospectively enrolled. Patients were included if they had a prior Latarjet, and a history and physical examination findings consistent with recurrent anterior shoulder instability. Patients were excluded if they had prior neurologic injury, a seizure disorder, bone graft requirements to the humeral head, or findings of multidirectional or posterior instability. History of shoulder instability was documented, including initial dislocation history, time of instability, number of prior procedures, and examination findings, as well as plain radiographic data and computed tomography (CT) scan obtained on all patients, and arthritis graded with Samilson and Prieto (SP) grade. All patients were treated with hardware removal, capsulo-labral release with subsequent repair and bony reconstruction via fresh distal tibial allograft to the glenoid. Outcomes pre- and post-revision were assessed with ASES (American Shoulder and Elbow Score), Single Assessment Numerical Evaluation (SANE), and Western Ontario Shoulder Index (WOSI), and statistically compared. All patients underwent a CT scan of the distal tibial allograft at a minimum time point 4 months after surgery. Results: There were 31 patients enrolled (all males), with mean age 25.5 (range, 19 to 38), and with a mean follow-up of 47 months (range, 36 to 60) after the revision with distal tibial allograft. All patients after their Latarjet presented with recurrent shoulder dislocation (11/31) or recurrent subluxation (20/31) and all patients had recurrent shoulder instability on examination. Radiographs demonstrated two fixation screws in all cases, mean SP grade of 0.5 (range, I to III), and CT scan demonstrated that mean 78% of the Latarjet coracoid graft had resorbed (range, 50% to 100%). Preoperative outcomes improved for ASES (40 to 92, p=0.001), SANE (44 to 91, p=0.001), and WOSI (1300 to 310, p=0.001). There were no recurrences, and a final CT scan of the distal tibia revision demonstrated a mean 92% of DTA remained, but 98% union at the glenoid-DTA interface. Conclusion: Although the failed Latarjet with subsequent instability remains a challenge, treatment with fresh a distal tibial allograft provided substantial improvement in terms of stability and function. The vast majority of the failed Latarjet procedures had near complete resorption of the coracoid graft and

many had hardware complications. Additional long-term studies are necessary to determine the efficacy of this challenging revision population.

Paper 71 Bipolar Bone Loss And Glenoid Bone Loss Alone are Both Associated with Failure After Arthroscopic Anterior Shoulder Stabilization Ryan T. Li, MD1, Elan J. Golan, MD1, Kevin William Wilson, MD1, Bryson P. Lesniak, MD2, Albert Lin, MD3. 1University of Pittsburgh/UPMC Medical Education Program, Pittsburgh, PA, 2University of Pittsburgh Medical Center, Pittsburgh, PA, 3UPMC Center for Sports Medicine, Pittsburgh, PA Objectives: Glenoid and humeral bone loss are both known risk factors for failure after anterior shoulder stabilization. Several models have previously been proposed to characterize bone loss and its association with recurrent instability. The purpose of this study was to determine the association of failure after arthroscopic anterior stabilization with three different models of shoulder instability. Methods: 128 individuals who underwent primary anterior shoulder stabilization between 2007-2015 were included in this study. Subjects were excluded on the basis of prior shoulder surgery, multidirectional instability, presence of connective tissue disorder, and concomitant rotator cuff pathology. Glenoid bone loss and Hill-Sachs lesion size were measured using previously reported methods. Cases were defined as individuals who sustained either a subluxation or dislocation event after the index procedure, while controls were defined as individuals who did not. The association between failure and three different models of instability were investigated. In the first model, a receiver-operating curve was constructed to determine the amount of glenoid bone loss alone that would best predict failure. In the second model, lesions were classified as on-track or off-track based on the glenoid track concept. In the third model, a distance-to-dislocation was determined based on the glenoid track concept. Combinations of glenoid bone loss and distance-to-dislocation were varied to determine the combination that was most closely associated with failure. T-test, chi-square, and Fisher exact testing was conducted to determine associations between categorical and continuous variables with failure. Results: There were 44 cases and 80 controls. There was no difference in age (p =.72) and sex (p= .69) between the two cohorts. Receiver-operator analysis of glenoid bone loss alone demonstrated that a threshold value of approximately 12% could best predict failure (AOC = 0.72). 21/25 (84%) of individuals with at least 12% bone loss failed surgery compared to 23/103 (22.3%) who had less than 12% bone loss (p < .001). Using the glenoid track model, 4/4 (100%) of individuals with off-track lesions failed surgery compared to 40/124 (32%) with on-track lesions (p < .001). Using a bipolar bone loss model, the combination thresholds of 9% glenoid bone loss and 11 mm distance-to-dislocation was associated with failure in 18/20 (90%) of subjects while 26/108 (24.1%) of subjects who did not meet this threshold failed surgery (p < .001). Intra-rater reliability for glenoid bone loss (ICC = 0.79) and Hill-Sachs lesion size (ICC = 0.75) were excellent. Conclusion: In our study, a threshold value of 12% glenoid bone loss predicted failure following an arthroscopic Bankart repair and all off-track Hill-Sachs lesions failed as well. Further, when both glenoid

bone loss and glenoid track were subcritical, the combined use of a bipolar bone loss model accurately predicted failure. This model may be particularly useful for lesions felt to be on the cusp but not beyond threshold values for critical glenoid bone loss and off-track Hill-Sachs defects.

Paper 72 Risk Factors and Outcomes of Revision Arthroscopic Posterior Shoulder Capsulolabral Repair in Contact Athletes Justin W. Arner, MD1, Sachidhanand Jayakumar, BS2, Dharmesh Vyas, MD, PhD1, James P. Bradley, MD1. 1University of Pittsburgh Medical Center, Pittsburgh, PA, 2University of Pittsburgh School of Medicine, Pittsburgh, PA Objectives: Risk factors and outcomes of revision arthroscopic posterior capsulolabral repairare currently not well defined in contact athletes.Evaluation of risk factors for contact athletes who require revision arthroscopic posterior unidirectional capsulolabral repair is needed. Methods: A total of 186 contact athletes’ shoulders that underwent arthroscopic posterior capsulolabral repair at minimum 2 year follow-up were reviewed. Those who required revision surgery were compared with those who did not. Parameters assessed included age, gender, labral and/or capsular injury, level of sport, and return to sport. Glenoid bone width, bone version, labral width, and labral version were also compared. Results: Eleven shoulders required revision surgery (5.9%) at mean 12.0 year follow-up. The only significant risk factor was glenoid bone width (revision=26.4 mm vs. non-revision=29.1 mm, p=0.005). Cartilage version (p=0.676), labral version (p=0.539), and bone version (p=0.791) were not significantly different between groups, nor was labral width (p=0.751). Gender (p=0.326), labral injury (p=0.349), capsule injury (p=0.683), and level of sport (p=0.381) were not significant factors for requiring revision surgery. Both return to sport at the same level (revision=16.7% vs. non-revision=72.1%, p<0.001) and overall return to sport (revision=50% vs. non-revision=93.7%, p<0.001) was significantly worse in the revision group. Of those who had revision surgery, 33.3% stated their original surgery was not worthwhile, which was significantly higher than the 4.5% in the non-revision group (p=0.041). Conclusion: Contact athletes underwent revision arthroscopic posterior capsulolabral repair at an incidence of 5.9% at 12 year follow-up. The only significant risk factor for requiring revision surgery was smaller glenoid bone width. Return to play was significantly worse in those who required revision surgery. This data is essential for patient selection, optimal treatment techniques, and patient education as posterior shoulder capsulolabral repair in contact athletes that require revision has not previously been evaluated.

Paper 73 Best Practice Guidelines for Hip Arthroscopy in Femoroacetabular Impingement: Results of a Delphi Process Thomas Sean Lynch, MD1, Anas Minkara1, Stephen Kenji Aoki, MD2, Asheesh Bedi, MD3, Srino Bharam, MD4, John C. Clohisy, MD5, Joshua David Harris, MD6, Christopher M. Larson, MD7, Jeffrey J. Nepple, MD8, Shane Jay Nho, MD, MS9, Marc J. Philippon, MD10, James T. Rosneck, MD11, Marc R. Safran, MD12, Allston J. Stubbs, MD, MBA13, Robert W. Westermann, MD14, J. W. Thomas Byrd, MD15 1Columbia University, New York, NY, 2University of Utah, Salt Lake City, UT, 3University of Michigan, Ann Arbor, MI, 4Srino Bharam, MD, New York, NY, 5Washington University, St Louis, MO, 6Houston Methodist Hospital, Houston, TX, 7Minnesota Orthopaedic Sports Medicine Institute at Twin Cities Orthopedics, Edina, MN, 8Washington University, Saint Louis, MO, 9Midwest Orthopaedics at Rush, Chicago, IL, 10Steadman Clinic, Vail, CO, 11Cleveland Clinic, Garfield Heights, OH, 12Stanford Sports Medicine Center, Redwood City, CA, 13Wake Forest University, Winston Salem, NC, 14University of Iowa Healthcare, Iowa City, IA, 15Nashville Sports Medicine Foundation, Nashville, TN Objectives: Treatment algorithms for the arthroscopic management of femoroacetabular impingement syndrome (FAI) remain controversial due to a paucity of evidence-based guidance. Consequently, significant variability in clinical practice exists between different practitioners, necessitating expert consensus. The purpose of this study is to establish Best Practice Guidelines (BPG) using formal techniques of consensus building among a group of experienced hip arthroscopists driven by the results of a systematic review and meta-analysis. The scope of these guidelines includes preoperative recommendations, intraoperative practices, and postoperative protocols. Methods: The validated Delphi process and nominal group technique (NGT), utilized by the Centers for Disease Control and peer-reviewed orthopedic literature, were used to formally derive consensus among 15 surgeons in North America. Participants were surveyed for current practices, presented with the results of a meta-analysis and systematic literature review, and asked to vote for or against inclusion of non-leading, impartially-phrased items during three iterative rounds while preserving the anonymity of participants’ opinions. Agreement greater than 80% was considered consensus, and items near consensus (70%-80% agreement) were further queried using the NGT in a moderated group session at the American Orthopaedic Society for Sports Medicine (AOSSM) annual meeting. Results: Participants had a mean of 12.3 years of practice (range: 1-29 years) and performed an annual mean of 249 (range 100 to 500+) hip arthroscopies, with a combined total of approximately 52,580 procedures. Consensus was reached for the creation of BPG consisting of 27 preoperative recommendations, 15 intraoperative practices, and 10 postoperative protocols. The final checklist was supported by 100% of participants. Conclusion: We developed the first national consensus-based Best Practice Guidelines for the surgical and nonsurgical management of FAI. The resulting consensus items can serve as a tool to reduce the

variability in pre-, intra-, and postoperative practices and guide further research for arthroscopic management of FAI.

Paper 74 Hip Arthroscopy for Femoroacetabular Impingement Syndrome Performed with Modern Surgical Techniques Provides High Survivorship and Durable Outcome Shane Jay Nho, MD, MS1, Gregory Louis Cvetanovich, MD2, Edward C. Beck3, William H. Neal3, Joshua David Harris, MD4, Alexander E. Weber, MD5, Richard C. Mather, MD6. 1Midwest Orthopaedics at Rush, Chicago, IL, 2Ohio State University Hospital Program, Columbus, OH, 3Rush University Medical Center, Chicago, IL, 4Houston Methodist Hospital, Houston, TX, 5University of Southern California, Los Angeles, CA, 6Duke Health, Durham, NC Objectives: To analyze predictors of clinical failure as defined by revision hip arthroscopy or conversion to total hip arthroplasty (THA) as well as predictors of inferior outcomes defined as the not reaching Minimally Clinical Important Difference (MCID) or Patient Acceptable Symptomatic State (PASS) for Hip Outcome Score-Activities of Daily Living Subscale (HOS-ADL). Methods: Prospective data on all patients who underwent primary hip arthroscopy with routine capsular closure for the treatment of femoroacetabular impingement syndrome (FAIS) by a single, fellowship-trained surgeon between January 2012 and November 2015 were collected and analyzed. Inclusion criteria consisted of clinical and radiographic diagnosis of symptomatic FAIS, failed conservative management, and undergoing hip arthroscopy to correct FAIS with a minimum of two-year follow-up. Exclusion criteria consisted of prior ipsilateral hip surgery and hip arthroscopy for an indication other than FAIS. Baseline demographic data and radiographic parameters were collected and patient-reported outcomes (PROs) were obtained at baseline and at a minimum of two-years postoperatively. Rates of clinical failure and inferior clinical outcomes were recorded at a minimum of two-years postoperatively then stepwise linear regression was used to identify patient-related and imaging-related factors as predictors of each, respectively. Results: Out of 1,161 eligible patients, 949 (81.7%) completed PROs at a minimum of two-years postoperatively. The average age was 32.8 ± 12.4 years with a mean BMI of 25.4 ± 10.7 kg/m2. The overall clinical failure rate was 2.2% (n=21) including eleven cases of revision hip arthroscopy and eleven cases of conversion to THA (one patient underwent revision then subsequent THA). The inferior clinical outcome group consisting of patients who failed to reach MCID for HOS-ADL included164 patients while those who failed to reach PASS for HOS-ADL included 353 patients. In the regression model, poor articular cartilage, hypertension, lateral rim impingement on physical exam, history of back pain/spine pathology, limp on presentation, decreased daily physical activity, greater preoperative alpha angle, weakness in abduction with knees extended, and prolonged symptom duration were predictive of clinical failure (all p-values<0.05). Predictors of failing to reach MCID for HOS-ADL included: prolonged symptom duration , history of back pain/spine pathology, Tonnis grade >1 , being a current/former smoker , pain with ischial palpation , lateral rim impingement , snapping iliotibial band, and pain with resisted sit-up and over the greater trochanter. Predictors of failing to reach PASS for HOS-ADL included: prolonged symptom duration, decreased daily physical activity, workman’s compensation, history of

anxiety and/or depression, snapping iliotibial band, limp on examination, and pain with palpation of the spine/sacroiliac joint (all p-values<0.05). Conclusion: The clinical failure rate of hip arthroscopy may be lower than previously reported. Reoperation is predicted by medical comorbidity, lack of preoperative athletic activity, and multiple positive physical exams. Inferior clinical outcomes are predicted by prolonged symptom duration, back pain, being a current/former smoker, a history of a psychiatric comorbidity, as well as numerous signs on physical examination.

Paper 75 Pattern of Inflammatory Molecules in Cartilage of the Impingement Zone in FAI Hips Suggests Origin of Hip Degeneration Cecilia Pascual-Garrido, MD1, Masahiko Haneda2, Muhammad Farooq Rai, PhD2, Robert H. Brophy, MD2, John C. Clohisy, MD3 1Washington University School of Medicine, Saint Louis, MO, 2Washington University School of Medicine, St. Louis, MO, 3Washington University School of Medicine, St Louis, MO Objectives: Femoroacetabular impingement (FAI) is considered a common cause of articular cartilage damage and early hip osteoarthritis (OA) in the young-adult patients. Molecular inflammation is believed to be one of the main initiators of hip OA. Matrix metalloproteinase (MMP)-13 and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 are known to function as extracellular matrix degrading enzymes in OA joints and have been shown to increase during the process of OA onset. Interleukin (IL)-1β is considered one of the key cytokines involved in the pathogenesis of OA. The aim of this study is to characterize inflammation and early OA pathways in cartilage from the head-neck impingement area in patients with symptomatic FAI cam. Methods: Cartilage samples were obtained in the head neck-junction area from 37 patients undergoing hip surgery between May 2017 and July 2018. Nine patients had a clinical diagnosis of FAI cam (FAI cam) and 15 patients presented advanced OA secondary to FAI cam (OA FAI). These cartilage samples were compared to cartilage samples obtained from similar head neck-junction area from 13 patients with advanced OA secondary to developmental dysplasia of the hip with no impingement (OA DDH). Radiographically, the α-angle was utilized to confirm hip impingement. All histological sections were stained with Safranin-O to assess cartilage degeneration. OARSI grade and Mankin score were used to quantify degenerative OA changes. Immunohistochemistry was performed for IL-1β, MMP-13 and ADAMTS-4. Quantification of immunopositive cells was performed in a blinded fashion. One-way analysis of variance with Tukey's post hoc test was applied to analyze differences between three groups. Results: FAI cam patients were significantly younger than OA FAI patients (p<0.001) and OA DDH patients (p=0.0461) (Table 1). The average α-angle was significantly higher in the FAI cam and OA FAI groups than the OA DDH group (p<0.001). Cartilage samples from the FAI cam and the OA FAI groups showed degenerative changes. The average OARSI grade was significantly (p<0.01) higher in FAI cam (4.0±0.4) and OA FAI (3.6±0.9) compared to OA DDH (2.2±0.6). The average Mankin score was significantly (p<0.001) higher in FAI cam (7.6±1.2) and OA FAI (6.9±1.8) than OA DDH (4.1±0.7). IL-1β was expressed in cartilage samples from all groups, although the pattern varied.IL-1β was expressed mainly in the superficial layer in the OA DDH group but throughout all cartilage layers in the FAI cam and OA FAI groups. The % immunopositive cells were significantly (p<0.001) higher in FAI cam (58.1±8.9) and OA FAI (71.3±12.4) than OA DDH (28.9±6.3). Similar pattern of distribution was observed for MMP-13 (72.7±11.3, 70.2±18.2 vs 38.0±8.6; p<0.001, p<0.001) and ADAMTS-4 (73.1±7.3, 82.0±12.3 vs 45.3±12.7; p<0.001, p<0.001) (Figure 1).

Conclusion: Osteoarthritic changes are evident in the cartilage from the head-neck area of patients with FAI cam morphology. Inflammatory molecules were evident in both early and late stages of hip impingement, suggesting the head-neck impingement area is a potential mediator of inflammation and joint degeneration.

Paper 76 Early Surgical Intervention for Femoroacetabular Impingement Syndrome Provides Clinically Significant Outcome Improvement Kyle N. Kunze1, Edward C. Beck1, Benedict Uchenna Nwachukwu, MD, MBA1, Junyoung Ahn1, Shane Jay Nho, MD, MS2 1Rush University Medical Center, Chicago, IL, 2Midwest Orthopaedics at Rush, Chicago, IL Objectives: The purpose of the current study is to assess the outcomes of hip arthroscopy for FAIS according-timing of surgical intervention. Methods: Patients undergoing arthroscopic intervention for FAIS with minimum two year follow-up were included. All patients completed the hip outcome score (HOS)-activities of daily living (ADL), HOS-sports subscale (HOS-SS), modified Harris hip score (mHHS), international hip outcome tool-12 (IHOT-12), and visual analog scales (VAS) for pain and satisfaction. Patients were stratified by time with FAIS symptoms until surgical intervention. We compared 3-6 months of symptoms with other subsequent time frames (6-12 months, 12-24 months, and >24 months). Clinically significant outcome was determined using the minimal clinically important difference (MCID) and patient acceptable symptomatic state (PASS). Results: A total of 1,094 patients with mean (+ standard deviation) age 32.3+12.4 years and follow-up 30.8+6.7 (range:24-58) months were included. Patients undergoing surgery at 3-6 months of symptoms had no significant differences in outcome compared-those in the 6-12 month group except for the IHOT-12 (p:0.028). Patients with symptom duration of 12-24 months and greater than 24 months had worse outcome across all outcome measures (p<0.0001 for symptoms >24 months). Patients in the 3-6 month symptom group had increased likelihood for achieving MCID on HOS ADL (OR:1.81; 1.20-2.73), and HOS-SS (OR:1.90; 1.11-3.17), as well as PASS on the HOS-ADL (OR:1.85; 1.34-2.56) and HOS-SS (OR:1.58; 1.14-2.18). In multivariate regression analysis, symptom duration was the most predictive of VAS pain (Beta:3.10, 95% Confidence Interval [95%CI]:1.56-4.63; p<0.001) and satisfaction scores (Beta:-4.16, 95%CI:-6.14- -2.18; p<0.001). Conclusion: In patients with FAIS, surgical intervention early after the onset of symptoms (3-6 months) is associated with superior outcomes when compared to patients who underwent surgical intervention beyond this time frame. This information may help guide preoperative decision making on behalf of surgeons and patients who are considering delaying intervention.

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Paper 77 Predictors of Failure After Surgical Treatment of Femoroacetabular Impingement: Results of a Multicenter Prospective Cohort of 621 Hips Jeffrey J. Nepple, MD1, Asheesh Bedi, MD2, Ira Zaltz, MD3, Christopher M. Larson, MD4, Daniel J. Sucato, MD, MS5, Paul Beaule, MD6, Young-Jo Kim, MD7, ANCHOR Group8, John C. Clohisy, MD9. 1Washington University, Saint Louis, MO, 2University of Michigan, Ann Arbor, MI, 3Beaumont Hospital, Royal Oak, MI, 4Minnesota Orthopaedic Sports Medicine Institute at Twin Cities Orthopedics, Edina, MN, 5Texas Scottish Rite Hospital for Children, Dallas, TX, 6The Ottawa Hospital, Ottawa, ON, Canada, 7Children's Hospital, Boston, MA, 8Washington University School of Medicine, Saint Louis, MO, 9Washington University, St Louis, MO Objectives: Surgical treatment of femoroacetabular impingement attempts to improve patients’ symptoms through treatment of intra-articular labrochondral pathology and correction of underlying bony deformity. The purpose of the current study was to determine independent predictors of failure after surgical treatment of femoroacetabular impingement in a large prospective multicenter cohort study. Methods: A prospective cohort study of the surgical treatment of FAI was performed. A total of 760 hips undergoing primary surgical treatment of FAI were enrolled across seven surgeons. Patient characteristics, baseline patient reported outcomes (PROs), imaging findings, intraoperative pathology, and surgical treatments were prospectively recorded. A total of 621 hips (81.6%) with minimum one year follow-up were included in the current study (mean 4.3 years). The mHHS was assessed relative to the minimally clinically important difference (MCID, 8 points) and patient acceptable symptom state (PASS, 74 points). Univariate analyses were performed to identify factors significantly associated with failure. Multivariate logistic regression was performed to identify independent predictors of failure. Results: A total of 621 hips undergoing surgical treatment of FAI were assessed at a mean 4.2 years postoperatively. This cohort had a mean age of 29.8 and included 56.8% females. Multivariate logistic regression identified independent predictors of each failure definition. Failure A (THA) was independently associated with increasing age, acetabular microfracture (both p<0.001), and femoral head chondroplasty (p=0.02). Failure B (THA or revision surgery) was independently associated only with lower preoperative mHHS (p<0.001) (p=0.01). A lower failure C (clinical failure) was independently associated with participation in competitive athletics (p=0.01), BMI (p<0.001), and male gender (p<0.001). Conclusion: This large multicenter cohort demonstrates the outcomes of FAI treatment at a mean of 4.3 years postoperative. Rates of THA and revision surgery were 4.0% and 6.9%. An additional 14.8% of patients demonstrates clinical failure based on patient-reported outcomes.

Paper 78 Comparison of Tendon Lengthening with Traditional vs. Accelerated Rehab Following Achilles Tendon Repair: A Randomized Controlled Trial Kelechi Okoroha, MD1, Najib Ussef, MD2, Erik Eller, MD3, Ferras Zeni, MD4, Vasilios Moutzouros, MD5. 1Rush University Medical Center Program, Chicago, IL, 2Henry Ford Hospital, detroit, MI, 3Henry Ford Hospital, Detroit, MI, 4Henry Ford Hospital, Bloomfield Hills, MI, 5Henry Ford Medical Group, Novi, MI Objectives: Operative repair of Achilles tendon ruptures have shown successful outcomes. However, little is know about the amount of tendon or repair site lengthening after repair and if lengthening is affected by rehab protocols. The purpose of our study was to compare lengthening of the Achilles tendon after surgical repair, comparing traditional and accelerated rehab protocols. Methods: Twenty patients undergoing primary repair of Achilles tendon ruptures were assessed for participation. We performed a prospective randomized controlled trial in accordance with the CONSORT (Consolidated Standards of Reporting Trials) 2010 statement. The study arms included operative repair of Achilles tendon rupture with either accelerated (graduated weight bearing at 2 weeks) or traditional rehab (weight bearing at 6 weeks). During repair, two 2-mm tantalum beads with laser-etched holes were sutured to the Achilles tendon at the repair site. Beads were evaluated via CT scans immediately post-operatively and at 12 weeks. X-rays were obtained at time 0 and then at 2, 6, and 12 weeks. The primary outcome of the study was the difference in tendon or repair site lengthening between the study arms. Randomization was by a computerized algorithm. The observer was blinded and the patient was not blinded to the intervention. Results: Zero patients declined participation and all 20 patients were included for final analysis. All patients showed statistically significant lengthening at two weeks following surgery. There was a trend toward increased lengthening at 6 weeks in the accelerated rehab group (9.9mm, range 2.6 -13.9mm) compared to the traditional rehab group (4.1mm, range 1.5 -9.0mm), although this was not statistically significant; p = .07. However the final amount of tendon lengthening at 12 weeks after surgery was not different between the accelerated rehab group (14.4mm, range 11.7 -17.0mm) and the traditional rehab group (13.4mm, range 10.7 -17.0mm); p = .38. Conclusion: This study’s findings suggest that all patients undergoing operative repair of Achilles tendon ruptures have significant lengthening after surgery. Although there was a trend toward increased lengthening at 6 weeks in the accelerated rehab group, there was no difference in tendon lengthening at final follow up between the two groups.

Paper 79 Outcomes Following Treatment of Talar Osteochondral Lesions with a Mixture of Particulate Allogenic Cartilage Extracellular Matrix and Bone Marrow Aspirate Concentrate: A Case Control Series Mark C. Drakos, MD, Taylor Nicole Cabe, BA, Carolyn Sofka, MD, Peter D. Fabricant, MD, MPH, Jonathan T. Deland, MD. Hospital for Special Surgery, New York, NY Objectives: There continues to be a general lack of consensus regarding the optimal treatment for osteochondral lesions of the talus (OLTs). Microfracture, once considered the gold-standard, has been associated with poor long-term results due to the formation of biomechanically inferior reparative fibrocartilage as opposed to hyaline cartilage. Particulate allogenic cartilage extracellular matrix offers a promising solution as an adjuvant therapy; however, there is currently minimal objective evidence to indicate its effect on post-operative outcomes. This study compares post-operative radiographic and clinical outcomes following treatment of OLTs with an adjuvant mixture of particulate cartilage extracellular matrix and bone marrow aspirate concentrate (BMAC) against outcomes following microfracture with or without BMAC. Methods: Patients diagnosed with an OLT and treated by a fellowship-trained orthopedic surgeon were screened for inclusion. Those whose surgical intervention included microfracture, microfracture augmented with BMAC alone, or microfracture augmented with a mixture of BMAC and particulate allogenic cartilage extracellular matrix were eligible for this case-control study. Lesion size, location, and concurrent injuries were recorded following retrospective chart review. Foot and Ankle Outcome Scores (FAOS) were collected pre-operatively and at a minimum of 1 year post-operatively through the prospective Registry database at the authors’ institution. Modified magnetic resonance observation of cartilage repair tissue (MOCART) scoring evaluated the structural quality of repaired lesions on MRIs collected greater than six months post-operatively. Differences in post-operative MOCART and FAOS scores were evaluated using ANOVA tests. Results: Forty-seven patients treated with microfracture alone, forty-seven treated with microfracture augmented by BMAC, and fifty-two treated with an adjuvant mixture of particulate allogenic cartilage extracellular matrix and BMAC were identified at a minimum of 2 years post-operatively. Average MOCART scores were significantly different between treatment groups (p=0.03). At an average follow-up of 10.86 months, patients who received adjunctive therapy had an average MOCART score of 73.5 ± 11.13. At an average follow-up of 23.06 months and 43.6 months respectively, patients treated with microfracture and BMAC and microfracture alone scored 63.33 ± 22.23 and 55 ± 23.92. There was no detectable statistically significant difference in post-operative FAOS scores between treatment groups. With respect to revision surgery, two patients (3.84%) originally treated with adjuvant particulate cartilage extracellular matrix and BMAC have required a secondary surgery as opposed to nine patients (9.57%) treated with microfracture and BMAC or microfracture alone.

Conclusion: Increases in post-operative FAOS scores compared to pre-operative FAOS scores for all treatment groups indicate patients’ function and symptoms improved regardless of intervention received. However, significantly higher MOCART scores for the particulate cartilage extracellular matrix and BMAC treatment group suggest adjuvant treatment may help achieve better post-operative fill and structural integrity. Thus, long-term outcomes and the quality of reparative tissues may be improved through use of adjuvant treatments such as particulate allogenic cartilage extracellular matrix and BMAC.

Paper 80 Arthroscopy in Lateral Ankle Ligament Stabilization Surgery: Costs, Complications, Intra-Articular Defect Diagnosis, and Reoperations G. Matthew Heenan1, Kisan B. Parikh, MD2, Armin Tarakemeh2, Scott M. Mullen, MD2, John Paul Schroeppel, MD3, Bryan George Vopat, MD4 1University of Kansas Medical Center, Kansas Cit, KS, 2University of Kansas Medical Center, Kansas City, KS, 3Kansas University Orthopedics and Sports Medicine, Kansas City, KS, 4University of Kansas, Overland Park, KS Objectives: Lateral ankle ligament stabilization may be performed with concomitant arthroscopy. Arthroscopy has been shown to aid in the diagnosis of intra-articular defects that often accompany lateral ankle ligament injuries. This study compares the differences in cost, complications, newly diagnosed intra-articular defects, and reoperations among patients with ankle sprain/chronic instability who underwent lateral ankle ligament repair/reconstruction with or without concomitant arthroscopic procedures. Methods: Data was collected from the PearlDiver Technologies Humana dataset using CPT and ICD9/10 codes. Patients included in this study (n=2,188) had records of ankle sprain or ankle instability prior to or on the same day as one of two procedures: lateral ankle ligament repair (n=1,141) or lateral ankle ligament reconstruction (n=1,063). This population was subdivided by whether patients had records of arthroscopic procedure(s) on the same day as the ligament surgery. This yielded four groups: repair with arthroscopy (n=219), repair without arthroscopy (n=922), reconstruction with arthroscopy (n=325), reconstruction without arthroscopy (n=738). Cost, complications, newly diagnosed intra-articular defects, and reoperations were assessed. Results: Average cost per patient was higher for both arthroscopy groups: repair with arthroscopy ($6,207.78) versus repair without arthroscopy ($3,677.11; p < 0.0001); reconstruction with arthroscopy ($5,758.21) versus reconstruction without arthroscopy ($4,601.13; p = 0.0039). There was a significantly higher proportion of patients with complications in the reconstruction without arthroscopy group than in the reconstruction with arthroscopy group (7.59%, 4.31%; p = 0.0431), but the difference between repair groups was insignificant (p = 0.0626). The proportion of patients with newly diagnosed intra-articular defects was significantly higher in both arthroscopy groups: repair with arthroscopy (53.0%) versus repair without arthroscopy (35.6%; p < 0.0001); reconstruction with arthroscopy (56.0%) versus reconstruction without arthroscopy (39.8%; p < 0.0001). There was a significantly higher proportion of patients who underwent reoperation for intra-articular defects in the combined (repair plus reconstruction) arthroscopy group (7.18%) than in the combined non-arthroscopy groups (4.91%; p = 0.049). Most importantly, the average time until reoperation for intra-articular defects was significantly shorter in the combined arthroscopy group (271.923 days) than in the combined non-arthroscopy group (411.473 days; p = 0.024).

Conclusion: Concomitant arthroscopy with lateral ankle ligament surgery is more expensive but does not appear to increase the overall complication rate and may allow surgeons to diagnose and treat more intra-articular pathology. Among patients requiring reoperation for intra-articular defects, the average time to reoperation was nearly 5 months shorter for patients receiving arthroscopy than for patients who did not receive arthroscopy.

Paper 81 Comparison of the Rate of Nonunion or Delayed Union in Fifth Metatarsal Fractures Receiving Anti-Inflammatory Medications Brandon Barnds, MD1, G. Matthew Heenan, Mr.1, Armin Tarakemeh1, Scott M. Mullen, MD1, John Paul Schroeppel, MD2, Bryan George Vopat, MD3 1University of Kansas Medical Center, Kansas City, KS, 2Kansas University Orthopedics and Sports Medicine, Kansas City, KS, 3University of Kansas, Overland Park, KS Objectives: Controversy exists regarding the effect of non-steroidal anti-inflammatory drugs (NSAIDs) on fracture healing. Our retrospective study uses a private payer database to isolate patients diagnosed with 5th metatarsal (MT) fractures and compare the rate of delayed open reduction and internal fixation (ORIF) or non/malunion repair as a surrogate for nonunion or delayed union, in those prescribed anti-inflammatories and those not prescribed anti-inflammatories. Methods: Data was collected from the PearlDiver Technologies Humana dataset using CPT and ICD-10 codes. All patients included had a diagnosis of 5th MT fracture and did not receive ORIF or repair of non/malunion within 60 days of diagnosis. Two groups were then created based on the presence or absence of insurance claim records for anti-inflammatory medications within 60 days of diagnosis. The number of patients in each group who underwent ORIF or non/malunion repair after 60 days post-diagnosis was determined, and the rates were compared using a chi-square analysis. Results: 10,626 patients had a diagnosis of 5th MT fracture and did not undergo early repair/ORIF (within 60 days). 1,615 had records of insurance claims for anti-inflammatories within 60 days of diagnosis, leaving 9,011 who did not receive these medications. 18 (1.11%) patients who received an anti-inflammatory medication underwent ORIF or repair of non/malunion after 60 days post-diagnosis. 44 (0.49%; p=0.0055) subjects who did not receive an anti-inflammatory prescription underwent ORIF or repair of non/malunion at after 60 days post-diagnosis. Conclusion: The rate of delayed ORIF or non/malunion repair of 5th MT fractures, a surrogate for delayed union or nonunion in an insurance database study, was significantly higher in subjects receiving anti-inflammatories within 60 days of diagnosis. This study isolates a specific fracture and finds a negative correlation between NSAIDs and fracture healing. Further, this provides valuable information to help guide future higher level studies.

Paper 82 Electromyographic Evidence of Excessive Achilles Tendon Elongation During Isometric Contractions After Achilles Tendon Repair Malachy P. McHugh, PhD, Karl F. Orishimo, MS, Ian J. Kremenic, MEng, Julia Adelman, Stephen J. Nicholas, MD Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, NY Objectives: It has been proposed that increased tendon elongation after Achilles tendon repair contributes to selective weakness in end-range plantar flexion (Mullaney et al 2006). Excessive tendon elongation during maximum voluntary contraction (MVC) means greater muscle fiber shortening. Since mean frequency (MF) of the electromyogram (EMG) increases with muscle fiber shortening, it was hypothesized that during isometric plantar flexor MVCs MF would be higher on the involved versus non-involved side. Therefore, the purpose of this study was to examine MF during isometric MVCs in patients with Achilles tendon repairs. Methods: Maximum isometric plantar flexion torque was measured at 20° and 10° dorsiflexion, neutral, and 10° and 20° plantar flexion in 17 patients (mean±SD age, 39±9 years; 15 men, 2 women) 43±24 months after surgery (range, 9 months to 8 years). Surface EMG signals were recorded during strength tests. MF was calculated from Fast Fourier Transforms of medial gastroc (MG) lateral gastroc (LG) and soleus (S) EMG signals. Effect of weakness on MF was assessed using analysis of variance. Based on reported plantar flexor MF values it was estimated that with 17 subjects there would be 80% power to detect a 16% difference in MF between involved and noninvolved legs at P<0.05. Results: Patients had marked weakness in 20° plantar flexion (deficit 28±18%, P<0.01; 14 of 17 deficit >20%) but no significant weakness in 20° dorsiflexion (deficit 8±15%, P=0.20; 4 of 17 deficit >20%). MF increased moving from dorsiflexion to plantar flexion (P<0.001) but overall was not different between involved and noninvolved sides (P=0.22). However, differences in MF between the involved and noninvolved sides were apparent in the patients with marked weakness. At 10° plantar flexion 8 of 17 patients had marked weakness (>20% deficit). MF at 10° plantar flexion was significantly higher on involved versus noninvolved side in patients with weakness but this was not apparent in patients with no weakness (side by group P=0.014; Table 1). MF at 10° plantar flexion average across the 3 muscles was 13% higher on the involved versus noninvolved side in patients with weakness (P=0.012) versus 3% lower in patients with no weakness (P=0.47). Conclusion: Higher MF on the involved versus noninvolved side in patients with significant plantar flexion weakness is consistent with greater muscle fiber shortening. This indicates that weakness was primarily due to excessive lengthening of the repaired Achilles tendon. If weakness were simply due to atrophy, a lower MF would have been be expected and patients would have had weakness throughout the range of motion. Surgical and rehabilitative strategies are needed to prevent excessive tendon elongation and weakness in end-range plantar flexion after Achilles repair.

Table 1: EMG MF (Hz) on Involved (I) and Noninvolved (N) Legs at 10° Plantar Flexion

MG I MG N I v N S I S N I v N LG I LG N I v N WEAK 193±34 169±34 P=.02 181±21 168±23 P=.13 185±47 157±27 P=.04 NOT WEAK 165±31 170±23 P=.63 165±20 168±24 P=.70 154±26 162±38 P=.54

Paper 83 Comparison of Achilles Tendon Healing After Exposure to Combusted Tobacco, Vaping, and Control in a Rat Model Patrick Kennedy, MD, DPT1, Kaitlin Saloky, BS2, Aditya Yadavalli, BS3, Erin Barlow, BS3, Michael Aynardi, MD1, Matthew Garner, MD1, Jesse Bible, MD1, Greg Lewis, PhD1, Aman Dhawan, MD1. 1Penn State Milton S Hershey Medical Center Bone and Joint Institute, Hershey, PA, 2Geisinger Commonwealth School of Medicine, Scranton, PA, 3Penn State Milton S Hershey Medical Center School of Medicine, Hershey, PA Objectives: The negative effects of smoking have been well documented following orthopedic injury. Though nicotine has been shown to be detrimental to musculoskeletal tissue healing, nicotine in the form of “Vaping” is being increasingly used as a perceived healthier alternative to actual smoking. It may theoretically obviate many of the harmful volatiles and chemicals contained within combusted tobacco that are additionally harmful to musculoskeletal healing, beyond just nicotine. The literature has yet to establish the benefits, or lack thereof, to exposure of e-cigarettes and their effect on tendon healing when compared to traditional combusted tobacco. Our objective was to evaluate the biomechanical and histological effects on Achilles tendon repair between inhaled combusted tobacco versus isolated nicotine exposure via vaping versus a control group in a small animal (Sprague Dawley Rat) model. Methods: 54 Sprague Dawley rats were randomly placed in a control, vaping, or cigarette cohort. Each group contained 17 rats for exposure and they were exposed six days per week. The smoking cohort was exposed to 2 unfiltered University of Kentucky research cigarettes in a smoking chamber (Image 1). The vaping group was exposed to e-cigarette vapor with equivalent nicotine exposure as compared to the cigarette group, over ten minutes at a flow rate of 2.4 L/min. The control group was placed in the smoking chamber with room air flowing through the chamber. All rats received their respective daily exposures for 4 weeks prior to surgery where transection and repair of the Achilles tendon was performed. Following surgery, the rats received 2 additional weeks of smoking vs vaping vs control exposure. After sacrifice, Achilles tendons were harvested and tested with tensile and a load to failure model (Image 2). Histological samples were sent for analysis. Results: Tensile load testing evaluated maximum force to rupture and tissue stiffness amongst the three cohorts. The control group demonstrated highest mean tensile strength of 41.0 N (18.3-55.1 N), with the cigarette cohort having the second highest mean tensile strength at 37.3 N (14.0-54.7 N), and finally the vaping group had the lowest at 32.28 N (17.8-45.1 N). One-way ANOVA with heterogeneous of variance was used for evaluation. There was a significant difference noted in load to failure when comparing controls to e-cigarettes (p=0.026). No statistical difference was seen between controls vs cigarettes (p=0.35). Histological analysis is in progress.

Conclusion: Our investigation demonstrates that in a rat model, isolated nicotine exposure via “vaping” significantly impedes biomechanical healing properties of Achilles tendon surgical repair. Though smoking resulted in a lower maximum force to failure as compared to control, this difference was not significant. While E-cigarettes are often utilized as a perceived “safer” alternative to smoking combusted tobacco, this study suggests that use of e-cigarettes may be more detrimental to tendon healing than combusted tobacco in a rat Achilles model.

Paper 84 Quadricep Femoris Strength at Return to Sport Identifies Limb at Increased Risk of Future ACL Injury after ACL Reconstruction in Young Athletes Mark V. Paterno, PhD, PT, ATC1, Mitchell J. Rauh, PhD, PT, MPH, FACSM2, Staci Thomas, MS3, Timothy E. Hewett, PhD, FACSM4, Laura C. Schmitt, PhD, PT5 1Division of Sports Medicine, Cincinnati Children's Hospital, Cincinnati, OH, 2San Diego State University, San Diego, CA, 3Cincinnati Children's Hospital, Milford, OH, 4Mayo Clinic, Rochester, MN, 5The Ohio State University, Columbus, OH Objectives: The ability of current return to sport (RTS) criteria to identify young, active patients after ACL reconstruction (ACLR) independently, at high risk for future ipsilateral or contralateral ACL injury is limited. The purpose of this study was to determine if meeting current, standard RTS criteria collectively, or in part, would identify young athletes at risk for an ipsilateral or contralateral ACL injury after primary ACLR and RTS. The tested hypothesis was the likelihood of an ipsilateral or contralateral 2nd ACL injury in the first 2 years after RTS would be the same in groups that successfully met or failed to meet all RTS criteria prior to RTS. The second hypothesis was that quadriceps femoris strength at the time of RTS would identify which limb was at greatest risk for future ACL injury. Methods: One hundred eighty-one patients (116 female) with a mean age of 16.7±2.9 years old underwent ACLR and were released to return to pivoting/cutting sports. These patients were enrolled in a prospective, observational cohort study, completed a RTS assessment and were tracked for occurrence of an ipsilateral graft tear or contralateral ACL injury after ACLR for 24 months. The RTS assessment included 6 tests: isometric quadriceps strength, 4 functional hop tests and the International Knee Documentation Committee (IKDC) patient reported outcome survey. Limb symmetry index (LSI) was calculated for strength and hop test assessments [(inv/uninv)*100]. Subjects were classified into groups that successfully passed all 6 RTS tests at a level of 90 compared to those that failed to meet all 6 criteria. Chi Square tests and Fisher Exact Tests were used to determine if successfully passing all 6 RTS measures resulted in a reduced risk of 2nd ACL injury in the first 24 months after RTS as well as to assess if ability to successfully pass individual RTS criteria resulted in reduced risk of 2nd ACL injury. Results: Thirty-nine (21.5%) patients suffered a 2nd ACL injury with 18 ipsilateral graft failures and 21 contralateral ACL tears in the first 24 months after RTS following ACLR. At the time of RTS, 57 patients (31.5%) achieved LSI values of 90% or greater on all testing as well as an IDKC value of 90 or greater. At this level, there was no difference in ipsilateral graft failures between patients who passed all RTS criteria (15.8%) and those who failed at least 1 criterion (7.3%; p=0.08). There was also no difference in contralateral ACL injuries between patients who passed all RTS criteria (7.0%) and those who failed at least 1 criterion (13.7%; p=0.22). When individual RTS criterion were evaluated, patients who failed to achieve 90% quadriceps strength LSI were 84% less likely to suffer an ipsilateral graft failure (OR=0.16; 95%CI: 0.04, 0.74;p=0.009), but 3 times more likely to suffer a contralateral ACL injury (OR=2.5; 95%CI:1.0, 6.5;p=0.05).

Conclusion: Current criteria to evaluate readiness to return young athletes to pivoting and cutting sports, may not identify young, active patients independently at high risk for a future ipsilateral graft tear or contralateral ACL injury. Inability to achieve 90% LSI on an isometric quadriceps strength assessment resulted in a reduced risk of ipsilateral graft failure, but an increased risk in contralateral ACL injury after ACLR and RTS. Further investigation is needed on the relationship between quad strength and side of future ACL injury and whether other factors may help contribute to a predictive model of future ACL injury specific to limb.

Paper 85 Mid-Term Patient Reported Outcomes and Return to Sport for Physeal Sparing ACL Reconstruction in Skeletally Immature Patients Lauren K. Szolomayer, MD1, Carl W. Nissen, MD2, Christine Mary Kelly, MS, ATC3, Regina Kostyun, MSEd ATC4 1UCONN Orthopaedic Surgery, Farmington, CT, 2Connecticut Children's Medical Center, Farmington, CT, 3Connecticut Children's Medical Center/Elite Sports Medicine, Farmington, CT, 4Elite Sports Medicine, a Division of Connecticut Children's Medical Center, Farmington, CT Objectives: Physeal-sparing techniques for anterior cruciate ligament (ACL) reconstruction have previously been described as safe treatment for adolescent ACL tears in patients with open physes, however few studies to date have reported on return-to-sport or patient reported outcome scores for this specific patient population. This study examined patient reported outcomes in children who underwent a physeal-sparing ACL reconstruction with a minimum of two-year follow-up. Methods: Surgical logs of ACLR performed at a single pediatric/adolescent sports medicine center from 2011 to 2016 were reviewed. Patients with open physes who had ACLR with a hybrid physeal sparing or all-epiphyseal technique were identified. Patients were treated by one of two pediatric sports trained orthopedic surgeons. Their demographics, operative reports, rehabilitative course, time to return-to-play, and post-operative course were retrospectively reviewed. Prospective patient reported outcomes scores, ACL-Return to Sport after Injury (ACL-RSI) and International Knee Documentation Committee (IKDC) or Pediatric IKDC (Pedi-IKDC), and return to sport questionnaire including pre-injury primary sport and competition level, ability to return to pre-injury level of competition following ACLR and subsequent ACL injury were collected. Results: There were 49 patients who met inclusion criteria. Prospectively collected data was obtained for 25 patients at an average of 4.6 (range 2.1-8.0) years following surgery. The average chronological age of patients at time of surgery was 12.8 ± 1.4 years with an average bone age of 13.5 ± 1.3 years. At mid-term follow-up, the average chronological age was 17.2 ± 2.0 years. Average Pedi-IKDC or IKDC score was 94.2 ± 9.2 and ACL-RSI Score was 89.2 ± 18.3. There were 23 patients who considered themselves athletes prior to surgery, 8 patients identifying as recreational athletes competing in town or school leagues and 15 patients identifying as competitive athletes participating on youth travel or club leagues. All patients reported the ability to return to their primary sport following ACLR, with 74% returning to the same or higher level of competition, of which 6 were recreational athletes and 11 were competitive athletes. In addition, 6 patients did not complete outcomes data, but had suffered tear of their ipsilateral (3) or contralateral (3) side and were treated at the same facility. These patients were included in calculation of overall re-tear rate of 12.5% (5 patients) and contralateral tear of 25% (8 patients).

Conclusion: Mid-term results of patients treated with a hybrid physeal-sparing or all-epiphyseal ACLR were favorable, with adolescents reporting a high level of functional ability and strong psychological readiness to engage in athletic activities. Re-tear and contralateral tear rates were equivalent to other reported studies. These physeal-sparing techniques demonstrate the ability for young athletes to successfully remain physically active and involved in their sports several years following surgery.

Paper 86 Outcomes Following Acl Reconstruction Using Patellar Tendon Versus Hamstring Tendon Autograft In Adolescent Athletes: An Age, Sex, And Bmi-matched Comparative Cohort Study Benton E. Heyworth, MD1, Elizabeth S. Liotta1, Peter D. Fabricant, MD, MPH2, Ashley J. Bassett, MD3, Cameron Waites4, Patricia Miller1, Dennis E. Kramer, MD1, Mininder S. Kocher, MD, MPH1, Lyle J. Micheli, MD1. 1Boston Children's Hospital, Boston, MA, 2Hospital for Special Surgery, New York, NY, 3Rothman Institute / Thomas Jefferson University Hospital, Philadelphia, PA, 4Harvard Medical School, Boston, MA Objectives: The purpose of this study is to compare the re-tear rates and medium-term functional outcomes in matched cohorts of adolescent athletes who underwent primary anterior cruciate ligament reconstruction (ACLR) with patellar tendon/bone-tendon-bone autograft (BTB) versus hamstring tendon autograft (HS). Methods: An initial cohort of 731 patients, aged 13-19 years, who underwent ACLR-BTB or ACLR-HS between 2003-2015 at a pediatric tertiary care hospital by one of 5 surgeons, was identified through a comprehensive electronic medical record database query. Propensity score matching was performed through a logistic regression model, based on characteristics frequently used by some surgeons to guide graft selection: age, sex, and body mass index (BMI). The resultant cohort of 269 patients allowed for a 1:2 (BTB:HS, 83:186) match. A chart review was performed to identify patient demographics, surgical data, and post-operative outcomes, including ACL re-tear and length of clinical follow-up. Patients were additionally contacted to obtain longer term sport participation and re-injury data that may have been investigated or addressed at outside institutions, as well as to obtain patient reported outcomes (PRO) using validated knee function and activity questionnaires (Pedi-IKDC and HSS-Pedi FABS). Individual questions from the Pedi-IKDC that related to anterior knee pain or kneeling pain were specifically investigated to assess the potential effect of these factors, commonly cited aspects of donor site morbidity associated with BTB grafts, on overall scores within this adolescent population. Results: No significant differences were seen in demographic and clinical characteristics of the two matched graft-based cohorts (overall mean clinical follow-up: 54 months), as listed in Table 1. In the sub-population providing PROs (52% response rate, mean PRO follow up: 81 months), no significant differences were seen in activity level, median Pedi-IKDC scores, or knee pain. BTB patients demonstrated superior scores regarding ability to kneel than HS patients. Rates of ACL graft re-tear were not significantly different between groups, both when calculated based on all possible follow-up methods (ACLR-BTB: 11%; ACLR-HS: 12%; p: 0.72), or amongst patients responding to long-term follow up.

Conclusion: Despite previous studies, including large, multi-country registry-based analyses, demonstrating lower re-tear rates following ACLR-BTB than ACLR-HS, the current study, focused exclusively on adolescent cohorts matched for age, sex, and BMI, showed no difference in graft re-tear rates between the two cohorts at medium-term follow-up. Moreover, activity scores and overall functional knee outcome scores appear to be equivalent between these younger graft-based populations, with no suggestion of increased donor site morbidity with BTB autograft, as it relates to knee pain or kneeling ability. For skeletally mature adolescents, graft choice may not influence outcome following ACL reconstruction. Consistent with previous studies, the current study reveals relatively high ACL re-tear rates in adolescents, the sub-population most affected by this common injury.

Paper 87 Can Combined Trans-physeal and Lateral Extra-Articular Pediatric ACL Reconstruction Techniques Be Employed to Reduce ACL Re-Injury While Allowing for Growth? Henry B. Ellis, MD1, Nathan Boes2, Parker Mitchell3, Charles Wyatt, PNP3, Philip L. Wilson, MD4. 1Texas Scottish Rite Children's Hospital, Dallas, TX, 2Texas Scottish Rite Hospital for Children, Dallas, TX, 3Texas Scottish Rite Hospital for Children, Plano, TX, 4Texas Scottish Rite Hospital for Children, Frisco, TX Objectives: To describe outcomes, including failure rates, following a pediatric ACL reconstruction (ACLR) employing combined trans-physeal technique with hamstring autograft (TPH) and a hybrid extra-articular technique using iliotibial band autograft (ITB). Methods: Consecutive skeletally immature patients undergoing combined TPH/ITB ACLR from 1/2012 to 4/2017 were reviewed. With the goal of decreasing ACL graft re-injury in this high-risk group; this technique employed anterior-medial portal drilling for TPH, with an extra-osseous femoral ITB technique and intra-articular combined TPH/ITB grafts fixed within the tibial bone tunnel (Figure 1). Inclusion required a minimum 12 months follow up; exclusions were prior knee surgery and multi-ligamentous injury. Demographics, bone-age (hand), standing alignment XR for growth and mechanical axis grade, and PROs were documented. T-tests, Mann-Whitney tests, and Spearman’s correlation coefficients were employed. Results: 60 knees in 59 adolescents underwent the combined TPH/ITB ACLR, with 49 knees meeting inclusion criteria with a mean follow up = 23 months (r = 12-48m). Only 1/49 knees (2%) sustained ACL re-injury. Mean age was 12.9y (11-16y) with 29 males (mean bone-age = 14.1) and 19 females (mean bone-age =13.3). There was a high level return to pre-operative sport. No families reported cosmetic, functional alignment or length concerns, and no clinical deformity was diagnosed. Outcome measures at final follow up indicated a high functional level with a mean Pedi-IKDC = 90.39 and mean Pedi-Fabs = 22.66. To critically assess growth, a cohort of 22 knees (mean age = 12.8y) with > 18 months of growth remaining at surgery were evaluated at maturity. No difference was seen in mean operative and non-operative leg growth (54.1mm and 53.0mm). One patient, 1/22 (4.5%), had a final LLD > 10 mm (12mm), and peri-operative alignment difference [0-GII (central compartment) valgus]. Growth and alignment were not significantly associated with age, bone age, height, weight, demonstrated growth, or pre-operative alignment. Conclusion: Combined TPH/ITB ACLR in adolescent patients resulted in return to high activity levels (Pedi-Fabs = 22.66), and a low (2%) re-injury rate at an average of 23 months. A novel pediatric ACLR employing combined trans-physeal hamstring and extra-osseous iliotibial band grafts merits further study as a technique for reducing re-injury in high-risk, growing adolescents by maximizing articular graft size while adding anterior-lateral rotational knee control.

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Paper 88 Long-term Results after Repair of Isolated Meniscus Tears in Patients 18 Years and Younger: An 18-Year Follow-up Study Michella Hagmeijer, Nicholas I. Kennedy, Adam J. Tagliero, Bruce A. Levy, MD, Michael J. Stuart, MD, Daniël B. Saris, MD, PhD, Diane L. Dahm, MD, Aaron John Krych, MD. Mayo Clinic, Rochester, MN Objectives: Meniscus repair is desirable over resection to prevent post-meniscectomy arthritis, especially in young and active patients. However, long-term data is currently lacking following isolated meniscus repair, particularly in the pediatric population. The purpose of this study was to report long-term follow-up of isolated meniscus tears treated by meniscus repair in a pediatric population, and to compare those results to previous mid-term follow-up data reported. We hypothesized that these patients would have satisfactory function and reoperation rates at long-term follow-up. Methods: Patients less than 18 undergoing repair of an isolated (without concomitant ACL injury) meniscus tear performed between 1990 and 2005 were included. At the time of final followup, recurrent tear, reoperations, and IKDC and Tegner scores were determined. With logistic regression, the overall failure between different tear types was calculated. Wilcoxon signed ranks tests were performed to calculate the differences in clinical outcome for different time-points, and Spearman coefficients were calculated for Tegner and IKDC with different variables. Results: At an average followup of 17.6 years (13.1 - 26.0 years), 32 patients with 33 isolated meniscus repairs (29M : 3F) with an average age of 16.1 (9.9 - 18.7) were included in this study. At early follow-up, complex tears (80%) had a higher overall failure rate compared to simple tears (18.2%). However, no further failures occurred since mid-term follow-up with any tear type. At final follow-up, the average IKDC score was 92.3, which was significantly increased when compared to both preoperative 65.3 (p< 0.0001) and mid-term scores, 90.2 (p= 0.01). However, the average Tegner score (6.5) was significantly lower than both pre-operative 8.3 (p< 0.0001) and mid-term 8.4 (p< 0.0001) scores. There was no correlation for Tegner or IKDC values with any risk factors. Conclusion: In conclusion, this study demonstrates overall good to excellent long-term clinical outcomes following isolated meniscus repair in a pediatric population. Early failure and reoperation rates were variable depending on tear type, with complex multiplanar tears having more failures at short-term follow-up. However, at long-term follow-up, IKDC and Tegner scores were not significantly different for those with complex tears compared to other tear types.

Paper 89 High Rate of Recurrent Meniscus Tear and Lateral Compartment Osteoarthritis in Patients Treated for Symptomatic Lateral Discoid Meniscus: A Long-Term Population-Based Study Orlando Sabbag, MD, Mario Hevesi, MD, Thomas L. Sanders, MD, Christopher L. Camp, MD, Diane L. Dahm, MD, Bruce A. Levy, MD, Michael J. Stuart, MD, Aaron John Krych, MD. Mayo Clinic, Rochester, MN Objectives: Little is known about the natural history and long-term outcome of a surgically treated symptomatic lateral discoid meniscus. The goals of this study were to describe the rate and factors associated with recurrent lateral meniscus tears and progression to symptomatic lateral compartment osteoarthritis (OA) in patients surgically treated for a symptomatic lateral discoid meniscus. Patients with surgically treated lateral discoid meniscus have a high incidence of meniscus re-tear and progression to lateral compartment OA. Methods: A large, geographic database was reviewed to identify and confirm patients presenting with symptomatic lateral discoid meniscus between 1998 and 2015. Charts were reviewed to document treatment and outcomes at a minimum clinical follow-up of two years. Results: 70 discoid meniscus patients (30 F, 40 M) with a mean age of 27 years (Range: 2.0-66.0) were followed for an average of 5.8 years (Range 2.0-23.7). Sixty patients underwent surgical management: 49 (82%) patients underwent partial lateral meniscectomy and 11 (18%) underwent meniscus repair (including saucerization). Tear-free survival following surgery was 93% at 2 years, 69% at 5 years, and 40% at 8 years. Overall progression to symptomatic lateral compartment OA in the surgical group was 10% at 2 years, 23% at 5 years, and 48% at 8 years. Of those patients who developed lateral compartment OA, 55% (11/20) had a Kellgren-Lawrence score 2 or greater at last radiographic follow-up. Young age and open growth plates were associated with increased incidence of postoperative re-tear (HR: 0.96, CI: 0.93-0.99, p = 0.01). Increased age at diagnosis and BMI ≥ 30 were associated with increased risk of progression to lateral compartment OA on final radiographs. Conclusion: Patients with a surgically treated lateral discoid meniscus tear had a high rate of recurrent meniscus tear at long-term follow-up (60% at 8 years) that was associated with young age. Approximately 48% of surgically treated patients developed symptomatic lateral compartment OA at eight years from initial presentation. The risk of progression to OA increased with older age at diagnosis and BMI ≥ 30.

Paper 90 Outcomes of Discoid Meniscus Repairs in Children and Adolescents Crystal A. Perkins, MD, Michael T. Busch, MD, Melissa A. Christino, MD, S. Clifton Willimon, MD. Children's Healthcare of Atlanta, Atlanta, GA Objectives: Discoid meniscus tear patterns vary, but typically involve horizontal cleavage tears of the central discoid component with or without anterior or posterior meniscocapsular tears. Classically, the central discoid component is saucerized and meniscocapsular tears are repaired. Recent data suggests that meniscal preservation provides long-term benefits over resection1-2. However, many meniscal transplants are performed secondary to unsalvaged or unsalvageable discoid meniscus tears3. Reoperation rates after meniscus repairs vary greatly4-6, with some series reporting high rates of reinjury and reoperation, but there are no large series of pediatric discoid meniscus repairs in the literature. The purpose of this study is to describe the outcomes of meniscus repair and saucerization in pediatric patients with symptomatic discoid menisci. Methods: A single-institution retrospective review was performed of consecutive pediatric patients with surgical treatment of a discoid meniscus tear over a five-year period. Inclusion criteria were age less than 18 years, a symptomatic torn discoid meniscus treated with knee arthroscopy with meniscus repair, and minimum 4-month follow-up. A chart review was performed to describe tear location, tear pattern, and repair type (inside-out, outside-in, all-inside, and hybrid). Hybrid repair constructs were defined as those that used 2 or more repair types. The primary outcome was revision meniscus surgery. Results: Forty-four patients were identified to meet inclusion criteria. There were 23 males and 21 females with a mean age of 12.4 years (range 5 - 17 years). The right knee was affected in 61% of patients. The lateral meniscus was involved in all patients. Tear patterns included anterior meniscocapsular (19 patients, 43%), posterior meniscocapsular (14 patients, 30%), radial (7 patients, 16%), and bucket-handle (5 patients, 11%). Tears most commonly involved the posterior horn and body (21 patients, 48%) or posterior horn (16 patients, 36%) Arthroscopic meniscus repair was performed in all patients. Forty-three patients (98%) also underwent saucerization. Marrow stimulation, as a biological approach to improve repair healing, was performed in 14 patients (32%). The distribution of repair types and number of sutures for each type is listed in the table below. Mean follow-up was 19 months (range 4 - 70 months). Four patients (9%) underwent revision meniscus surgery following the primary repair, including 2 all-inside repairs and 2 partial meniscectomies. There were no statistically significant differences between patients who did or did not require a secondary surgery with respect to sex, age, tear location, tear pattern, repair type, or number of sutures. During follow-up, 9 patients (20%) had surgery for a symptomatic discoid meniscus in the contralateral knee.

Conclusion: Saucerization and repair of discoid lateral meniscus tears in the pediatric population have good outcomes with low rates of reoperation. Appropriate saucerization, followed by an arthroscopic assessment of stability and tear patterns is critical to successful treatment of symptomatic discoid menisci. If tissue quality permits, meniscal preservation should be considered in all patients to avoid the consequences of subtotal meniscectomy.

Paper 91 The Effect of a Single Freeze-Thaw Cycle on Matrix Metalloproteases in Different Human Platelet-Rich Plasma Formulations: A Prospective Cohort Study Kaitlyn E. Whitney1, Mitchell Kennedy2, Grant Dornan1, Jorge Chahla, MD, PhD3, Thos A. Evans, MD4, Marc J. Philippon, MD5, Robert F. LaPrade, MD, PhD4, Johnny Huard, PhD1 1Steadman Philippon Research Institute, Vail, CO, 2Steadman Philippon Research Institute, Yakima, WA, 3Steadman Philippon Research Institute, Chicago, IL, 4The Steadman Clinic, Vail, CO, 5Steadman Clinic, Vail, CO Objectives: The possibility of preserving platelet-rich plasma (PRP) from young, healthy individuals for future use is a compelling approach to reduce or delay degenerative processes, presuming that the retention of the biological properties are maintained. The purpose of this study was to measure and compare matrix metalloproteinases (MMP) isoform concentrations between whole blood (WB), leukocyte-rich PRP (LR-PRP) inactivated (LR-I) and activated (LR-A), leukocyte-poor PRP (LP-PRP) inactivated (LP-I) and activated (LP-A). Methods: Following institutional review board approval (2017-36), 24 donors that were physically and mentally healthy were prospectively enrolled in the study. Approximately 60 mL of WB was drawn from each donor to produce inactivated and activated LP-PRP and LR-PRP using manual processing methodology, as previously described. A complete blood count for WB and inactivated PRP products was obtained to verify that concentration of platelets was achieved. WB, LP-I, and LR-I samples were set aside for immunoassay and analysis. The LP-I and LR-I products were activated with 10% calcium chloride and recombinant thrombin in a red-top 10 mL vacutainer tube. Blood fractions were either immediately assayed and analyzed (fresh) or stored at -80℃ for 24 hours, 72 hours, and 160 hours. Commercial kits (EMD Millipore) were used according to manufacturer’s instructions for protein content: MMP-1, MMP-3, MMP-9, MMP-10, and MMP-12. A standard methodology for the Luminex 200® system was used as previously published. A pairwise Wilcoxin rank test was performed for statistical calculation. Results: Twenty-two healthy donors (n = 12 females, n = 10 males) with a mean age of 37.7 (range: 21 to 60), and average BMI of 23.7 kg/m2, were used in the final analysis. MMP-1 significantly increased between fresh and 160 hours in WB (p<0.05) (Figure 1), and significantly increased between fresh and 24 hours and 160 hours in LR-A (p<0.05) (Figure 4). MMP-3 significantly decreased between fresh and 24 hours, 72 hours, and 160 hours in LR-A (p<0.05) (Figure 4). MMP-9 significantly increased between fresh and 160 hours in WB, LR-A, and LR-I (p<0.05) (Figures 1, 2 & 4). MMP-12 significantly decreased between fresh and 24 hours in LR-A (Figure 4), while MMP-12 significantly decreased between fresh and 24 hours, 72 hours, and 160 hours in WB, LR-I, and LP-I (p<0.05) (Figures 1, 2 & 3). MMP-10 was not statistically different amongst fresh and freezing time points in all WB and PRP preparations. Interestingly, there was no statistical difference between MMP concentrations and freezing timepoints in LP-A. There were no significant correlations between MMPS and age, BMI or sex.

Conclusion: In this study, we evaluated the influence of short-term freezing (-80℃) on MMP concentrations in WB, inactivated PRP, and activated PRP formulations. Our results suggest that certain MMP isoforms, can either increase or decrease in response to freezing in WB, inactivated PRP, and activated PRP formulations. The development of PRP preservation approaches through minimal manipulation, without attenuating its biological properties, represents an important step in PRP mediated tissue regeneration and repair.

Paper 92 The Proximal and Distal Effects of Blood Flow Restriction Therapy on Upper and Lower Extremity Strengthening: A Randomized Controlled Trial Eric N. Bowman, MD1, Rami El-shaar, MD2, Heather Milligan, PT3, Greg Jue, PT4, Karen Mohr, PT5, Patty Brown, PT6, Drew M. Watanabe, BS7, Orr Limpisvasti, MD5 1Vanderbilt University Medical Center, Nashville, TN, 2Kerlan-Jobe Orthopaedic Clinic Program, Los Angeles, CA, 3Elite OrthoSport PT, Los Angeles, CA, 4Select Physical Therapy, Los Angeles, CA, 5Kerlan-Jobe Orthopaedic Clinic, Los Angeles, CA, 6Patty Brown Physical Therapy, Los Angeles, CA, 7Kerlan-Jobe Institute, Los Angeles, CA Objectives: Blood flow restriction (BFR) therapy consists of low-intensity exercise performed under reduced venous return due to an inflatable tourniquet. This produces similar physiologic and clinical effects to high-intensity routines with less joint and tissue stress. Postoperative patients may benefit from more efficient rehabilitation. Proximal and distal effects of BFR have been evaluated, however, minimal literature exists on its use in orthopaedic conditions. The purpose of this study was to determine the effects of low-intensity BFR therapy both proximal and distal, in the upper and lower extremities. Methods: This was a prospective, randomized controlled trial of healthy subjects completing a standardized 6-week course of BFR therapy. Subjects were randomized to BFR therapy on one extremity or to a control group. Subjects were excluded for cardiac, pulmonary, or hematologic disease, pregnancy, or previous surgery in the extremity. Data collected at baseline and completion included: limb circumferences, isokinetic, and manual strength testing. Results: Forty subjects completed the protocol. Average age was 27.7 years; 54% were female. For both upper and lower extremity groups, a statistically significant increase was observed in manual and isokinetic strength both proximal and distal to the BFR tourniquet when compared to both the non-tourniquet extremity and the control group (p<0.05). Limb circumference significantly increased in the upper (p<0.01) and lower extremities (p=0.02). A significant increase in manual strength was noted in shoulder abduction and scaption, and hip extension and abduction even in the non-tourniquet BFR extremity compared to the control group (p<0.05). Conclusion: Low-intensity BFR therapy led to greater increases in muscle strength and hypertrophy. Similar strengthening effects were seen in proximal and distal muscle groups. Strength increases in the contralateral BFR extremity may corroborate a systemic effect. This study provides data to further evaluate the efficacy and safety of BFR therapy in operative and non-operative orthopaedic conditions.

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Paper 93 Expanding the Potential of Nonoperative Therapies In Advanced Knee Osteoarthritis: Treatment Response to Repeat Administration Triamcinolone Acetonide Extended-Release Is Similar Across Kellgren-Lawrence Grades 2-4 Deryk G. Jones, MD1, Andreas H. Gomoll, MD2, John C. Richmond, MD3, Andrew I. Spitzer, MD4, Virginia B. Kraus, MD, PhD5, Kim Huffman, MD, PhD5, Amy Cinar, PhD6, Joelle Lufkin, MPH6, Scott Kelley, MD6. 1Ochsner Clinic Foundation, Jefferson, LA, 2Hospital for Special Surgery/Cornell Medical Center Program, New York, NY, 3New England Baptist Hospital, Dedham, MA, 4Cedars-Sinai Orthopaedic Center, Los Angeles, CA, 5Duke University School of Medicine, Durham, NC, 6Flexion Therapeutics, Inc., Burlington, MA Objectives: Triamcinolone acetonide extended-release (TA-ER) is approved in the US to treat pain associated with knee osteoarthritis (OA). Intra-articular corticosteroids (IACS) are often used to manage recurrence of pain and symptoms during the prolonged course of OA. Effectiveness of IACS in advanced knee OA is unknown, and lack of effective nonoperative treatments may accelerate consideration of total knee arthroplasty (TKA). This post hoc subgroup analysis of a Phase 3b, single-arm, open-label study (NCT03046446) evaluated the efficacy of initial and repeat administration TA-ER in knee OA with a range of radiographic severity classified by Kellgren-Lawrence (KL) grade. Methods: Patients aged ≥40 years with symptomatic knee OA for ≥6 months, KL Grade 2-4, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) -A (pain) total sum score ≥6, and index knee pain for >15 days during the prior month received the 1st injection of TA-ER on Day 1. Patients received the 2nd injection at the first visit (Week 12, 16, 20, or 24) at which repeat dose criteria were met (ie, patient benefited from and tolerated the 1st injection without safety concerns and was clinically indicated to receive the 2nd injection). Patients who received 2 injections were evaluated every 4 weeks up to 52 weeks after the 1st injection. Patients who did not benefit from the 1st injection at Week 12 completed at Week 12. Patients who did not meet repeat dose criteria by Week 24 completed at Week 24. Safety was evaluated via treatment-emergent adverse events (TEAEs), and by index-knee radiography at end of study. Exploratory efficacy endpoints included WOMAC-A (pain), -B (stiffness), -C (function), and Knee Injury and Osteoarthritis Outcome Score-Quality of Life following each injection. Results: Of 208 enrolled patients, 179 received 2 injections. Of these, 56 (31.3%) had KL Grade 2, 68 (38.0%) had KL Grade 3, and 55 (30.7%) had KL Grade 4. The patient population reflected the ‘real-world’ knee OA population (Table). Demographics and baseline disease characteristics were generally similar across KL grade subgroups; however, as expected, age and time since OA diagnosis increased with KL grade. Prior index-knee OA treatments did not correlate with KL grade except for increased use of IA hyaluronic acid. The incidence of TEAEs and index-knee TEAEs were similar across KL grades (Table). Most TEAEs were Grade 1 or Grade 2 and there were no unexpected TEAEs. There were no indications of chondrolysis, osteonecrosis, subchondral insufficiency fractures, or clinically significant subchondral bone changes in any subgroup. Response rates for the 1st injection and median times to 2nd

injection were 95% and 120 days for KL Grade 4, 96% and 118 days for KL Grade 3 and 94% and 113 days for KL Grade 2. Regardless of KL grade, mean WOMAC-A (pain) scores were comparable following injections (Figure). At 12 weeks after both the 1st and 2nd injections, mean scores were similar for patients with KL Grade 4 (1.34 and 1.36), KL Grade 3 (1.37 each), and KL Grade 2 (1.24 and 1.20) (Figure). Conclusion: Overall and across baseline KL grades, repeat administration of TA-ER using a dosing schedule tailored to patient response was well tolerated, with no radiographic evidence for an impact on cartilage. In this ‘real-world’ patient population, TA-ER reliably reduced OA symptoms with similar improvements observed after both injections across KL grade subgroups, including those with KL Grade 4 who may otherwise be considering TKA.

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Paper 94 Recall Bias in Retrospective Assessment of Preoperative Patient Reported Outcomes Matthew J. Gotlin, MD1, Samuel Baron1, Matthew T. Kingery1, Joseph McCafferty, Medical Student2, Laith M. Jazrawi, MD1, Robert J. Meislin, MD1 1NYU Langone Orthopedic Hospital, New York, NY, 2New York Medical College, Valhalla, NY Objectives: Patient reported outcomes (PROs) are measures of function, disability, and health status that may offer a unique assessment of provider quality and performance. The gold-standard method for collecting PROs is the prospective assessment of preoperative to postoperative change. This requires data collection before an intervention and then again after the intervention. This method is not always feasible due to unforeseen cases or emergencies, logistical and infrastructure barriers, and cost issues. In such cases a retrospective approach serves as a potential alternative. In this model, a patient is asked to complete an assessment about their perceived preoperative status during a time period sometime after the surgery. Although this method has its advantages, there is a particular risk of recall bias. There are conflicting conclusions regarding the reliability of the recalled preoperative PROs after orthopedic procedures. The aim of our study was to assess the agreement between prospectively and retrospectively collected PROs for a common, low-risk procedure. Methods: Patients that underwent arthroscopic rotator cuff repair between May 2012 and September 2017 at the study institution were identified. Inclusion criteria consisted of primary arthroscopic rotator cuff repair and preoperative prospectively collected American Shoulder and Elbow Surgeons Standard Shoulder Assessment Form (ASES) scores. All of the patients completed the ASES form preoperatively at their pre-assessment appointment. Patients were then contacted in the postoperative period and asked to recall their preoperative condition while completing another ASES form. Results: Seventy-one patients were included in this analysis (mean age 56.18 ± 10.48 years). The mean duration of symptoms from initial onset to the time of surgery was 8.54 ± 9.28 months. There was an average of 37.53 ± 17.02 months between the preoperative ASES and the recall ASES. Recall ASES scores were significantly lower than preoperative ASES scores (31.65 ± 16.87 vs 50.92 ± 19.57, p < 0.001). Less severe preoperative shoulder dysfunction was predictive of a greater difference between preoperative ASES and recall ASES (β = -0.60, R2 = 0.350, p < 0.001) (see Figure). Each 10-point increase in preoperative ASES score was predictive of a 6.04 point greater mismatch between preoperative and recall ASES. Likewise, a longer symptomatic period prior to surgery was associated with a greater ASES mismatch (R2 = 0.063, p = 0.029). The duration of time between surgery and recall was not a significant predictor of a difference between preoperative and recall ASES. Conclusion: This study demonstrated that there is poor agreement between prospectively and retrospectively collected preoperative PROs in the setting of rotator cuff surgery. Patient’s recalled ASES scores were significantly lower than their prospectively recorded ASES scores. This could lead to an overestimation of perceived benefit or effectiveness of the intervention. Our data supports prior studies

that demonstrated that retrospective PROs are subject to recall bias and have been found to produce more favorable results than prospectively monitored health status data from the same patient. Our study supports the use of prospectively collected PROs and retrospective PROs should only be used in situations where baseline assessments are not possible.

Paper 95 Return-to-Play after Concussion in American versus European Professional Soccer Players: A Comparative Short-Term Analysis of Performance and Longevity Sergio M. Navarro, BS1, Heather S. Haeberle, BS2, Albert S. Jang2, Salvatore Joseph Frangiamore, MD3, Lutul D. Farrow, MD4, Mark S. Schickendantz, MD5, Prem N. Ramkumar, MD, MBA6 1Baylor College of Medicine Program, Houston, TX, 2Baylor College of Medicine, Houston, TX, 3Summa Health Orthopaedics and Sports Medicine, Akron, OH, 4The Cleveland Clinic Sports Health Center, Garfield Heights, OH, 5Cleveland Clinic Sports Health, Cleveland, OH, 6Cleveland Clinic, Cleveland, OH. Objectives: Many studies have focused on the long-term impact of concussions in professional sports, but few have investigated short-term effects. This study examines concussion effects on individual players in the Major League Soccer (MLS) and English Premier League (EPL) by assessing 1) return-to-play (RTP) time, 2) career length, and 3) performance. Methods: Contracts, transactions, injury reports, and performance statistics from 2008-17 were obtained from the official MLS and EPL online publications. Players who sustained a concussion were compared with the 2008-17 non-concussed player pool. Career length was analyzed using Kaplan-Meier survival curves and athletes were stratified by player age, experience, and longevity. Player performance changes were evaluated between the years before versus after concussion. RTP and games missed were analyzed and compared. Results: Of the 1,784 eligible MLS and 2,001 eligible EPL players evaluated over the 10-year period, 102 MLS players sustained 165 concussions and 124 EPL players sustained 142 concussions resulting in injury protocol initiation. MLS players on average missed 7.5 games after a concussion, with 33.5 days missed, whereas EPL players on average missed 0.5 games after a concussion with 9.5 days missed, which was statistically different (p<0.001, p<0.0001). Performance was reduced at all non-goalie positions for goals and assists post-concussion for players in the MLS and in the EPL (p < 0.01). Concussed MLS players playing non-goalie positions scored 2.5 points/year less following a concussion and played in 20 fewer games/year on average. Concussed EPL players playing non-goalie positions scored 3.1 points/year less following a concussion and started in 5.8 fewer games/year on average. Concussed MLS and EPL goalies saw no significant change in performance, although EPL goalies played 3.2 additional games/year on average (p <0.05). The probability of playing a full season post-concussion was not significantly decreased compared with the non-concussed pool (p > 0.05) in both leagues. Conclusion: This study investigating the short-term effects of concussion on professional soccer players demonstrates that performance is reduced for non-goalie players, without a significant difference in career longevity between concussed and non-concussed controls.

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Paper 96 Does Short Rest with Thursday Night Games Influence Injury Rates in the NFL? Jose Raul Perez, MD, Jonathan Burke, MPH, Abdul Zalikha, BS, Nicholas Schiller, MS, Andrew NL Buskard, MS, Dhanur Damodar, MD, Lee D. Kaplan, MD, Michael G. Baraga, MD. University of Miami Sports Medicine Institute, Coral Gables, FL Objectives: The objective of this study was to evaluate the impact rest time between games may have on injury rates as it pertains to overall incidence, injury location and player position. Methods: For this descriptive epidemiological study, data was obtained from official NFL gamebooks. In-game injuries were queried for all regular season games from all 32 teams over the course of four seasons (2013 to 2016). Only injuries which resulted in a stoppage of time during gameplay were included. Player position and injured body part were taken from the following week’s injury report. Rest periods between games were classified as short (4 days), regular (6-8 days), or long (10+ days) rest. Positions were categorized into Quarterback, Skill (wide receiver, running back and defensive backs), Lineman, and Other (fullback, linebacker and tightend). Overall observed injury rates, as well as injury rates specific to anatomic location and player position, were analyzed in correlation to different rest periods. Statistical significance was determined using the ANOVAprocedure of observed mean injuries per game. Pairwise analysis, through 2 sample T-test, was conducted to assess statistical significance between short, regular and long rest. Results: A total of 2,846 injuries were identified throughout the four seasons. ANOVA testing of all 3 cohorts taken together demonstrated a statistically significant difference between injuries/game between short, regular, and long rest (p = 0.012). With short rest, a mean of 1.26 injuries/game were observed (95% CI 1.046, 1.470), which was statistically significantly different when compared to the 1.53 observed injuries/game with regular rest (95% CI 1.463, 1.601; p = 0.029). Games with short rest were not found to be significantly different when compared to the 1.34 observed injuries/game associated with long rest (95% CI 1.186, 1.486; p = 0.555). Regarding player positions, only the Other cohort achieved statistically significantly less observed injuries/game with games played on Thursday compared to regular (p=0.0002) and long (p = 0.026). The quarterback position was the only position which sustained more injuries than expected with games played on Thursday compared to both regular and long rest; however, these results did not reach statistical significance (p = 0.09). No statistical difference was found regarding injury location in correlation to differences in rest periods. Conclusion: Our data suggests that there is a significant association between the amount of rest between games and observed injuries in the NFL. Interestingly, Thursday night games were found to have fewer injuries per game when compared to games played on regular rest. Subgroup analysis revealed fewer observed injuries with short rest for linebackers, fullbacks, and tightends. Although quarterbacks were observed to have more injuries than expected on short rest, this did not reach statistical significance. The results of this study do not support that less rest associated with Thursday

night games leads to higher injury rates; however, quarterback injury rates may potentially be impacted with shortened rest.

Paper 97 The Effectiveness of Mandated Headgear Use in High School Women’s Lacrosse at Reducing the Rate of Head and Face Injuries Samuel L. Baron, BS1, Shayla J. Veasley2, Matthew T. Kingery, BA1, Michael J. Alaia, MD1, Dennis A. Cardone, DO1 1NYU Langone Health, Department of Orthopedics, New York, NY, 2NY Department of Education, New York, NY Objectives: There has been continued controversy regarding whether or not headgear use in women’s lacrosse will increase or decrease the rate of head injuries. In 2017, the Public Schools Athletic of New York City became the first high school organization in the country to mandate ASTM standard F3137 headgear for all women’s lacrosse players. The purpose of this study is to investigate the effect of mandated headgear use on the rate of head and face injuries in high school women’s lacrosse. Methods: This was a prospective cohort study. The study group included eight varsity and junior varsity women’s lacrosse teams, as well as their game opponents, who were mandated to wear F3137 headgear for all practice and game events over the course of the 2017 and 2018 seasons. Certified athletic trainers assessed and documented all injuries that occurred as a result of participation on the lacrosse teams and athlete exposures were estimated based on the number of team practice and game events. Injury rates were compared with those from the High School RIO (Reporting Information Online) injury data reports from the 2009 to 2016 seasons. Results: Over the study period, 17 total injuries were reported during 22,397 exposures for an injury rate of 0.76 injuries per 1,000 athlete-exposures. Two head/face injuries, both of which were classified as concussions, were reported during the study for a head/face injury rate and concussion rate of 0.09 per 1,000 athlete-exposures. The headgear cohort demonstrated significant decreases in rates of in-game head/face injury (RR 0.141, 95% CI [0.004, 0.798]), in-game concussion (RR 0.152, 95% CI [0.004, 0.860) and practice non-head/face injury (RR 0.239, 95% CI [0.049, 0.703]) when compared to the control cohort. Conclusion: Mandated use of F3137 headgear was shown to be effective at lowering the rate of head or face injury and concussions in women’s lacrosse. Additionally, mandated headgear use was also shown to lower the rate of injury to body locations other than the head or face during practice.

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Paper 98 The Histopathology of the Degenerative Proximal Biceps Tendon Travis John Dekker, MD1, Angel Chen, MS2, Nicholas J. Kwon2, John Steele3, William C. Eward, DVM, MD2, Grant Garrigues4, Samuel Bruce Adams, MD5, Alison P. Toth, MD2. 1The Steadman Philippon Clinic, Vail, CO, 2Duke University, Durham, NC, 3Duke University Medical Center-Orthopaedic Residency Program, Durham, NC, 4Rush University, Chicago, IL, 5Duke University AFFL Hosps, Durham, NC Objectives: Surgical treatment of proximal biceps tendinopathy remains a source of great controversy. Current surgical treatment debates center around the fixation location and not the quality of the tendon because little is known about the intra-tendinous pathology to guide this debate. Therefore, this study aims to evaluate two distinct anatomic regions of pathologic biceps tendons with regard to intra-tendinous architecture, painful neurotransmitters, and inflammatory modulators: the intra-articular portion and the extra-articular portion lying in the bicipital groove. Methods: Eleven human degenerative biceps tendons were obtained post-tenodesis. They were divided into intra- and extra-articular portions. They underwent histologic staining with hematoxylin and eosin and Alcian blue as well as immunohistochemistry staining for substance P, tyrosine hydroxylase, and neurofilament. Tendon architecture was assessed according to the modified BONAR tendon score. Immunohistochemistry staining was quantified using ImageJ density analysis. Portions of the tendon sections were cultured for 48 hours and the resultant secretome was assessed for Substance P secretion with ELISA analysis. Results: Composite BONAR scores demonstrated pathologic tendons with no significant difference between the intra-articular biceps tendon and the portion of the tendon within the bicipital groove (p= 0.31). Immunohistochemistry (IHC) analysis demonstrated significantly (p&lt0.05) increased uptake of substance P in the bicipital groove tendon compared to the intra-articular tendon while tyrosine hydroxylase did not (p&gt0.05). Stained substance P and tyr hydroxylase was intimately associated with intra-tendinous vascularity. ELISA results demonstrated significantly increased secretion of substance P in the bicipital groove tendon compared to the intraarticular portion. Conclusion: This study shows abnormal architecture, increased release and staining of painful neurotransmitters, and secretion of substance P from the proximal biceps tendon up to the distal aspect of the bicipital groove. Despite varied surgical techniques for tenodesis, this study supports the removal of the entirety of the long head of the biceps to the distal portion of the bicipital groove.

Paper 99 Comparison of Traditional Physical Therapy to Internet-Based Physical Therapy after Knee Arthroscopy: A Prospective Randomized Controlled Trial Comparing Patient Outcomes and Satisfaction Christopher Hadley1, Mikayla McGrath2, John P. Prodoehl3, Steven B. Cohen, MD4, William D. Emper, MD5, Sommer Hammoud, MD5, Michael G. Ciccotti, MD5, Kevin B. Freedman, MD6, Shyam Brahmabhatt2, Donald William Mazur, MD2 1Rothman Insitute, Philadelphia, PA, 2Rothman Institute, Philadelphia, PA, 3Sidney Kimmel Medical College, Philadelphia, PA, 4Rothman Institute, Media, PA, 5Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA, 6Rothman Institute at Thomas Jefferson University Hospital, Bryn Mawr, PA Objectives: Knee arthroscopy results in significant improvements in functional outcomes, pain and quality of life for patients suffering from meniscal tears. Traditionally, patients have undergone formal physical therapy (PT) after knee arthroscopy to regain function. Prior studies have demonstrated that patients who undergo internet-based PT after total knee arthroplasty performed as well as patients receiving traditional PT, but this has not been studied in the knee arthroscopy population. The goal of this study is to compare traditional outpatient physical therapy to internet-based physical therapy in patients undergoing knee arthroscopy for partial meniscectomy. Methods: Patients undergoing knee arthroscopy from October 2017 to September 2018 for partial meniscectomy were enrolled. Patients were randomized to either an outpatient or internet-based physical therapy program. Participants in the outpatient physical therapy were prescribed PT for 2 sessions per week for 4-6 weeks while participants in the online physical therapy group were instructed to login daily to track progress and complete their exercises a minimum of 3 times per week. Additionally, participants completed 4 questionnaires: VR-12 mental and physical health, International Knee Documentation Committee (IKDC), Modified Cincinnati Rating System (MCRS) and Lysholm pre-operatively, 1 week, 6 weeks and 6 months after surgery. The primary outcome of knee function was measured via the IKDC. Results: Of the 97 patients who met the inclusion criteria, 51 (52.6%) were in the internet-based physical therapy group and 46 (47.4%) were in the outpatient PT group. There were 57 males (58.8%) and 40 females (41.2%). Participants in the online physical therapy group logged into the platform an average of 2.74 times pre-operatively and 14.99 times post-operatively. Additionally, patients viewed their PT exercise videos, on average, 5.58 times pre-operatively and 36.71 times post-operatively. At final follow-up, there was no significant difference in the primary outcome with an average IKDC score for the online physical therapy (71.83) compared to outpatient PT group (74.23) [p = 0.699]. Additionally, there was no significant difference noted in the three secondary outcome measures between the internet-based physical therapy group and the outpatient PT group at final follow-up (Table 1). Furthermore, no significant difference was noted between the two patient cohorts pre-operatively and 1 week and 6 weeks after surgery in all four outcome measures (Table 1).

Conclusion: The results of our study indicate that patients using internet-based PT had similar functional outcomes as patients using traditional outpatient PT following knee arthroscopy for partial meniscectomy.

Paper 100 Healthy Pediatric Athletes Have Significant Baseline Limb Asymmetries on Common Return to Sports Performance Tests John Magill1, Trevor Lentz, PT2, Heather Myers1, Jonathan C. Riboh, MD3 1Duke University, Durham, NC, 2Duke University, Gainesville, FL, 3Duke Sports Science Institute, Durham, NC Objectives: Return to sport (RTS) after anterior cruciate ligament (ACL) reconstruction in children is associated with a higher risk (~30%) of subsequent ACL injury than in adults. Most RTS testing protocols use Limb Symmetry Indices (LSI) on physical performance tests (PPTs) to assess an athlete’s readiness for sport. This assumes that in a healthy state, both lower extremities are and should be equal. We hypothesized that in the pediatric population, baseline limb asymmetry exists, limiting the clinical utility of LSIs. Since LSI > 90% is often used as a clinical cutoff for RTS, we defined a test as valid if 80% of healthy volunteers had an LSI > 90% on that test. Methods: This study included healthy, uninjured volunteers (n = 63) between the ages of 6 and 18 [mean age = 10.7 +/- 3.2 years; 34 females (54%)]. Pubertal Maturity Observation Scores (PMOS) were calculated for all individuals. Demographic data including sex, chronologic age, Pubertal Maturity Observational Score (PMOS), height, weight, and body mass index (BMI) were collected. Subjects performed ten common PPT’s including the lower quarter Y-balance, stork balance, stork balance on BOSU, single leg squat (SLS), SLS on BOSU, clockwise and counterclockwise quadrant single leg hop (SLH), forward SLH, timed SLH, and triple crossover SLH. Subjects performed the 10 PPT’s in the same order (listed above), however we randomly assigned the starting test and the starting limb to avoid practice effects. We conducted two trials on each leg for each test with the exception of the forward SLH, timed SLH, and triple crossover SLH, which were performed in triplicate. For analysis, we developed a composite score for each limb by averaging trials. We then calculated the absolute value of the side-to-side difference, and normalized this difference to the test mean to obtain a percentage side-to-side difference for each test (%STS). Multivariable linear regression analysis was performed to assess the effect of age on limb symmetry while correcting for body mass index (BMI), PMOS and sex. Results: All 63 subjects successfully completed testing. %STS were not normally distributed for any of the PPTs, therefore data were reported as medians and interquartile ranges. All PPTs showed baseline limb asymmetry, and none met our definition of validity (Figure 1). The most symmetric PPT was the clockwise quadrant hop test (%STS in females, median = 9.85, interquartile range = 4.63-18.7; %STS in males, median = 6.9, interquartile range = 3.64-14.04). The stork balance on BOSU test had the greatest limb asymmetry (%STS in females, median 41.4, interquartile range 10.1 - 71.3; %STS in males, median 47.6, interquartile range 18.2-66.7, Figure 2). PMOS was strongly correlated with chronologic age (Pearson’s ⍴ = 0.83), therefore PMOS was excluded as a predictor variable in regression models to avoid multicollinearity. Age was an independent predictor of %STS only for the stork test (β = -1.15, 95% CI = -1.92 to -0.38, p = 0.004), with older subject having less limb asymmetry.

Conclusion: Healthy children ages 6 - 18 years have significant baseline limb asymmetries on PPTs that are commonly used for RTS decision making after ACL reconstruction. None of the PPTs evaluated in this study met our definition of clinical validity. Limb symmetry was typically not affected by subject age. In light of these results, limb symmetry indices (LSI) should be utilized with caution in this population. Functional recovery may be better assessed by comparison to age and sex-specific norms.

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Paper 101 Risk Factors for Recurrent Anterior Shoulder Instability after Arthroscopic Stabilization in Adolescent Athletes Timothy Cheng, MD1, Eric W. Edmonds, MD2, Tracey P. Bastrom, MA1, Andrew T. Pennock, MD1. 1Rady Children's Hospital, San Diego, CA, 2Rady Children's Specialists San Diego, San Diego, CA Objectives: Arthroscopic stabilization has become the preferred surgery for adolescent athletes with anterior instability without significant bone loss. Although successful for most patients, 10-40% will experience recurrent instability. The purpose of the current study was to compare a consecutive series of patients who had failed an arthroscopic stabilization to an age and gender matched cohort of patients who had no evidence of recurrent instability with a goal of identifying risk factors for future instability. Methods: A retrospective review was undertaken of all patients undergoing an arthroscopic shoulder stabilization for anterior instability between 2009 and 2016. Patients over the age of 18 years and those with underlying syndromes affecting the musculoskeletal system were excluded. Two patient cohorts were identified: (1) Patients with recurrent instability (frank dislocations or subluxations) after their arthroscopic stabilization; (2) An age and gender matched cohort of patients with no recurrent instability at a minimum of 2 years follow-up from surgery. Patient demographic, injury, radiographic, and surgical variables were recorded. In particular, bone loss measurements were performed on both the glenoid and humerus, and Hill-Sachs lesions were classified as “on-track” or “off-track”. Variables at p<0.10 on univariate analysis were entered into a binary logistic multivariate regression analysis. Results: 35 patients were identified that failed an arthroscopic stabilization at a mean of 1.2 ± 1.0 years after their index surgery. A separate age and gender matched cohort of 35 patients was also identified with no symptoms of recurrent instability. Univariate analysis identified the following 4 risk factors for recurrent instability (glenoid bone loss > 10%, glenoid retroversion < 5◦, skeletal immaturity, and patients with more than one pre-surgical instability event). Collision sport participation, the presence and size of a Hill-Sachs deformity, and the glenoid track were not predictive of failure. Multivariate regression analysis revealed that loss of glenoid retroversion, skeletal immaturity, and a greater number of prior instability events best predicted future recurrence with two risk factors having a 3x increased risk and patients with all three risk factors having a 4x increased risk of recurrent instability after arthroscopic stabilization. Conclusion: Anterior glenoid bone loss, glenoid version, skeletal immaturity, and multiple pre-operative instability events are risk factors for failed arthroscopic stabilization in adolescent athletes with anterior instability. In the setting of multiple risk factors, patients and families should be counselled of the increased odds of surgical failure and other forms of surgical stabilization may need to be considered.

Paper 102 Shoulder Surgery in Professional Baseball Players Peter Nissen Chalmers, MD1, Brandon J. Erickson, MD2, John D'Angelo3, Anthony A. Romeo, MD4. 1University of Utah, Salt Lake City, UT, 2Rothman Institute, New York, NY, 3Major League Baseball, New York, NY, 4Rothman Institute, New York City, NY Objectives: Injury rates are increasing in professional baseball players. There is little information regarding shoulder surgeries in these athletes. The purpose of this study is to report the incidence, procedure type, demographics, and return to sport (RTS) rate of shoulder surgeries in MLB players. Methods: All MLB players who underwent surgery between 2012-2016 were identified from a database prospectively maintained by the MLB. Demographic information as well as details regarding the procedure were recorded. RTS rates were determined. Only those players with a minimum of six month follow-up were included. Results: There were 581 shoulder surgeries (542 players) performed, and thus the incidence of shoulder surgery among professional baseball players is 1.48%. Pitchers accounted for the majority of players who had shoulder surgery (60%). Overall, 19% surgeries were performed on players in the majors and most players were between 20-25 years old. The majority of procedures were performed on the posterior and anterior labrum. Of these, 67% involved labral repair. Within surgeries that addressed the rotator cuff, 84% involved debridement, most tears were articular sided (87%), and 75% involved the supraspinatus. Overall, 11% of players had a history of prior shoulder surgery and 76% had spent time on the disabled list prior to surgery. The overall rate of RTS was 63%, with 86% of those who returned returning to at least the same level of play as prior to surgery or higher. Of those who returned to their prior level of play, 73% later ascended to a higher level of play or were not able because they were in the major leagues pre-operatively. Conclusion: Shoulder surgery is uncommon among MLB players. Of those players who undergo surgery, the majority are pitchers and minor league players. Most procedures involve the labrum. Rotator cuff tears are mostly articular sided supraspinatus tears. Overall RTS rates are 56%, with only 41% able to return to the same level of play as before surgery.

Paper 103 Predictors of Radiographic Osteoarthritis 2-3 Years after ACL Reconstruction: Data from MOON Onsite Nested Cohort Morgan H. Jones, MD1, Sameer R. Oak, MD1, Jack T. Andrish, MD2, Robert H. Brophy, MD3, Charles L. Cox, MD4, Warren R. Dunn, MD, MPH5, David C. Flanigan, MD6, Braden C. Fleming, PhD7, Laura J. Huston, MS8, Christopher C. Kaeding, MD6, Michael Kolosky, DO9, Thomas Sean Lynch, MD10, Robert A. Magnussen, MD, MPH6, Matthew J. Matava, MD3, Richard D. Parker, MD11, Emily K. Reinke, PhD12, Erica Scaramuzza13, Matthew V. Smith, MD14, Carl S. Winalski, MD15, Rick W. Wright, MD16, Alex Zajichek, M.S.17, Kurt P. Spindler, MD1 1Cleveland Clinic Orthopaedic Sports Health, Cleveland, OH, 2Cleveland Clinic Department of Orthopaedics, Cleveland, OH, 3Washington University Orthopedics, Chesterfield, MO, 4Vanderbilt Sports Medicine, Nashville, TN, 5UW Health at The American Center, Madison, WI, 6The Ohio State University, Columbus, OH, 7Bioengineering Labs, Providence, RI, 8Vanderbilt Orthopaedic Institute, Nashville, TN, 9Massachusetts General Hospital, Boston, MA, 10Columbia University, New York, NY, 11Cleveland Clinic Orthopaedic Sports Health, Mayfield Heights, OH, 12Duke University Med. Ctr., DSSI, Durham, NC, 13Vanderbilt University, Nashville, TN, 14Washington University in St. Louis, Chesterfield, MO, 15Clevleand Clinic Orthopaedics Department, Cleveland, OH, 16Washington University, Saint Louis, MO, 17Cleveland Clinic Department of Quantitative Health Sciences, Cleveland, OH Objectives: Multiple studies have shown patients are susceptible to post-traumatic osteoarthritis (PTOA) after anterior cruciate ligament (ACL) injury even with ACL reconstruction (ACLR). Prospective studies using multivariate analysis to identify risk factors for PTOA are lacking. This study aims to identify baseline predictors of radiographic PT OA after ACLR at an early time point and hypothesizes that meniscal injury and cartilage lesions will be associated with worse radiographic OA using the Osteoarthritis Research Society International (OARSI) atlas criteria. Methods: 421 patients who underwent ACLR returned onsite for standardized posteroanterior metatarsophalangeal radiographs a minimum of 2 years after surgery. At baseline, demographics, graft type, meniscal status/treatment, and cartilage status were collected. OARSI atlas criteria were used to grade all knee radiographs. Multivariable ordinal regression models identified baseline predictors of radiographic OARSI grades at follow-up. Results: The mean age was 19.8 years with 51.3% females. Higher age (odds ratio (OR) 1.06) and BMI (OR 1.05) were statistically significantly associated with higher OARSI grade in the medial compartment. Patients with a meniscal repair and a partial meniscectomy had statistically significantly higher OARSI grades in the medial compartment (meniscal repair OR 1.92 and meniscectomy OR 2.11) and in the lateral compartment (meniscal repair OR 1.96 and meniscectomy OR 2.97). Graft type, cartilage lesion, sex, and Marx activity scales had no significant association with OARSI grade.

Conclusion: Older patients with a higher BMI who have an ACL tear with concurrent meniscal tear requiring partial meniscectomy or meniscal repair should be advised of their increased risk of developing radiographic OA. Alternatively, patients with an ACL tear with an articular cartilage lesion can be reassured that they are not at increased risk of developing radiographic knee OA at 2-3 years following ACLR.

Paper 104 Arthroscopic Treatment for Shoulder Instability with Glenoid Bone Loss Using Distal Tibia Allograft Augmentation: Two Year Outcomes Rakesh Ebnezar, MS(Ortho),DNB(Ortho), Ivan H. Wong, MD. Dalhousie University, Halifax, NS, Canada Objectives: To analyse the clinico-radiologic outcomes of patients who underwent an all arthroscopic procedure to treat shoulder instability with glenoid bone loss using a distal tibial allograft; with a minimum 2 year follow-up. Methods: A retrospective chart review of prospectively collected data was completed for patients who underwent arthroscopic stabilization with Bankart repair and allograft bony augmentation of the glenoid; by the same surgeon. Western Ontario Shoulder Instability Index (WOSI), Disability of the Arm Shoulder and Hand (DASH), Veterans Rand - 12 and MARX questionnaires were completed pre and post-operatively. Radiological assessment was performed with radiographs and CT scans obtained pre-operatively and at approximately one year post surgery. Results: A total of 41 patients (29 males, 12 females) with a mean age of 26 ± 9 years were included. An excellent safety profile was observed, with no intraoperative complications, neurovascular injuries, adverse events, bleeding, or infections. At 2- year follow-up, there was statistically significant improvement of the WOSI score when compared preoperatively (preoperative=62.6 ± 17.06; at 2-year=22.96± 12.92; p<0.001). The mean pre-operative bone loss was 30.32 % (SD ± 7.90). There were no cases of non- union or partial union. No resorption of the graft (grade 0) was seen in 42% patients, whereas 42% and 16% of patients had grade 1 and grade 2 resorption; respectively. There was 100% healing at the interface between allograft and native glenoid. The mean sagittal dimension of the remaining allograft post-operatively was 5.10 ± 2.27 mm in the patients with ≥50% resorption which indicates there was still bone graft present and there was no complete resorption. Mean post-operative external rotation for the population was also observed to near full. Conclusion: Arthroscopic stabilization with DTA augmentation has an excellent outcome at 2-year follow-up; long-term follow-up studies are necessary for better assessment of outcomes.