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1Clinical Communication

Tibial plateau levelling osteotomy in 69 small breed dogs using conically coupled 1.9/2.5 mm locking platesA clinical and radiographic retrospective assessment

G. Cosenza1; U. Reif1; F. M. Martini21Tierklinik Dr. Reif, Böbingen, Germany; 2Unità operativa chirurgia e traumatologia veterinaria, Dipartimento di scienze medico-veterinarie, Università degli Studi di Parma, Italy

KeywordsComplications, small breed dogs, stifle, retro-spective study, TPLO, tibial plateau levelling osteotomy

SummaryObjective: To report clinical experiences with the tibial plateau levelling osteotomy (TPLO) procedure in small breed dogs with cranial cruciate ligament (CCL) disease using specific, conically coupled, 1.9/2.5 mm lock-ing plates and evaluating short-term compli-cations and outcome.Methods: Medical records of small breed dogs (<15 kg) that underwent TPLO using 1.9/2.5 mm locking plates were reviewed retrospectively. The preoperative, postoper-ative and six to eight weeks postoperative ti-bial plateau angle (TPA) measurements were determined from the radiographic images. Lameness evaluation was assessed subjec-tively preoperatively and six to eight weeks postoperatively.

Results: Sixty-nine small breed dogs (n = 79 stifles) were included in the study. Mean (± SD) preoperative TPA was 29.0 ± 3.4°, post-operative TPA was 5.8 ± 2.5°, and six to eight weeks postoperative TPA was 7.3 ± 4.1°. Sixteen complications occurred in 12 out of 79 TPLO procedures: three were in-traoperative (intra-articular screw place-ment) and 13 were postoperative compli-cations, of which nine were identified as minor complications not requiring surgical reintervention, and four as major compli-cations requiring additional surgical inter-vention, including tibial tuberosity fracture (n = 1), osteomyelitis (n = 1), screw failure (n = 1), and plate breakage (n = 1). Lameness scores by clinical assessment reduced from a median value of 3/4 preoperatively to 1/4 at six to eight weeks postoperatively.Clinical significance: 1.9/2.5 mm locking plates appear to be a valid choice of implant for the stabilization of unilateral TPLO in small breed dogs.

Correspondence to:Dr. Giovanni Cosenza Schönhardter Straße 36D-73560 Böbingen-NordGermanyPhone: +49 1575 3122744E-mail: [email protected]

Vet Comp Orthop Traumatol 2015; 28: ••–••http://dx.doi.org/10.3415/VCOT-14-09-0135Received: September 1, 2014Accepted: May 26, 2015Epub ahead of print: June 3, 2015

Introduction Cranial cruciate ligament disease has been recognized as a cause of hindlimb lameness in both small and large breed dogs since

1926 (1). Cranial tibial thrust is the cran-ially directed shear force on the tibia with respect to the femur generated during weight bearing (2). The cranial cruciate ligament contributes to passive opposition

of cranial tibial thrust. Deficiency of the cranial cruciate ligament permits cranial ti-bial translation during weight bearing, re-sulting in degradation of the hyaline carti-lage matrix, inflammation, and osteoar-thritis (3–5). Slocum and Slocum proposed that cranial tibial thrust magnitude is di-rectly proportional to the tibial plateau angle (TPA) (6). It has been suggested that small breed dogs may have a higher TPA than large breed dogs, with TPA ranging from 21° to 34° (mean: 27.4°) and 27° to 40° (mean TPA not reported) (7, 8). A high TPA in small breed dogs has been associ-ated with caudal deformity of the proximal tibia (9, 10).

Concern about body weight as a vari-able in the management of dogs with cran-ial cruciate ligament rupture was first ex-pressed in 1984 (11). In that study, conser-vative management resulted in acceptable hindlimb function in up to 85% of small breed dogs (<15 kg) with cranial cruciate ligament disease (11, 12). However, re-covery time was prolonged (mean: 4 months) and 14.3% of dogs remained lame (12). Extra-capsular stabilization consists of placing one or more extracapsular su-tures across the joint to neutralize the cran-ial tibial thrust statically. Extra-capsular stabilization improves stability and hind-limb function during the postoperative period (13–15). However, long-term stifle stability relies on periarticular fibrosis, and suture failure resulting in joint instability does occur more commonly than one may expect, especially in dogs with a high activ-ity level (15–20).

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2 G. Cosenza et al.: A clinical and radiographic retrospective assessment

A greater TPA in smaller dogs may pro-duce a greater cranial tibial thrust and could theoretically contribute to early fail-ure of extra-capsular stabilization tech-niques. Therefore, performance of a tibial osteotomy with the aim of levelling the ti-bial slope may be more appropriate in this population of dogs. Tibial plateau levelling osteotomy provides stifle stability by neu-tralizing tibiofemoral shear forces dynami-cally (6, 21).

Increased tibial plateau rotation associ-ated with a high TPA may result in a lack of buttress support of the tibial tuberosity. It has been suggested that rotation beyond the point of patellar ligament insertion would make the tibial tuberosity more sus-ceptible to fracture (22, 23). To obviate this problem, a combination of tibial plateau le-velling osteotomy and cranial tibial closing wedge osteotomy has been proposed in dogs with a steep TPA, however this may be technically demanding in small breed dogs due to the small bone (22). Tibial pla-teau levelling osteotomy in small breed dogs with a high TPA (>30°) has been re-ported previously without encountering ti-bial tuberosity fracture (24).

Both conventional and locking plates are available for small breed dogs. Locking screws help maintain the tibial plateau position during plate application (25). Small plate contouring discrepancies and subtle shifts in alignment when tightening conventional screws can have a great im-pact on both osteotomy compression and corrected tibial plateau angle (24–27).

Tibial plateau levelling osteotomy using a 4-hole 1.9/2.5 mm conically-coupled locking T-plate in small breed dogs with a steep TPA has been reported previously (24). We report our experience using dif-ferent 1.9/2.5 mm locking plates in small breed dogs with particular focus on a coni-cally-coupled locking L-plate.

Material and methods

Medical records of dogs that underwent ti-bial plateau levelling osteotomy utilizing 1.9/2.5 mm conically-coupled locking platesa at a referral centre (Tierklinik in Böbingen) between January 2008 and No-vember 2014 were reviewed. Inclusion

criteria included a body weight of less than 15 kg, cranial cruciate ligament disease confirmed by mini-arthrotomy, complete medical records including preoperative and six to eight week postoperative subjective lameness scoring (0 = no lameness, 1 = mild, 2 = moderate, 3 = severe, 4 = non weight-bearing) by a board-certified sur-geon (UR), and preoperative, postoperative and six to eight week postoperative radio-graphs.

Excluded from the study were dogs with incomplete medical records that could not be returned for follow-up examination six to eight weeks after surgery, dogs with neu-rological diseases, severe systemic diseases, or any other injuries or diseases such as pa-tellar luxation, hip dysplasia, Legg-Calvé-Perthes disease in the limb being treated for cranial cruciate ligament disease, and dogs that underwent surgery on the limb being treated for cranial cruciate ligament disease for conditions other than cranial cruciate ligament disease. Information ob-tained included breed, sex, age, body weight, pre-, postoperative and six to eight week postoperative TPA, meniscal damage and treatment, saw blade size, implants ap-plied, and complications.

All osteotomies were secured with tibial plateau levelling osteotomy plates of the mini-implant series (1.9/2.5 mm system) which were able to accommodate both 1.9 mm and 2.5 mm screws. The locking plate consisted of a stainless steel plate with tita-nium alloy bushing inserts and titanium self-tapping screws with a conical head that lock into the bushing inserts of the plate by conical coupling (28).

Using a standard anaesthesia protocol, dogs were premedicated with levometha-doneb, and anaesthesia was induced with propofol and maintained with isoflurane in oxygen. All dogs received a single adminis-tration of cefazolin (22 mg/kg IV) and car-profen or tolfenamic acid preoperatively. The dogs were positioned in dorsal recum-bency with the pelvic limb suspended for surgery.

All dogs underwent a craniomedial parapatellar mini-arthrotomy for stifle ex-

ploration, and inspection of both cruciate ligaments and menisci. Meniscal injuries were treated by partial meniscectomy. After fascial incision and reflection of the sartorius muscle, no additional dissection of musculature cranial or caudal to the proximal segment was performed. A se-micylindrical osteotomy of 12 or 15 mm radius was made without use of a jig. Ro-tation of the proximal fragment was tem-porarily maintained with an anti-rotational Kirschner wire and pointed reduction forceps.

The locking plate was then contoured such that the proximal two screws would converge to avoid invasion of the osteot-omy gap and to improve fixation of the caudal part of the proximal tibial bone fragment. The plate was positioned on the medial surface of the tibia in a matter that best fitted the bone contour and osteotomy. Whenever possible, the plate was oriented such that the caudal margin was placed parallel to and adjacent to the caudal cortex of the tibial shaft. The type of implant was subjectively chosen by the surgeon preop-eratively, considering body weight, the size and conformation of the tibia, and the amount of rotation of the proximal frag-ment. In every case, the plate was secured with 2.5 mm locking screws in both the proximal fragment and the tibial diaphysis. The anti-rotational Kirschner wire was re-moved and the surgical site closed in layers.

Radiographs were reviewed by one author (UR), with the observer blinded to all data. All measurements were made on digital radiographsc using the built-in tool on a standard diagnostic imaging software systemd. The TPA was measured using the tangential and conventional methods (29). Postoperative mediolateral radiographs were also used to determine whether ro-tation of the proximal fragment was beyond the point of patellar ligament inser-tion. Osteotomy healing was assessed on the six to eight weeks postoperative radio-graphs using a modified version of a pre-viously developed grading system (Inter-national Society of Limb Salvage) (23, 30,

a Fixin®: Intrauma S.r.l., Rivoli, Italyb L-Polamivet®: MSD Animal Health GmbH,

Unterschleißheim, Germany

c workstation - easyvet XDR2 cuattro direct digital detector: Toshi

d easyimage version 8.0.0.05, DICOM-viewer:




3

Surgery

Seventy-nine tibial plateau levelling osteot-omy procedures were performed in 69 dogs by one board-certified surgeon. Bilateral simultaneous tibial plateau levelling osteot-omy procedures were not performed. Me-niscal injuries were apparent in 22 stifles and all were treated by partial meniscec-tomy. Osteotomy radius was 12 mm in 20 stifles (mean body weight: 6.1 ± 1.2 kg) and 15 mm in 59 stifles (mean body weight 9.7 ± 1.7 kg) (▶ Figure 1). The most common plate used was the 1.2 mm thick and 25 mm long L-platee ( n = 38, ▶ Figure 2), fol-

Breeds were as follows: Jack Russell Ter-rier (n = 11), West Highland White Terrier (n = 6), Australian Terrier (n = 4), Havan-ese (n = 3), Yorkshire Terrier (n = 3), Bi-chon Frise (n = 2), Bolonka Zwetna (n = 2), Cairn Terrier (n = 2), Norwich Terrier (n = 2), Shetland Sheepdog (n = 2), Beagle (n = 1), Chihuahua (n = 1), Coton de Tulear (n = 1), Fox Terrier (n = 1), Lhasa Apso (n = 1), Miniature Schnauzer (n = 1), Patterdale Terrier (n = 1), Pug (n = 1), Shi Tzu (n = 1), Toy Poodle (n = 1), Welsh Corg (n = 1). Twenty-one dogs were mixed-breed. There were 26 spayed and 16 entire females, and 11 castrated and 16 entire males. Mean age was 8.5 ± 2.8 years and mean body weight was 8.8 ± 2.2 kg. Median preoperative sub-jective lameness score was 3 (range: 2–4).

G. Cosenza et al.: A clinical and radiographic retrospective assessment

31). Bone union was defined as fusion of the osteotomy line, the presence of bridg-ing callus, or the disappearance of the os-teotomy lines and scored as follows: 1 = poor union <25% (no callus); 2 = fair union 25–50% healing; 3 = good union >50–75% healing; and 4 = excellent union >75% healing.

Dogs were typically discharged six to 24 hours after surgery with instructions to the owner to administer carprofen (2 mg/kg daily) for 10 days. No routine postoperative antimicrobial therapy was administered. Patients were re-examined five to 10 days after surgery. Postoperative care consisted of six week confinement to a cage or a single room except for leash walks of 10–15 minutes two to three times daily.

Complications were defined as any un-desirable outcome associated with the sur-gical procedure and were classified de-pending on severity as major (surgical in-tervention required) or minor (managed nonsurgically).

Statistical analysis

Data were reported as mean ± SD for normally distributed data, or median and range for non-parametric data. Distribu-tions of categorical and continuous vari-ables associated with complications were compared by use of a two-tailed Fisher's exact test and independent t test, respect-ively. The two methods of TPA measure-ment were compared by linear regression analysis with non-normal errors. For all analyses, a value of p <0.05 was considered significant.

ResultsSignalment

Eighty dogs (96 stifles) fulfilled the initial criteria for inclusion: all were less than 15 kg in bodyweight and treated by tibial pla-teau levelling osteotomy using 1.9/2.5 mm Fixin® plates. However, 11 dogs (17 stifles) were excluded from the study; five dogs (7 stifles) had medial patellar luxation or were treated surgically for patellar luxation and six dogs (10 stifles) were lost to follow-up. Thus, 69 dogs (79 stifles) were included.

Figure 1 Relationship between body weight and the saw blade used to perform the osteotomy.

A B

Figure 2 A) Preoperative mediolateral and caudocranial views of a right tibia and stifle of a dog with a high tibial plateau angle (34°) and great subluxation of the tibia. B) Immediate postoperative medi-olateral and caudocranial views showing rotation of the proximal fragment to level the tibial plateau and fixation with a locking L-plate and four screws.

e FIXIN® V2007, Intrauma S.r.l., Rivoli, Italy




4

Figure 3 1.9/2.5 mm locking plates used in the study.

3 5 7 9 11 13 15

Body weight (kg)

Plates

V2001/V2021

V2003

V2007

Figure 4 Relationship between body weight and plate used.

A B C


lowed by the 1.5 mm thick and 32 mm long T-platesf ( n = 27), and the 1.2 mm thick and 25 mm long T-plateg (n = 14, ▶ Figure 3, ▶ Figure 4). Seven dogs were treated with cephalexin (22–30 mg/kg PO) for 10 days postoperatively.

Radiographic assessment

No significant difference between the two methods of TPA measurement was ob-

served. Mean (± SD) preoperative TPA was 29.0 ± 3.4°, postoperative TPA, 5.8 ± 2.5° and six to eight weeks postoperative TPA 7.3 ± 4.1°. The mean change in TPA be-tween postoperative and six to eight weeks postoperative radiographs was 1.4 ± 1.6°. The proximal fragment was rotated beyond the point of patellar ligament insertion in 38 stifles (48.1%). Median osteotomy heal-ing grade was 3 (range: 3–4).

Complications

Sixteen complications were recorded in 12 out of 79 tibial plateau levelling osteotomy

procedures. Intra-operative complications (intra-articular screw placement) occurred in three dogs. The malpositioned screws were replaced with a shorter screw im-mediately after surgery and radiographs showing proper screw length and orien-tation were obtained.

Thirteen postoperative complications occurred: four major complications required an additional surgical interven-tion and the remainder nine were minor complications. Major complications in-cluded one tibial tuberosity fracture, one osteomyelitis, one screw failure, and one plate breakage.

Tibial tuberosity fracture was apparent four weeks after surgery (▶ Figure 5) as the owner noticed the dog becoming acutely lame. This was treated with Kirschner wire fixation and tension band placement. Eight weeks after revision surgery, osteomyelitis caused by a multi-resistent Staphylococcus aureus was diagnosed, thus plate removal as part of infection treatment was perform-ed. Outcome in terms of radiographic heal-ing and lameness evaluation after eight weeks was assessed as good.

Failure of the caudal screw in the proxi-mal fragment occurred in one stifle. The dog had a persistent lameness and a local infection of the incision site. Radiographs taken 16 weeks following tibial plateau le-velling osteotomy procedure demonstrated good osteotomy healing and no implant loosening. However, implant removal led to the detection of the broken screw just below the screw head. At the six weeks fol-low-up examination, the lameness had re-solved.

Plate breakage was apparent three weeks postoperatively in the stifle of a 12 kg mixed breed dog treated by tibial plateau levelling osteotomy using the 1.2 mm L-plate. The owners reported excessive ac-tivity within 10 days of surgery. The plate was removed and the osteotomy re-stabil-ized by a 3.0/3.5 mm locking T-plateh. Healing was progressing at six to eight weeks with active callus formation and no lameness was noted.

Minor complications included surgical site infection (n = 6) and seroma (n = 3).

h FIXIN® V3001, Intrauma S.r.l., Rivoli, Italy

f FIXIN® V2001/V2021, Intrauma S.r.l., Rivoli, Italyg FIXIN® V2003, Intrauma S.r.l., Rivoli, Italy




5

Figure 5 Mediolateral views of the right stifle of a dog with a tibial tuberosity fracture. A) Radiographic images taken three weeks after surgery. B) Radio-graphic images following revision surgery, which was performed with two Kirschner wires and a tension band wire. C) Osteomyelitis occurred nine weeks after revision surgery. D) Following implant removal. E) The osteotomy line was still apparent after three months.

A B C D E

quently occurring complications, but were not observed in our study (33). This may be in part attributable to the short follow-up time in our dogs (33–38). Nevertheless, thorough evaluation of the meniscus using a probe should be performed in order to diagnose latent tears, which may result in persistent lameness after tibial plateau le-velling osteotomy (39, 40).

Intra-articular screw placement oc-curred in three stifles. The occurrence of this complication is more of a technical error (41). Greater experience with tibial plateau levelling osteotomy using this plate system in small breed dogs may influence the type and incidence of complications over time (42). Since screw direction is im-posed in locking plates, contouring of the plate may redirect the angle of the locking screws.

Depending on plate availability and subjective choice of the surgeon, different 1.9/2.5 mm locking plates were used to se-cure the osteotomy. Special features of these implants include the plate head that is specifically designed to facilitate ad-equate screw purchase in the proximal bone segment. High TPA resulting in great rotation causes the caudal portion of the proximal fragment to protrude beyond the caudal cortex of the tibial shaft, as a result the osteotomy fixation becomes technically

7.3 ± 4.1°. We observed an overall compli-cation rate of 15.2% (12/79 stifles), but no predisposing factor for postoperative com-plications was found. The locking plates in our study resulted in a stable fixation of 77 out of 79 osteotomies. Lameness scores by clinical assessment reduced from median 3/4 preoperatively to 1/4 at six to eight weeks postoperatively.

Preoperative TPA of 29.0 ± 3.4° is con-sistent with the findings of similar studies in small breed dogs, reporting a higher TPA compared to other dogs (7, 8, 26). Possible explanations are that small breed dogs have a physiologically steeper TPA, or that small breed dogs with cranial cruciate ligament disease and a lower TPA respond well to other treatment options and there-fore referral is not sought (7). Moreover, what in the past has been referred to as a caudal deformity of the proximal tibia, has to be considered the physiological tibia conformation in small breed dogs (9, 10). Caudal bowing of the proximal tibia as-sociated with caudal sloping of the tibial plateau is a common finding in small breed dogs, and it results in a higher TPA com-pared to medium- and large breed dogs.

Meniscal injuries were found in 27.8% of stifles, which is similar to the ranges of 10–70% in large breed dogs (32–37). Late meniscal tears have been reported as fre-


All surgical site infections resolved after antimicrobial therapy with oral cephalexin (22–30 mg/kg) for 10 days.

Short-term complications were not sig-nificantly associated with sex (p = 0.95), age (p = 0.67), body weight (p = 0.75), me-niscal injury (p = 0.45), preoperative TPA (p = 0.79), postoperative TPA (p = 1), six to eight weeks postoperative TPA (p = 1), change in TPA from postoperatively to six to eight weeks postoperatively (p = 0.28), rotation of the proximal fragment beyond the point of patellar tendon insertion (p = 0.38), saw blade size (p = 0.67), or type of implant (p = 1) .

Subjectively assessed median lameness scores six to eight weeks postoperatively were between 0 (n = 39) and 1 (n = 40).

Discussion

In our study tibial plateau levelling osteot-omy procedures utilizing 1.9/2.5 mm coni-cally-coupled locking TPLO plates in 79 stifles of small breed dogs were evaluated. Mean (± SD) preoperative TPA was 29.0 ± 3.4°, postoperative TPA was 5.8 ± 2.5°, and six to eight weeks postoperative TPA was

i FIXIN® V2021 and V2007, Intrauma S.r.l., Rivoli, Italy





challenging. For this reason, the L-shaped plate was designed to ensure appropriate osteotomy fixation and plate placement parallel to the caudal cortex of the tibial diaphysis. Furthermore, temporary stabili-zation prior to plate fixation is possible in some platesi by inserting Kirschner wires through additional plate holes, but was never performed in our study.

Tables reporting the saw blade size and the implant used in relation to the body weight can be used as guidelines when per-forming tibial plateau levelling osteotomy in small breed dogs using these plates. Care must be taken not to undersize the implant, as it happened in one of our cases. A 1.2 mm L-plate broke three weeks after surgery in a 12 kg mixed breed dog. This finding suggests that the use of the 1.2 mm L-plate should be limited to dogs weighing less than 12 kg. Finally, factors other than weight, such as bone size, bone quality, age, conformation of the tibia, and osteotomy placement have to be considered when choosing the type of implant.

High TPA need increased rotation of the proximal fragment that may result in ti-bial tuberosity fractures. Risk factors for this include a thin postoperative tibial crest, a postoperative increase in TPA, a gap in the cranial aspect of the osteotomy after fixation, a single-session bilateral ti-bial plateau levelling osteotomy procedure, and lack of osteotomy planning (43–46). Also, a lack of caudal buttress support due to rotation beyond the point of patellar ligament insertion was proposed as a risk factor, but this was not confirmed by an-other study (22, 43).

Postoperative tibial tuberosity width greater than 10 mm has been suggested to be critical in avoiding tibial tuberosity frac-tures in large breed dogs, but not in small breed dogs (24, 43). The tibial crest in dogs in our study population was usually promi-nent, but rarely fractured, even in extreme rotations (maximum TPA: 38.00°) of the ti-bial plateau. Rotation beyond the patellar ligament insertion was performed in 38/79 stifles without major complications, sug-gesting that this condition is not a risk fac-tor for tibial tuberosity fracture in small breed dogs. An inappropriately placed os-teotomy resulting in a narrow tibial crest

was considered to be the cause of a tibial tuberosity fracture in one dog in our study.

Mean postoperative change in TPA was 1.4 ± 1.6°, which supported previous evi-dence that use of a locking plate results in improved maintenance of TPA compared with non-locking systems (24–26). A mini-mum of two bicortical locking screws per fragment are typically recommended (47). The locking plates used in our study allow-ed two screws in each fragment, except in one stifle, as the caudal screw in the proxi-mal fragment was found to be broken at 16 weeks. This complication occurred three times in another study and has been at-tributed to the steep TPA in small breed dogs and the increased degree of rotation causing the proximal fragment to displace more caudally (24). The caudal part of the construct has been suggested to be initially non-load sharing, potentially explaining the propensity for failure of the screw at this point (24).

Plate removal was performed in two stifles, because of infection, which has been reported as a complication in 3.6% to 8.4% of tibial plateau levelling osteotomies (48–50). A multi-resistent Staphylococcus aureus was isolated in one stifle following surgical correction of a tibial tuberosity fracture. The other stifle had an infection that was associated with implant failure.

While complication rates in previous studies reported 14.8% to 28% for tibial plateau levelling osteotomies using conven-tional plates in large breed dogs, 9.7% to 11.4% for tibial plateau levelling osteot-omies using both conventional and locking plates in large breed dogs, and 36% in small-and medium sized dogs, we observed an overall complication rate of 15.2% (12/79 dogs presented complications) (26, 33, 41, 45, 51–53). The use of different defi-nitions and classification of complications could certainly explain complication rate differences between retrospective studies, making it difficult to directly compare re-sults of each study. Nevertheless, unlike comparable retrospective studies, no pre-disposing factor for postoperative compli-cations was found (33, 41, 45, 51–53). Pre-viously reported risk factors include breed, sex, body weight, arthrotomy, complete ligament ruptures and a TPA greater than 30°.

Other types of locking plates for small breed dog tibial plateau levelling osteotomy have been developed recently. The Synthes plates stabilize the osteotomy with three screws in each fragment and have combi-holes that may be used to provide inter-fragmentary compression. Thus, Synthes TPLO locking plates theoretically offer im-proved stability of the fixation. Because of the often small size of the proximal tibial fragment, placement of three screws can be technically demanding. The plates used in our study provided adequate stability with just two screws in each fragment, which re-sulted in healing of all the osteotomies, ex-cept for two stifles.

In our opinion, advantages of the Fixin® TPLO plates include the plate thickness. Due to the presence of a bushing insert, the thickness required for adequate conical coupling is not related to the plate thick-ness. This allows implants to be thin. Com-pared to the 2.0/2.4 Synthes® TPLO plates (2.3 mm thickness), Fixin® plates have a plate thickness of 1.2 mm or 1.5 mm. Thin implants are less stiff and much easier to contour and are ideal for distal extremities where there is less soft tissue coverage. However this could predispose to plate breakage.

Several limitations should be considered when interpreting the data of this study. The retrospective nature of our study rep-resents a main limitation. Furthermore, clinical outcome assessment methods were limited to physical and radiographic exam-inations that were performed by one sur-geon. Limited data on outcome was toler-ated, as the focus of our study was on the technical feasibility of 1.9/2.5 mm Fixin® TPLO plates in small breed dogs, rather than on the clinical outcome. No objective assessments of limb use, such as force-plate analyses and kinematic gait evaluations, were obtained. Therefore, these findings have to be interpreted in light of this lack of objective data.

In summary, the tibial plateau levelling osteotomy procedure was performed in small breed dogs using 1.9/2.5 mm Fixin® plates. Short-term complications included a tibial tuberosity fracture associated with an inadequate osteotomy placement and a plate breakage. Plate removal as part of an infection treatment was performed in two




7G. Cosenza et al.: A clinical and radiographic retrospective assessment

cases, one of which was associated with screw failure. Complication rate is com-parable to large breed dogs, but no predis-posing factor for postoperative compli-cations was found. The Fixin® locking plates used in this study resulted in suc-cessful osteotomy healing of 77 out of 79 osteotomies, and were considered to be a valid choice for the stabilization of tibial plateau levelling osteotomy in small breed dogs.

Conflict of interest

The authors declare no conflict of interest related to this report.

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tibial plateau levelling osteotomy in 69 small breed dogs ... · small plate contouring...

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