21SProceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

initial fixation of the uppermost screw or hook and start of correction from

there by either cantilever or compression maneuvers exert much more

stress force on interspinous and supraspinous ligaments of adjacent

segment creating tension on facet joint capsule leading to subluxation of

the joint. Our new approach is that fixation and start of correction one level

below the uppermost screw secure the adjacent segment and prevent stress

force in the segment adjacent to most proximal instrumented segment.

PURPOSE: To determine whether our new surgical strategy prevents proxi-

mal junctional kyphosis or not in surgical treatment of Scheuermann kyphosis.

STUDY DESIGN/SETTING: Retrospective comparative study.

PATIENT SAMPLE: Between the years of 1996 and 2007, 37 adolescents

with Scheuermann disease undergoing surgery were included in the study.

OUTCOME MEASURES: From the immediate postoperative and last

follow-up standing AP radiographies; proximal junctional angle was calcu-

lated and compared. Proximal junctional angle is defined as the cranial

endplate of the upper instrumented vertebrate to the cranial endplate of

one vertebrate above. Proximal junctional kyphosis was defined if proxi-

mal junctional angle O 10 degrees and at least 10 degrees greater than

the corresponding preoperative measurement.

METHODS: In all patients, the upper instrumented vertebra was T2. In the

group1 (13 patients), after placing pedicle screws or hooks, correction has

started from T2 to going down with cantilever and segmental compression

maneuvers. In the group 2 (24 patients), after placing pedicle screws or hooks,

instead of upper most segment; locking was started from one below vertebra

(T3 in our cases) and going down to distal segments. Correction was done by

cantilever and segmental compression maneuvers in the main thoracic defor-

mity as previously defined. After finishing correction, loose T2 pedicle screws

or hooks were fixed to rod in situ, without applying any corrective force.

RESULTS: The mean postoperative follow-up was 54 (24-112) months. All

patients were male and the average age was 17.5 years. The mean preopera-

tive kyphosis angle was 82 degrees in group 1 and 84 in group 2. The mean

postoperative kyphosis angle in groups 1 and 2 were 32.5 and 29 respectively.

Four of 13 patients in group 1 showed PJK of more than 10 degrees (mean of

18 degrees) and the proximal junctional angle changed only 3 degrees in

favor of kyphosis during the postoperative follow-up period in group 2. There

were no infection, pseudoarthrosis and neurological complications seen

during follow-up period.

CONCLUSIONS: We have compared the efficacy of our technique with

classical correction technique in terms of prevention of PJK. While 4 of

13 (30%) patients with classical technique developed PJK (3 of them were

reoperated), no PJK was seen in patients in whom our new approach was

performed. Besides the traditional methods for prevention of PJK, above

defined strategy will prevent the mechanical failure at the uppermost

instrumented segment. Our clinical and radiological results with this tech-

nique supports the efficacy of our new approach.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.049

40. Pedicle Screw vs. Hybrid/Hook Instrumentation for Lenke Type

1 and 2 Adolescent Idiopathic Scoliosis: What Happens When

Judges are Blinded to the Instrumentation?

Vincent Arlet, MD1, Jean Ouellet2, Kirkham Wood, MD3, Francis Shen,

MD1, Donald Chan, MD1, Shilt Jeffrey, MD4, Ernesto Bersusky, MD5,

John Hicks, MD1, Vasantha Reddi, PhD1; 1University of Virginia,

Charlottesville, VA, USA; 2McGill University, Montreal, Quebec, Canada;3Massachusetts General Hospital, Boston, MA, USA; 4St Alphonsus

Regional Medical Center, Boise, ID, USA; 5Hospital De Pediatria

Garrahan, Buenos Aires, Argentina

BACKGROUND CONTEXT: The superiority of pedicle screws over hy-

brid/hooks in the treatment of adolescent idiopathic scoliosis of Lenke 1

and 2 remains unresolved.

PURPOSE: The purpose of this study is to compare pedicle screws with

hybrid/hook instrumentation in the treatment of adolescent idiopathic

scoliosis, Lenke types 1 and 2, with special attention to cosmesis and un-

instrumented spine.

STUDY DESIGN/SETTING: Retrospective Study of prospectively col-

lected data of patients with adolescent idiopathic scoliosis treated with ei-

ther pedicle screw or hybrid/hook instrumentation.

PATIENT SAMPLE: A total of 38 patients taken from our database of sur-

gical cases of adolescent idiopathic scoliosis were included in this study.

OUTCOME MEASURES: Outcomes of surgery with the two instrumenta-

tion techniques were evaluated using (a) Subjective measures: Overall radio-

graphic result, radiographic result of uninstrumented spine and Cosmesis

including overall cosmetic result, shoulder balance, trunk shift, rib hump,

and waist asymmety before and after surgery; (b) Objective measures: Cobb

angle of instrumentend and uninstrumented spine, number of fused verte-

brae, global and sagittal balance, tilt of last instrumented vertebrae, and disc

angulation; (c) Health-related quality of life through SRS-24 questionnaire.

METHODS: Radiographs and clinical photos of 38 cases of thoracic AIS

of Lenke 1 and 2, treated with either pedicle screws or hybrid/hooks were

subjectively assessed by four spine surgeons (SRS Travelling Fellows) for

radiographic and operative cosmetic result, shoulder balance, trunkshift,

rib hump and waist asymmetry. Instrumentation in the radiographs was

blocked, with only the non-instrumented part visible. Surgeons were also

asked to guess the instrumentation in the radiographs. Seventy six photo-

graphs of patients before and after surgery were assessed for cosmesis by

ten non-medical judges for overall cosmetic score, overall balance, shoul-

der balance, waist asymmetry and shoulder blade prominence. Objective

assessment of radiographs and clinical photos were performed for Cobb

angle of instrumented and non-instrumented spine, global coronal and sag-

ittal balance, number of unfused vertebrae, disc angulation, tilt of last in-

strumented vertebra, shoulder balance, waist asymmetry, rib prominence

and percent correction. SRS-24 questionnaire was used to measure

health-related quality of life in patients.

RESULTS: Subjective assessments by surgeons and non-medical judges

showed no significant difference by instrumentation (p$0.05) for all variables.

Out of the 152 guesses by surgeons of the cases with instrumentation blocked in

the radiographs, they were unable to guess the instrumentation in 89% of the

cases. Objective assessment of all variables and SRS-24 scores of all 5 domains

showed no significant difference by instrumentation (p$0.05).

CONCLUSIONS: In this first-ever conducted study in a blinded fashion,

subjective and objective assessments and SRS-24 scoring showed no sig-

nificant difference between the instrumentations used to treat AIS for

Lenke 1and 2 curves. Superiority of one instrumentation over the other

could not be established.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.050

41. Rod Strength: Is it an Important Factor in Coronal and Sagittal

Realignment after Surgery for Adolescent Idiopathic Scoliosis?

Suken Shah, MD1, Peter Newton, MD2, Baron Lonner, MD3,

Harry Shufflebarger, MD4, Tracey Bastrom, MA5, Michelle Marks, PT6;1Wilmington, DE, USA; 2Rady Children’s Hospital and Health Center -

San Diego, San Diego, CA, USA; 3New York University, New York, NY,

USA; 4Miami Children’s Hospital, Miami, FL, USA; 5Rady Children’s

Hospital, San Diego, CA, USA; 6Harms Study Group Foundation, Tucson,

AZ, USA

BACKGROUND CONTEXT: With modern instrumentation, significant cor-

onal correction of a structural spinal deformity is possible. A side effect of pow-

erful segmental correction of AIS with pedicle screws is induction of

hypokyphosis in the thoracic spine. In an effort to mitigate the ‘‘hypokyphos-

ing’’ effect ofpedicle screws, surgeons may choose touse rods withhigheryield

strength in order to pull the spine dorsally into kyphosis with a contoured rod.

PURPOSE: The purpose of this study was to evaluate if higher strength

rods provide better coronal and sagittal plane restoration in patients with

Adolescent Idiopathic Scoliosis (AIS).

22S Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

STUDY DESIGN/SETTING: Patient data from a multicenter, prospec-

tive database was evaluated.

PATIENT SAMPLE: Patients with preoperative thoracic kyphosis (T5-

T12) less than 20� who underwent posterior spinal fusion for AIS with

segmental pedicle screw instrumentation (N 5 247) were included in this

analysis.

OUTCOME MEASURES: Radiographic data preoperatively and postop-

eratively were compared.

METHODS: Four groups based on the type of rods used (5.5 mm):

titanium (Ti), standard stainless steel (SS), high strength (HS SS), and ultra

high strength (UH SS) were analyzed.

RESULTS: When corrected for flexibility, coronal curve correction wassimilar

among the SS groups (74%) and significantly better than Ti (58%) (p!0.001). In

the sagittal plane, all rod types were able to improve kyphosis (p!0.01), espe-

cially the ultra high strength stainless steel (UH SS) rods (10.6� to 16.1�), but the

difference among rod types was not significant, likely due to variability in the Ti

group. There were no complications of the higher strength rods, such as screw

pullout or instrumentation failure. In one and two-year follow up, there was no

significant of loss of correction in any of the groups.

Figure. Illustation of kyphosis restoration by rod type (Std SS 5 Standard SS, HS SS 5

High strength SS, UH SS 5 Ultra High strength SS, Ti 5 Titanium).

CONCLUSIONS: Yield strength of rods used in the surgical correction of

AIS is an important biomechanical consideration. While rod contouring

and derotation may also be important, the choice of rod strength appears

to affect the outcome of postoperative correction. Higher strength rods

are more effective in coronal and sagittal plane restoration of deformities.

Stainless steel performs better than titanium when evaluating segmental

pedicle screw constructs, even in the challenging scenario of kyphosis

restoration with posterior surgical techniques in the hypokyhotic patient.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.051

42. Low Profile Pelvic Fixation Using S2 ALAR Iliac (S2AI) Fixation

in the Pediatric Population Improves Results at 2-Year Minimum

Follow-Up

Paul Sponseller, MD1, Ryan Zimmerman, MD1, Phebe Ko2,

Khaled Kebaish, MD1, Albert Pull Ter Gunne, MD1, Ahmed Mohammed,

MD1, Tai-Li Chang1; 1Johns Hopkins University, Baltimore, MD, USA;2Baltimore, MD, USA

BACKGROUND CONTEXT: Anchor stability and prominence are prob-

lems with pelvic fixation in pediatric spinal deformity surgery. A new method

of iliac fixation with a starting point in the S2 ala offers in-line anchors that

are deep under the midline muscle flap.

PURPOSE: The purpose of this study was to report the clinical results of

this technique. Specific attention was paid to correction of pelvic obliquity,

anchor prominence and need for revision surgery, in order to compare this

technique to prior methods of iliac fixation.

STUDY DESIGN/SETTING: Prospective cohort study in a large, tertiary

care center associated with a major teaching hospital. Consecutive patients

operated on by a single, senior orthopaedic surgeon were included.

PATIENT SAMPLE: Thirty-two consecutive patients with the S2AI tech-

nique and O2y follow-up were studied. Diagnoses were 23 cerebral palsy,

2 myelomeningocele, and 7 syndromic. Fusion was 15.8 levels (SD 2.7, R

12-18). S2AI patients were compared with 17 prior patients who had pel-

vic fixation using traditional sacral and iliac screws.

OUTCOME MEASURES: Outcomes included coronal and pelvic obliq-

uity correction, sacropelvic pain, screw placement, implant prominence,

radiographic lucency, need for revision and infection.

METHODS: Clinical examinations, hospital records, radiographs and CT

scans were analyzed. Student’s paired t-tests were used to assess statistical

significance.

RESULTS: Mean age at surgery was 14.3 y (R 9.8-19.3). S2AI screws were

67 mm (R 45-85) in length (Fig 1) and 7-9 mm in diameter. Pelvic obliquity

was corrected 21.162.3� (74%) using the S2AI technique and 11.462.5�

(52.9%) using traditional iliac screws. Cobb angle correction was

48.764.5� (73%) using the S2AI technique and 51.163.1� (63%) using tra-

ditional iliac screws. S2AI fixation had better pelvic obliquity correction

(p50.03) but there was no difference in Cobb correction. Three of 64 screws

showed adjacent lucencies of 1.3 mm (R 1.0-2.0). CT scans of 23 patients

showed no intrapelvic protrusion, but three screws protruded laterally (all

!5 mm). One early patient required revision to bilaterally longer iliac screws

to relieve pain. There were 2 superficial infections in the S2AI group and 1

deep infection in the traditional group. No S2AI patient had implant promi-

nence, skin breakdown or anchor migration versus 3 in the traditional group.

CONCLUSIONS: S2AI pelvic fixation produces satisfactory results with

improved correction of pelvic obliquity and fewer clinical complications

than prior techniques. Radiographic and clinical anchor stability is satis-

factory at two year follow-up.

Figure. Pre- (A) and postoperative (B) AP radiographs showing pelvic fixation using

the S2AI technique with excellent correction of coronal curvature and pelvic obliquity

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.052