Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

Abstract

BACKGROUND CONTEXT Proximal junctional kyphosis (PJK) is a significant concern following long posterior spinal fusion. Biomechanically, proximal hook placement at the upper instrumented vertebra have been shown to allow a more gradual transition to normal motion compared with pedicle screws in a long posterior instrumented spinal fusion. PURPOSE The purpose of this study was to evaluate the risk of developing proximal junctional kyphosis with sublaminar hooks versus pedical screw fixation at the upper instrumented vertebra of a posterior spine fusion for adult spinal deformity. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE Consecutive patients who underwent elective posterior spinal fusion for adult deformity at a single academic institution from 2008 to 2014 with a minimum of 2years of follow-up were identified. Patients with proximal hooks and those with proximal screws were separated into 2 groups. OUTCOME MEASURES Preoperative, first postoperative, and final postoperative standing radiographs were reviewed. Radiographic assessments included: sagittal vertical axis (SVA), pelvic incidence, lumbar lordosis, thoracic kyphosis, T1 pelvic angle (TPA) and kyphosis at one- and two-levels above the upper instrumented vertebra (UIV+1, UIV+2). Two common methods of assessing PJK were used. At two levels above the upper instrumented vertebra (UIV+2), kyphosis greater than 10° and more than a 10° increase from the preoperative film was defined as PJK. At UIV+1, PJK was defined as a greater than 15° increase from the preoperative film. METHODS Multivariate logistic regression was used to test the association between proximal hooks and development of PJK while controlling for differences in patient and operative characteristics. RESULTS A total of 142 patients fulfilled inclusion criteria. Average follow-up was (52.8 ±29.1 months). There were no significant differences in demographic characteristics between the 2 groups. Patients with sublaminar hooks at the UIV presented with significantly fewer instances of PJK using UIV+1 (44.0% vs. 63.1%; p=.029) and UIV+2 (52.0% vs. 76.1%; p=.048) measurements compared to those who received pedicle screws at the UIV. Patients with laminar hooks experienced a significantly greater increase in SVA from preoperative to immediate postoperative (13.6±11.6 mm vs. 1.8±12.4 mm; p CONCLUSIONS Laminar hooks at the upper instrumented vertebra were associated with reduced rates of PJK compared with pedicle screws in patients who undergo deformity-correcting spine fusion for adult spinal deformity. This information may be useful for operative planning to minimize the occurrence of PJK after adult deformity surgery.