225. Global alignment and proportion score does not predict proximal junctional kyphosis

Abstract

BACKGROUND CONTEXT Proximal junctional kyphosis (PJK) is a devastating complication of adult spinal deformity (ASD) surgery. Optimal alignment specifications to maximize quality of life while limiting PJK have yet to be defined. Previous studies have primarily examined sagittal vertical axis (SVA) to determine likelihood of PJK. More recently, other alignment parameters such as thoracic-pelvic angles (TPAs) and age-adjusted alignment have been examined. PURPOSE The goal of this study is to examine the relationship between GAP, TPAs, and bracing with likelihood of developing PJK. STUDY DESIGN/SETTING A retrospective chart review was conducted to identity ASD patients with at least 1 year of radiographic follow up. PATIENT SAMPLE Patients who underwent fusions to the pelvis and >4 levels fused from 2013 to 2018 and have 1-year postoperative alignment x-rays were included. OUTCOME MEASURES The rate of radiographic PJK (change of 10-20°) and severe PJK (change>20°) was determined for each group. Reoperation rates were also collected. METHODS Surgical records were reviewed to determine patient sample. Chart and X-ray review were conducted to determine spinopelvic alignment parameters, GAP scores, bracing, and reoperation. X-rays were reviewed up to one year postoperatively in order to determine PJK. RESULTS A total of 81 patients were included (mean 64y 63%F); baseline and 1-year postoperative alignment did not differ between PJK and no PJK patients. There was no PJK in 53.1%, 30.9% had PJK from 10-20°, and 16% had sPJK. Of these, 7 patients had revision surgery: 1 for PJK and 1 for rod fracture. Postop bracing was used in 54% of patients. There was no difference in sPJK according to brace use. At baseline, 79% of patients had severely disproportioned GAP, 16% moderate, 5% proportioned. Of severely disproportioned, 63% had no change in GAP at 1 year. Improved GAP was not associated with sPJK (improved: 22% vs no change: 18%, p=.72). Greater correction of the UIV-PA was associated with a larger PJK angle change (R=.26) as was the 1 year T1-UIV angle (R=.30), both p .05. CONCLUSIONS There was no correlation between PJK and GAP alone or change in GAP; it is notable that these patients tended to be disproportioned pre and postop. Greater correction of UIV-PA and larger postop T1-UIV was associated with greater PJKA change; suggesting that the greater alignment correction led to greater likelihood of it failing. Our data suggest bracing was not effective in preventing PJK. These parameters may help surgeons understand alignment targets in ASD. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.