P100. Upper instrumented vertebral pelvic angle and risk of proximal junctional kyphosis at 2- year follow-up

Abstract

BACKGROUND CONTEXT There remains a need for practical radiographic parameters to help predict risk of proximal junctional kyphosis (PJK) in adult patients undergoing multilevel posterior fusion. The upper instrumented vertebral pelvic angle (UIVPA) is a novel measure of sagittal alignment that is easy to measure and can account for both spinal inclination and pelvic retroversion. We hypothesize that the further the UIV is from the center of gravity, the higher the risk of PJK. PURPOSE The purpose of this study is to evaluate the association between UIVPA and risk of PJK in adult patients undergoing 6-level fusion. STUDY DESIGN/SETTING Retrospective cohort study at single academic institution. PATIENT SAMPLE Adult patients with minimum two-year follow-up who underwent ≥6 level posterior spinal fusion. OUTCOME MEASURES PJK, proximal junctional failure (PJF). METHODS In this retrospective cohort study, adult patients with two-year follow-up and ≥6 levels of posterior fusion for spinal deformity were included. The UIVPA was measured between a line from the UIV centroid to the center of the femoral head to a line from the center of the sacrum to the center of the femoral head. PJK was defined as a >10° kyphotic angle between the UIV and the vertebra 2 levels above. Proximal junctional failure (PJF) was defined as PJK that required surgery. Patients who developed PJK and those who did not were compared with respect to UIVPA, T1 pelvic angle (T1PA), pelvic tilt, sagittal vertical axis and central sacral vertical line. RESULTS There were 291 patients with an average 3.0 years follow-up enrolled in the study. Fifty (17%) patients were diagnosed with PJK and 29 (10%) qualified for PJF. The average UIVPA for all patients was 19.5° preop. Patients with PJK had significantly higher preoperative UIVPA than those without PJK or PJF (25.6 vs 16.2 p CONCLUSIONS UIV pelvic angle correlates well with established measures of sagittal spinopelvic alignment, such as T1PA, SVA and pelvic tilt. Patients with PJK and PJF at least two years from surgery were more likely to have a significantly higher preoperative UIVPA than their counterparts. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.