Saturday, September 29, 2018 10:30 am–12:00 pm Applying Deformity Concepts in Your Practice

Abstract

BACKGROUND CONTEXT Proximal junctional failure (PJF) is a serious complication following ASD surgery. Patients undergoing caudal extension of fusion and spinal realignment may be at decreased risk of PJF if there is a new upper instrumented vertebra (UIV). PURPOSE To determine if patients with an existing instrumentation constructs undergoing distal extension of fusion have decreased rates of PJF. STUDY DESIGN/SETTING Retrospective cohort study with propensity matching of prospectively collected multicenter patient data. PATIENT SAMPLE A total of 754 adult spinal deformity patients. OUTCOME MEASURES Proximal junctional failure. METHODS Prospective multicenter cohort of 754 adult patients undergoing thoracolumbar fusion for ASD were analyzed. A total of 41 patients undergoing distal extension of or osteotomy through prior fusion with an unchanged UIV were identified. PJF was defined as either proximal junction (PJ) angle ≥ 28.0° and Δ PJ angle ≥21.6°) or by listhesis. Propensity score matching was performed for unaltered UIV patients and new UIV patients for age, BMI, number of levels fused, UIV, frailty score, ΔSVA, Δ PI-LL and ΔTPA and were compared for rates of PJF. RESULTS Patients with an unaltered UIV had a 0% rate of radiographic PJF, compared to 13.8% of those with a new UIV (p=.012). Mean time to PJF was 11.2 months (range: 0.5-33.7). Prior to propensity matching, unaltered UIV patients had worse sagittal malalignment with a higher PI-LL (27.0 vs. 16.6; p=.003), and SVA (90.6 mm vs. 68.5 mm; p=.073) and underwent larger sagittal alignment correction (ΔSVA −55.6 mm vs. -43.1 mm; p=.049). After propensity matching, all radiographic and demographic parameters were similar (p>.05), and PJF rates remained lower in the unaltered UIV patients compared to the new UIV patients (0% vs. 8.5%; p=.009) CONCLUSIONS Despite worse preoperative sagittal deformity and larger operative correction, patients undergoing distal extension of fusion with unaltered upper instrumented vertebra (UIV) experienced a 0% rate of proximal junctional failure, compared to 13.8% of ASD patients undergoing surgery with a new UIV (p=.01), This study suggests that the etiology of PJF includes acute soft tissue trauma and lack of adjacent segment bony remodeling as contributing factors. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.