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

Abstract

BACKGROUND CONTEXT Postoperative reciprocal changes (RC) associated with varying factors of PJK in ASD fusions of the lumbo-pelvic spine are poorly understood. PURPOSE The aim of this study was to explore RC in the cervical spine associated with varying factors (severity, onset, patient age, and need for revision) of proximal junctional kyphosis (PJK) in patients undergoing corrective lumbo-pelvic fusions. STUDY DESIGN/SETTING Retrospective review of a prospectively, consecutively enrolled multicenter adult spinal deformity (ASD) database. PATIENT SAMPLE A total of 284 ASD patients. OUTCOME MEASURES RC parameters included cervical sagittal vertical axis (cSVA), c2 slope (C2S), T1 slope minus cervical lordosis (TS-CL), cervical lordosis (CL) and thoracic kyphosis (TK). METHODS Inclusion: ASD patients >18 y/o, undergoing fusions from the thoracic spine (UIV: T6–T12) to the pelvis with one year and two years radiographic follow-up data. ASD was defined as: coronal cobb angle ≥20°, sagittal vertical axis ≥5 cm, pelvic tilt ≥25°, and/or thoracic kyphosis ≥60°. PJK was defined as a ≥10° measure of the sagittal Cobb angle between the inferior endplate of the UIV and the superior endplate of the UIV+2. Patients were grouped by mild (10°–20°) and severe (>20°) PJK at one-year follow-up propensity score matching (PSM) controlled for CCI, age, PI and UIV. Unpaired and paired t test analyses determined difference between RC parameters and change between time points (BL-one year, BL-two years). Pearson bi-variate correlations analyzed associations between RC parameters and PJK descriptors. Reop and no reop patients were PSM independent of PJK degree. Unpaired t tests compared change in RC parameter across groups. RESULTS A total of 284 ASD patients with lumbo-pelvic fusions extending from the mid-thoracic spine (UIV: T6: 1.1%; T7: 0.7%; T8: 4.6%; T9: 9.9%; T10: 58.8%; T11: 19.4%; T12: 5.6%) into the pelvis were studied. The severe (S: n=91) vs. mild (M: n=91) PJK analysis consisted of 182 patients. Significant difference between M and S groups were observed in TKΔ1Y (−16.8 vs. −22.8, P=.001), TS-CLΔ1Y (−.62 vs. 2.8, P=.037), cSVAΔ1Y (−1.8 vs. 1.9, P=.032), C2 slope (C2S)Δ1Y(−1.6 vs. 2.3, P=.022), and T1 slope(T1S)Δ2Y(1.9 vs. 5.5, P=.024). Correlation between age and cSVAΔ1Y (R=.153, P=.034), and incidence of reoperation within 1Y and TKΔ1Y (R=-.144, P=.029) was found. Incidence of progressive PJK correlated with TKΔ1Y (R=−.249, P=.002) and T1SΔ2Y (32.0 vs. 37.5, p CONCLUSIONS RC in unfused portions of the spine differed between individuals with mild and severe PJK at one year postoperative. Patients with severe PJK experienced increases in TS-CL, TK, cSVA and C2S between BL and one year, which differed from their mild PJK counter-parts. By two years, severe and mild groups exhibited similar amounts of change in cervical RC parameters coinciding with significant difference between the T1SΔ2Y of these groups. In patients with severe PJK, proximal adjustment of the spine localizes on the cervico-thoracic junction over time.