P95. A comparative analysis of thoracic decompensation versus proximal junctional kyphosis in response to adult spinal deformity corrective surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> Thoracic decompensation (TD) represents a distinct radiographic complexity from proximal junctional kyphosis (PJK). Few studies exist on the occurrence of TD following adult spinal deformity (ASD) corrective surgery. <h3>PURPOSE</h3> To assess the incidence of TD following ASD-corrective surgery in comparison with the occurrence of PJK. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort. <h3>PATIENT SAMPLE</h3> A total of 689 ASD patients. <h3>OUTCOME MEASURES</h3> ASD, TD, PJK, thoracic compensation. <h3>METHODS</h3> ASD patients with complete baseline (BL) and two-year (2Y) followup were included. Patients were divided into groups: those who developed TD: T4-T12 >54.2° and those who developed PJK. Further analysis assessed outcomes among patients with both TD and PJK (TDPJK). Thoracic compensation was defined as expected thoracic kyphosis minus BL thoracic kyphosis. Means comparison tests and multivariable logistic regression analysis assessed differences between patient groups. <h3>RESULTS</h3> A total of 373 patients met inclusion criteria. Patient breakdown by radiographic outcome was: TD (N=31), PJK (N=223) and TDPJK (N=119). Age, gender, and ASD-mFI were similar between TD and PJK patients. TD patients were more likely to be osteoporotic than PJK patients, p < 0.05. Procedures on TD patients were less invasive and utilized a shorter construct (9.3 vs 11.5 levels; both p < 0.05). TD patients had significantly greater cervical lordosis, thoracic kyphosis, and lumbar lordosis than PJK patients at BL and 2Y follow-up, all p < 0.05. Thoracic compensation was significantly associated with TD (OR 1.07 [CI 1.04-1.09], p < 0.001) controlling for age, ASD-mFI, and invasiveness. TDPJK had the highest complication rate (84.9%), significantly greater than PJK patients (70.9%), and TD patients (61.3%), both p < 0.05. PJK patients were 78.7% less likely to develop PJF than TDPJK patients (OR 0.213 [CI 0.101-0.453], p < 0.001). <h3>CONCLUSIONS</h3> Patients who developed thoracic decompensation were more likely to present with osteoporosis, but had less invasive procedures and levels fused than patients with proximal junctional kyphosis. The tradeoff between fusing too much resulting in proximal junctional kyphosis and fusing too little predisposing to thoracic decompensation can serve as the basis of future studies to determine optimal construct length to balance these two risks. Thoracic compensation was predictive of postoperative thoracic decompensation in adult spinal deformity-correction. Patients who developed TDPJK had the highest rate of complications and greater odds of junctional failure. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.