Risk Factors for PJK After Posterior Long-Segment Internal Fixation for Chronic Symptomatic Osteoporotic Thoracolumbar Fractures with Kyphosis

Background: This study aimed to analyze the risk factors for proximal junctional kyphosis (PJK) for patients with chronic symptomatic osteoporotic thoracolumbar fractures (CSOTLF) and kyphosis who underwent long-segment internal fixation. Methods: : We retrospectively reviewed the records of patients with CSOTLF complicated with kyphosis who underwent posterior multilevel internal fixation in our hospital between January 2013 and June 2018. The patients’ age, sex, body mass index (BMI), bone mineral density (BMD), smoking status, cause of injury, comorbidities, injury segments, and American Spinal Injury Association (ASIA) grading non-surgical data; posterior ligament complex (PLC) injury, upper and lower instrumented vertebral position (UIV and LIV, respectively), number of fixed segments surgical data, proximal junctional angle (PJA), sagittal vertebral axis (SVA), pelvic incidence (PI), lumbar lordosis (LL), pelvic incidence-lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), and sacral slope (SS) surgical indicators were collected. Patients were divided into postoperative PJK and non-PJK groups. Results: : This study included 90 patients; among them, 30 (31.58%) developed PJK postoperatively. All patients were followed up for >24 months (mean 32.5 months). Univariate analysis showed significant differences in age, BMI, BMD, PLC injury, UIV, and LIV fixation position, number of fixation stages, and preoperative PJA, SVA, PI-LL, and SS between the two groups (P 0.05). Multifactorial logistic regression analysis showed that age >70 years (OR=32.279, P28 kg/m 2 (OR=7.876, P<0.05), BMD T value <-3.5 SD (OR=20.836, P<0.05), PLC injury (OR=13.981, P20° (OR=13.301, P<0.05) were risk factors for PJK after posterior long-segment internal fixation in elderly patients with CSOTLF complicated with kyphosis. Conclusions: : Elderly patients with CSOTLF and kyphosis aged >70 years with BMI >28 kg/m 2 , BMD 20°, and PLC injury have increased risk of PJK after posterior long-segment internal fixation. Considering these findings, weight control, osteoporosis treatment, soft tissue protection, and spinal sagittal balance restoration are important to prevent PJK.