Proximal Junctional Failure After Adult Spinal Deformity Surgery

Study Design. Systematic review and meta-analysis Objective. To identify patient-related, operative, radiographic, and bone quality predictive risk factors associated with proximal junctional failure (PJF) following adult spinal deformity (ASD) surgery and evaluate diagnostic performance of opportunistic CT-derived bone quality metrics. Summary of Background Data. PJF is a severe complication of ASD correction associated with pain, deformity progression, and reoperation. While numerous risk factors have been proposed, reported associations are inconsistent, and clinical utility of opportunistic bone quality assessment remains uncertain. Methods. PubMed, Embase, and CENTRAL were searched from inception to January 2026. Observational studies reporting PJF after ASD surgery with extractable comparative data were included. Random-effects meta-analyses were used. Diagnostic accuracy of Hounsfield unit measurements was summarized using pooled sensitivity, specificity, and area under curve (AUC). Results. Twenty-eight studies encompassing 4560 patients were included, of whom 1064 (23.3%) developed PJF. Patients with PJF were older (MD 2.59 y, P <0.001) and had worse baseline disability and pain. Binary osteoporosis status was not consistently associated with PJF, though continuous bone measures were predictive, including lower DEXA T-scores (MD -0.55, P <0.001), and CT attenuation at upper instrumented vertebra (MD -28.97 units, P <0.0001) and immediately cranial adjacent vertebra (MD -32.67 units, P <0.0001). Radiographically, PJF was associated with greater preoperative sagittal misalignment, including higher pelvic tilt and sagittal vertical axis, lower lumbar lordosis, and greater pelvic incidence-lumbar lordosis mismatch. Fusion length and upper instrumented level (dichotomized at T10) were not significantly associated with failure. Hounsfield units demonstrated good diagnostic performance (pooled AUC 0.86). Conclusion. PJF after ASD surgery reflects the interaction between sagittal misalignment, correction strategy, and junctional structural capacity. Continuous bone quality measures, particularly opportunistic Hounsfield unit assessment, show potential for risk stratification and may inform targeted preventive strategies in biologically vulnerable patients, pending prospective validation.