OPLL Is Associated With a CT-Defined Fracture/Dislocation-Free Injury Phenotype but Not AIS-Grade Conversion in Elderly Cervical Spinal Cord Injury

STUDY DESIGN: Retrospective multicenter cohort study. OBJECTIVE: To determine whether ossification of the posterior longitudinal ligament (OPLL) identifies a CT-defined fracture/dislocation-free injury phenotype in older patients with traumatic cervical spinal cord injury (SCI), whether midsagittal canal occupancy reflects admission neurological severity, and whether OPLL predicts AIS-grade conversion. SUMMARY OF BACKGROUND DATA: OPLL is considered a structural substrate for cervical cord injury without bony failure after trauma. However, its roles as an injury-pattern marker, severity metric, and recovery predictor remain unclear. METHODS: We analyzed 328 patients aged ≥65 years with traumatic cervical SCI from a 7-center registry. OPLL was present in 117 (36%) and classified on CT by subtype. CT-defined fracture/dislocation-free injury was the mechanistic endpoint, and ≥1-grade AIS improvement the functional endpoint. Multivariable logistic regression, multiple imputation, and center-level and energy-stratified sensitivity analyses were performed. RESULTS: OPLL-positive patients more often had fracture/dislocation-free injury (83% vs. 69%; adjusted OR 2.01, 95% CI 1.01-4.01). Estimates were consistent across sensitivity analyses, including multiple imputation (OR 2.20, 1.13-4.29), and numerically stronger after high-energy trauma (78% vs. 49%; interaction P=0.12). DISH showed the opposite association (OR 0.42, 0.20-0.89). Intramedullary T2 signal co-localized with the OPLL level in 94-98% of localizable T2-positive OPLL cases. Canal occupancy did not discriminate severe injury (AUC 0.44, 95% CI 0.29-0.59). OPLL was not associated with AIS-grade conversion (39% vs. 40%; OR 0.93, P=0.81) across sensitivity and fixed-time-point analyses. Age was the most consistent recovery predictor (OR 0.92/year, 95% CI 0.88-0.95). CONCLUSION: In older patients with traumatic cervical SCI, OPLL on emergency CT identifies a fracture/dislocation-free injury pattern and localizes the injured cord, supporting MRI evaluation of the ossified level even without fracture. OPLL neither grades severity by canal occupancy nor predicts AIS-grade conversion and is better interpreted as an anatomical rather than prognostic marker. LEVEL OF EVIDENCE: 3.