Clinical and radiological characteristics associated with revision anterior surgery after initial posterior decompression for cervical ossification of the posterior longitudinal ligament: a time-to-event analysis.

内容摘要

Posterior decompression is widely used for cervical ossification of the posterior longitudinal ligament (OPLL) because of its technical simplicity and relatively low complication rates. However, in patients with severe anterior compression, extensive ossification, or unfavorable sagittal alignment, posterior decompression alone may be insufficient, occasionally necessitating anterior surgery. The clinical and radiological characteristics of such patients and the effectiveness of anterior revision surgical strategies remain incompletely understood. To characterize baseline clinical and radiological factors associated with the need for additional anterior surgery after posterior decompression for cervical OPLL and to evaluate neurological recovery following anterior revision surgery. Retrospective single-center cohort study. A total of 442 patients with cervical OPLL treated between 1984 and 2025 were reviewed. Among 325 patients who underwent posterior surgery, 21 required additional anterior surgery (posterior-anterior [PA] group), corresponding to 6.5% of posterior cases. For each PA case, 2 age- and sex-matched controls treated with posterior surgery alone were selected (posterior-only [P] group). Neurological function assessed using the Japanese Orthopedic Association (JOA) score, recovery after posterior surgery, additional improvement after anterior surgery, radiographic parameters (spinal canal occupation ratio, cervical alignment, OPLL type, and K-line status), and postoperative complications. Clinical and radiological data were retrospectively analyzed. JOA scores were recorded preoperatively, after posterior surgery, and, in the PA group, after anterior surgery. Radiographic assessments included cervical sagittal alignment, OPLL morphology, maximum canal occupation ratio, and K-line status. Time to anterior revision surgery was analyzed using Kaplan-Meier survival curves and Cox proportional hazards modeling with 2 prespecified variables (K-line status and canal occupancy ratio) to avoid overfitting. Patients requiring revision demonstrated more severe radiological features including a higher canal occupancy ratio and more frequent K-line (-) alignment. Neurological function improved after anterior surgery within the PA group, however, recovery was partial, consistent with salvage surgery. Cox analysis demonstrated that K-line (-) status and high canal occupancy were associated with earlier revision. Complications after anterior surgery, including cerebrospinal fluid leakage and approach-related events, were more frequent in the PA group, but no catastrophic neurological injuries occurred. Patients requiring anterior revision surgery after posterior decompression for cervical OPLL demonstrate distinct radiological characteristics, including severe canal compromise, extensive ossification, and unfavorable sagittal alignment. Anterior revision surgery provides partial neurological recovery and should be considered a salvage rather than restorative procedure.