Outcomes of Surgery for Thoracic Myelopathy Owing to Thoracic Ossification of The Ligamentum Flavum in a Nationwide Multicenter Prospectively Collected Study in 223 Patients

Study Design. Prospectively collected, multicenter, nationwide study. Objective. The aim of this study was to investigate recent surgical methods and trends, outcomes, and perioperative complications in surgery for thoracic ossification of the ligamentum flavum (T-OLF). Summary of Background Data. A prospective multicenter study of surgical complications and risk factors for T-OLF has not been performed, and previous multicenter retrospective studies have lacked details for these items. Methods. Surgical methods, pre- and postoperative thoracic myelopathy (Japanese Orthopedic Association [JOA] score), symptoms, and intraoperative neurophysiological monitoring were investigated prospectively in 223 cases. Differences in these factors between fusion and nonfusion procedures for T-OLF were examined. The minimum follow-up period was 2 years after surgery Results. The mean JOA score was 6.2 points preoperatively, and 7.9, 8.2, and 8.2 points at 6 months, 1, and 2 year postoperatively, giving mean recovery rates of 35.0%, 40.9%, and 41.4% respectively. Posterior decompression and fusion with instrumentation was performed in 109 cases (48.9%). There were 45 perioperative complications in 30 cases (13.5%), with aggravation of motor disturbance in the lower extremities being most common (4.0%, n = 9). Patients treated with fusion had a significantly higher BMI, rate of gait disturbance, ossification occupation rate of OLF at computed tomography, and intramedullary high intensity area at magnetic resonance imaging ( P < 0.01). The preoperative JOA score was lower ( P < 0.05) and the JOA recovery rate at 1 year after surgery was significantly higher in cases treated without fusion (44.9% vs. 37.1%, P < 0.05). Conclusion. The high rate of surgery with instrumentation of 48.9% reflects the current major trend toward posterior instrumented fusion surgery for T-OLF. Fusion surgery with instrumentation may be appropriate for patients with severe OLF and preoperative myelopathy. A further prospective study of long-term outcomes is required with a focus on optimal surgical timing and the surgical procedure for T-OPLL. Level of Evidence: 3