Predictive Factors for a Poor Surgical Outcome With Thoracic Ossification of the Ligamentum Flavum by Multivariate Analysis A Multicenter Study

Study Design. Retrospective multi-institutional study. Objective. The purpose of this study was to describe the surgical outcomes in patients with ossification of the ligamentum flavum (OLF) and determine the influence of an ossified anterior longitudinal ligament (OALL) on the clinical features and surgical outcomes in thoracic OLF. Summary of Background Data. Detailed analyses of surgical outcomes of thoracic OLF have been difficult because of rarity of this disease. Methods. We identified 96 patients (77 males and 19 females with a mean age at surgery of 63.4 +/- 10.3 yr) who underwent surgery for thoracic OLF and investigated their preoperative symptoms, severity of symptoms and myelopathy, disease duration, magnetic resonance imaging and computed tomographic findings, surgical procedure, intraoperative findings, and postoperative recoveries. The presence of OALL found at or near the most severely affected OLF level on sagittal computed tomographic images was classified into 1 of the following 4 types: (1) "no discernible type" (type N); (2) "one-sided type" (type O); (3) "discontinuous type" (type D); and (4) "continuous type" (type C). Multivariate logistic regression analysis was used to compute odds ratios and 95% confidence intervals to identify the risk factors associated with surgical outcomes. Results. The mean Japanese Orthopaedic Association score was 5.6 points preoperatively and 7.8 points 2 years postoperatively, yielding a mean recovery rate of 44.6%. Disease duration, presence of ossified dura mater, and type D OALL were the important factors for predicting surgical outcomes. Conclusion. After evaluating surgical outcomes on the largest sample size of OLF surgical procedures thus far, our results show that disease duration, ossification of the dura mater, and the presence of type D OALL were risk factors related to surgical outcomes.