Predictive factors of poor surgical outcome in thoracic ossified ligamentum flavum: A multivariate analysis

Objective: Ossified ligamentum flavum (OLF) of the spine is a rare cause of compressive myelopathy. OLF is prevalent in Asian countries. Surgery is the only treatment option for symptomatic patients. The recovery after surgery depends upon multiple clinical and radiological factors and varies significantly. We report our series of surgically managed thoracic OLF and the factors predicting poor outcomes. Methods: A retrospective study was conducted including 52 patients who underwent surgery for thoracic OLF. The pre-operative clinical status, radiology findings, intraoperative observations and complications were analyzed with post-op clinical outcomes. The mean follow-up period was 24 months (range 12-72). Results: There were 35 males and 17 females with a mean age of 49.5 years (range: 30-75). The mean duration of symptoms was 13 months (range: 1 month to 5 years). The mean modified Japanese Orthopedic Association (mJOA) score was 5.8 preoperatively, 5.5 postoperatively and improved to 7.5 at the last follow-up. A good recovery rate (>50 %) was found in 18 patients, poor recovery (<50 %) in 24 patients, seven remained unchanged and three patients had worsened. In univariate analysis, the statistically significant factors for the recovery rate were the number of OLF levels, CT axial classification (tuberous type), associated OALL and cervical OPLL, T2W cord signal changes, ossification of dura mater, dural tear, and CSF leak. Dural tear and the number of OLF levels were the most predictive factors for the poor outcome on multivariate analysis. Conclusion: Predictors of poor surgical outcomes are the extent of OLF involved and dural tear. The patient improves with rehabilitation despite the immediate postoperative deterioration.