Objective       To investigate the clinical characteristics of thoracic ossification of ligamentum flavum (OLF)

and to analyze the factors influencing postoperative efficacy of thoracic OLF.      Methods       A retrospective analysis was performed in 28 patients who underwent surgical treatments to thoracic OLF in the hospital and were successfully followed up from June 2001 to June 2010. Modified Japanese Orthopedic Association (JOA) scale (maximum total score of 11) was applied to evaluate the patients’ nerve functions pre- and postoperatively and recovery rate (RR) was applied to evaluate treatment efficacy. The influencing factors on OLF efficacy were analyzed using Pearson correlation and intra-group comparison using t-test.      Results       The most common initial symptoms were numbness (78.6%) and motor dysfunction (71.4%) in the lower extremities. The pre- and postoperative JOA scores were 4.5±2.2 and 8.5±2.6 respectively (P0.05). The postoperative RR was (59.2±28.2) %

according to which the efficacy of the OLF patients were classified as 15 excellent (53.6%)

7 good (25.0%)

3 moderate (10.7%) and 3 bad (10.7%). The efficacy of thoracic OLF operation was related to the preoperative course

JOA score and intramedullary signal change

but not related to age

sex

location and the number of segmental lesion and whether complicated with other spinal diseases.       Conclusion     Preoperative course

JOA score and intramedullary signal change were important predictive factors for surgical outcome of thoracic OLF. Operations of decompression in early period could promote OLF patients’ symptoms alleviation and neurological recovery.