OBJECTIVETo explore the correlation between CT classification and operative method and to discuss its therapeutic effect.

METHODSFrom January of 2001 to June of 2010, 30 patients with thoracic ossification of ligamentum flavum were reviewed retrospectively, including 22 males and 8 females with an average age of 52.8 years old (ranged from 37 to 68 years old). The course of duration ranged from 2 months to 6 years. Single segment lesion was in 11 cases and multiple segments were in 19 cases. Two patients were accompanied by cervical ossification of ligamentum flavum and 1 was accompanied by ossification of posterior longitudinal ligament. The ossified lesions were located at T1,2 to T4,5 in 5 cases,T5,6 to T8,9 in 7 cases, T9,10 to T11,12 in 12 cases, at the upper and middle thoracic levels in 2 cases, at the middle and lower thoracic levels in 4 cases. They were divided into 2 types according to the morphologic features of the CT scan:simple type, 18 segments with lateral, slice or unfused type; complex type, 42 segments with thickened, fused or nodular type. The clinical manifestation was paralysis of upper motor neuron in 21 cases, and of upper and lower motor neuron in other 9 cases. Sphincter dysfunction was found in 26 cases. Preoperative JOA sphincter function score was 1.97 +/- 0.56. Preoperative modified JOA motor function score of lower limb was 1.20 +/- 0.76. Different surgical procedure was applied to one of the 2 types. For the simple type, an en bloc laminectomy was performed. However,for the complex type, a laminar shelling decompression was done. Laminectomy combined with internal fixation and lateral fusion was performed in patients whose decompressive areas were wider.

RESULTSThe mean decompression length was 3.1 lamina (2 to 6 lamina). Cerebrospinal fluid leakage was found in 3 cases and hematoma in incision was found in 1 case. The mean follow-up duration was 26 months (12 to 96 months). Twenty-two patients with the feel of constriction of trunk or lower limbs were completely recovered; 18 cases with sensation disturbance, numbness and pain of the lower limb were totally recovered, and relived in 10 cases. Postoperative JOA sphincter function score was 2.73 +/- 0.45, comparing with the preoperative score, and the difference was significant (P < 0.01). Postoperative JOA motor function score was 3.57 +/- 0.77, comparing with the preoperative score, and the difference was significant (P < 0.01 ). The lower limb function relief rate was 86.1%, 24 patients got an excellent results, 3 good, 2 poor and 1 bad.

CONCLUSIONDifferent surgical procedures will be safely and effectively applied to treat thoracic ossification of ligamentum flavum according to CT classification.