Clinical and prognostic analysis of ossified ligamentum flavum in a Chinese population.

OBJECT: The authors performed a retrospective study of clinical and radiological data obtained in 27 Chinese patients with myelopathy induced by ossification of the ligamentum flavum (OLF) who underwent surgery between March 1990 and March 2002. The factors related to surgical outcome of thoracic OLF-induced myelopathy were also assessed.
METHODS: The preoperative clinical features and radiological findings were reviewed retrospectively. Preoperative and postoperative neurological status was assessed using the Japanese Orthopaedic Association (JOA) scoring system and the Nurick Scale. The ossified lesions were classified into five types (lateral, extended, enlarged, fused, and tuberous). Multiple linear regression and logistic regression analyses were performed to establish the factors affecting surgical outcome. The patients' chief complaints were lower-limb weakness and gait disturbance (93%), numbness and sensory deficit (89%), and low-back pain (48%). The coexisting pathological entities were disc herniation, canal stenosis, and ossification of posterior longitudinal ligament. The ossified ligamentum flavum was mainly located at the T10-12 (67%) and T1-3 (15%) levels. Symptoms in 26 patients improved but resolved completely in only 14 after surgery. The mean overall JOA score was 5.3 +/- 1.9 preoperatively and 7.9 +/- 2.3 postoperatively. There is a significant difference between the pre- and postoperative neurological status (p < 0.05) determined by the Student t-test. The recovery rate was 46.3 +/- 9.4%. Multiple regression analysis revealed negative correlation between the duration of preoperative symptoms and surgical outcome as well as a positive correlation between the preoperative JOA score and surgical outcome. Logistic regression analysis demonstrated that fecal and/or urinary incontinence, positive patellar and/or ankle clonus, and intramedullary high T2-weighted magnetic resonance (MR) imaging signal change had negative effects on the surgical outcome.
CONCLUSIONS: The clinical and radiological features of OLF in the Chinese population are similar to those observed in the Japanese population. The duration of preoperative symptoms and JOA score are the most important predictors of the postoperative JOA score and recovery rate. The patients with fecal and/or urinary incontinence, positive patellar and/or ankle clonus, and intramedullary high T2-weighted MR imaging signal change were at higher risk of poor outcome after surgery.