Outcome of surgery for a symptomatic herniated thoracic disc in relation to preoperative characteristics of the disc

Background. This report presents general information on herniated thoracic discs, their clinical manifestations as well as surgical treatment, and examines the differences in the surgical outcome based on disc characteristics. Methods. This study includes 33 thoracic discectomies in 29 patients with a ventrally situated herniated thoracic disc reaching to the thoracic cord. Using preoperative computed tomography scanning and magnetic resonance imaging, the direction of the disc was classified as either central or lateral, and disc consistency classified as either soft or hard. Clinical outcome was assessed according to the Japanese Orthopedic Association (JOA) Score for thoracic myelopathy. The score was obtained by analysing motor, sensory and bladder function. Recovery rate was assessed, comparing preoperative and postoperative status based on disc characteristics. The correlations between outcome, symptom duration and recovery rate were also investigated. Findings. Clinical outcome according to the JOA Score showed significant postoperative improvement, increasing from 7.0 +/- 3.1 points to 8.2 +/- 2.7 points postoperatively (p < 0.01). The mean recovery rate was 12.4 +/- 56.9%, and 16 patients (55.2%) showed improvement. In the soft disc group, there was improvement in all categories, but the hard disc group showed no improvement. The central disc group showed improvement in sensory function, but the lateral disc group showed little improvement. Regression analysis revealed a statistically significant correlation between the preoperative and postoperative score, symptom duration and recovery rate. Conclusions. Clinical outcome after surgery of a herniated thoracic disc proved successful, especially when the disc was considered to have a soft consistency. In order to decide the optimal surgical strategy and prospective surgical outcome, disc characteristics, including consistency and direction of prolapse should be considered preoperatively.