The change and relationship between clinical outcome and backward translation and expansion of spinal cord in multilevel cervical myelopathy after laminectomy and lateral mass screw fixation

English Keywords:Cervical myelopathy  Laminectomy  Spinal cord shift  Outcome  Correlation

English Abstract:

  【Abstract】 Objectives: To investigate the change of spinal cord backward drift and expansion after posterior laminectomy decompression and lateral mass screw fixation for multilevel cervical myelopathy and the relationship between curative effect and the spinal cord′s change. Methods: From July 2011 to January 2014, 32 patients with multilevel cervical myelopathy underwent laminectomy and lateral mass screw fixation in our hospital. C2-7 Cobb angle was measured in neutral neck lateral radiograph before and after operation. Using Photoshop cs5 software, the distance of each intervertebral space after decompression from the upper posterior vertebral body margin to the anterior and posterior margin of the spinal cord was measured respectively in the MRI sagittal T2 weighted median film. And the distance of each intervertebral space of the expansion and the midpoint of backward drift of spinal cord was calculated and the average value was take. The JOA scores at preoperation and the last follow-up were recorded, as well as the improvement rate. The changes of C2-C7 Cobb angle and JOA score were compared before and after operation. Correlation analysis was performed between the whole spinal cord drifting distance and postoperative cervical Cobb angle, and between the improvement rate of JOA and the whole drifting distance/expansion of spinal cord. The preoperative and postoperative C2-C7 Cobb angle and JOA score were compared by paired t test, and Pearson analysis was used for the analysis of correlation. Results: Patients were followed up for 11 to 22.5 months, averaging 15.8±4.7 months. The symptoms improved after surgery, preoperative and postoperative Cobb angle was 5.8°±1.2° and 18.5°±5.5° respectively, JOA score was 8.8±2.5 and 14.5±2.0 respectively, and the difference was statistically significant(P<0.05). The JOA improvement rate was (65.4±34.4)%（26%-100%）. The whole spinal cord drifting distance was 2.7±1.8mm(1.0-4.5mm), and the average spinal cord expansionary distance was 1.9±1.4mm(0.8-3.4mm). No obvious correlation was found between spinal cord drifting distance and postoperative cervical curvature(r=0.11, P>0.05). Low correlation between the JOA recovery rate and the whole spinal cord drifting distance(r=0.40, P=0.025) and moderate correlation between the JOA recovery rate and the average spinal cord expansionary distance(r=0.67, P=0.037) were noted. 2 cases suffered from C5 nerve root palsy and were cured by correspondant treatment for 3 weeks to 3 months. Conclusions: Laminectomy and lateral mass screw fixation is satisfactory due to its back drifting and expansion of spinal cord. There is positive correlation of the JOA recovery rate with the spinal cord drifting and expansion distance.