| Objective: To observate the posterior movement and the functional restoration of the cervical spinal cord after posterior decompression in the patients with cervical spondylotic myelopathy(CSM), so as to investigate the degree, regular rule, mechanism, clinical meaning of the spinal posterior movement and analyse the affecting factors of the spinal functional restoration after posterior operation.Methods:1.We performed C3-7 single open-door laminoplasty in 20patients and performed C3-7 laminectomy in 12patients. All patients had MRI and JOA score preoperation and postoperation after 3 months.2.We used the middle sagittal Plane of T1 image in MRI to measure the front gap of spinal cord in C3-C7 vertebral level preoperation and postoperation, as well as the cervical curvature index after operation.3.Measured value were accounted and analyzed statistically. The average posterior movement of the spinal cord were compared between laminoplasty and laminectomy. We analyzed the change about the front gap of spinal cord in C3-C7 vertebral level preoperation and postoperation. Analysis of variance was used to analyse defference of the posterior movement in defferent vertebral level. The correlation between the posterior movement of spinal cord and the cervical curvature index were analyzed using coefficient of product-moment correlation.4.All patients were divided into two groups according to the improving rate of JOA score. We compared the defference of the age, JOA score before operation and the average posterior movement of spinal cord in two groups.Result: In all patients, the mean value about average posterior movement of cervical spinal cord after operations was 1.6mm(S=1.0mm). The mean JOA score preoperation was 10.63 (S=1.77), but The mean JOA score postoperation was 13.57 (S=1.50) . The improving rate of JOA score after operations were from 33.33% to 80.00%, mean value was 50.93%. The front gap of spinal cord postoperations was wider than preoperations (p＜0.001). The greatest mean value of spinal posterior movement in defferent vertebral level was at C5, C4 and C6 taked second place, the lowest was at C3 and C7, but the defference had not statistical meaning. The age in the goodness group of JOA improving rate was below the non-goodness group, but JOA score before operation was above the non-goodness group. There was no defference in the spinal posterior movement between two groups. Only one patient had appeared C5nerve root palsy after operation.Conclusion:1.This study approved the existence of the posterior movement of spinal cord after posterior decompression, this posterior movement was foreign to the cervical front convex. There was no defference in the ability of this posterior movement for defferent vertebral level.2.According to the result of our study and the mechanical principle, we considered that posterior movement of cervical spinal cord after posterior decompression had a bearing on the expansion of dural sac and the pressure front cervical cord, it was a morphological change of the spinal cord due to exterior stress effect. This posterior movement was not depend on "Bowstring" theory.3.The study on the posterior movement of spinal cord after operation redounded to alter the conteroversy about selection of operative approach.Through our study, we suggested:①Cervical front convex leveling off and cervical kyphosis were not contraindication of posterior operation for the spinal posterior movement.②When the anterior pressure is wider than 4mm, the postoperation result will be affected. 4.This study did not found the direct evidence that C5 nerve root palsy had related to the posterior movement of spinal cord. This relation should be analyzed using a study of more samples.5. The premature functional restoration of spinal cord after posterior decompression for CSM were related to the age and JOA score before operation, was not related to the degree of the spinal posterior movement. Further study about prognosis of CSM was necessary, most of all was multifactor study. |
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