Dose Spinal Cord Shifting Affect Clinical Outcomes After Traditional Cervical Posterior Decompression

PART1 Clinical Significance of Posterior Spinal Cord Shifting by Extensive Posterior DecompressionObjective: Current techniques used for cervical laminoplasty for multisegmental cervical spondylotic myelopathy (CSM) are consecutively performed between the C3 and C6-7 levels with expectation that the spinal will shift backward to keep it clear of anterior compression. However, the clinical significance of the posterior spinal cord shifting remains controversial. Some surgeons have reported that the degree of posterior shifting is correlated with the surgical outcome, while others reported that the degree of shifting over an extensive range is not. To investigate the clinical significance of posterior spinal cord shifting after cervical laminoplasty, we conducted by comparing the degree of shifting and surgical outcome in which the C3 and C6 or C7 levels were consecutively decompressed.Methods: From July 2003 to June 2008, 65 patients with cervical spondylotic myelopathy were reviewed in the study, which consisted of 59 male and 6 female patients. The mean age was 58.4 (range, 40-75), 54 patients who underwent open-door laminoplasty and 11 patients who underwent extensive cervical laminoplasty. The recovery rate was calculated using preoperative and postoperative JOA scores for each patient; and for each patient's magnetic resonance imaging, the postoperative cervical curvature index was obtained according to Ishihara's method and the magnitude of postoperative backward shifting of the spinal cord was measured.Results: All cases were followed up for 24～55months, average 31 months. The average JOA recovery rate was 63.1%±16.9% for group A, 59.5±22.3% for group B and 54.3%±9.8% for group C. There was no significant difference in JOA recovery rate among three groups. Loss of cervical curvature indices was 3.6%±2.4% in group A , 3.1%±2.7% in group B and 4.2%±3.1% in group C. There was no significant difference in loss of cervical curvature indices among three groups. The rate of patients with evident axial symptoms was 18.2% in group A, 36.7% in group B and 53.8% in group C, and the difference was statistically significant ( P< 0.05).Conclusion: The recovery rate and curvature index after posterior decompression surgery is not correlated with the backward shifting of the spinal cord, and no correlation was also found between the curvature index and posterior shifting of the spinal cord. There is a correlation between axiality symptom and backward shifting of the spinal cord.PART 2 Dose Spinal Cord Shifting Affect Clinical Outcomes After Traditional Cervical Posterior Decompression?Objective: Regarding decompression surgery used to treat multisegmental cervical spondylotic myelopathy (CMS), the clinical significance of posterior shifting of the spinal cord after extensive cervical laminoplasty remains controversial. For the purpose of reducing the injury cause by the operation, we started to use selective laminoplasty for CSM patients with 2- to 3-level stenosis identified by magnetic resonance imaging (MRI). These new procedure, which interfered limited number of posterior spinal arches, have presented as good surgical outcomes as extensive traditional open-door laminoplasty, which interfered posterior arches between C3-C7.We conducted the study where where backward shifting of the cervical spinal cord after selective laminoplasty was compared with that after open-door laminoplasty in relation to the clinical results of each procedure.Methods: From June 2004 to September 2007, 65 patients of cervical spondylotic myelopathy were reviewed in this study, which consisted of 41 male and 24 female patients. The mean age was 56.3(range, 39-75). Among them, 33 patients underwent extensive cervical laminoplasty (investigational group) and 32 patients underwent open-door laminoplasty (control group). The recovery rate was calculated using preoperative and postoperative JOA scores for each patient; and for each patient's magnetic resonance imaging, the postoperative cervical curvature index and the magnitude of postoperative shifting distance of the spinal cord was also measured and compared.Results: All cases were followed up for 26-47months, average 34 months. There was no significant difference of preoperative JOA recovery rate and cervical curvature indices between two groups. The magnitude of the postoperative posterior shifting of the spinal cord was 1.4mm±0.6mm in investigational group and 3.3mm±1.2mm in control group. The average JOA recovery rate was 60.5%±21.3% for investigational group, 61.1%±17.9% for control group. There was no significant difference of JOA recovery rate between two groups. Loss of cervical curvature indice was 3.3%±1.7% in investigational group, 3.1%±2.4% in control group. There was no significant difference of loss of cervical curvature indices between two groups. The rate of patients with evident axial symptoms was 19.4% in group A, 35.6% in group B,and the difference was statistically significant (P<0.05). Conclusion: The recovery rate and curvature index after posteriordecompression surgery is not correlated with the distance backward shifting of the spinal cord, and no correlation was found between the curvature index and posterior shifting distance of the spinal cord. There is a correlation between axial symptom and posterior shifting distance of the spinal cord.