Clinical significance of posterior spinal cord shifting after open-door laminoplasty

Objective To investigate the clinical significance of posterior spinal cord shifting after two different types of laminoplasty for multilevel cervical myelopathy.Methods From June 2004 to September 2007,65 patients with cervical spondylotic myelopathy were reviewed in this study,including 41 males and 24 females with an average age was 56.3 years (range,39-75).Among them,33 patients underwent selective laminoplasty and 32 patients underwent open-door laminoplasty.There were no significant differences of preoperative JOA scores and cervical curvature index between two groups.After one year follow -up,the posterior shifting of spinal cord,Japanese Orthopaedics Association (JOA) recovery rate,loss of curvature index and axial symptom for each patient were calculated.Results All cases were followed up for average 34 months (range,26-47).There was significant difference of the postoperative posterior shifting between the two groups,which was (1.4±0.6) mm in selective laminoplasty group and (3.3±1.2) mm in opendoor laminoplasty group,respectively.The average JOA recovery rate was 60.5％±21.3％ and 61.1％±17.9％ in selective laminoplasty and open-door laminoplasty group,respectively.There was no significant difference of JOA recovery rate between the two groups.Loss of cervical curvature indices was 3.3％±1.7％ and 3.1％± 2.4％ in selective laminoplasty and open-door laminoplasty group,respectively,with no significant difference between the two groups.The rate of patients with evident axial symptoms was 18.2％ and 33.3％ in selective laminoplasty group and open-door laminoplasty group,and the difference of the scores of cervical axial symptom was statistically significant.Conclusion The degree of the postoperative posterior shifting of the spinal cord in open-door laminoplasty group was greater than that in selective laminoplasty group.The posterior shifting of the spinal is correlated with cord,axial symptom but not the recovery rate and curvature index. Key words: Cervical vertebrae;  Spinal cord compression;  Decompression, surgical