Abstract: Objective: To discuss the relationship of C5 never palsy incidence and difference risk factor after cervical open door laminoplasty. Methods： This study involved the patients with cervical spondylotic myelopathy who nuderwent expansive open door laminoplasty between January 2009 and December 2012. All the patients were average follow up (24.9 + 2.6) months. They were classified into two groups according to whether occur C5 palsy，group A ,20 cases occur C5 palsy and group B，234 cases without. Compare two groups of different risk factors and postoperative C5 palsy occurred, analyze the factors may affect the C5 palsy occurred. Results: All cases received follow-up (24.9 + 2.6) months on average, compared two groups of patients in postoperative changes of risk factors for postoperative CCI（t=10.015 P＜0.05）, lamina open angles (（t=5.125 P＜0.05）), spinal cord shift (t=10.159 P＜0.05), the difference is statistically significant. Preoperative intramedullary high signal 、OPLL（Ossification Of Posterior Longitudinal Ligament）、Intervertebral foramen stenosis differences without statistical significance. C5 palsy risk factors, according to the results of Logistic regression analysis of multiple factors in the Spinal cord shift, lamina open angles, postoperative CCI and statistical correlation between C5 palsy, OR（95%CI）:3.542（2.465~9.254）、2.035（1.684~2.359）、9.126（4.425~17.273）. Conclusion: The Angle of open door too large; CCI and spinal cord shift is risk factors for postoperative C5 palsy.

Key words: Laminoplasty, C5 nerve palsy, lamina open angles, CCI, Spinal cord shift