Risk Factor Analysis for C5 Palsy after Double-Door Laminoplasty for Cervical Spondylotic Myelopathy

STUDY DESIGN A retrospective comparative study. PURPOSE To clarify the risk factors related to the development of postoperative C5 palsy through radiological studies after cervical double-door laminoplasty (DDL). OVERVIEW OF LITERATURE Although postoperative C5 palsy is generally considered to be the result of damage to the nerve root or segmental spinal cord, the associated pathology remains controversial. METHODS A consecutive case series of 47 patients with cervical spondylotic myelopathy treated by DDL at our institution between April 2008 and April 2015 were reviewed. Postoperative C5 palsy occurred in 5 of 47 cases after DDL. We investigated 9 radiologic factors that have been reported to be risk factors for C5 palsy in various studies, and statistically examined these between the two groups of palsy and the non-palsy patients. RESULTS We found a significant difference between patients with and without postoperative C5 palsy with regards to the posterior shift of spinal cord at C4/5 (p=0.008). The logistic regression analyses revealed posterior shift of the spinal cord at C4/5 (odds ratio, 12.066; p=0.029; 95% confidence interval, 1.295-112.378). For the other radiologic factors, there were no statistically significant differences between the two groups. CONCLUSIONS In the present study, we showed a significant difference in the posterior shift of the spinal cord at C4/5 between the palsy and the non-palsy groups, indicating that the "tethering phenomenon" was likely a greater risk factor for postoperative C5 palsy.