• Jianjun Zhao, Qinghao Zhao, Zezheng Liu, Shanxi Deng, Liang Cheng, Weijia Zhu, Rusen Zhang, Runxun Ma, Huibo Yan, and Qingchu Li.
• Department of Orthopedics, The Third Affiliated Hospital of Southern Medical University, No. 183, Zhongshan Rd West, Guangzhou, 510630, China.
• Spine J. 2020 Nov 1; 20 (11): 1776-1784.

BackgroundPostoperative C5 palsy is not an uncommon complication in patients who undergo expansive open-door laminoplasty. However, the etiology is unclear and likely multifactorial. Nerve root lesions and spinal cord lesions have been previously proposed theories.PurposeTo investigate the anatomical mechanism of postoperative C5 palsy after cervical expansive open-door laminoplasty.Study DesignA dissection-based study of eight embalmed human cadavers.MethodsThe anatomy was studied in eight whole cervical cadavers (three females, five males), prepared with formaldehyde, whose ages at the time of death ranged from 54 to 78 years. Dissection was performed on the intervertebral foramen and spinal canal. In the C3-C7 of the cervical vertebra, the extraforaminal ligaments and the meningovertebral ligaments were observed. The length, width, and thickness of the ligaments were measured with a Vernier caliper. After an expansive open-door laminoplasty was performed, the shape of the dural sac was changed, and displacement of the nerve root was observed. In addition, the lengths of the anterior rootlets were measured. This study has been supported by grants from Science and Technology Planning Project of Guangdong Province (CN) (Grant No. 2017B020210010) without potential conflict of interest-associated biases in the text of the paper.ResultsOne hundred seventy-seven extraforaminal ligaments were found to connect the spinal nerve to the surrounding structures. After an expansive open-door laminoplasty was performed, posterior distension of the dural sac and movement of the spinal cord and nerve root were found. The spinal cord was closely attached to the ligamentum flavum by meningovertebral ligaments. In addition, the length of the C5 intradural rootlets (5.81-10.59 mm) was the shortest among the vulnerable segments.ConclusionTraction on and posterior movement of the extradural roots may be the main pathologic mechanism of postoperative C5 palsy when expansive open-door laminoplasty is performed. The meningovertebral ligaments and extraforaminal ligaments might play an important role in the occurrence of postoperative C5 palsy.Clinical SignificanceThis study provides clinicians with a more detailed understanding of the anatomic structure and potential mechanism of C5 palsy. Consideration of the meningovertebral ligaments and the intervertebral foramen may provide new directions for reducing the incidence of this complication.Copyright © 2020 Elsevier Inc. All rights reserved.

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