Foraminal Ligaments Tether Upper Cervical Nerve Roots: A Potential Cause of Postoperative C5 Palsy

Abstract

Background Nerve root tethering upon dorsal spinal cord (SC) migration has been proposed as a potential mechanism for postoperative C5 palsy (C5P). To our knowledge, this is the first study to investigate this relationship by anatomically comparing C5–C6 nerve root translation before and after root untethering by cutting the cervical foraminal ligaments (FL). Objective The aim of this study is to determine if C5 root untethering through FL cutting results in increased root translation. Methods Six cadaveric dissections were performed. Nerve roots were exposed via C4–C6 corpectomies and supraclavicular brachial plexus exposure. Pins were inserted into the C5–C6 roots and adjacent foraminal tubercle. Translation was measured as the distance between pins after the SC was dorsally displaced 5 mm before and after FL cutting. Clinical feasibility of FL release was examined by comparing root translation between standard and extended (complete foraminal decompression) foraminotomies. Translation of root levels before and after FL cutting was compared by two-way repeated measures analysis of variance. Statistical significance was set at 0.05. Results Significantly more nerve root translation was observed if the FL was cut versus not-cut, p = 0.001; no difference was seen between levels, p = 0.33. Performing an extended cervical foraminotomy was technically feasible allowing complete FL release and root untethering, whereas a standard foraminotomy did not. Conclusion FL tether upper cervical nerve roots in their foramina; cutting these ligaments untethers the root and increases translation suggesting they could be harmful in the context of C5P. Further investigation is required examining the value of root untethering in the context of C5P.

Fibrous Connection Between Cervical Nerve and Zygapophysial Joint and Implication of the Cervical Spondylotic Radiculopathy

“…Our results indicate that the tensile stress caused by movement of the zygapophysial joints could be transmitted to the cervical nerves via the fibrous bands. Additionally, the anatomical relationships between EFLs and postoperative C5 palsy have been recently reported 22,23 . Jack et al 22 have shown that the cervical nerve root increases mobility after cutting the cervical foraminal ligaments.…”

“…Additionally, the anatomical relationships between EFLs and postoperative C5 palsy have been recently reported. 22,23 Jack et al 22 have shown that the cervical nerve root increases mobility after cutting the cervical foraminal ligaments. Accordingly, they suggested that foraminal ligaments play an integral role in the nerve root tethering and prevent the translation of the cervical nerve roots, which could potentially contribute to the pathogenesis of C5 palsy.…”

Risk factors for C5 palsy: a systematic review and multivariate analysis

“…An anatomical study by Jack et al found that an extended foraminotomy with resection of the foraminal ligaments allowed greater translation of the C5 nerve, thus reducing the tension experienced by the nerve. 37 However, it should be noted that the greater the size of the foraminotomy, the less bone there is available for lateral mass fixation and the greater the risk for instability if fusion is not performed. One of the publications included in this work specifically examined the relationship between foraminotomy and C5P.…”