2035 Quantitative Morphological Characterization of Cervical Spinal Nerve Roots and Neuroforamina: An In Vitro Human Cadaveric Model

INTRODUCTION: No unifying theory explains the pathophysiology of postoperative C5 palsy. Increased ratio of nerve-to-foraminal diameter is thought to contribute to increased susceptibility of the C5 nerve root to iatrogenic injury. This postulation has not been investigated with gross and microanatomic studies. METHODS: Ten fresh frozen human cadaveric cervical spine specimens underwent microanatomic measurements of the left and right C3-C8 neuroforaminal (Nf) and nerve root surface areas (Nr). Nfs were measured with micro-computed tomography (Micro-CT), while Nrs, with calipers. NRSA/NFSA ratio for each level was calculated as a surrogate for foraminal stenosis. All specimens were dissected, photographed and nerve root exiting angles were measured. RESULTS: A Decreasing order of Nfs and Nrs were observed for C3, C8, C7, C5, C6, C4, and C6, C5, C7, C8, C4, C3 levels respectively. Linear regression analysis between Nf and Nr demonstrated positive linear relationship for all levels, except for C4 and C8, where there was negative linear relationship. One-way ANOVA did not reveal differences in NRSA/NFSA ratios between levels. C5 nerve root was noted to have the most acute angle (48.6±43.6°), while C8, the least acute (3.2±6.91°). CONCLUSIONS: This is the first anatomical study to investigate the dimensions of cervical neuroforamina and nerve roots using Micro-CT. The findings of this study do not support the hypothesis that C5 level has the most stenotic foramen. C6 level had the greatest relative stenosis, however, this difference did not reach statistical significance. The clinical significance of the C5 nerve root having the most acute angle is unclear, however, this may serve as a basis for greater susceptibility of this root for iatrogenic traction injury.