European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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An anatomical study of the cervical spinal cord and root to investigate the mechanism of paralysis of the arm after posterior decompression was performed using 14 cadavers of Japanese adults. It revealed that in the intervertebral foramen, extradural portions of the anterior and posterior roots of the cervical spinal cord lay separately in caudal-rostral relation, and the anterior root passed through the narrowest portion of the foramen isolatedly, i.e. the superior notch of the superior articular process. After laminectomy, a posteromedial shift of the dura-root junction occurred in combination with the posterior enlargement of the dual tube, and it showed two effects on the roots, one a relaxing effect on rootlets and the other, a traction effect on the extradural portion of a root. ⋯ With anchoring of the anterior root inside the foramen, a traction injury of the anterior root develops. The predominance of paralysis at the middle cervical level could be explained by the higher degree of anterior protrusion of the superior articular process and the more frequent degenerative changes here than at other levels. These factors might inhibit the gliding abilities of the roots inside the foramina, with the formation of perineural fibrosis, predisposing the roots to damage by the traction force.