The Cervical Spine and Spondylosis

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Abstract
The changes seen in the cervical spine in cervical spondylosis have in the past been attributed to degeneration of the intervertebral discs associated with local dehydration. Recent studies have shown that the first macroscopic change in the intervertebral disc is partial displacement of the nucleus pulposus in either a vertical or horizontal direction. Narrowing of the intervertebral disc appears to be due to partial displacement of nuclear material although nuclear displacement may occur without immediate narrowing of the intervertebral disc. Similarly the occurrence of osteophytes at the uncinate process appear to be the result of nuclear displacement usually with narrowing of the intervertebral disc. The changes that occur in the intervertebral discs and adjacent vertebrae as a result of nuclear displacement are similar to those described in osteo-arthritis of other joints. In a series of 287 cervical intervertebral discs examined by a new technique, 102 (35.5%) showed partial nuclear displacement in either a vertical or horizontal direction. The incidence of vertical nuclear displacement was approximately the same as that of horizontal nuclear displacement. After the fourth decade the incidence of nuclear displacement increased rapidly but it did not parallel the increase in age. The process initiating the intervertebral disc disturbance is unknown although trauma, either massive or insidious wear and tear, appears to be an important factor. Abnormal absorption of fluid by the nucleus pulposus and agents which promote this may play a part in the causation of the process. The normal anatomical relationship of the cervical vertebrae and intervertebral discs to the spinal cord and the method of blood supply to the cord are salient factors in the consideration of the neurological sequelae associated with cervical spondylosis. The obliquity of the spinal nerve roots, the relative shape of the cervical spinal cord to canal and the reduction of the size of the spinal canal during extension of the neck help to explain some of the discrepancies previously reported in cases of cervical spondylosis with neurological disturbances. The presence of so-called “synovial half-joints” in the cervical spine as described by Luschka (1858) have not been confirmed; however the cervical intervertebral discs in autopsy specimens frequently contain fissures between the lateral lamellar fibres of the annulus fibrosus. The size of the vertebrae, intervertebral discs and the spinal canal measured on standard lateral radiographs is greater in the male than the female, although the relative size of the spinal canal to the vertebral body is less in the male than in the female. However, in both male and female the height of the normal intervertebral disc in the mid-line is approximately 45% of the height of the subjacent vertebral body. The spinal cord derives its blood supply from the ascending and descending branches of the radicular arteries which traverse the intervertebral foramina. These foramina can be constricted by osteophytes or by protrusions produced by partial nuclear displacement. The variability in the number of radicular arteries requires further investigation for this may play a role in the production of the myelopathy that occurs in spondylosis and in other diseases affecting the spinal cord. The neurological sequelae that occur in cervical spondylosis are not entirely dependent upon the changes in the spine but appear to be influenced by the prevailing anatomical circumstances, in particular the size of the spinal canal. The normal cervical spinal canal varies considerably in its antero-posterior measurement at different vertebral levels; it is narrowest at the commonest sites of spondylosis (the mid and lower cervical spine). The spinal canal may be narrowed by posterior disc protrusions, by osteophytes or subluxation. All of these may occur without neurological disturbances. However, when localized myelopathy is due to spondylosis the spinal canal frequently appears to be narrower than the normal range throughout its extent (i.e. C. 1 to C. 7). The hereditary, developmental or environmental factors which influence the size of the spinal canal are as important in the production of localized spondylotic myelopathy as the changes in the intervertebral discs and vertebrae which constitute the spondylosis. Les altérations relevées sur la colonne cervicale en cas de Spondylose ont été attribuées dans le passé à la dégénération des disques intervertébraux associée à de la deshydratation locale. Des études récentes ont montré que la première lésion macroscopique apparaissant dans le disque intervertébral est un déplacement partiel du nucléus pulposus en direction verticale ou horizontale. L'aplatissement du disque intervertébral semble dû à un déplacement partiel de tissu nucléaire, quoiqu'un tel déplacement puisse s'effectuer sans qu'apparaisse immédiatement l'aplatissement. De même l'apparition d'ostéophytes est le résultat de déplacement discal accompagné généralement d'aplatissement de l'espace intervertébral. Les lésions relevées dans le disque et les vertèbres adjacentes lors de déplacements nucléaires sont semblables à celles décrites dans l'ostéo-arthrite d'autres articulations. Dans une série de 287 disques intervertébraux examinés à l'aide d'une technique nouvelle, 102 (35,5%) ont montré un déplacement partiel du nucléus en direction verticale ou horizontale. La fréquence était à peu près la même dans l'une que dans l'autre direction. Après la quarantaine la...

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