Biomechanical considerations in the surgical management of cervical spondylotic myelopathy.

Based on a review of previous studies and our opinion, biomechanical considerations suggest the following guidelines for the surgical management of CSM. It is not recommended that the dura mater, the pia mater, and the dentate ligaments be transected in the surgical treatment of CSM. Anterior decompression and fusion, preferably with the Smith-Robinson technique, is recommended for patients with anterior impingement of the spinal cord at one or two levels in the absence of a narrow spinal canal. This procedure is also advantageous when there is significant radiculopathy associated with the level(s) of pathology. Posterior decompression is recommended when there are three or more levels involved, and particularly when there is developmental stenosis of the canal, ie, a DAD below 13 mm and a SAD below 11 mm. Laminectomy and laminoplasty for CSM may not be any different as regards surgical outcome. One well-controlled study showed only one difference, a decrease in the ability of the laminoplasty patients to extend the neck. If there is evidence of instability or a potential for it, posterior decompression procedures should be accompanied by a facet fusion, or in the case of laminoplasty, some fusion modification such as that described by Itoh and Tsuji. There may also be circumstances in which significant multilevel anterior spur formation and compression in association with a stenotic canal should be treated with anterior and posterior surgery with appropriate attention to maintaining adequate stability. The advantages and disadvantages of these various surgical procedures and their relative appropriateness in various clinical situations will be gradually clarified through well-designed and executed laboratory and clinical investigations.