[The dorsal approach in degeneratively changed cervical spine].

The posterior approach to the cervical spine was the only method of access to the spinal canal until the anterior approach was developed by Robinson and Smith, and Cloward. With the accumulation of experience in posterior decompression for cervical spondylotic myelopathy (CSM), successful laminectomy was guaranteed only when lordotic alignment of the cervical spine, wide and extensive laminectomy for adequate posterior shift of the spinal cord, and stability of the spine were ensured after surgery. The thick scar formation occasionally seen subsequent to postlaminectomy hematoma could lead to an unfavorable outcome. The insertion of surgical instruments, such as a Kerrison rongeur or a curette, into the spinal canal without being aware of how narrow the canal is, or uneven decompression of the spinal cord during resection of the laminae can impinge on or distort the spinal cord and result in deterioration of neurological function. Several authors have pointed out that postoperative loss of neural function is a hazard of surgical intervention. Owing to the poor results of conventional laminectomy for cervical compression myelopathy related to the problems mentioned above, Kirita developed extensive simultaneous decompression laminectomy to avoid distortion of the spinal cord by the edges of the resected laminae. Hattori devised an expansive Z-shaped laminoplasty in which the posterior wall of the spinal canal was preserved by Z-plasty of the prepared laminae. This was an attempt to prevent the invasion of scar tissue, i.e., the so-called laminectomy membrane, which was believed to be a cause of late neurological regression. He also expected that the laminae reconstructed by Z-plasty would provide support for the spine. The introduction of high-speed air-drills allowed successful development of this procedure. In 1977, Hirabayashi introduced an epoch-making laminoplasty, the expansive open-door laminoplasty. He described the advantages of this procedure as: possibility of decompressing multiple levels of the spinal cord simultaneously, better postoperative support of the neck, allowing earlier mobilization of the patients, prevention of postoperative kyphotic deformity of the cervical spine, and reduced mobility of the cervical spine postoperatively, which helps to prevent late neurological deterioration and progression of OPLL. Subsequent to the Hirabayashi laminoplasty, various modifications and supplementary procedures have been devised for further improvement of the safety and efficacy of decompression, and for improved stability of the spine. Aims, advantages and disadvantages of laminoplasty: The aims of the laminoplasty are to expand the spinal canal, to secure spinal stability and to spare the protective function of the spine. Preservation of mobility of the spine is also a goal of this procedure for multiple level involvement. Decompression can be extended along the nerve root by facetectomy. Preservation of the posterior spinal structures permits reinsertion of the nuchal muscles and the spinal ligaments after they have been totally or partially detached. This prevents kyphosis or listhesis of the cervical spine, which often develops after laminectomy, particularly in subjects below 50 years of age. Reconstructive procedures for reattaching muscles and/or ligaments to the spinous processes are added to the laminoplasty, improving the dynamic or ligamentous stability of the spine.