Clinical Study on Enlargement of the Cervical Spinal Canal without Laminectomy in Cervical Myelopathy : with special reference to follow-up results

In order to accomplish posterior decomression for cervical myelopathy, a new surgical method, enlargement of the cervical spinal canal without laminectomy was developed by Prof. Hattori in 1971 and have been performed on 78 cases with cervical myelopathy in the author's department. The author made its report on the results of clinical and radiographical scudies on the cases which were operated with upon this method, with special reference to the follow-up results. The subjects of this study are 37 cases of cervical osteochondrotic myelopathy (COM), 36 of myelopathy due to ossification of the posterior longitudinal ligament (OPLL) and 5 of cervical cord injury. Of 78, 49 cases were able to be followed up for more than a year. The 49 cases consisted of 27 COM, 21 OPLL and 1 cord injury. The longest observation period was 7 years and 11 months, and the average length was approximately three years. The results are as follows : 1) Clinical results of all the 78 cases at the time of discharge were, excellent in 22 cases, good in 33, fair in 14, unchanged in 9 and none worsened. In COM the excellent and good were 83.8%, 63.9% in OPLL and 20% in cord injury. 2) In 49 followed-up cases the excellent and good are 77.6% at the time of discharge and were also 77.6% throughout the follow-up period. 3) The percentage of the spinal canal enlargement obtained was 25.2% at the time of discharge and 22.4% at the time of follow-up. The enlargement obtained after operation has been maintained at the time of follow-up. 4) Thinned laminae at the time of discharge got thickned as time passed. The thickenning of the laminae were mainly observed at the dorsal side and no osseous projection were found inside the spinal canal. 5) Change of alignment and increase of spondylotic findings of the cervical spine occurred in only a few cases after operation. Their degrees were generally slight and did not influence clinical results. 6) In no case instability appeared anew or became worse after operation. These results indicate that this method overcome many disadvantages of ordinary laminectomy and is very effective as a posterior approach for cervical myelopathy.