Fifty-three patients who were operated on for the myelopathy due to OPLL in our clinic from 1973 to 1982 were analysed in this paper. Postoperative recovery rate (criteria by Japanese Orthopedic Association) were poor or worse in 9 patients (19%): 4 with severe, 5 with moderate and none with mild myelopathy before operation. Among the patients with severe myelopathy preoperatively, the causative factors for the poor prognosis were thought to be the age at operation and the hyperostosis in another level of the spinal canal. On the other hand, 5 cases with moderate myelopathy showed marked complications complications such as hepatic myelopathy, brain embolism, meningitis and so on. We concluded that the patients with myelopathy due to OPLL should be operated on before the moderate stage unless the conservative treatment showed any effective recovery.
