This study compared the long-term outcome of cervical spondylotic myelopathy (CSM) with that of the ossification of the posterior longitudinal ligament of the cervical spine (OPLL) after suspension laminotomy, which was developed in the authors' clinic. Seventy-six patients who received follow-up care for more than 5 years were available for analysis. The duration of the follow-up period averaged 97.8 months (range 61–160 months). Radiological and neurological analyses were performed in these 76 patients (50 with CSM and 26 with OPLL). There were no differences in sex, age, follow-up period, and preoperative neurological status between the two groups.
In the quantitative study of the dural configuration, 43 patients (86%) with CSM and 17 patients (65.4%) with OPLL attained complete decompression 1 month after surgery. At long-term follow-up review, complete decompression was maintained in 42 patients (84%) with CSM but in only seven patients (26.9%) with OPLL. The neurological evaluation improved markedly at early follow up in both groups but declined insignificantly at the last follow-up review, particularly in the OPLL group. Of 12 patients (24%) with CSM and 10 patients (38.5%) with OPLL whose neurological recovery grades later deteriorated, four (8%) with CSM and nine (34.6%) with OPLL demonstrated reconstriction causing spinal cord compression at long-term follow-up review. For the remaining eight patients (16%) with CSM, who were older than 70 years on average at last follow-up review, no radiological explanation was found. These long-term results indicate that OPLL does not resolve as well as CSM after suspension laminotomy; they both may have late deterioration due to reconstriction that occurs occasionally in CSM and frequently in OPLL.