Trauma-induced myelopathy in patients with ossification of the posterior longitudinal ligament

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Abstract
Object. In these prospective and retrospective studies the authors evaluated trauma-induced myelopathy in patients with ossification of the posterior longitudinal ligament (OPLL) to determine the effectiveness of preventive surgery for this disease. Methods. The authors studied 552 patients with cervical OPLL, including 184 with myelopathy at the time of initial consultation and 368 patients without myelopathy at that time. In the former group of 184 patients retrospective analysis was performed using an interview survey to ascertain the relationship between onset of myelopathy and trauma. In the latter group of 368 patients prospective examination was conducted by assessing radiographic findings and noting changes in clinical symptoms apparent during regular physical examination. The follow-up period ranged from 10 to 32 years (mean 19.6 years). In the retrospective investigation, 24 patients (13%) identified cervical trauma as the trigger of their myelopathy. In the prospective investigation, 70% of patients did not develop myelopathy over a follow-up period greater than 20 years (determined using the Kaplan—Meier method). Of the 368 patients without myelopathy at the time of initial consultation, only six patients (2%) subsequently developed trauma-induced myelopathy. Types of ossification in patients who developed trauma-induced myelopathy were primarily a mixed type. All patients in whom stenosis affected 60% or greater of the spinal canal developed myelopathy regardless of a history of trauma. Conclusions. Preventive surgery prior to onset of myelopathy is unnecessary in most patients with OPLL.