Risk factors for acute cervical spinal cord injury associated with ossification of the posterior longitudinal ligament.

STUDY DESIGN: Retrospective review. OBJECTIVE: To identify risk factors for traumatic cervical spinal cord injury (SCI) associated with ossification of the posterior longitudinal ligament (OPLL) by comparing patients with SCI and those with cervical myelopathy (CM) associated with OPLL. SUMMARY OF BACKGROUND DATA: Although the prevalence of OPLL among patients with cervical SCI is high, little is published about the risk factors for SCI associated with OPLL. METHODS: We evaluated 3 groups of patients: 34 with SCI associated with OPLL, 32 with CM associated with OPLL, and 32 normal controls. Developmental canal diameter, spinal canal stenosis, type of OPLL, and presence of ossification of the anterior longitudinal ligament (OALL) were evaluated using 3-dimensional computed tomography. RESULTS: The mean age of the SCI group was 71.5 years, significantly more than that of the CM group (63.3 years). The SCI and CM groups had significantly smaller developmental canals than controls. Canal stenosis caused by OPLL was significantly more severe in the CM group than in the SCI group. There were no significant differences in sex distribution or the type of OPLL. Mixed or segmental types of OPLL were the main cause of SCI and CM. The SCI group showed a significantly higher incidence of OALL (56%) than the CM group (22%). Cervical SCI occurred at the edge of the OPLL or OALL in 20 patients (59%). If limited to mixed or continuous types of OPLL, 18 of the 19 patients (95%) sustained SCI at the edge of the OPLL or OALL. CONCLUSION: Risk factors for cervical SCI associated with OPLL were being elderly, having a mixed or segmental type of OPLL, and presence of OALL. Most instances of SCI occurred at edges of the OPLL or OALL. Severe spinal canal stenosis caused by OPLL was not an essential risk factor for developing SCI.