Comparative Study of Surgical Treatment and Nonsurgical Follow Up for Thoracic Ossification of the Posterior Longitudinal Ligament: Radiological and Clinical Evaluation

Study Design. A prospective clinical study of factors related to myelopathy deterioration caused by thoracic myelopathy because of ossification of the posterior longitudinal ligament (T-OPLL). Objective. The objective of the study was to investigate factors related to myelopathy deterioration caused by T-OPLL. Summary of Background Data. Detailed analyses of factors related to myelopathy deterioration caused by T-OPLL have not been reported. Methods. Twenty-two patients (group O) received observation therapy because of the absence of or mild myelopathy, which was defined as walking unaided or with support, and a Japanese Orthopedic Association (JOA) score above 7 points; and 24 patients (group S) were treated with posterior decompression and fusion with instrumentation. Age, sex, body mass index (BMI), presence of diabetes mellitus (DM), and JOA score were obtained for all patients. Radiologically, the T-OPLL level, number of T-OPLLs, canal diameter ratio (CDR), morphology, ossification of the ligamentum flavum (OLF), and cervical OPLL were examined on reconstructed CT, and the presence of hyperintense areas (HIAs) on T2-weighted sagittal MR images. Results. In total, the patients included 22 males and 24 females and had an age range from 18 to 80 years. Sex, DM, JOA score in each domain, OPLL location, OPLL number, CDR of OPLL, morphology, OLF, and cervical OPLL did not differ significantly between groups N and S. However, cases in group N had a significantly higher age, lower weight, lower BMI, lower discontinuous rate on sagittal CT, and a lower HIA rate on MRI. Postoperatively, discontinuous segments connected and became continuous across the disc space in all patients in group S without progression of OPLL thickness. Conclusion. Age, weight, BMI, discontinuity between rostral and caudal OPLL lesions, and occurrence of a high intensity area on MRI are likely to be associated with development of myelopathy.