• Kei Ando, Shiro Imagama, Kazuyoshi Kobayashi, Tetsuro Hida, Kenyu Ito, Mikito Tsushima, Yoshimoto Ishikawa, Akiyuki Matsumoto, Yoshihiro Nishida, and Naoki Ishiguro.
• Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine.
• Spine. 2016 Jul 7.

Study DesignA prospective clinical study of factors related to myelopathy deterioration due to Thoracic myelopathy due to ossification of the posterior longitudinal ligament (T-OPLL).ObjectiveThe objective of the study was to investigate factors related to myelopathy deterioration due to T-OPLL.Summary Of Background DataDetailed analyses of factors related to myelopathy deterioration due to T-OPLL have not been reported.Methods22 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 Orthopaedic Association (JOA) score above 7 points; and 24 patients (group S) were treated with posterior decompression and fusion with instrumentation. Age, gender, 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.ResultsIn total, the patients included 22 males and 24 females and had an age range from 18 to 80 years. Gender, 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.ConclusionsAge, 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.Level Of Evidence3.

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