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Prevalence, Distribution, and Morphology of Thoracic Ossification of the Posterior Longitudinal Ligament in Japanese: Results of CT-Based Cross-sectional Study

Mori, Kanji MD, PhD; Imai, Shinji MD, PhD; Kasahara, Toshiyuki MD, PhD; Nishizawa, Kazuya MD, PhD; Mimura, Tomohiro MD, PhD; Matsusue, Yoshitaka MD, PhD

doi: 10.1097/BRS.0000000000000153

Study Design. A cross-sectional study.

Objective. To gain an insight into the prevalence, morphology, and distribution of thoracic ossification of the posterior longitudinal ligament of the spine (T-OPLL) by computed tomography (CT) and review of the literature.

Summary of Background Data. The epidemiology and cause of T-OPLL remains obscure. To date, to the best of our knowledge, there is no study that has comprehensively evaluated the thoracic spine by CT to assess the prevalence, distribution, and morphology of T-OPLL in a sufficiently large size of sample with wide distribution of age.

Methods. The participants of this study were the patients who have undergone chest CT for the examination of pulmonary diseases in our institute. The patients with previous thoracic spine surgery and younger than 15 years were excluded. Prevalence, distribution, and morphology of T-OPLL were reviewed.

Results. A total of 3013 patients (1261 females and 1752 males) with the mean age of 65 years were recruited. The CT-based evidence of T-OPLL was noted in 56 (38 females and 18 males) individuals (1.9%). Most frequently encountered type was liner type, followed by continuous cylindrical type and mixed type. Continuous waveform and beaked type were less frequently encountered. Statistical analyses revealed that T-OPLL was noted at a significantly higher rate among the females. The mean age of T-OPLL–positive males was significantly higher than that of T-OPLL–negative males. Furthermore, there was significant difference of body mass index between T-OPLL–positive and T-OPLL–negative individuals. Most of T-OPLLs were confirmed in higher or middle thoracic regions and the highest peak was found at T3–T4. T-OPLL was noted after the age of 40 years with the peak distribution found at the age of 60 years.

Conclusion. The prevalence of T-OPLL in Japanese was 1.9%. Further studies that characterize definitive subtypes of T-OPLL on CT are warranted so as to establish possible association between clinical manifestations and size and/or subtypes of T-OPLL.

Level of Evidence: N/A

To date, this study is the first report of CT-based prevalence of thoracic ossification of the posterior longitudinal ligament (T-OPLL). The prevalence of T-OPLL in Japanese was 1.9% and it is more frequent in females. This study revealed significant association between sex (female preponderance), obesity (high body mass index), and T-OPLL.

From the Department of Orthopaedic Surgery, Shiga University of Medical Science, Tsukinowa-cho, Seta, Otsu, Shiga, Japan.

Address correspondence and reprint requests to Kanji Mori, MD, PhD, Department of Orthopaedic Surgery, Shiga University of Medical Science, Tsukinowa-cho, Seta, Otsu, Shiga, 520-2192, Japan; E-mail:

Acknowledgment date: September 12, 2013. Revision date: November 11, 2013. Acceptance date: November 18, 2013.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Health and Labour Science Research Grants funds were received in support of this work.

No other financial associations that may be relevant or seen as relevant to the submitted manuscript.

© 2014 by Lippincott Williams & Wilkins