title: Prevalence, distribution, and morphology of thoracic ossification of the posterior longitudinal ligament in Japanese: results of CT-based cross-sectional study.
abstract: METHODS
  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.
  
  
  BACKGROUND
  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.
  
  
  CONCLUSIONS
  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.
  
  
  METHODS
  N/A.
authors.affiliation: From the Department of Orthopaedic Surgery, Shiga University of Medical Science, Tsukinowa-cho, Seta, Otsu, Shiga, Japan.
authors.forename: Kanji
authors.initials: K
authors.lastname: Mori
authors.forename: Shinji
authors.initials: S
authors.lastname: Imai
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kasahara
authors.forename: Kazuya
authors.initials: K
authors.lastname: Nishizawa
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mimura
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Matsusue
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D017887:Ossification of Posterior Longitudinal Ligament / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology; D015995:Prevalence; D012196:Review Literature as Topic; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult