title: Epidemiology of nontraumatic osteonecrosis of the femoral head in Japan.
abstract: OBJECTIVE
  To elucidate the epidemiology of nontraumatic osteonecrosis of the femoral head (ONFH), and to estimate the annual incidence rate in Japan.
  
  
  METHODS
  We examined, over the course of 3 years, personal records and radiographic images from the national registry of documents used for the study of nontraumatic ONFH in patients in Aichi Prefecture, Japan (population: 7.4 million). Those patients not meeting the diagnostic criteria according to the Japanese Investigation Committee for nontraumatic ONFH were excluded from this study.
  
  
  RESULTS
  A total of 285 out of the 327 patients who applied for the national registration of nontraumatic ONFH during the 3-year study met the diagnostic criteria for personal records, radiographic images, and magnetic resonance images. Forty-two patients (12.8%) were not considered to have nontraumatic ONFH. The mean age of patients was 50.4 years, and the male-female ratio was 2.1:1. Nontraumatic ONFH was steroid-induced in 135 cases (47.4%), alcohol-associated in 87 cases (30.5%), steroid-induced and alcohol- associated in 14 cases (4.9%), and idiopathic in 49 cases (17.2%).
  
  
  CONCLUSIONS
  The age-adjusted annual incidence of nontraumatic ONFH in Aichi Prefecture was estimated at 138.5 patients.Thus the annual incidence rate in Japan (population 128 million) was 1.91/100,000.
authors.affiliation: Nagoya University Hospital, Nagoya University Graduate School of Medicine , Nagoya , Japan.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Ikeuchi
authors.forename: Yukiharu
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: Taisuke
authors.initials: T
authors.lastname: Seki
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Takegami
authors.forename: Takafumi
authors.initials: T
authors.lastname: Amano
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishiguro
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D002648:Child; D005260:Female; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000473:pathology; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011859:Radiography; D055815:Young Adult
keywords: Epidemiology; Femoral head; Incidence rate; Nontraumatic osteonecrosis