title: A clinicopathologic study of osteonecrosis in the osteoarthritic hip.
abstract: OBJECTIVE
  To investigate the incidence and nature of secondary osteonecrosis observed in osteoarthritis (OA) of the femoral head.
  
  
  METHODS
  This study is based on a retrospective review of the histopathologic and radiologic materials obtained from 906 consecutive cases (1007 femoral heads) diagnosed as OA.
  
  
  RESULTS
  Secondary osteonecrosis was recognized grossly and confirmed microscopically in 38.2% of the femoral heads. The lesions were categorized into two types based on shape, size and depth; 'shallow' flat lesion (median axis 3-10 mm, depth 2-3 mm) with or without cysts (368 cases, 36.5%), and 'deep, wedge-shaped' large lesion (more than 20 mm across and 10 mm in depth) with or without cyst (17 cases, 1.7%). In the 'shallow' flat lesion, the age ranged from 25 to 88 (average 66), the female/male ratio was 0.8, and the location of osteonecrosis correlated best with the direction of migration in OA. In the 'deep, wedge-shaped' lesion, the age ranged from 56 to 92 (average 70), the female/male ratio was 1.8, and the location of osteonecrosis was similar to that found in primary osteonecrosis.
  
  
  CONCLUSIONS
  Two different types of osteonecrosis were observed in OA. 'Shallow' osteonecrosis may be pressure necrosis as a result of eburnation, while 'deep, wedge-shaped' osteonecrosis appears to be an independent phenomena presumably caused by similar causal factors to those in primary osteonecrosis.
authors.affiliation: Department of Orthopaedic Pathology, Hospital for Special Surgery, New York, NY 10021, USA.
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.forename: T
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: K B
authors.initials: KB
authors.lastname: Lee
authors.forename: P G
authors.initials: PG
authors.lastname: Bullough
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009519:New York City / Q000453:epidemiology; D015207:Osteoarthritis, Hip / Q000150:complications* / Q000000981:diagnostic imaging / Q000473:pathology; D011859:Radiography; D012189:Retrospective Studies