title: The natural history of untreated asymptomatic osteonecrosis of the femoral head: a systematic literature review.
abstract: BACKGROUND
  An asymptomatic hip with osteonecrosis is typically discovered as the contralateral hip of a patient with one symptomatic joint. Treatment of the asymptomatic hip is controversial. While some authors claim a benign natural history, others have reported a rate of femoral head collapse exceeding 50%. The purpose of this report was to systematically review the published literature regarding asymptomatic osteonecrosis of the femoral head to evaluate the overall prevalence of progression to symptomatic disease and/or femoral head collapse as well as to determine whether various radiographic and demographic factors influence progression of the disorder.
  
  
  METHODS
  A comprehensive literature search was performed to identify prognostic studies evaluating asymptomatic hip osteonecrosis. Demographic, radiographic, and outcome data were extracted from all relevant studies. The prevalence of progression to symptomatic disease and/or femoral head collapse was determined. Next, outcomes were stratified by lesion size, lesion location, radiographic stage, associated risk factors and/or disease, and the level of evidence of the study.
  
  
  RESULTS
  Sixteen studies that included a total of 664 hips were available for an analysis of outcomes. Overall, 394 hips (59%) had progression to symptoms or collapse. Differences in outcomes based on lesion size, lesion location, and radiographic stage at the time of diagnosis were seen. Small, medially located lesions had the best prognosis, with a prevalence of collapse of <10%. Patients with sickle cell disease had the highest frequency of progression, and those with a history of systemic lupus erythematosus had the most benign course.
  
  
  CONCLUSIONS
  Data extracted from previously published studies suggest that asymptomatic osteonecrosis has a high prevalence of progression to symptomatic disease and femoral head collapse. While small, medially located lesions have a low rate of progression, the natural history of asymptomatic medium-sized, and especially large, osteonecrotic lesions is progression in a substantial number of patients. For this reason, it may be beneficial to consider joint-preserving surgical treatment in asymptomatic patients with a medium-sized or large, and/or laterally located, lesion.
authors.affiliation: Center for Joint Preservation and Replacement, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, 2401 West Belvedere Avenue, Baltimore, MD 21215, USA. mmont@lifebridgehealth.org
authors.forename: Michael A
authors.initials: MA
authors.lastname: Mont
authors.forename: Michael G
authors.initials: MG
authors.lastname: Zywiel
authors.forename: David R
authors.initials: DR
authors.lastname: Marker
authors.forename: Mike S
authors.initials: MS
authors.lastname: McGrath
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Delanois
mesh_terms: D018450:Disease Progression; D005271:Femur Head Necrosis / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D012307:Risk Factors