title: Does the extent of osteonecrosis affect the survival of hip resurfacing?
abstract: BACKGROUND
  The effect of the extent of osteonecrosis on the survival of hip resurfacing for osteonecrosis of the femoral head (ONFH) has not been well documented, but is a potentially important variable in the decision to perform resurfacing.
  
  
  OBJECTIVE
  We examined (1) the relationship between the volume of osteonecrosis in the femoral head before surgery and the extent of the residual necrotic bone after femoral head machining, (2) how the extent of the residual necrotic bone relative to the resurfaced femoral head (after femoral head machining) affected the survival of total hip resurfacing for patients with ONFH, and (3) how the extent of the necrotic bone relative to the entire femoral head (before femoral head machining) affected the survival and clinical outcome scores of patients who underwent total hip resurfacing.
  
  
  METHODS
  Thirty-three patients (39 hips) who underwent hip resurfacing were reviewed after a mean followup of 8 years. The extent of osteonecrosis in the femoral head and residual osteonecrosis in the implant bony bed after femoral head machining were estimated using a three-dimensional MRI-based templating system.
  
  
  RESULTS
  There was a statistically significant difference in the extent of osteonecrosis before and after femoral head machining, although the two were well correlated (r = 0.97). The mean percentage of osteonecrosis in the implant bony bed after femoral head machining was 5% smaller than that relative to the entire femoral head (range, -9% to 15%). There were no significant differences in implant survival between groups with small and large osteonecrosis classified by either the total amount of osteonecrosis before surgery or residual osteonecrosis after femoral head machining.
  
  
  CONCLUSIONS
  The extent of osteonecrosis in the femoral head significantly decreased after femoral head machining. Neither the residual osteonecrosis volume in the implant bony bed after femoral head machining nor the total amount of osteonecrosis before femoral head machining had significant influence on the survival of hip resurfacing.
authors: Department of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, Yamadaoka 2-2, Suita, Osaka, 565-0871, Japan.
authors: Satoshi
authors: S
authors: Nakasone
authors: Masaki
authors: M
authors: Takao
authors: Takashi
authors: T
authors: Sakai
authors: Takashi
authors: T
authors: Nishii
authors: Nobuhiko
authors: N
authors: Sugano
mesh_terms: D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D018450:Disease Progression; D005260:Female; D005270:Femur Head / Q000473:pathology*; D005271:Femur Head Necrosis / Q000150:complications / Q000175:diagnosis / Q000601:surgery; D005500:Follow-Up Studies; D006621:Hip Joint / Q000473:pathology* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D061825:Metal-on-Metal Joint Prostheses; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure / Q000209:etiology*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D015996:Survival Rate; D055815:Young Adult
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