title: Sex differences in the morphological failure patterns following hip resurfacing arthroplasty.
abstract: BACKGROUND
  Metal-on-metal hybrid hip resurfacing arthroplasty (with a cementless acetabular component and a cemented femoral component) is offered as an alternative to traditional total hip arthroplasty for the young and active adult with advanced osteoarthritis. Although it has been suggested that women are less appropriate candidates for metal-on-metal arthroplasty, the mechanisms of prosthesis failure has not been fully explained. While specific failure patterns, particularly osteonecrosis and delayed type hypersensitivity reactions have been suggested to be specifically linked to the sex of the patient, we wished to examine the potential influence of sex, clinical diagnosis, age of the patient and the size of the femoral component on morphological failure patterns in a large cohort of retrieved specimens following aseptic failure of hip resurfacing arthroplasty.
  
  
  METHODS
  Femoral remnants retrieved from 173 hips with known patient's sex were morphologically analyzed for the cause of failure. The results were compared with the control group of the remaining 31 failures from patients of unknown sex. The odds ratios (OR) and 95% confidence intervals (CI) of the following morphologically defined variables were calculated using logistic regression analysis: periprosthetic fractures (n=133), osteonecrosis (n=151), the presence of excessive intraosseous lymphocyte infiltration (n=11), and interface hyperosteoidosis (n=30). Logistic regression analysis was performed both unadjusted and after adjustment for sex, age, the size of the femoral component, and preoperative clinical diagnosis.
  
  
  RESULTS
  Femoral remnants from female patients had a smaller OR for fracture (adjusted OR: 0.29, 95% CI 0.11, 0.80, P for difference=0.02) and for the presence of osteonecrosis (adjusted OR: 0.16, 95% CI 0.04, 0.63, P for difference=0.01). However, women had a higher OR for both the presence of excessive intraosseous lymphocyte infiltration (adjusted OR: 10.22, 95% CI 0.79, 132.57, P for difference=0.08) and interface hyperosteoidosis (adjusted OR: 4.19, 95% CI 1.14, 15.38, P for difference=0.03).
  
  
  CONCLUSIONS
  Within the limitations of this study, we demonstrated substantial sex differences in distinct failure patterns of metal-on-metal hip resurfacing. Recognition of pathogenically distinct failure modes will enable further stratification of risk factors for certain failure mechanisms and thus affect future therapeutic options for selected patient groups.
authors: Institute of Pathology, Department of Medical Biometry and Epidemiology, University Medical Center Hamburg-Eppendorf, Germany.
authors: Andrea
authors: A
authors: Hinsch
authors: Eik
authors: E
authors: Vettorazzi
authors: Michael M
authors: MM
authors: Morlock
authors: Wolfgang
authors: W
authors: Rüther
authors: Michael
authors: M
authors: Amling
authors: Jozef
authors: J
authors: Zustin
mesh_terms: D000367:Age Factors; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D011475:Prosthesis Failure; D012737:Sex Factors