title: No difference in early cellular response of the pseudo-synovial membrane after total hip arthroplasty: comparison of 3 combinations of bearing materials.
abstract: BACKGROUND
  Wear-resistant bearing materials may hypothetically reduce chronic inflammation in the pseudosynovial membrane as compared to less wear-resistant bearing materials such as polyethylene. We assessed the foreign body response in the pseudosynovial membrane in vivo after total hip replacement.
  
  
  METHODS
  37 patients from a larger prospective randomized trial of 225 patients had biopsies taken arthroscopically from the artificial hip joint (i.e. the pseudosynovial membrane) 1 year after insertion of the implant. All patients had an identical hip prosthesis (Bimetric-RingLoc) except for the bearing materials, which consisted of polyethylene on zirconia, CoCr on CoCr, or alumina on alumina. Histological quantification was performed on 2-mum-thick semi-thin plastic sections or paraffin sections by point counting technique to compare the volume fraction of macrophages, granulomas and endothelial cells in biopsies of the pseudosynovial membrane.
  
  
  RESULTS
  The median macrophage volume fractions for polyethylene-on-zirconia bearing material (n = 15), CoCr-on-CoCr (n = 9), and alumina-on-alumina (n = 11) were 0.02, 0.04, and 0.004, respectively. The median granuloma volume fractions for polyethylene-on-zirconia (n = 13), CoCr-on-CoCr (n = 9), and alumina-on-alumina (n = 13) were 0.02, 0.04, and 0.02, respectively. The median endothelial cell volume fractions for polyethylene-on-zirconia (n = 15), CoCr-on-CoCr (n = 9), and alumina-on-alumina (n = 11) were 0.03, 0.02, and 0.05, respectively. Statistical analysis showed no significant differences between the three groups with the different bearings with respect to volume fraction of macrophages, granulomas and endothelial cells.
  
  
  CONCLUSIONS
  Our study demonstrated that a granulomatous inflammation is a common finding in non-loose implants as early as 1 year after the operation not demonstrating a difference in macrophages and granuloma formation with the various bearing materials. Thus a high volume fraction of macrophages was found in the osteoarthritis control group compared to the operated group.
authors.affiliation: Department of Orthopaedic Surgery, Frederiksberg University Hospital, Frederiksberg, Denmark. many@dadlnet.dk
authors.forename: Marianne
authors.initials: M
authors.lastname: Nygaard
authors.forename: Folmer
authors.initials: F
authors.lastname: Elling
authors.forename: Lone
authors.initials: L
authors.lastname: Bastholm
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.forename: Arne
authors.initials: A
authors.lastname: Borgwardt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods; D001706:Biopsy / Q000379:methods; D005260:Female; D005271:Femur Head Necrosis / Q000601:surgery; D005500:Follow-Up Studies; D005549:Foreign-Body Reaction / Q000209:etiology / Q000276:immunology / Q000473:pathology*; D015745:Granuloma, Foreign-Body / Q000473:pathology; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000473:pathology* / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013583:Synovial Membrane / Q000473:pathology