title: Effect of femoral head size on metal-on-HXLPE hip arthroplasty outcome in a combined analysis of six national and regional registries.
abstract: BACKGROUND
  HXLPE (highly cross-linked polyethylene) has greater wear resistance compared with UHMWPE (ultra-high molecular weight polyethylene), which may contribute to improving the outcomes of total hip arthroplasty with a large femoral head. However, no information is available regarding the effect of femoral head size on the survivorship of HXLPE hip prostheses. The aim of the present study was to provide evidence regarding whether femoral head size has an effect on the risk of revision when an HXLPE liner is used on a metal head.
  
  
  METHODS
  A distributed health data network was developed by the ICOR (International Consortium of Orthopaedic Registries). Six national and regional registries are participating in this network: Kaiser Permanente, HealthEast, the Emilia-Romagna region in Italy, the Catalan region in Spain, Norway, and Australia. Data from each registry were standardized and provided at an aggregate level for each of the variables of interest. Patients with osteoarthritis who were forty-five to sixty-four years of age and had undergone uncemented total hip arthroplasty were included in the present study. Analyses were performed on the basis of individual patient profiles, utilizing the variables collected from each registry. The outcome of interest was the time to the first revision (for any reason). Survival probabilities and their standard errors were extracted from each registry for each unique combination of the covariates and were combined through multivariate meta-analysis utilizing linear mixed models to compare survivorship for <32-mm, 32-mm, and >32-mm femoral head sizes.
  
  
  RESULTS
  A total of 14,372 total hip arthroplasties were included in the study. The five-year rate of revision surgery varied from 1.9% to 3.2% among registries. The risk of revision did not differ significantly between <32-mm and 32-mm head sizes (HR [hazard ratio] = 0.91, 95% CI [confidence interval] = 0.69 to 1.19) or between >32-mm and 32-mm sizes (HR = 1.05, 95% CI = 0.70 to 1.55).
  
  
  CONCLUSIONS
  The results of our study provide relevant data to orthopaedic surgeons deciding on the use of a larger articulation in a metal-on-polyethylene bearing. A larger head diameter should not be considered a detriment to device survival when an HXLPE liner is used. However, efforts to force the use of a large-size implant appear unsupported, as similar survivorship was observed for all head diameter groups.
authors.affiliation: Novartis Farmacéutica, SA, Carrer de la Marina, 206, 08013 Barcelona, Spain.
authors.forename: Alex
authors.initials: A
authors.lastname: Allepuz
authors.affiliation: The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Mollendalsbakken 11, N-5021 Bergen, Norway.
authors.forename: Leif
authors.initials: L
authors.lastname: Havelin
authors.affiliation: Department of Orthopedic Surgery, Kaiser Permanente, 280 West MacArthur Boulevard, Oakland, CA 94611.
authors.forename: Thomas
authors.initials: T
authors.lastname: Barber
authors.affiliation: Weill Cornell Medical College, 402 East 67th Street, New York, NY 10065.
authors.forename: Art
authors.initials: A
authors.lastname: Sedrakyan
authors.affiliation: Australian Orthopaedic Association National Joint Replacement Registry, Discipline of Public Health, MDP DX 650 511, University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Graves
authors.affiliation: Register of the Orthopaedic Prosthetic Implants (RIPO), c/o Medical Technology Laboratory, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bordini
authors.affiliation: Summit Orthopedics, 2090 Woodwinds Drive, St. Paul, MN 55125.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hoeffel
authors.affiliation: Surgical Outcomes & Analysis Department, Kaiser Permanente, 8954 Rio San Diego Drive, Suite 406, San Diego, CA 92108.
authors.forename: Guy
authors.initials: G
authors.lastname: Cafri
authors.affiliation: Surgical Outcomes & Analysis Department, Kaiser Permanente, 8954 Rio San Diego Drive, Suite 406, San Diego, CA 92108.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Paxton
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005260:Female; D005269:Femur / Q000601:surgery*; D006617:Hip Dislocation / Q000209:etiology / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D016896:Treatment Outcome