title: Short-term wear evaluation of thin acetabular liners on 36-mm femoral heads.
abstract: BACKGROUND
  Dislocation remains the leading cause of revision THA. One approach to decreasing prosthetic dislocation risk has been the use of larger femoral head component sizes. The upper limit of head size in metal-on-polyethylene hip arthroplasty has historically been limited because of concerns about increased wear on thin polyethylene components. It is not known to what degree this concern should apply to more wear-resistant polyethylene components.
  
  
  OBJECTIVE
  We therefore determined (1) in vitro wear rates of polyethylene liners of varying thicknesses, (2) whether there were differences in the microscopic wear characteristics as a function of polyethylene thickness, and (3) whether thin polyethylene components resulted in early catastrophic failures.
  
  
  METHODS
  We used a hip wear simulator to compare the wear performance of 12 highly crosslinked polyethylene acetabular inserts. The internal diameter of all components was 36 mm, and there were three samples tested of each thickness (1.9, 3.9, 5.9, or 7.9 mm). Testing was conducted for 2.4 million cycles. Gravimetric mass loss was converted to volumetric loss, which was subsequently converted to theoretical linear penetration rates.
  
  
  RESULTS
  Wear rates decreased with increasing polyethylene thickness. Mean ± SD wear rates for the 1.9-, 3.9-, 5.9-, and 7.9-mm groups were 5.0 ± 0.5, 3.2 ± 0.3, 2.5 ± 1.1, and 2.2 ± 1.3 mm(3)/million cycles, respectively (p < 0.016). Calculated penetration rates were 0.015, 0.012, 0.011, and 0.010 mm/million cycles, respectively (p < 0.016). There were no catastrophic failures in any group.
  
  
  CONCLUSIONS
  Thinner polyethylene components demonstrated higher wear rates, although even the highest wear rate observed in the thinnest polyethylene specimen was lower than that commonly reported for noncrosslinked polyethylene components. While encouraging, these findings should be validated in vivo before clinical recommendations can be made.
authors.affiliation: Center for Joint Preservation and Reconstruction, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, 2401 West Belvedere Avenue, Baltimore, MD, 21215, USA.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Johnson
authors.forename: LaQuawn
authors.initials: L
authors.lastname: Loving
authors.forename: Lizeth
authors.initials: L
authors.lastname: Herrera
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Delanois
authors.forename: Aiguo
authors.initials: A
authors.lastname: Wang
authors.forename: Michael A
authors.initials: MA
authors.lastname: Mont
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000704:Analysis of Variance; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D002858:Chromium Alloys; D019544:Equipment Failure Analysis; D005270:Femur Head / Q000601:surgery*; D006622:Hip Prosthesis; D016014:Linear Models; D008422:Materials Testing; D020959:Polyethylene / Q000737:chemistry*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D002858:Chromium Alloys; D020959:Polyethylene