title: Low wear of a second-generation highly crosslinked polyethylene liner: a 5-year radiostereometric analysis study.
abstract: BACKGROUND
  A sequentially irradiated and annealed, second-generation highly crosslinked polyethylene (XLPE) liner was introduced clinically in 2005 to reduce in vivo oxidation. This liner design has also been shown to reduce wear in vitro when compared with conventional and first-generation crosslinked liners. To date, there is only one study reporting an in vivo wear rate of this liner at 5 years' followup. However, that study used measurements made from plain radiographs, which have limited sensitivity, particularly when monitoring very low amounts of wear.
  
  
  OBJECTIVE
  What is the amount and direction of wear at 5 years using radiostereometric analysis (RSA) in patients who had THAs that included second-generation XLPE?
  
  
  METHODS
  We prospectively reviewed 21 patients who underwent primary cementless THA with the same design of XLPE acetabular liner and 32-mm articulation. Tantalum markers were inserted during surgery and all patients had RSA radiographs at 1 week, 6 months, and 1, 2, and 5 years postoperatively. Femoral head penetration within the acetabular component was measured with UmRSA(®) software. One patient died and two had incomplete radiographs leaving 18 radiographic series for analysis.
  
  
  RESULTS
  The mean amounts of proximal, two-dimensional, and three-dimensional head penetration between 1 week and 5 years were 0.018, 0.071, and 0.149 mm, respectively. The mean proximal, two-dimensional, and three-dimensional wear rates calculated between 1 year and 5 years were all less than 0.001 mm/year with no patient recording a wear rate of more than 0.040 mm/year.
  
  
  CONCLUSIONS
  The head penetration of a second-generation XLPE liner remained low at 5 years and the wear rate calculated after the first year was low in all directions. This low level of wear remains encouraging for the future clinical performance of this material.
authors.affiliation: Centre for Orthopaedic and Trauma Research, Level 4 Bice Building, University of Adelaide and Royal Adelaide Hospital, North Terrace, Adelaide, 5000, South Australia, Australia, stuart.callary@health.sa.gov.au.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Callary
authors.forename: John R
authors.initials: JR
authors.lastname: Field
authors.forename: David G
authors.initials: DG
authors.lastname: Campbell
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D019544:Equipment Failure Analysis; D005260:Female; D057918:Fiducial Markers; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D020959:Polyethylene / Q000528:radiation effects; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis; D013314:Stress, Mechanical; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D020959:Polyethylene
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