title: The effect of poly sterilization on wear, osteolysis and survivorship of a press-fit cup at 10-year followup.
abstract: BACKGROUND
  During the mid-1990s when our institution was using a press-fit porous-coated cup without supplemental initial fixation for primary THA, the manufacturer transitioned from gamma irradiation to gas plasma for the terminal sterilization of their polyethylene liners.
  
  
  OBJECTIVE
  At minimum 10-year followup, we asked whether the fixation achieved by solely relying on a press-fit would be durable and how different liner sterilization methods affected radiographic wear, osteolysis, and survivorship.
  
  
  METHODS
  We retrospectively reviewed 373 patients who underwent 398 primary THAs with a press-fit porous-coated cup between March 1995 and December 1996. Mean age at time of surgery was 61.5 ± 13.3 years and mean followup was 10.4 ± 3.7 years. We determined reasons for revision, survivorship, femoral head penetration, osteolysis, and wear-related complications.
  
  
  RESULTS
  Among 20 revisions involving any component, seven were associated with wear and osteolysis. Kaplan-Meier survivorship, using component revision for any reason as an end point, was 95.7% (95% confidence interval, 93.6%-97.9%) at 10 years. Noncrosslinked liners sterilized with gas plasma demonstrated a mean head penetration rate of 0.20 ± 0.09 mm/year compared with 0.13 ± 0.07 mm/year for liners sterilized with gamma irradiation in air and 0.09 ± 0.04 mm/year for liners sterilized with gamma-irradiation with barrier packaging without oxygen. THAs with increased volumetric wear tended to demonstrate larger osteolytic lesions (r = 0.40) and there tended to be less osteolysis among the liners sterilized with gamma-irradiation with barrier packaging without oxygen. However, there was no difference in survivorship among the sterilization groups and there has been no cup or stem loosening associated with osteolysis.
  
  
  CONCLUSIONS
  Durable biologic fixation through 10-year followup can be achieved by solely relying on an initial press-fit. Noncrosslinking gas plasma for terminal sterilization of the polyethylene liners was associated with greater head penetration rate than gamma irradiation.
  
  
  METHODS
  Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors: Anderson Orthopaedic Research Institute, PO Box 7088, Alexandria, VA 22307, USA.
authors: Charles A
authors: CA
authors: Engh
authors: Cara C
authors: CC
authors: Powers
authors: Henry
authors: H
authors: Ho
authors: Sarah E
authors: SE
authors: Beykirch-Padgett
authors: Robert H
authors: RH
authors: Hopper
authors: C Anderson
authors: CA
authors: Engh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D016009:Chi-Square Distribution; D005260:Female; D005720:Gamma Rays / Q000009:adverse effects; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010014:Osteolysis / Q000000981:diagnostic imaging / Q000209:etiology / Q000517:prevention & control*; D058626:Plasma Gases / Q000009:adverse effects; D020959:Polyethylene / Q000528:radiation effects; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013242:Sterilization / Q000379:methods; D013314:Stress, Mechanical; D013997:Time Factors; D016896:Treatment Outcome; D014768:Virginia; D055815:Young Adult
chemical_list: D058626:Plasma Gases; D020959:Polyethylene