title: Low wear, high stability - promises of success in a moderately cross-linked cup?
abstract: OBJECTIVE
  Cross-linking has proven effective in reducing polyethylene wear in total hip replacements. However, increasing the amount of cross-links will impair other mechanical properties of the polyethylene. The optimal threshold of crosslinking has still not been established. This led to the development of a moderately cross-linked (5 Mrad) cemented cup in which wear and stability is yet to be determined.
  
  
  METHODS
  A total of, 70 hips were included in this case series on the cemented Marathon® cup. Mean age of the patients was 78 years (SD 15). We measured wear and migration by radiostereometry at 3, 12 and 24 months.
  
  
  RESULTS
  The proximal wear rate estimate between 3 to 24 months was 0.036 mm/year, and a total proximal wear estimate at 2 years of 0.11 mm (95% CI 0.09-0.14). Translations and rotations along the 3 cardinal axes were all at or below the precision limit, and less than what is believed to be predictive of later loosening, namely 0.2-1 mm for proximal migration. The cups remained stable after the initial "bedding in" that occurred during the first 3 months.
  
  
  CONCLUSIONS
  Our results indicate that moderate cross-linking (5Mrad) yields low wear and high stability in this specific acetabular cup, comparable to other cups with higher cross-linking.
authors.affiliation: 1 Orthopaedic Department, Oslo University Hospital, Ullevål, Oslo - Norway.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Flatøy
authors.forename: Jonas
authors.initials: J
authors.lastname: Rydinge
authors.forename: Jon
authors.initials: J
authors.lastname: Dahl
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Röhrl
authors.forename: Lars
authors.initials: L
authors.lastname: Nordsletten
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001843:Bone Cements; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D015207:Osteoarthritis, Hip / Q000601:surgery*; D020959:Polyethylene; D011474:Prosthesis Design; D012189:Retrospective Studies
chemical_list: D001843:Bone Cements; D020959:Polyethylene