title: No increased migration in cups with ceramic-on-ceramic bearing: an RSA study.
abstract: Ceramic-on-ceramic hip replacements might stress the bone interface more than a metal-polyethylene because of material stiffness, microseparation, and sensitivity to impingement. To ascertain whether this potentially increased stress caused an increased cup migration we compared a ceramic-on-ceramic with a metal-on-polyethylene implant for cup migration. Sixty one patients (61 hips) undergoing THA for osteoarthritis were randomized to ceramic on ceramic (Ce/Ce) or cobalt-chromium on cross-linked polyethylene bearings (PE) in the same uncemented cup shell. Migration was followed with RSA. At 2 years we observed similar mean cup translations in the 3 directions (0.07-0.40 mm vs. 0.05-0.31 mm, Ce/Ce vs. PE), as well as similar rotations around the 3 axes (0.31-0.92 degrees vs. 0.57-1.40 degrees). WOMAC and SF-36 scores were also similar and no radiolucent lines or osteolysis found. The large migration seen in some cups in both implant groups will require close monitoring to ascertain the reasons. Mean proximal wear of the polyethylene liners measured 0.016 mm between 2 and 24 months. Our data suggest there is no increased cup migration in the ceramic-on-ceramic implant compared with the metal-on-polyethylene, and they seem an equally safe choice. However, the low wear measured with the more versatile and less expensive cross-linked polyethylene makes it a strong contender.
  
  
  METHODS
  Therapeutic Level I. See the Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Perth Orthopaedic Institute, the University of Western Australia.
authors.forename: Zong-Ke
authors.initials: ZK
authors.lastname: Zhou
authors.forename: Ming G
authors.initials: MG
authors.lastname: Li
authors.forename: Niclas
authors.initials: N
authors.lastname: Börlin
authors.forename: David J
authors.initials: DJ
authors.lastname: Wood
authors.forename: Bo
authors.initials: B
authors.lastname: Nivbrant
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D002516:Ceramics; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D016896:Treatment Outcome