title: Deformation of the Zurich cementless acetabular cup caused by implantation in a canine cadaver model.
abstract: OBJECTIVE
  To evaluate the change in geometry of the Zurich total hip arthroplasty (THA) acetabular component after implantation.
  
  
  METHODS
  Hemipelves from adult mix-breed dogs weighing between 20 and 25 kg.
  
  
  METHODS
  Digital image correlation imaging was performed prior to, immediately after, and 24 hours after impaction of Zurich THA acetabular component, and after removal of the cup from the specimen. Patterns of deformation were qualitatively described, and maximal deformations were compared between time points.
  
  
  RESULTS
  All cups deformed after implantation into the hemipelves by "pinching" in a cranial-caudal direction and dorsoventral expansion, resulting in an ellipsoid configuration to the peripheral rim. The mean ± SD maximum deformation at the rim immediately post-impaction was 0.202 ± 0.052 mm, or approximately 0.4 mm of diametrical deformation. Deformation did not change after the 24-hour saline bath. Impaction and subsequent extraction had a marginal effect on the original cup geometry, as maximum deformation at the rim after cup extraction was 0.074 ± 0.032 mm, relative to prior to impaction.
  
  
  CONCLUSIONS
  The original Zurich cup geometry is distorted as a consequence of the press-fit mechanism. Further studies are required to determine whether deformation induced by impaction has any association with polyethylene wear rates or other prosthesis-related complications.
authors.affiliation: Comparative Orthopedics Biomechanics Laboratory, University of Florida, Gainesville, Florida.
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Panjeton
authors.affiliation: Comparative Orthopedics Biomechanics Laboratory, University of Florida, Gainesville, Florida.
authors.forename: Stanley E
authors.initials: SE
authors.lastname: Kim
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida.
authors.forename: Kelvin
authors.initials: K
authors.lastname: Chang
authors.affiliation: Comparative Orthopedics Biomechanics Laboratory, University of Florida, Gainesville, Florida.
authors.forename: Lindsey S
authors.initials: LS
authors.lastname: Palm
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Ifju
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000818:Animals; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D001696:Biomechanical Phenomena; D002102:Cadaver; D004285:Dogs; D006622:Hip Prosthesis / Q000662:veterinary*; D023421:Models, Animal; D011474:Prosthesis Design; D011475:Prosthesis Failure