title: Computerized virtual surgery demonstrates where acetabular rim osteophytes most reduce range of motion following total hip arthroplasty.
abstract: BACKGROUND
  Acetabular osteophytes are common findings during total hip arthroplasty (THA).
  
  
  OBJECTIVE
  This study was designed to determine the extent to which osteophytes may limit range of motion (ROM) and in which locations impingement is likely to occur if osteophytes are not removed during surgery.
  
  
  METHODS
  Computer-aided design was used to compare ROM of a modern hip implant in four cadaver models with and without 10-mm acetabular rim osteophytes added. A clock face, with 12 o'clock at the superior pole of the right acetabulum, was used to map impingement.
  
  
  RESULTS
  The osteophyte model limited ROM in flexion (101° v. 113°, p = 0.03), 90° of flexion with internal rotation (16.7° v. 31.6°, p = 0.01), and external rotation (30.4° v. 49.5°, p = 0.01). Impingement occurred between 7 and 8 o'clock in external rotation and 1 and 2 o'clock in the other two motions.
  
  
  CONCLUSIONS
  Osteophytes in these positions have the greatest impact on ROM and should be removed during THA.
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Rodriguez-Elizalde
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Alyssa M
authors.initials: AM
authors.lastname: Yeager
authors.affiliation: Division of Orthopaedic Surgery, Department of Surgery, University of Toronto, 100 College Street, Toronto, ON M5G 1L5 Canada.
authors.forename: Bheeshma
authors.initials: B
authors.lastname: Ravi
authors.affiliation: Department of Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Lipman
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Salvati
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Geoffrey H
authors.initials: GH
authors.lastname: Westrich
keywords: acetabular osteophytes; computer-aided design; dislocation; range of motion; total hip arthroplasty