title: Stem design and dislocation after revision total hip arthroplasty: clinical results and computer modeling.
abstract: The effect of the size and shape of the neck and the taper of the femoral stem on dislocation rate after revision total hip arthroplasty was examined. Design I had a large (14/16), long taper with a circular neck cross-section; a fixed 42-mm offset; and a neck that was anteverted relative to the stem. Design II was characterized by a smaller (12/14), shorter taper; a trapezoidal neck cross-section; a progressive (40-50 mm) offset; and no neck anteversion relative to the stem. The stems were digitized and placed through a range of motion using virtual reality software, and the cross-sectional area of the neck, length of the taper, and total arc of motion before impingement between the neck and liner were compared. The dislocation rate at a minimum of 2 years' follow-up was 15.4% (8 of 52) for design I compared with 4.3% (2 of 46) for design II. This finding was consistent with the results of computer modeling, which showed that design I had a cross-sectional area that was 32% greater and a total arc of motion that was 76% less compared with design II. The results suggest that neck and taper design may be an important factor in dislocation after revision total hip arthroplasty.
authors.affiliation: Department of Orthopaedic Surgery, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA. rbarrack@switchboard.net
authors.forename: R L
authors.initials: RL
authors.lastname: Barrack
authors.forename: R A
authors.initials: RA
authors.lastname: Butler
authors.forename: D R
authors.initials: DR
authors.lastname: Laster
authors.forename: P
authors.initials: P
authors.lastname: Andrews
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006617:Hip Dislocation / Q000209:etiology / Q000503:physiopathology*; D006621:Hip Joint / Q000503:physiopathology*; D006622:Hip Prosthesis; D006801:Humans; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012086:Reoperation