title: Computer-assisted cup placement techniques in total hip arthroplasty improve accuracy of placement.
abstract: Malposition of the acetabular component during hip arthroplasty increases the occurrence of impingement, reduces range of motion, and increases the risk of dislocation and long-term wear. To prevent malpositioned hip implants, an increasing number of computer-assisted orthopaedic systems have been described, but their accuracy is not well established. The purpose of this study was to determine the reproducibility and accuracy of conventional versus computer-assisted techniques for positioning the acetabular component in total hip arthroplasty. Using a lateral approach, 150 cups were placed by 10 surgeons in 10 identical plastic pelvis models (freehand, with a mechanical guide, using computer assistance). Conditions for cup implantations were made to mimic the operating room situation. Preoperative planning was done from a computed tomography scan. The accuracy of cup abduction and anteversion was assessed with an electromagnetic system. Freehand placement revealed a mean accuracy of cup anteversion and abduction of 10 degrees and 3.5 degrees, respectively (maximum error, 35 degrees). With the cup positioner, these angles measured 8 degrees and 4 degrees (maximum error, 29.8 degrees), respectively, and using computer assistance, 1.5 degrees and 2.5 degrees degrees (maximum error, 8 degrees), respectively. Computer-assisted cup placement was an accurate and reproducible technique for total hip arthroplasty. It was more accurate than traditional methods of cup positioning.
authors.affiliation: Department of Orthopaedic Surgery, University Hospital of Geneva, HUG, Switzerland. Brigitte.Jolles@chuv.hospvd.ch
authors.forename: Brigitte M
authors.initials: BM
authors.lastname: Jolles
authors.forename: Patrick
authors.initials: P
authors.lastname: Genoud
authors.forename: Pierre
authors.initials: P
authors.lastname: Hoffmeyer
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D055590:Electromagnetic Phenomena; D006801:Humans; D008953:Models, Anatomic; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted