title: Comparison of femoral head penetration using RSA and the Martell method.
abstract: Radiostereometry has high precision and accuracy measuring polyethylene wear in total hip arthroplasty but requires a specialized setup. The Martell method is simpler and can be used on larger populations. The hypothesis that the radiostereometry analysis and the Martell analysis would yield comparable wear data from the same group of patients having total hip arthroplasty was tested. A group of twenty-five total hip arthroplasty patients who had both radiostereometry and standard anterior-posterior pelvic and cross-table lateral radiographs of sufficient quality for analysis were identified. The films were taken at postoperative periods of 6 weeks, 1 year, 2 years, and 5 years. Femoral head penetration was measured by both methods at each time point. The median penetration rates measured by each method decreased over time. Penetration results were affected by method of analysis, time, and dimension, with greater penetration for Martell compared with radiostereometry at each time point, greater penetration with increasing time for each method, and larger three-dimensional magnitude compared with two-dimensional analysis.
  
  
  METHODS
  Case series Level IV. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Orthopaedic Biomechanics and Biomaterials Laboratory and the Adult Reconstructive Unit of the Department of Orthopaedic Surgery of Massachusetts General Hospital and Harvard Medical School, Boston, 02114, USA. cbragdon@partners.org
authors.forename: Charles R
authors.initials: CR
authors.lastname: Bragdon
authors.forename: John M
authors.initials: JM
authors.lastname: Martell
authors.forename: Meridith E
authors.initials: ME
authors.lastname: Greene
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Estok
authors.forename: Jonas
authors.initials: J
authors.lastname: Thanner
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
authors.forename: William H
authors.initials: WH
authors.lastname: Harris
authors.forename: Henrik
authors.initials: H
authors.lastname: Malchau
mesh_terms: D001175:Arthrography / Q000379:methods*; D019644:Arthroplasty, Replacement, Hip; D005270:Femur Head / Q000000981:diagnostic imaging* / Q000601:surgery; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D010780:Photogrammetry; D011475:Prosthesis Failure; D015203:Reproducibility of Results