title: Independent Evaluation of a Mechanical Hip Socket Navigation System in Total Hip Arthroplasty.
abstract: BACKGROUND
  Acetabular cup malpositioning during total hip arthroplasty may lead to impingement, instability, wear-induced osteolysis, and increased rates of revision surgery. The purpose of this study was to independently evaluate the accuracy of acetabular cup orientation using a novel mechanical navigation device.
  
  
  METHODS
  An adjustable, reusable mechanical navigation device was used in a consecutive series of patients. Angles (inclination and anteversion) were measured by 2 independent reviewers with a validated 2-dimensional/3-dimensional matching application using a preoperative computed tomographic scan and a postoperative plain film.
  
  
  RESULTS
  There were no outliers for inclination or anteversion for errors within 10° of the preoperative plan. There were 6 (12.8%) outliers for inclination and 11 (23.4%) for anteversion for errors within 5° of the preoperative plan. All patients simultaneously met both targets when an outlier was considered 10°, whereas 30 (63.8%) simultaneously met both targets when the criteria was tightened to 5°. The absolute errors for both inclination and anteversion were significantly less than both 5° and 10° (P<.001).
  
  
  CONCLUSIONS
  This device reliably navigates acetabular cup inclination and anteversion individualized for each patient to within 10° of a preoperative plan. Outliers increased when this criteria is tightened to 5° but still appears to be more accurate than conventional acetabular cup component placement. Further research is warranted to assess the clinical impact of reducing outliers using this device.
authors.affiliation: Colorado Joint Replacement, Denver, Colorado.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Jennings
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: Timmothy R
authors.initials: TR
authors.lastname: Randell
authors.affiliation: Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, North Carolina.
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Green
authors.affiliation: Institute for Surgical Technology and Biomechanics University of Bern Stauffacherstrasse 78, CH-3014 Bern Switzerland.
authors.forename: Guoyan
authors.initials: G
authors.lastname: Zheng
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Wellman
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D007592:Joint Diseases / Q000601:surgery*; D008297:Male; D012189:Retrospective Studies; D013238:Stereotaxic Techniques; D025321:Surgery, Computer-Assisted
keywords: acetabular position; hip arthroplasty; mechanical navigation; navigation; outliers