title: Reduced variability in cup positioning: the direct anterior surgical approach using navigation.
abstract: OBJECTIVE
  Correct positioning of the acetabular component is important in total hip arthroplasty (THA). We evaluated the effect of an imageless navigation system on the accuracy of cup positioning using a minimally invasive direct anterior approach.
  
  
  METHODS
  Hip replacements were performed in 44 cadaveric hips (22 cadavers) that were divided randomly into 2 groups. In the study group, THA was performed using an imageless navigation system. In the control group, no navigation system was used. CT scans were taken postoperatively. Using 3D reconstructions, the cup position was determined in relation to the frontal pelvic plane. The goal was to place each cup at 45 degrees of inclination and 20 degrees of anteversion, as recommended by the manufacturer.
  
  
  RESULTS
  In the navigated group, there was a statistically significantly smaller range of deviation from the target angles of inclination and anteversion relative to the control group.
  
  
  CONCLUSIONS
  We conclude that imageless navigation improves the accuracy of cup placement in minimally invasive THA using the direct anterior approach.
authors.affiliation: Department of Orthopedics, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Nogler
authors.forename: Eckart
authors.initials: E
authors.lastname: Mayr
authors.forename: Martin
authors.initials: M
authors.lastname: Krismer
authors.forename: Martin
authors.initials: M
authors.lastname: Thaler
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D011859:Radiography; D025321:Surgery, Computer-Assisted