title: Randomised controlled trial comparing two methods of acetabular cup positioning during total hip arthroplasty.
abstract: BACKGROUND
  Acetabular cup positioning is an important technical aspect in total hip arthroplasty. Most surgeons estimate cup abduction angle during surgery with the insertion rod position according to the patient's body anatomical landmarks or other reference points in the operating room. High acetabular component abduction angle is associated with an increased risk of dislocation, premature polyethylene wear and osteolysis.
  
  
  METHODS
  To evaluate the potential benefits of a new technique for vertical acetabular cup positioning, 100 acetabular cups were randomised to be inserted with or without an inclinometer. Abduction angles were measured on postoperative radiographs by 2 evaluators blind to the treatment group.
  
  
  RESULTS
  Of the cups, 57% (27/47) were positioned within the desirable abduction angle range of 40-49 with the inclinometer, compared with 50% (27/53) by visuospatial perception (p=0.454). The proportion of cups positioned outside a safe angle range of 30-55 was low in both groups: 6% (3/47) for the inclinometer group versus 4% (2/53) for the visuospatial perception group (p=0.536).
  
  
  CONCLUSIONS
  The use of an inclinometer did not significantly improve the acetabular cup abduction angle obtained by our group of surgeons when compared with visuospatial perception. Newer techniques such as navigation may be useful in further optimising cup positioning and reducing the outliers.
authors.affiliation: Orthopaedic Division, Department of Surgery, Maisonneuve-Rosemont Hospital, Montral, Qubec, Canada. pa.vendittoli@videotron.ca; pa_vendittoli@hotmail.com
authors.forename: P A
authors.initials: PA
authors.lastname: Vendittoli
authors.forename: M
authors.initials: M
authors.lastname: Ganapathi
authors.forename: N
authors.initials: N
authors.lastname: Duval
authors.forename: P
authors.initials: P
authors.lastname: Lavoie
authors.forename: A
authors.initials: A
authors.lastname: Roy
authors.forename: M
authors.initials: M
authors.lastname: Lavigne