title: Comparison of Three-Dimensional Planning-Assisted and Conventional Acetabular Cup Positioning in Total Hip Arthroplasty: A Randomized Controlled Trial.
abstract: BACKGROUND
  Malpositioning of the acetabular cup during total hip arthroplasty increases the risk of dislocation, edge-loading, squeaking, early wear, and loosening. We hypothesized that the use of three-dimensional (3-D) visualization tools to identify the planned cup position relative to the acetabular edge intraoperatively would increase the accuracy of cup orientation. The purpose of this study was to compare 3-D planning-assisted implantation and freehand insertion of the acetabular cup.
  
  
  METHODS
  This was a prospective randomized controlled study of two groups of twenty-eight patients each. In the first group, cup positioning was guided by 3-D views of the cup within the acetabulum obtained during 3-D preoperative planning. In the control group, the cup was placed freehand. All of the patients were operated on by the same surgeon, through a minimally invasive direct anterior approach with the patient in the supine position. Cup anteversion and abduction angles were measured on 3-D computed tomography (CT) reconstructions. The main evaluation criterion was the percentage of outliers according to the Lewinnek safe zone.
  
  
  RESULTS
  Operative time did not differ between the two groups. The cup anteversion was more accurate in the 3-D planning group (mean difference from the planned angle [and standard deviation], -2.7° ± 5.4°) compared with the freehand-placement group (6.6° ± 9.5°). According to the Lewinnek safe zone, overall, the percentage of outliers was lower in the 3-D planning group (21%; six patients) than in the control group (46%; thirteen patients). According to the Callanan safe zone, the percentage of outliers was also lower in the 3-D planning group (25% versus 64%). Although cup abduction was also restored with greater accuracy in the 3-D planning group, on the basis of the Lewinnek safe zone, the percentage of abduction outliers was comparable between groups, with fewer high-abduction values, but more low-abduction values, in the 3-D planning group.
  
  
  CONCLUSIONS
  Preoperative 3-D planning increased the accuracy of anteversion restoration and reduced the percentage of outliers without increasing the operative time. In this study, the same advantage could not be demonstrated for abduction.
  
  
  METHODS
  Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Hôpitaux Universitaires La Pitié Salpêtrière-Charles Foix, AP-HP, Paris, France hedisari@yahoo.fr.
authors.forename: Elhadi
authors.initials: E
authors.lastname: Sariali
authors.affiliation: INRIA, Saclay, France.
authors.forename: Nadia
authors.initials: N
authors.lastname: Boukhelifa
authors.affiliation: Hôpitaux Universitaires La Pitié Salpêtrière-Charles Foix, AP-HP, Paris, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Catonne
authors.affiliation: Hôpitaux Universitaires La Pitié Salpêtrière-Charles Foix, AP-HP, Paris, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Pascal Moussellard
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000601:surgery; D010147:Pain Measurement; D056888:Patient Positioning / Q000379:methods; D011300:Preoperative Care / Q000379:methods; D016059:Range of Motion, Articular / Q000502:physiology*; D020127:Recovery of Function; D018570:Risk Assessment; D012720:Severity of Illness Index; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D014463:Ultrasonography