title: Accuracy of angle and position of the cup using computed tomography-based navigation systems in total hip arthroplasty.
abstract: OBJECTIVE
  The objectives of this study were to evaluate the accuracy of computed tomography (CT)-based navigation and to investigate whether the level of surgeon experience affects the accuracy of cup positioning under navigation.
  
  
  METHODS
  This study investigated 117 hips in 103 patients who underwent primary total hip arthroplasty (THA) by 7 surgeons using a CT-based navigation system. Pre- and postoperative CT images were matched using a volume registration technique. Postoperative cup angles and positions were then measured using the same pelvic coordinates, and results were compared for experienced and inexperienced surgeons.
  
  
  RESULTS
  The mean absolute error of the cup angle was 1.8 ± 1.6° for inclination and 1.2 ± 1.1° for anteversion. The mean absolute errors of cup position were 1.9 ± 1.5 mm, 1.4 ± 1.2 mm, and 1.9 ± 1.3 mm on the x-, y- and z-axes, respectively. No significant differences in accuracy were identified between experienced and inexperienced surgeons.
  
  
  CONCLUSIONS
  The absolute spatial error of cup position was ≤ 2 mm for each axis, and the angle error was ≤ 2° for the angles of inclination and anteversion. This navigation system could therefore help surgeons perform accurate cup placement irrespective of the surgeon's level of experience.
authors.affiliation: Department of Orthopaedic Surgery, Kyowakai Hospital , Osaka , Japan .
authors.forename: Daiki
authors.initials: D
authors.lastname: Iwana
authors.forename: Nobuo
authors.initials: N
authors.lastname: Nakamura
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Miki
authors.forename: Makoto
authors.initials: M
authors.lastname: Kitada
authors.forename: Takehito
authors.initials: T
authors.lastname: Hananouchi
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sugano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging / Q000601:surgery; D019644:Arthroplasty, Replacement, Hip; D002983:Clinical Competence; D015331:Cohort Studies; D005260:Female; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000601:surgery; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome