title: Pelvis and total hip arthroplasty acetabular component orientations in sitting and standing positions: measurements reproductibility with EOS imaging system versus conventional radiographies.
abstract: BACKGROUND
  The literature has recently underlined the interest of pelvic and acetabular component orientation measurements in the standing and sitting position. Radiographic follow-up of total hip arthroplasty (THA) is based on standard AP and lateral X-rays. The use of EOS™ 2D imaging system reduces patient's radiation exposure compared to conventional X-rays. However, using this system, the validity and reproducibility of angular measurements, have not been studied yet for the measurement of pelvic and acetabular parameters in patients with THA.
  
  
  OBJECTIVE
  The EOS™ 2D imaging system offers similar advantages to conventional X-rays in the measurement of pelvic and acetabular orientation parameters which are commonly used.
  
  
  METHODS
  Five angular parameters characterizing pelvic tilt and acetabular cup orientation were determined using the same digital measurement Imagika™ software based on two series of standard X-rays and EOS™ 2D images acquired in both standing and sitting positions. Radiographs from 50 patients with unilateral THA were measured three times by two observers. Intra- and interobserver reproducibility using each method was independently studied then paired comparison was performed.
  
  
  RESULTS
  The ICC and Spearman rank correlation coefficient demonstrated an excellent EOS/conventional X-ray correlation. According to the parameters, the mean difference between these two imaging modalities ranged from 0.30° to 3.43° (P<0.05). The intra- and interobserver variability ranged from ± 2.97° to ± 6.46° using the EOS™ imaging system and from ± 4.26° to ± 10.22° using conventional X-rays (P<0.05).
  
  
  CONCLUSIONS
  The EOS™ 2D imaging system may replace conventional X-rays in the assessment and monitoring of pelvic and acetabular cup orientation in THA.
  
  
  METHODS
  Level III. Prospective diagnostic study.
authors.affiliation: Department of orthopaedic and trauma surgery, Pitié-Salpêtrière hospital, 47-83, boulevard de l'Hôpital, 75634 Paris cedex 13, France. lazennec.jy@wannadoo.fr
authors.forename: J Y
authors.initials: JY
authors.lastname: Lazennec
authors.forename: M A
authors.initials: MA
authors.lastname: Rousseau
authors.forename: A
authors.initials: A
authors.lastname: Rangel
authors.forename: M
authors.initials: M
authors.lastname: Gorin
authors.forename: C
authors.initials: C
authors.lastname: Belicourt
authors.forename: A
authors.initials: A
authors.lastname: Brusson
authors.forename: Y
authors.initials: Y
authors.lastname: Catonné
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010384:Pelvic Bones / Q000000981:diagnostic imaging* / Q000601:surgery; D011182:Postoperative Care / Q000379:methods; D011187:Posture; D011446:Prospective Studies; D011830:Radiation Effects; D015203:Reproducibility of Results; D018570:Risk Assessment; D025321:Surgery, Computer-Assisted / Q000009:adverse effects / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome