title: Inter-Rater and Intra-Rater Repeatability and Reliability of EOS 3-Dimensional Imaging Analysis Software.
abstract: Quantifying ideal component position for the acetabulum and stem during total hip arthroplasty (THA) has been described by many methods. A new imaging method using low-dose digital stereoradiography, the EOS imaging system, is a biplanar low-dose X-ray system that allows for 3-dimensional modeling of lower limbs and semiautomated measurement of pelvic parameters and implant alignment.
  
  
  
  Twenty-five patients who underwent primary THA by a single surgeon between October 2014 and December 2014 were retrospectively selected. Only patients with unilateral THA without associated spine pathologies were included, totaling 16 right hips and 9 left hips. There were 8 men and 17 women in the cohort, with a mean age of 67 years (range, 53-82). Three individuals performed measurements of pelvic parameters and implant alignment on 3 separate occasions. An interclass correlation of >0.75 was accepted as evidence of excellent agreement and a confirmation of measurement reliability.
  
  
  
  Before reviewing patient radiographs, 4 pelvic phantom models were analyzed using the EOS 3-dimensional software to verify accuracy. All anatomic and implant measurements performed by the 3 independent reviewers showed interobserver and intraobserver agreement with interclass correlation >0.75.
  
  
  
  Three-dimensional modeling of hip implants with the EOS imaging system is a reasonable option for the evaluation of component position after THA.
authors.affiliation: Northwestern University, Feinberg School of Medicine, Chicago, IL.
authors.forename: Alysen L
authors.initials: AL
authors.lastname: Demzik
authors.affiliation: Department of Orthopaedic Surgery, Northwestern University, Chicago, Illinois.
authors.forename: Hasham M
authors.initials: HM
authors.lastname: Alvi
authors.affiliation: Department of Orthopaedic Surgery, Northwestern University, Chicago, Illinois.
authors.forename: Dimitri E
authors.initials: DE
authors.lastname: Delagrammaticas
authors.affiliation: Department of Orthopaedic Surgery, The University of Chicago, Chicago, Illinois.
authors.forename: John M
authors.initials: JM
authors.lastname: Martell
authors.affiliation: Department of Orthopaedic Surgery, Northwestern University, Chicago, Illinois.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Beal
authors.affiliation: Department of Orthopaedic Surgery, Northwestern University, Chicago, Illinois.
authors.forename: David W
authors.initials: DW
authors.lastname: Manning
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D017760:Bone Malalignment / Q000000981:diagnostic imaging; D003198:Computer Simulation; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging* / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000592:standards*; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010384:Pelvic Bones / Q000000981:diagnostic imaging* / Q000601:surgery; D019047:Phantoms, Imaging; D011184:Postoperative Period; D059869:Radiostereometric Analysis / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012984:Software
keywords: EOS imaging; radiographic analysis; total hip arthroplasty