title: The influence of hip rotation on femoral offset in plain radiographs.
abstract: OBJECTIVE
  Adequate restoration of femoral offset (FO) is critical for successful outcome after hip arthroplasty or fixation of hip fracture. Previous studies have identified that hip rotation influences the projected femoral offset (FOP) on plain anteroposterior (AP) radiographs, but the precise effect of rotation is unknown.
  
  
  METHODS
  We developed a novel method of assessing rotation-corrected femoral offset (FORC), tested its clinical application in 222 AP hip radiographs following proximal femoral nailing, and validated it in 25 cases with corresponding computed tomography (CT) scans.
  
  
  RESULTS
  The mean FORC was 57 (29-93) mm, which differed significantly (p < 0.001) from the mean FOP 49 (22-65) mm and from the mean femoral offset determined by the standard method: 49 (23-66) mm. FORC correlated closely with femoral offset assessed by CT (FOCT); the Spearman correlation coefficient was 0.94 (95% CI: 0.88-0.97). The intraclass correlation coefficient for the assessment of FORC by AP hip radiographs correlating the repeated measurements of 1 observer and of 2 independent blinded observers was 1.0 and 1.0, respectively.
  
  
  CONCLUSIONS
  Hip rotation affects the FOP on plain AP radiographs of the hip in a predictable way and should be adequately accounted for.
authors: Department of Trauma , Hand and Reconstructive Surgery, University of Giessen and Marburg, Marburg , Germany.
authors: Philipp
authors: P
authors: Lechler
authors: Michael
authors: M
authors: Frink
authors: Aashish
authors: A
authors: Gulati
authors: David
authors: D
authors: Murray
authors: Tobias
authors: T
authors: Renkawitz
authors: Benjamin
authors: B
authors: Bücking
authors: Steffen
authors: S
authors: Ruchholtz
authors: Christoph Kolja
authors: CK
authors: Boese
mesh_terms: D001175:Arthrography / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001858:Bone Nails; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D006620:Hip Fractures / Q000000981:diagnostic imaging* / Q000601:surgery*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008954:Models, Biological; D015588:Observer Variation; D016059:Range of Motion, Articular; D020127:Recovery of Function; D015203:Reproducibility of Results; D012399:Rotation; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data