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BACKGROUND AND PURPOSE: 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. PATIENTS AND 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. INTERPRETATION: Hip rotation affects the FOP on plain AP radiographs of the hip in a predictable way and should be adequately accounted for.

Original publication

DOI

10.3109/17453674.2014.931196

Type

Journal article

Journal

Acta Orthop

Publication Date

08/2014

Volume

85

Pages

389 - 395

Keywords

Arthrography, Arthroplasty, Replacement, Hip, Bone Nails, Femur, Hip Fractures, Hip Joint, Hip Prosthesis, Humans, Models, Biological, Observer Variation, Range of Motion, Articular, Recovery of Function, Reproducibility of Results, Rotation, Tomography, X-Ray Computed