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Abstract
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.
PL and CKB developed the study design and performed data collection, analysis, interpretation, and writing. MF, AG, BB, SR, AM, and TR performed data interpretation and critical revision.
We are grateful for useful advice and suggestions from Hagen Langhuth, MSc, Jochen Schröder, MD, Vinzenz Pfeifer, and Laura Waltl, MSc.
No competing interests declared.