Abstract
PURPOSE: This study aimed to propose a technique to quantify dynamic hip screw (DHS®) migration on serial anteroposterior (AP) radiographs by accounting for femoral rotation and flexion. METHODS: Femoral rotation and flexion were estimated using radiographic projections of the DHS® plate thickness and length, respectively. The method accuracy was evaluated using a synthetic femur fixed with a DHS® and positioned at pre-defined rotation and flexion settings. Standardised measurements of DHS® migration were trigonometrically adjusted for femoral rotation and flexion, and compared with unadjusted estimates in 34 patients. RESULTS: The mean difference between the estimated and true femoral rotation and flexion values was 1.3° (95% CI 0.9-1.7°) and -3.0° (95% CI - 4.2° to -1.9°), respectively. Adjusted measurements of DHS® migration were significantly larger than unadjusted measurements (p = 0.045). CONCLUSION: The presented method allows quantification of DHS® migration with adequate bias correction due to femoral rotation and flexion.