Radiographic quantification of dynamic hip screw migration

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