Kinematic radiography of the hip joint after hip resurfacing arthroplasty

This study aimed to evaluate the usefulness of dynamic radiography using a dynamic flat-panel detector (FPD) system after hip resurfacing arthroplasty (HRA). A total of 32 hips of 26 patients who underwent HRA were included. Sequential images of active abduction in the supine position and flexion in the 45° semilateral position were obtained using the FPD system. We examined the imaging findings of impingement between the acetabular component and femoral neck with cooperative motion at maximal exercise. Moreover, the central component coordinate of the acetabulum and femoral head sides was measured. For abduction motion, impingement was detected in two (6.3 %) hips between the superior portion of the femoral neck and acetabular component. For flexion motion, impingement was detected in 19 (59.4 %) hips. There were no findings of subluxation between the acetabular component and femoral neck after impingement, but cooperative motion of lumbar and pelvic flexion was observed. There was no significant difference in the center-to-center distance regardless of the presence or absence of impingement. Detailed postoperative kinematics of the hips after HRA showed that the proposed dynamic FPD system could reveal acquired impingement and cooperative motion as dynamic images and possibly reveal findings that would be unobservable using static images.