In Vivo Determination of Femoral Head Loci Pathways During Gait In Subjects Having Either A Metal-On-Metal or Metal-On Polyethylene THA

Twenty subjects were analyzed in vivo using video fluoroscopy. Ten subjects had a metal-on-metal (MOM) THA and ten subjects had a metal-on-polyethylene (MOP) THA. All THA subjects were implanted by the same surgeon and judged clinically successful (Harris hip scores >94.0). Each subject performed normal gait while under frontal fluoroscopic surveillance. The two-dimensional (2D) fluoroscopic videos were converted into 3D using a computer automated model-fitting technique (Figure 1) (Sarojak, 1998). Five distinct femoral head positions were defined in the femoral head reference frame and transformed in the acetabular cup reference frame. At various flexion angles, these five loci positions were located, tracked and plotted with respect to flexion angle and time (Figure 2). In Vivo Determination of Femoral Head Loci Pathways During Gait In Subjects Having Either A Metal-On-Metal or Metal-On Polyethylene THA