Motion Capture based Dynamic Assessment of Hip Joint Cartilage Contact Pressure during Daily Activities

Hip joint cartilage contact stresses are clinically relevant and necessary to improve our understanding of hip osteoarthritis. Therefore, the objective of this paper is to assess the contact pressure changes during series of dynamic postures such as slow walking, normal walking, fast walking, descending stairs and ascending stairs. A standard anatomical model is built from CT images and twenty kinematical models are constructed using a motion capture system. A two-step adjusted-iterative closest point method is proposed to register the anatomical model with the motion capture recorded kinematical model. After the registration, acetabular cartilage contact pressure is analyzed by a finite element method. According to simulation results among twenty subjects, the contact pressure distribution of walking and stairs movements are mostly uniform during a cycle of movement. The peak of contact pressure appears at the transition location from superior to posterior. The peak of contact pressure happens almost at the time of heel-strike. The contact area is changing from anterior to superior-posterior and ending at anterior for all the activities. These results demonstrate the trends for normal hip contact pressure in cartilage during daily activities. These results also provide guidance for the diagnosis of osteoarthritis. The location at transition from superior to posterior should be paid more attention in the diagnosis of osteoarthritis. And the osteoarthritis patient should try to avoid the movement of ascending and descending stairs.