A novel total hip resurfacing design with improved range of motion and edge-load contact stress

• The prosthesis design showed a significant increment of range of motion.
• The new design reduces the contact pressure when edge contact occurs.
• Edge load and micro-separation wear effect were evaluated in a hip joint simulator.

A new hip resurfacing prosthesis design was assessed and compared in terms of kinematics and contact stress regarding to the conventional hip resurfacing prosthesis. For this purpose both designs were virtually implanted in a cadaveric computer-aided design model. Commercial software was employed to simulate the movements of flexion, abduction and internal rotation at 90° of flexion to determinate the impingement between femoral neck and acetabular cup. On the other hand, the edge load effect as consequence of different acetabular component inclinations and micro-separations were analyzed by finite element analysis for both designs. In addition, this effect was validated in the hip joint simulator FIME II. The results of the new design exhibited a significant motion increment before impingement of 12.8° ± 1.3° for flexion, 13.3° ± 3.1° for extension, 7.8° ± 1.9° for abduction and 13.1° ± 3.2° for internal rotation. Moreover, the new design showed a reduction of the contact stress and stripe wear during the running-in due to the micro-separation effect.