People whose hip joints have degenerated due to arthritis, trauma, or disease frequently suffer from potentially debilitating joint pain. In many of these cases, joint replacement surgery can restore the patient to a normal lifestyle. In particular, hip resurfacing is becoming increasingly popular, particularly for the young patient population. The theoretical advantages of hip resurfacing when compared with total hip replacement include minimal resection of the femoral head and improved joint stability. Resurfacing may also load the proximal femur in a more physiological manner, thereby reducing bone loss due to stress shielding. Exponent engineers developed high resolution, 3-D finite element models of the proximal femur implanted with a hip resurfacing device. The reduction of strain energy within the superolateral femoral head was determined to be of sufficient magnitude to invoke early bone resorption. Less reduction of stress was demonstrated when the implant was completely debonded from bone. This has also been confirmed in retrievals of resurfacing components that exhibit osteoclastic activity in the proximal femoral head immediately underlying the loading platform. Surgical placement of the femoral component was also found to lead to increased resorption, especially around the periphery of the neck, when the femoral offset was reduced for a valgus oriented implant.
