Anisotropic bone remodeling of a biomimetic metal-on-metal hip resurfacing implant.

Hip resurfacing (HR) is a highly attractive option for young and active patients. Some surgeons have advocated cementing the metaphyseal stem of the femoral component to improve fixation and survivorship of HR. However, extending component fixation to the metaphysis may promote femoral head strain shielding, which in turn may reduce survival of the femoral component. Replacing the metallic metaphyseal stem by a composite material with bone-matching properties could help to alleviate this phenomenon. This study uses finite element analysis to examine the strain state in the femoral head for three types of implant fixation: an unfixed metallic stem, an osseointegrated biomimetic stem and a cemented metallic stem. Bone remodeling is also simulated to evaluate long-term bone resorption due to strain shielding. Results show that the unfixed stem causes strain shielding in the femoral head, and that cementing the stem increases strain shielding. The biomimetic stem does not eliminate the strain shielding effect, but reduces it significantly versus the metallic cemented version. The current finite element study suggests that an osseointegrated metaphyseal stem made of biomimetic material in hip resurfacing implants could become an interesting alternative when fixation extension is desired.