Strategies for improving fixation of femoral components in total hip arthroplasty.

As strategies are considered for improving fixation of femoral components in total hip arthroplasty (THA), one is challenged to exceed the standard set by contemporary cement procedures. However, despite the improved ten- to 15-year clinical results anticipated with current cementing techniques, the limited fatigue strength of polymethylmethacrylate warrants continued investigation of alternative systems, particularly for younger patients and in revision arthroplasty. Design considerations for femoral stems for cementless THA include (1) initial mechanical stability afforded by the stem shape, (2) strength and stiffness of the stem, and (3) surface features relating to biocompatibility and attachment to bone. In one approach a fit-and-fill algorithm has been implemented to design stems that maximize contact between prosthesis and cortex in priority areas to achieve stability. Titanium is recommended for the fabrication of such stems because of its corrosion resistance, its biocompatibility, and its modulus, which is lower than that of cobalt-chromium alloy. Long-term fixation of these implants will be dependent upon the maintenance of normal strain patterns in the host bone. Achievement of this goal will require additional strategies that combine optimal fit and optimal material properties of the prosthesis.