Effect of local density changes on the failure load of the proximal femur.

Hip fracture among the elderly is a large and growing public health issue. Presently, all therapies approved for treatment and prevention of osteoporosis involve pharmacological agents that act systemically. In this study, we evaluated the feasibility of preventing osteoporotic hip fractures with local, rather than systemic, therapy. Our hypothesis is that local therapy to increase bone density may be as effective as systemic therapy in reducing fracture risk. Thus, the goal of this investigation was to use finite element analyses to study the effect of a localized increase in bone density on the strength of an osteopenic, human femur. Finite element predictions of the failure load were made after increasing the bone density within small regions in the proximal femur. The outcome variable from these analyses was the predicted load required to break a femur in a simulated fall to the side with impact on the greater trochanter. Increasing the density by 25% relative to baseline values in a small region (0.86 cm3) of the femoral neck increased the predicted failure load by 6.2%. The same density increase in a much larger region (4.92 cm3) increased the failure load by 15%. Inclusion of more than one region of increased density provided little additional benefit. In comparison, when the density of the entire femur was increased by 5% relative to baseline values, the predicted failure load increased by 5.4%. These findings suggest that agents capable of inducing increased bone density in small regions of the proximal femur have the potential to reduce the risk of hip fracture.