Age-related hypermineralization in the female proximal human femur

Hip fracture incidence increases exponentially with age in virtually every human population that has been studied. In spite of this, relatively few st udies have examined age-related changes in the metaphyseal cortex of the pr oximal femur. The present study investigates cortical aging changes in the female proximal femur, with particular reference to regions of hypermineral ization. Thirty-three femora from Caucasian females were obtained at autops y and analyzed using backscattered electron imaging. Variations in hypermin eralized tissue area, cortical bone area, and porosity were quantified with standard stereological methods. Cortical width was quantified with digital calipers. Gender differences were examined by statistical comparison with previously published results. Hypermineralized tissue volume was significan tly (P < 0.001) greater in elderly individuals. Hypermineralized tissue pre ferentially appeared near ligamentous or tendinous insertion sites, suggest ing the hypermineralized tissue may be a calcified fibrocartilage. Cortical width significantly (P < 0.001) decreased with age and porosity significan tly (P < 0.001) increased with age, however the changes were site-specific. The femoral neck and intertrochanteric cortices had a smaller change in co rtical width and porosity with age than the diaphysis, but the femoral neck and intertrochanteric cortices had a larger increase in hypermineralized t issue. Comparison with previous data suggests that cortical aging in the pr oximal femur is similar between males and females and is unlikely to explai n the higher incidence of fracture in females. However, the data strongly i ndicates that age-related changes in the femoral diaphysis cannot be direct ly extrapolated to either the femoral neck or intertrochanteric cortices. A nat Rec 255:202-211, 1999. (C) 1999 Wiley-Liss, Inc.