Mechanical properties of femoral diaphysis and femoral neck of female rats chronically exposed to various levels of cadmium.

The effect of chronic exposure to cadmium (Cd) on the mechanical properties of femoral diaphysis and femoral neck was investigated on a rat model of human exposure. Three-week-old female Wistar rats were exposed to Cd in drinking water at concentrations of 1, 5, 50, or 100 mg/L for 12 months. Biomechanical properties of the femoral diaphysis were evaluated in a three-point bending test and those of the femoral neck in a bending test with vertical loading of the head. Bone mineral content (BMC) and bone mineral density (BMD) at the whole femur, and BMD at the diaphysis and proximal femur (head and neck region) of the Cd-treated rats decreased in a dose-dependent manner, except for the diaphyseal BMD at a Cd concentration of 1 mg/L. Exposure to Cd concentrations of 1 and 5 mg/L had only little effect on the diaphyseal mechanical properties (decreased yield load with unchanged bending strength, stiffness, yield stress, ultimate stress, and Young modulus), whereas the bending strength and stiffness of the neck decreased and the yield load clearly tended to decline or declined. The effect of Cd at the two locations was more marked in the 50 and 100 mg/L groups, and changes in the bone geometry were observed in these animals. The results clearly revealed that chronic, even low-level, exposure to Cd results in demineralization and weakening of the femur. The femoral neck seems to be more vulnerable than the diaphysis to failure from Cd. We conclude that environmental exposure to Cd may be an important risk factor for femoral neck fracture.