The Biomechanical Integrity of Bone in Experimental Diabetes

Patients with diabetes mellitus incur a higher incidence of fractures compared to healthy individuals. This suggests that the structural integrity of the skeletal system may be compromised. To examine the biomechanical consequences of diabetes, we studied the structural integrity of the femur and tibia of rats with streptozotocin-induced diabetes. The induction of diabetes was confirmed by measuring blood glucose levels (>300 mg/dl). Seven-weeks following the establishment of diabetes, the animals were euthanized and the hind limbs removed. The femur and tibia of each hind limb were excised, and prepared for three point bending test on an Instron Materials Testing System. The results revealed a 37% decrease in maximum load (breaking strength) of the femur of diabetic rats when compared to controls. The diabetic femurs had 25% less deformation at maximum load compared to controls. Similarly, energy absorption capacity to yield point and toughness were reduced by 27 and 34%, respectively, in the diabetic femur. A 38% increase in the bending stiffness was observed in the femurs of diabetic rats. Similar results were obtained with the tibias of both groups. Measurement at the break point revealed that the bones of diabetic rats bore significantly less load, deformation and energy absorption capacity than controls. Overall, our findings warrant the conclusion that the diabetic state is associated with mechanical deterioration of bone, resulting in bones with inferior biomechanical integrity.