Influence of Storage Duration on Retention of Original Fracture Toughness

Accurate knowledge of bone properties is central in the prediction of failure and the development of injury treatment protocols. Often when bone properties are measured experimentally, bone specimens have to be chemically preserved prior to or during testing. Understanding the effect of the bone preservation method on the material properties is important. Degradation of properties due to preservation methods may lead to incorrect reporting of values of the bone properties. A salient question is, therefore, whether the preservation of bovine cortical bone in ethanol for extended periods of time affects fracture toughness; and if so, whether that affect is reversible. To answer these questions, a three-point bending test set-up was constructed to perform experiments over a period of 9 weeks. A total of 109 specimens of cortical bone of the same orientation were manufactured from the mid-diaphysis of the femur. These specimens were separated into three groups based on location in the femur; namely, medial, lateral, and posterior. The specimens were preserved in ethanol. At the end of each week, a sample of specimens was selected for testing, with the last sample tested after 9 weeks of preservation. It was shown that after 9 weeks of preservation in ethanol, followed by rehydration with physiological saline, the fracture toughness of the specimen was unchanged from that of the control specimen. Omission of rehydration in saline resulted in to an increased fracture toughness of up to 17%.