Standardization of Mechanical Experiments with Biomaterials

Abstract The ability to determine the effective modulus of elasticity of human cancellous bone tissue is clinically significant in many areas of biomedicine, including bone quality assessment, orthopedic treatment planning, and implant design. The modulus of elasticity can be determined from uniaxial compression experiments. Many research teams conduct compression tests on cancellous bone specimens, however, there is no laboratory testing standard for conducting such experiments. This makes it difficult to compare, analyze, and use the constants obtained. The study of bovine cancellous bone specimens was conducted in two laboratories: at Saratov University and Ishlinsky Institute for Problems in Mechanics RAS. Rectangular parallelepiped specimens for the experiments were prepared from lumbar vertebrae and knee joints. The relative height of the specimens is at least 5 units. The effective modulus of elasticity is calculated using the rod theory, which assumes that the specimen is in a state of uniaxial stress. The effect of deformation rate and preliminary cycling on the measured effective modulus of elasticity has been evaluated. It has been shown that two to three cycles of loading and unloading with preliminary cycling up to a deformation of 0.5% are sufficient to stabilize the stiffness of the specimen and the effective modulus. It has been found that in the compression rate range from 0.0009 to 0.009 s –1 , the experimental results do not depend on the deformation rate. The conclusions obtained are valid for “long” cancellous bone specimens with a relative height of at least 5 units. This study represents another step towards the development of a laboratory testing standard for uniaxial compression of cancellous bone specimens to determine their effective modulus of elasticity and other mechanical properties.