Mechanical properties of bone as a function of position and orientation

Abstract

This paper considers the variation in the mechanical properties of the long bones as a function of position and orientation with respect to the longitudinal axis of the bone. Small specimens of bovine tibiae were taken at various positions along the bone in three mutually perpendicular directions. These were tensile tested to failure and the fracture stress and elastic moduli measured. It was found that the long bone changes from being highly anisotropic at the mid-diaphysis to essentially isotropic at the epiphyses. The variation of mechanical properties between the axes were measured and mathematical models given to describe the behavior. A failure stress criterion for bone substance is given. A three-dimensional failure locus is given enabling one to predict the failure stress and direction of the failure of cortical bone under a given set of combined stresses.