Anisotropy of the Young's modulus of bone

Abstract

THE anisotropy in elastic deformation exhibited by compact bone sections is well known¹, but has been démonstrated mainly for orientations parallel to, (designated as longitudinal) or, normal to, (designated as transverse or radial), the long axis of the bone. Various models based on the concept that bone is a hydroxyapatite-reinforced collagen composite have been proposed (for example ref. 2) to account for the elastic behaviour of compact bone, as defined by the Young's modulus (E), but lack of data for a range of orientations has precluded one critical test of their validity. We report here preliminary measurements on the Young's modulus of mature bovine femur cortical bone for specimens orientated at various angles from 0° to 90° to the bone long axis. These results were obtained on a series of rectangular-shaped, machined, specimens (4 mm × 3 mm) with two different lengths (15 mm and 20 mm), by a novel differential ultrasonic technique, which is illustrated in Figs 1 and 2.