Properties of growing trabecular ovine bone - Part I: Mechanical and physical properties

Our aim was to determine the relationship between age and the mechanical an d physical properties of trabecular bone, to describe the patterns in which the variations in these properties take place, and to investigate the infl uence of the physical properties on the mechanical characteristics of trabe cular bone during growth. We used 30 lambs in three age groups and 20 sheep in two age groups. Cubes of subchondral bone were cut from the proximal ti bia according to a standardised protocol, We performed non-destructive comp ression tests of the specimens in three orthogonal directions and compressi on tests to failure in the axial direction. The physical properties of the specimens were also determined, The data were correlated with age and compa red in skeletally immature and mature animals. Multiple regression analyses were performed between the mechanical and the physical properties. Age correlated positively with elastic modulus, bone strength, energy absor ption to failure, elastic energy, mechanical anisotropy ratio, tissue densi ty, apparent density, apparent ash density, and bone mineral content, and i nversely with ultimate strain, viscoelastic energy absorption, relative ene rgy loss, the collagen content of bone and the percentage porosity, The val ues of all variables were significantly different in the skeletally mature and immature groups. The apparent density of trabecular bone tissue tvas fo und to be tbe major predictor of its compressive mechanical properties. Tog ether with the content of bone muscle and bone collagen, the apparent densi ty.