MAIN, R.P.*; DONOVAN, C.M.; BIEWENER, A.A.: Bone strain, bone geometry, and histology in the radii of goats through ontogeny

The measurement of patterns of in vivo bone strain in relation to ontogenetic growth is an area of vertebrate biomechanics that has received little attention. Furthermore, the examination of ontogenetic strain data in light of complementary information on bone geometry and microstructural architecture is even more rare. Here we present bone strain data from the radii of goats from two age groups (3 and 12 weeks of age) with previous data collected for adult goats during a variety of locomotor gaits (Biewener and Taylor, 1986). Bone strain patterns about the midshafts of the radii in these three age groups were examined in conjunction with the cross-sectional geometry of the bone and the microstructural architecture of the bone cortex. The ultimate goal of this study was to discover a functional link between bone mechanics (strain and limb loading) and both cross-sectional geometry and specific bone growth and remodeling patterns through ontogeny. We found that strain patterns in the goat radius were not consistent throughout ontogeny. Although only differing in magnitude on the medial and caudal sides of the bone, strain patterns measured on the cranial cortex in the three age classes were more variable. Whereas cranial and caudal cortices of 3 wk individuals were both loaded in net axial compression, the radii of older individuals experienced significantly greater bending which introduced a craniocaudal gradient of tensile to compressive strain. It seems likely that bone cross-sectional geometry and/or limb kinematics may be responsible for the differences in ontogenetic strain pattern observed. Possible links between functional strain patterns and bone histology are still being examined.