MAIN, R.P.*; DONOVAN, C.M.; BIEWENER, A.A.; Harvard University; Harvard University; Harvard University: Bone strain in the goat radius through ontogeny

Do functional bone strain patterns remain uniform during ontogenetic growth? Previous results obtained for chickens (Gallus) suggest that this is the case; but to date no study has examined this for any other species. We obtained in vivo bone strain measurements from the radial midshaft of young goats (Capra hircus) at two different ages (4 and 13 wks) and compared these with previously published data for adult goats (Biewener & Taylor, 1986). In vivo strain magnitudes collected from the cranial, caudal, and medial midshaft surfaces were variable both within and between the three age groups for all gaits examined. However, strain magnitudes were generally greater in the adults than in the younger goats. In addition, whereas adult goat strains showed a consistent pattern of cranial tension and caudal compression, indicating uniform bending during stance, a biphasic strain pattern was observed in the two younger age groups, indicating a reversal of bending during stance. In the younger goats, cranial compression and caudal tension observed during the first half of stance were reversed to cranial tension and caudal compression during the second half of stance. Significant strain was also observed within the radius during the second half of the limb�s swing phase in the younger goats. Cranial-caudal cross-sectional bone geometry and bone curvature were not significantly different between the three age groups, suggesting that differences in and more variable limb kinematics may underlie the variation observed in radial strain patterns during goat ontogeny.