A complementary theoretical and experimental investigation is proposed to test two hypotheses regarding the mechanical adaptation of cortical bone: (1) changes in a bone's homeostatic mechanical state relate to the spatial pattern of a remodeling response and that (2) quantification of these changes will accurately predict the location of remodeling under new loading conditions. The in vivo functionally-isolated turkey ulna will provide the means for experimentally defining and validating the osteogenic stimuli and a finite element model of the bone will provide theoretical predictions of the sites of remodeling activity. The proposed work will use a complementary approach of iteratively testing model predictions against experimental observations, refining the model, and re-testing new predictions. The five specific aims of the work are: (1) To determine the baseline multi-component stress/strain distributions in the turkey ulna generated by functional activity through a normal 24-hour period that reflects a state of remodeling equilibrium; (2) To create stress/strain distributions in the ulna distinct from normal and quantify the adaptive remodeling response (periosteal, endosteal, intracortical) stimulated by the new load environment; (3) To use a finite element model adjusted to the particular geometry of the specific bone modeled, plausible stress/strain parameters that initiate observed remodeling responses will be identified; (4) To use the FEM to predict the sites of remodeling activity under torsion; (5) To test model predictions with new experiments that apply torsion to the functionally isolated turkey ulna.
