Tension testing of wet bovine haversian cortical bone demonstrated
marked plastic behavior. Progressive surface decalcification of this bone
with dilute hydrochloric acid resulted in progressive decreases in the
tension yield point and the ultimate stress with no change in the yield
strain or ultimate strain unless decalcification was complete. The slope of
the plastic region remained identical throughout decalcification. These
findings are consistent with an elastic-perfectly plastic model for the
mineral phase of bone tissue in which the mineral contributes the major
portion of the tension yield strength. The slope or stiffness of the
plastic region of the stress-strain curve is a function only of the
properties of collagen, which itself plays a minor role in the tension
yield strength of bone.