Human cancellous bone possesses a stiffness ranging from 12 to 23 GPa; careful control and modification of manufacturing parameters to achieve similar strengths is imperative for practicality of integration. Correctly predicting the Youngs modulus for foams is imperative for actual biomedical integration; a mismatch of Youngs moduli between the implant and the bone can result in stress-shielding effects from a disproportional handling of stress. The implant which typically exhibits a higher Young's modulus than the bone will absorb most of the load. As a result of this imbalance, the starting bone density will be reduced, there will be tissue death and, eventually, implant failure.
Natural bone exhibits the ability to adjust local fiber away from the low-stress regions toward high stress regions through the distribution of porosity, thus maximizing overall comfort. Using finite element analysis, researchers examined the effect of filling pores with bone on mechanical properties. They concluded that bone ingrowth significantly improved the mechanical properties, evidenced by decreased localized plasticity and stress concentrations. In effect, the titanium foam in the study allowed the bone to exhibit its natural ability to adjust local fiber away from the low-stress regions toward high stress regions.
Experiments demonstrated that random combinations of pore size and shape result in lower Youngs moduli. Theoretical models for the quantification of Youngs moduli do not account for random pore size and shape distribution, so experimental measurements must be conducted in the presence of heterogeneous pore size and distribution. This is a limitation of the micro-mechanical models discussed above.