Mechanical properties of implantable biomaterials

This chapter was intended to review many of the terms used to describe the behavior of biomaterials including linear elastic, plastic, and viscoelastic behavior. Common testing methods for evaluating the behavior of biomaterials were also reviewed. Uniaxial loading, perhaps the most common testing procedure, can characterize both time-independent (i.e., linear elastic and plastic) and time-dependent (viscoelastic) materials with a controlled loading condition. Bending tests, because of their ease, are also popular and can describe linear elastic and plastic behavior fairly well. Vibratory methods to measure viscoelastic behavior, on the other hand, are less popular but are essential if the expected loading condition of the biomaterial will be fairly rapid. Taken together, these tests form the foundation for understanding the applicability of a specific material for use as an implant, and can be used to predict not only the failure thresholds for the implant but also the expected remodeling response of the bone once the implant has been placed in situ. For this reason, characterizing the mechanical properties of implant materials has been and will continue to be an important step in implant design.