Flexural Rigidity of Laboratory and Surgical Substitutes for Human Fibular Bone Grafts

Abstract

The purpose of this study was to measure flexural rigidity of two new synthetic fibular graft substitutes, and compare these data to the flexural rigidity of natural human fibulas. These substitutes were composite fiberglass surrogate fibulas, to be used in laboratory experimental studies, and porous tantalum cylinders, being researched as a bone graft substitute. Ten fiberglass surrogate fibulas and 13 porous tantalum rods were tested in a 4-point bending fixture. Both types of fibular graft substitute had flexural rigidities comparable to natural human fibulas. The fiberglass surrogate fibulas had much less inter-specimen variability in flexural rigidity than did the natural human fibulas (6%/10% vs. 36%/52% for A-P/M-L directions). The surrogate fibula is therefore appropriate for use in laboratory experimental studies of fibular grafts which will undergo bending. The flexural rigidity of the porous tantalum rods increased with relative density to the 1.2 power, as suggested by theory and empirical data for porous solids; thus, porous tantalum density and rod diameter can be varied to obtain the desired flexural rigidity.