The Piezoelectric Effect of Bone In Vitro

Abstract

The mechanism of bone deposition and resorption, under stress, is incompletely understood. The direct piezoelectric properties of bone have been suggested as playing an active role in the internal morphology of bone tissue. This study was designed to fabricate an apparatus and develop a technique to measure, quantitatively, the direct piezoelectric effect of the crystallites of bone. In vitro studies were done with bone samples taken from bovine femur. The samples were subjected to stress loading and were observed to exhibit a pressure-induced electrical phenomenon. The amplitude of the potentials generated was dependent upon the magnitude of the bony deformation. A linear relationship was observed to exist between the pressure applied and the potential generated. Polarity was found to be a function of the direction of force application. This may indicate that there is some interaction between internal surfaces of the bone that generate a potential on sliding past each other. From these observations it was reasoned that bone in vitro exhibits a piezoelectric effect. An attempt was made to distinguish as to which of the two fractions, organic or inorganic, was responsible for the potentials generated. One may postulate that the potentials, generated by the piezoelectric effect of bone, play a role in activating or in selectively inhibiting the cells of the bone cell system. Because the potentials measured were relatively weak, an alternate hypothesis may be that these potentials are associated with unidirectional fluxes of anions and cations from the bone towards the bone surfaces