A linear piezoelectric model for characterizing stress generated potentials in bone

Abstract

A comprehensive model is presented for the characterization of stress generated potentials (SGP) in bone, based entirely upon the linear piezoelectricity (PZE) of single crystal collagen. The model calls for a theoretical antiparallel polarization configuration in adjacent lamellae that yields to parallel polarization for minimization of free energy. The direction of reorientation is guided by a stress-gradient-induced trigger polarization that specifically determines the polarity in bending and artifactually determines polarity under normal stress. It describes a decoupling of the signs of the PZE tensor of single crystal collagen from the coordinates of the bone: hence, no assumption of the validity of a PZE matrix applied directly to bone can lead to correct results. The model is consistent with all major experimental SGP observations and provides a fresh viewpoint for externally applied electricity for bone stimulation.