ABSTRACT
A method is described for examining the mechanical environment of a bone fracture, which arises from routine weight-bearing activity. A 2-D geometric model of a fracture site is developed from orthogonal radiographs which are scanned and digitised. Bridging tissue (callus) forming periostealy and endostealy across the fracture is separated into regions of common tissue histology using the digitised images. Region boundaries are identified from the disparity in pixel illumination intensity between regions. Initially, material properties are found for each callus region from tests reported in the literature on new bone tissue at the same temporal points in healing. A linear elastic FE analysis is performed using Cosmos/M, in which the initial properties are adjusted iteratively until measured relative displacements of the bone fragment ends, during two-legged stance, match forces and moments at the fracture calculated using a lower limb biomechanics model. Approximate tissue histology may be identified from its location, the temporal point in healing and from its material properties. Peak dynamic stresses and strains within the tissue are then calculated for maximum displacements that are measured during walking activity. Solutions of the model may be used to examine the influence of the mechanical environment on the observed pattern of healing in real fractures. The procedure is illustrated for a single subject with a mid-diaphyseal, tibial fracture.
