On Colles’ Fracture: An Experimental Study Involving Structural and Material Testing

Abstract

A two-stage experimental program was conducted, which was aimed at examining the process of initiation/propagation of fracture in human radii under the conditions simulating a fall onto an outstretched hand. It involved a number of destructive tests on dried cadaver bones. The bones were first subjected to DXA as well as spiral CT measurements to establish the density properties and the details of geometry. Subsequently, the specimens were tested under controlled boundary conditions, to induce Colles’ type of fracture. Following these tests, samples of cortical bone tissue were extracted at different orientations with respect to the direction of osteons and tested in axial tension. The results of material tests were used to verify the performance of an anisotropic fracture criterion for the cortical tissue. It has been demonstrated that the proposed criterion can reproduce the basic trends in the directional dependence of the tensile strength characteristics. For the structural tests, a correlation was established between the geometric characteristics of the cortex, the strength properties and the fracture load for individual radii that were tested. It was shown that the morphological traits and/or the strength properties alone are not adequate predictors of the fracture load of intact radii. A rational assessment of the fracture load requires a mechanical analysis that incorporates the key elements of the experimental program outlined here, i.e., the information on bone geometry, material properties of the bone tissue, and the static/kinematic boundary conditions. A preliminary example of a finite element analysis, for one of the radii bones tested, has been provided.