Diametral compression of non-circular diaphyseal bone sections

Abstract

Many research endeavors involve strength testing of long bones, frequently using whole-bone four-point bending models. Recently, diametral compression of short sections has been used to quantify local mechanical parameters and effects of treatment, but testing of biologically derived samples entails a number of added complications, such as the non-circularity of bone sections, ambiguity of load orientation during testing, thickness variation in a section, and size and shape variation between sections in a single sample. In order to quantify the effects of these confounding factors, finite element diametral compression models of a number of bone sections were compared with simplified circular and elliptical sections. Each anatomic section was tested in all rotationally stable load configurations. A high degree of correlation was observed between the anatomic sections and their circular and elliptic analogs, indicating that meaningful comparisons may be made between bone sections of disparate geometry. The aspect ratio and shape of the bone sections did not have a significant impact on the maximum in-plane principal stresses, whereas stresses were strongly dependant on the mean thickness and spatial thickness variation. Some variation due to load orientation was observed. These results indicate that diametral ring compression testing of anatomic sections can be used effectively to measure structural and material parameters of long bones, and that anatomic variation can be successfully accommodated. The ability to use diametral compression testing should allow researchers to obtain many more samples from each specimen than whole-bone bending without the difficulty of extracting solid core or dog-bone samples.