Wedge indentation fracture of cortical bone: experimental data and predictions

The fracture of bone due to indentation with a hard, sharp object is of significance in surgical procedures and certain trauma situations. In the study described below, the fracture of bovine bone under indentation was measured experimentally and predicted using the theory of critical distances (TCDs), a theory, which predicts failure due to cracking in the vicinity of stress concentrations. The estimated indentation fracture force was compared with the experimental results in three different cutting directions. Under indentation, the material experiences high levels of compression and shear, causing cracks to form and grow. The direction of crack growth was highly dependent on the bone's microstructure: major cracks grew in the weakest possible structural direction. Using a single value of the critical distance (L=320 microm), combined with a multiaxial failure criterion, it was possible to predict the experimental failure loads with less than 30% errors. Some differences are expected between the behavior of human bone and the bovine bone studied here, owing to its plexiform microstructure.