X-ray Diffraction Technique with Imaging Plate for Detecting Surface Distribution of Residual Stress in Diaphysis of Bovine Femurs

Stress measurements of bone are essential for evaluating the risk of bone fracture, the cure of bone diseases (e.g., osteoporosis), and the bone adaptation. Previously, a method using X-ray diffraction (XRD) was used to assess the presence of residual stress in the diaphysis of bovine and rabbit extremities. However, the previous method required a complicated experimental setup, long irradiation time, and limitations of the sample size. To profoundly enhance the understanding of distribution and biomechanical implications of bone residual stresses, it is necessary to develop an alternative method that features a simple setup without limitations on the sample size and shape. An imaging plate (IP) can obtain the two-dimensional distribution of hydroxyapatite crystal deformation and has the potential to resolve the previously mentioned issues. The aim of this study was to develop a measurement system using an XRD technique with an IP for obtaining the surface distribution of residual stress in the diaphysis of extremities. A mid-diaphysis specimen taken from an adult bovine femur was irradiated with characteristic Mo-Kα X-rays under no external forces and the diffracted X-rays were detected by an IP in the reflection side. The residual stress in the bone axis was calculated from the XRD pattern. As a result, tensile residual stresses were detected at the diaphyseal surface, corresponding to the results of the previous method. The developed system reduced the irradiation time by two thirds and the limitations of the sample size were removed.