Analysis of Hounsfield Unit of Human Bones for Strength Evaluation

Abstract

The aim of the current study was to extend this line of research and to determine how well bone stiffness predicts yield strength, yield strain, ultimate stress, and ultimate strain for both cortical and cancellous tissue. As will be demonstrated, the mechanical properties of human vertebral cancellous bone in compression and cortical bone in tension are related in similar ways; yield strength and ultimate strength are highly correlated to bone stiffness by a relationship that is the same for both vertebral cancellous and habitually loaded cortical bone. Bone density is defined as means value expressed in Hounsfield units in each pixel. Bone material presents a complex behavior involving heterogeneous and anisotropic Mechanical properties. Moreover, one it is a living issue, therefore its microstructure and mechanical properties evolve with time, in a process called remodeling. This phenomenon has been studied from a long time, and there are many numerical models that have been formulated in the sense to predict the density distribution in various bones, mainly in the femur. A femur, tibia and mandible (all human) were scanned and the image stored in a Dicoma format. Mimics (Materialize, Leuven, Belgium) were used to read and then they were imported in Mimics again, and different material properties were assigned relating the bone mineral density with the Hounsfield Units (HU). There are different relationships between the bone. Then they were imported in MIMICS again, and different material properties were assigned relating the bone mineral density with the Hounsfield Units (HU) (50 materials were considered). In the literature different relationships between the bone apparent density and the HU can be found for the different bone types. In the present study we have used the one of Pang that was a relationship computed for the femur.