Role of Microcracking in Cortical Bones

Abstract

The influence of the microdefect interactions on the stress intensity factors (SIF’s) at the tip of the macrocracks in cortical bones is considered using one of the linear fracture mechanics models developed by Tamuzs at el[1]A human bone is a living organism governed by quite complex biological processes. However, at any given moment of time a frame of the human body is a mechanical structure of composite materials (of various mechanical properties for the different types of bones). As it is established experimentally [2], microcracks and other microdefects are present in cortical bones at every stage of life of the bone. They play a vital role in the process of remodeling of the bone. With age, the distances between microcracks are decreasing [10], making “bridges” (uncracked ligament) smaller that causes increase of SIF’s and decrease of the critical fracture load. In another words , a bone fracture can occur even without extraordinary external force. The objective of this work is to provide a mechanistic interpretation of interaction of macro-and microcracks in cortical bones. The structural integrity of a composite material of the bone is obviously vital for the work of the human body frame. Traditionally, the bone quality is defined in terms of bone mineral density (BMD), namely, the amount of bone mineral per unit of volume. The fracture of the bone may occur not only as a result of a single impact but may also be caused by the microcrack interactions resulting in so called stress fracture (without a major impact). Therefore, for comprehensive understanding of the bone fracture it is necessary to study the microstructural interactions in bones. As the linear fracture mechanics is considered by most researchers an appropriate tool for investigating failure processes in bones [2], the analysis of the stress intensity factors governing the hierarchy in macro-microcrack propagation and the amplification (“intrinsic”) and shielding (“extrinsic”) effects is conducted using solutions obtained in [1,4].