Fracture Mechanism and Fracture Toughness at the Interface between Cortical and Cancellous bone.

Abstract

Objective The micro-structure at the interface of cortical and cancellous bone is quite complicated. The fracture mechanism at this location is necessary for understanding the comprehensive fracture of whole bone. The goal of this study is to identify fracture toughness in terms of J integral and fracture mechanism at the interface between cortical and cancellous bone. Materials and Methods For this purpose, single edge notch bend (SENB) specimens were prepared from bovine proximal femur according to ASTM-E399 standard. Bone samples were prepared such that half of the sample width consist of cortical bone and other half of the width was cancellous bone; this interfacial bone is referred as corticellous bone. Elastic-plastic fracture mechanics was used to measure fracture toughness. The J integral (both elastic and plastic) was used to quantify the fracture toughness. Results The plastic part of J integral value (Jpl) of corticellous specimen was 9310 Jm-2, and shown to be 27 times of the J integral of the elastic part (Jel), 341 Jm-2. The total J integral of the corticellous bone was found to be 9651 Jm-2, which is close to two times of the cortical bone, 4731 Jm-2. Conclusions Present study observed that, J integral of corticellous bone is higher than cortical bone since, more energy is required for plastic deformation of corticellous bone due to crack branches and slowdown at the interface between cortical and cancellous bone.