3D Imaging of Indentation Damage in Bone

Abstract

Bone is a complex material comprising high stiffness, but brittle, crystalline bio-apatite combined with compliant, but tough, collagen fibres. It can accommodate significant deformation, and the bone microstructure inhibits crack propagation such that micro-cracks can be quickly repaired. Catastrophic failure (bone fracture) is a major cause of morbidity, particularly in aging populations, either through a succession of small fractures or because a traumatic event is sufficiently large to overcome the individual crack blunting/shielding mechanisms. Indentation methods provide a convenient way of characterising the mechanical properties of bone. It is important to be able to visualise the interactions between the bone microstructure and the damage events in three dimensions (3D) to better understand the nature of the damage processes that occur in bone and the relevance of indentation tests in evaluating bone resilience and strength. For the first time, time-lapse laboratory X-ray computed tomography (CT) has been used to establish a time-evolving picture of bone deformation/plasticity and cracking. The sites of both crack initiation and termination as well as the interconnectivity of cracks and pores have been visualised and identified in 2D and 3D.

Effect of radiation-induced damage of trabecular bone tissue evaluated using indentation and digital volume correlation

“…To investigate features in the micro/nano-scale, such as the residual deformation of the bone caused by the indentation and additionally extract important and more localised mechanical properties of bone tissue (i.e. via DVC), high-resolution and long exposure scans are required (Lowe et al, 2018;Peña Fernández et al, 2019). Long exposure to radiation is known to affect the mechanical properties of cortical bone and cartilage (Akkus et al, 2005 In this study, indentation was performed to assess the bone tissue mechanical properties before and after exposure in the X-CT. Highresolution XCT imaging was employed to visualise the region of indentation and the internal volume underneath the individual indents for subsequent DVC analysis and to visualise for the formation of cracks after radiation exposure.…”

“…Similar to Hengsberger et al, they used different parts of the same specimen for the imaging and indentation. More recently, Lowe et al, performed an in situ high-resolution XCT indentation in dried mouse femoral head, using a lab-XCT system, to visualise and track plastic deformation and crack propagation; an experiment that lasted 52 h (Lowe et al, 2018). Conventional lab-based XCTs use polychromatic x-ray cone beam, whereas Synchrotron CTs use monochromatic parallel beam.…”

Implant site preparation-related bone microdamage: An alternative ex vivo analysis of drilling speed protocols

“…In physiological conditions, especially regarding microcracks [10], this linear damage occurs in compression as it appears as ellipsoidal planes of separation, particularly in interstitial, extra-osteonal, highly mineralized areas within the cortex [11]. Besides the microcracks, other types of bone microdamage (e.g., microfractures and diffuse damage) are expected to occur and are important in the events leading to remodeling, both in cortical and cancellous bone [12,13].…”