A Novel Videography Method for Generating Crack-Extension Resistance Curves in Small Bone Samples

Abstract

Assessment of bone quality is an emerging solution for quantifying the effects of bone pathology or treatment. Perhaps one of the most important parameters characterising bone quality is the toughness behaviour of bone. Particularly, fracture toughness, is becoming a popular means for evaluating bone quality. The method is moving from a single value approach that models bone as a linear-elastic material (using the stress intensity factor, K) towards full crack extension resistance curves (R-curves) using a non-linear model (the strain energy release rate in J-R curves). However, for explanted human bone or small animal bones, there are difficulties in measuring crack-extension resistance curves due to size constraints at the millimetre and sub-millimetre scale. This research proposes a novel “whitening front tracking” method that uses videography to generate full fracture resistance curves in small bone samples where crack propagation cannot typically be observed. Here we present this method on sharp edge notched samples (<1 mm×1 mm×Length) prepared from four human femora tested in three-point bending. Each sample was loaded in a mechanical tester with the crack propagation recorded using videography and analysed using an algorithm to track the whitening (damage) zone. Using the “whitening front tracking” method, full R-curves and J-R curves could be generated for these samples. The curves for this antiplane longitudinal orientation were similar to those found in the literature, being between the published longitudinal and transverse orientations. The proposed technique shows the ability to generate full “crack” extension resistance curves by tracking the whitening front propagation to overcome the small size limitations and the single value approach.

Limited field radiation therapy results in decreased bone fracture toughness in a murine model

“…In this study, we found it possible to document progression of crack growth during loading using very high resolution reflected white light imaging. A similar approach was also recently used to document crack extension in rat tibia [ 35 ]. While reflected white light imaging does not have the resolution of SEM, it may be advantageous for cases where a very large number of test specimens (n = 135 in this study) are needed for statistical power considerations.…”

“…The method to calculate fracture toughness during crack initiation and growth was adapted from an approach developed by Carriero et al [ 25 ] where a crack path during mechanical loading of mouse femora was documented using environmental SEM. In this study, a high resolution imaging method was used to document the progression of crack growth, similar to the work of Katsamenis et al [ 35 ]. The projected crack extension was measured on the medial surface of the bone (Δa proj ), and this was used to calculate the instantaneous half crack angle (θ inst ), which in turn, along with the instantaneous load P, and cross sectional geometry of the bone, was used to calculate fracture toughness (K).…”

The inferomedial femoral neck is compromised by age but not disease: Fracture toughness and the multifactorial mechanisms comprising reference point microindentation

“…Fracture toughness testing was performed as previously described by (Katsamenis et al (2015); Katsamenis et al (2013)) with some modification for increased automation (primarily automatic selection of whitening area), allowing increased throughput, as indicated in Supplementary Fig. S1.…”

Imaging in real and reciprocal space at the Diamond beamline I13

“…More details can be found elsewhere 1,4 . Currently bio-medical and engineering/materials science applications are the most popular, while geo-physical (see figure 3) experiments have also been carried out with great success [8][9][10][11] . Mainly pink beam is used with filtering towards higher photon energies for materials science experiments.…”