Time-resolved internal strain fields of articular cartilage from synchrotron-based phase-contrast micro-tomography data: A digital volume correlation feasibility study

ABSTRACT With osteoarthritis (OA) progression, both mechanical and structural changes of articular cartilage occur. However, little is known about the interaction between the two. Digital volume correlation (DVC) could theoretically provide such insight, extracting the internal strain field from computed tomography (CT) datasets of the tissue under load. A recent study highlighted the possibility of time-resolved synchrotron-based phase contrast tomography (SR-PhC-µCT) on 4 mm Ø bovine articular cartilage samples. The aim of the current study was to assess the associated DVC uncertainties on these datasets through a zero-strain error analysis and virtual compression assessment. The DVC protocol was then applied to experimental data, extracting the time-resolved internal strain field of bovine articular cartilage during continuous dynamic loading and two steps of stress relaxation. The zero strain accuracy and precision remained below 10% of the experimental strain, confirming that the SR-PhC-µCT datasets are of sufficiently high image quality to permit DVC analysis. DVC was able to accurately extract the strain field with up to 15% compression. Thirty percent compression, however, appeared beyond this ability. This study highlights the importance of replicating the experimental configuration in assessing DVC uncertainty. When applied to experimental data, the internal response of the articular cartilage was depth, strain rate and strain magnitude dependent. The proposed methodology confirms the use of SR-PhC-µCT and DVC to extract the time-resolved internal strain field of articular cartilage, thereby permitting dynamic analysis of the mechanical response and its relation to degeneration.