Multiscale characterisation of subchondral trabecular bone changes in the osteoarthritic ankle

An increasingly younger population are seeking treatment for osteoarthritis of the ankle. Current late-stage surgical interventions sacrifice the upper levels of the distal tibia and talus to allow for joint replacement implantation. This can lead to multiple failure modes with regards to the success of the device, as well as low bone stock at revision. Changes to subchondral bone with osteoarthritis is well studied in the hip and knee, but the ankle remains highly under-reported. Medical imaging and validated computational modelling can provide predictive capabilities of bone properties in the ankle and help to inform surgical interventions.
Hence, the aim of the studies compiled in this thesis was to characterise the structural and mechanical changes to subchondral bone in the late-stage osteoarthritic ankle. Using mechanical characterisation and medical imaging, a specimen-specific finite element methodology was developed using porcine tissue and translated for use on non-diseased human trabecular bone to estimate tissue-level properties through the optimisation of grayscale-based material properties. Nanoindentation was used to directly measure tissue mechanical properties, which aided in assessing changes to the apparent-level stiffness of osteoarthritic bone. High-resolution medical imaging provided a means of detailed, three-dimensional morphological evaluation of the trabecular architecture, thus providing an insight to the remodelling of the bone with osteoarthritis and its influence on bone stiffness.
The porcine and non-diseased human FE models showed good agreement between computational and experimental stiffness values. Evaluation of osteoarthritic bone showed significant remodelling of trabecular microarchitecture, higher apparent stiffness, and altered tissue properties. Further investigation is needed to fully understand the impact of multiscale bone changes with osteoarthritis in the ankle, but this work has provided the foundations for understanding these changes. Such information will be crucial to aid future implant design and the development of joint strength prediction models using medical images, to inform surgical decisions.