Heterogeneous strain distribution in the subchondral bone of osteoarthritic femoral heads measured with digital volume correlation

Osteoarthritis affects the properties of the joints, changing its shape and mechanical response, and inducing pain to the patient. We still do not know how the complex structure of osteoarthritic bone deforms under load, due to the challenging experimental approaches required to evaluate the internal deformation in bone specimens. The goal of this study was to develop a method based on Digital Volume Correlation to elucidate whether the local deformation in osteoarthritic femoral heads are related to the degeneration of the subchondral bone due to the disease.  Whole femoral heads extracted from osteoarthritic patients during standard total joint replacement surgeries were mechanically tested within a high resolution micro-computed tomography scanner. The images of the undeformed and deformed specimens were processed with the BoneDVC algorithm to evaluate the bone deformation, which identified regions of highly localised deformation in function of the bone microstructure. This approach will be expanded in the future to identify the weakest regions of osteoarthritic femoral heads in a large database of specimens collected from different disease levels. 

Volumes of interest (VOIs) were extracted from one of the OA specimens to evaluate uncertainties within a representative total volume (blue), central region in the trabecular bone (green) and regions containing cysts (red) and sclerotic bone (yellow). (b) DVC strain fields for the four VOI’s under zero-strain (repeated images) and 1% virtual compressive apparent strain (1% VD). (ce) Little difference in the measures of standard deviation of the error (SDER) measures was observed across each of the four VOI’s, and with nodal spacings equivalent to 1.01, 1.95, 2.73 and 3.90 mm under each of the 0% compression and 1% and 5% virtual compressive apparent strain cases.

Ryan M, Oliviero S, Costa MC, Wilkinson M, Dall’Ara E: “Heterogeneous strain distribution in the subchondral bone of human osteoarthritic femoral heads, measured with digital volume correlation”; Materials, 2020; 13(20), 4619