Biomechanical testing of the calcified metacarpal articular surface and its association with subchondral bone microstructure in Thoroughbred racehorses

Abstract

Subchondral bone adaptation and fatigue likely alter joint surface mechanical properties. The aim of this study was to evaluate the relationship of calcified articular surface biomechanical properties in the distal palmar metacarpal condyle of Thoroughbred racehorses with subchondral bone microstructure and training history. Subchondral bone microstructure was evaluated using both micro- and clinical-computed tomography. Biomechanical properties of the calcified articular surface were tested with reference point indentation at the micron level. Articular surface toughness increased with commencement of race training, and was lower in horses that died as a result of musculoskeletal fatigue injury, had evidence of palmar osteochondral disease, had higher subchondral bone connectivity with more concave surfaces, and higher subchondral bone volume fraction. Further investigation of bone microstructural properties is warranted based on bone connectivity and surface shape findings. At clinically applicable imaging resolution, evidence of subchondral bone modelling may be an important indicator of articular surface biomechanical properties.