Third metacarpal condylar fatigue fractures in equine athletes occur within previously modelled subchondral bone

Qualitative assessment of bone density at the distal articulating surface of the third metacarpal in Thoroughbred racehorses with and without condylar fracture

“…A previous study observed a similar result in the palmar region whereby increased bone volume/total volume was observed in association with condylar fractures of MC3 when compared with limbs from racehorses without fractures [22]. A higher bone density was evident in all 6 regions of the lateral parasagittal groove in FX and NFX compared with control condyles.…”

“…Chronic loading may result in progression to a maladaptive state, whereby the process of bone remodelling is overwhelmed by stress-induced increases in bone density that may increase the risk for fracture [20]. A higher cortical bone density has been observed in the fractured limbs of racehorses compared with limbs from racehorses without fractures [21,22]. However, an in vitro study revealed that a greater breaking force was required to fracture MC3s with higher bone density [23]; therefore, a better understanding of the relationship of bone density and fracture is needed.…”

Musculoskeletal Pathology

“…41 Studies have identified the presence of such microdamage in sites of spontaneous fracture in racehorses, supporting the hypothesis that these are fatigue failure injuries. 42,43 Adaptive cortical modeling is commonly seen in the third metacarpus of racehorses as increased dorsal cortical thickness and increased distal subchondral bone density. 44 Trabecular bone adaptation is evidenced by sclerosis within the radial facet of the third carpal bone and the palmar aspect of the metacarpal condyle.…”

Metacarpus/metatarsus

“…41,46,52,61 In racehorses, the subchondral bone in the region of the condyles undergoes intense adaptive and maladaptive remodeling in response to the strains of high-speed exercise. [61][62][63] There is ample evidence, both grossly and histologically, of degenerative changes in the subchondral bone associated with lateral condylar fractures [64][65][66][67] (Fig. 16.10).…”