Role of subchondral bone remodelling in collapse of the articular surface of Thoroughbred racehorses with palmar osteochondral disease.

The research study investigates the cause of articular surface collapse in racehorses confronting palmar osteochondral disease. The study specifically explores if rapid localized bone resorption associated with reduced physical activity contributes to cartilage collapse. It was found that bone resorption contributed to the collapse of the calcified cartilage and was exacerbated by reduced-intensity exercise regimens.

Objectives and Methodology

• The research aimed at understanding the reasons behind the collapse of articular surface in racehorses suffering from palmar osteochondral disease. The specific objective was to see if localized bone deterioration associated with diminished physical activity led to this collapse.
• The study was cross-sectional, comparing metacarpal bones among horses at various stages of race training.
• Metacarpal bones from 36 racing Thoroughbred horses were examined using high-resolution peripheral quantitative computed tomography to determine the percentage of the articular surface that had collapsed. Further, backscattered scanning electron microscopy was used to quantify porosity and eroded bone surface.
• The racing and training histories of the horses were also obtained and compared with the imaging data.

Results and Findings

• The study observed the inward collapse of the calcified cartilage layer in 21 cases. It was found that the surface collapse was associated with a greater number of microfractures in the calcified cartilage and superficial subchondral bone.
• In the deeper bone (6-10 mm), there was a lower porosity with a greater extent of the articular surface collapse, whereas in the superficial bone (0-4 mm) there was no association between the articular surface collapse and porosity.
• The study also found that porosity and eroded surface of the superficial subchordal bone was higher in resting horses than in training horses. In resting horses, subchondral bone voids were highly concentrated, resulting in apparent loss of support for the overlying calcified cartilage layer.

Conclusions

• The collapse of the articular surface is common in cases of palmar osteochondral disease and appears to be a sequel to fatigue injury of subchondral bone.
• Focal subchondral bone resorption seems to contribute to the collapse of the calcified cartilage, and is intensified by a reduced-intensity exercise regimen.