Histologic and histomorphometric evaluation of midcarpal joint defects in Thoroughbreds raised with and without early conditioning exercise.

The research explores the effect of early physical conditioning on eventual midcarpal joint cartilage defects in Thoroughbred horses and does not find any substantial differences. The study also identifies abnormalities in the calcified cartilage, which could be a precursor to midcarpal osteochondral disease.

Methodology

• Participants were twenty-four midcarpal joints from twelve 18-month-old Thoroughbreds. The horses were divided into two groups: those that only had spontaneous exercise at pasture and those that received additional conditioning exercise from an average age of three weeks.
• The appearance of cartilage defects in midcarpal joints was evaluated. On the third and radial carpal bones, the presence or absence of abnormalities in the calcified cartilage (CC) was categorised at the dorsoproximal and dorsodistal articular surfaces.
• A histomorphometric assessment and statistical analysis were carried out specifically on the third carpal bone.

Findings

• The severity and number of defects did not show any significant difference between the exercise groups.
• Nine of the radial or third carpal bones demonstrated signs of a thicker CC with microcracks and matrix changes, increased vascularity, and changes at the osteochondral junction, yet without any histologic changes in the hyaline cartilage.
• When abnormalities were identified in the third carpal bones’ CC, the CC was considerably thicker (452 as opposed to 228 μm). However, there were no significant differences in the thickness of the hyaline cartilage (681 vs 603 μm), the vascular channel area in the subchondral bone (624,894 vs 490,320 μm(2)), or the number of vascular channels (15.9 vs 18.0).

Conclusion

• The distribution or severity of cartilage defects in the midcarpal joint did not appear to be influenced by early exercise routines.
• Abnormalities in the calcified cartilage, located beneath the undisrupted hyaline cartilage in the dorsoproximal part of the third carpal bone, could be the initial indicators of midcarpal osteochondral disease.