Medial femoral condyle morphometrics and subchondral bone density patterns in Thoroughbred racehorses.

This study examines the shape and bone density patterns of the medial femoral condyle (MFC), a part of the thigh bone, in Thoroughbred racehorses. The researchers have noted differences in bone density between the right and left limbs of the horses, suggesting a potential link to their track running patterns.

Study Design and Data Collection

• The research is based on the study of stifle joints from six Thoroughbred racehorses that were euthanized for reasons unrelated to hind limb lameness.
• The distal part of the left and right femurs from the cadavers was scanned using Computed Tomography (CT).
• The CT scans were analyzed by converting Hounsfield units (a unit measuring the radiodensity of a material in the scan) to dipotassium phosphate equivalent densities. This process was done with the help of a phantom (a device used to calibrate or control imaging devices).
• The team measured various parameters of the MFC, including width, length, height and curvature. Besides, subchondral bone plate densities and subchondral trabecular bone densities were also investigated in different sections across multiple planes.

Findings and Results

• The researchers found no significant difference in MFC width, length, and height between the left and right limbs.
• However, some parts of the right subchondral bone plate and subchondral trabecular bone (subchondral refers to the bone just beneath the joint cartilage) displayed significantly greater density than the corresponding sections on the left, both on frontal and sagittal planes.
• An irregularity or concavity in the otherwise convex articular surface of the cranial aspect (the front) of the MFC was identified in 11 of the 12 specimens.

Interpretation and Conclusion

• The identified disparity between left and right subchondral bone density patterns at the caudoaxial (rear and axial) aspect of the MFC might be due to the distinct cycles of repetitive asymmetric loading North American Thoroughbred racehorses undergo when they race in a counterclockwise direction.
• The irregular region found at the cranial aspect of the MFC could potentially be associated with the development of subchondral bone cysts in horses — a condition where fluid-filled holes form in the bone beneath the cartilage of a joint, causing lameness.