Femoral asymmetry in the Thoroughbred racehorse.

The research article investigates the occurrence of geometrical differences in the femurs of left and right sides in Thoroughbred racehorses, hypothesizing that these differences could be due to the pressure of competitive racing and repeated turns.

Methodology

• The study was conducted on eleven Thoroughbred racehorses based in New South Wales, Australia that were euthanized due to reasons not related to the study.
• Postmortem measurements of 37 different femoral characteristics were taken from the left and right femur bones of these horses.
• The measurements particularly concentrated on the areas where muscles and ligaments are attached, and which are known to have a role in hindlimb locomotion.

Results

• Out of all the characteristics measured, five were found to be statistically significantly larger in the left femurs compared to the right femurs.
• The areas showing significant differences between left and right limbs included proximal cranial and overhead medio-lateral widths, greater trochanter depth, depth of the fovea in the femoral head, and distal inter-epicondylar width.

Conclusions

• The researchers concluded that these left-right differences in femoral morphology were associated with muscle and ligament attachment sites.
• The irregularities in femur size on either side are potentially the result of selective pressure for racing performance on curved tracks, or asymmetrical loading of the horse’s outside hindlimb due to repeated negotiation of turns on such racetracks.