Radiographic measures of bone shape in young thoroughbreds during training for racing.

The research investigates if the changes in the shape of a particular bone (third metacarpal bone, or MC3) in young racehorses can be measured effectively using radiographs. The findings reveal that the shape of MC3 can indeed be measured during the race training period and that these changes are significant, particularly in horses experiencing shin soreness.

Objectives and Methodology

• The research primarily aims to explore if the changes in the shape of the third metacarpal bone (MC3), which usually occur during the first sessions of race training in young Thoroughbred horses, can be gauged using radiographic measures.
• To understand this, lateral radiographs were taken at several different points in time – the start of training, then every 2 weeks for 10 weeks thereafter, and finally at 6 months from the onset of training. These radiographs were taken of the MC3.
• Data was gathered about the widths of the dorsal cortex (DC), palmar cortex (PC), and medulla (M) at a certain position from a landmark on the bone (nutrient foramen) before each horse was identified from their radiographs.
• Following these measurements, certain ratios were calculated: one to find out proportionate difference between DC and M (z = DC/M); and another to find out combined proportion of DC and PC to M and DC to PC separately (RI = (DC + PC)/M* DC/PC).

Results and Conclusion

• Findings from the research indicate that the shape of the MC3 does change during racing training sessions, and such changes can effectively be measured using standard lateral radiographs.
• It was observed that the dorsal cortex (DC) became proportionally thicker than other bone dimensions in the dorsopalmar plane. This altered proportion was directly related to the training, highlighting its impact on the horse’s skeletal system.
• Further, the study noted that the increases in DC dimensions were more significant in horses recorded as being shin sore during racing than in those that had no recorded shin soreness. This could potentially indicate that shin soreness might be an outcome of these morphological changes, or it could be that these horses had more intense physical reactions to training.