TDK conference 2024

With the increasing use of standing computed tomography (CT), this imaging modality is being increasingly used in equine lameness diagnosis. Not only pathological changes can be detected with CT; it also facilitates objective measurements of bone density, allowing monitoring of adaptive changes that occur in response to training. To date, no research has documented CT changes in the density of the metacarpal condyles of young racehorses with a follow up of >1 year.

The aim of this study was to describe changes in density of the metacarpal condyles in Thorougbred racehorses during their first two years of training and racing. We also aimed to investigate potential differences in density among different areas of the distal part of the third metacarpal bone (McIII), and between the left and right limbs.

Forty non-lame Thoroughbred yearlings were included in the study. Computed tomographic examination of the metacarpophalangeal regions were performed prior to the start of racehorse training, and subsequently four times, approximately six months apart. The mean Hounsfield Unit (HU) measurements were obtained on standardised sagittal reconstructions in eight regions of the distal epiphysis of McIII (the lateral and medial parasagittal grooves, and the dorsal and palmar regions of the lateral and medial condyles). A paired t-test was used to investigate differences between mean HU measured at subsequent examinations, between the right and left limbs, and between medial and lateral, and dorsal and palmar aspects.

There was a significant difference between the HU values measured at the first and second examinations at all measurement sites (p<0.001). Between the second and third examinations, differences were only detected in the dorsal aspect of the lateral parasagittal groove (p=0.035) and in the palmar aspect of the lateral condyle (p=0.002). Comparing the third and fourth, and the fourth and fifth examinations, significant differences were seen in all regions except the dorsal part of the lateral condyle (p<0.028). In the dorsal aspect of the condyles, the mean HU value of the medial side was significantly greater than of the lateral side at the first four examinations (p<0.001). In most cases, the dorsal regions had higher HU values than the palmar regions. For the majority of measurements, there was no difference between the right and left forelimbs, except in the dorsal (p=0.006) and palmar (p=0.022) aspects of the lateral parasagittal groove at the fourth examination.

Our results indicate that the density of the metacarpal condyles of young racehorses increases with time spent in training. Furthermore, based on evaluation of mean HU measurements in different regions, it appears that the dorsal aspect of the medial condyle is exposed to the greatest loading.