TDK conference 2024

Existing research focuses mainly on the description of magnetic resonance (MRI) and, more lately, computed tomographic (CT) findings in the fetlock joint of Thoroughbred racehorses. The importance of osseous lesions in the fetlocks of non-racing sports horses has been recognised, but there are limited publications on fan-beam CT findings in the fetlock of showjumpers and no objective CT findings have been reported.

The aim of the study was to describe the densification pattern in the distal aspect of the third metacarpal bone in non-lame showjumpers by assessing the mean Hounsfield Unit (HU) values.

Fan-beam CT images of both front fetlock regions of 31 non-lame showjumpers with no clinical signs or history of metacarpophalangeal joint disease were analysed. The mean HU values were obtained in ten regions of interest in the distal third metacarpal bone in all limbs: in the dorsal and palmar aspects of the medial and lateral condyles, of the medial and lateral parasagittal grooves and of the sagittal ridge. Descriptive data analyses were performed and paired t-tests were used to compare mean HU in different regions of interest. Linear logistic regression was performed to investigate associations between regions with the greatest densification and age and competition level.

The mean HU was greater in the dorsal aspect than the palmar aspect at all measurement sites (p<0.001). A comparison between medial and lateral sides revealed that the mean HU was greater in the medial dorsal aspect, than in the lateral dorsal aspect (p<0.001). In the palmar aspect of the condyles and parasagittal grooves, there was greater mean HU laterally than medially, while dorsally the mean HU was greater in the medial aspect (p<0.001). There was a significant difference between the left and right forelimbs at all measurement sites; the greatest difference was seen in the palmar condyles (greater HU in the right than in the left forelimbs (p<0.001). There was significant positive association between mean HU in the dorsal and palmar aspects of the medial condyle and age (dorsal: p=0.002; palmar p=0.025) and competition level (dorsal: p<0.001; palmar: p=0.011). In the lateral condyle, significant positive association with age (p=0.045) and level (p= 0.010) was only seen in the dorsal aspect.

The main limitation of this study is a relatively small sample population. Furthermore, it cannot be ruled out that some horses had previous metacarpophalangeal joint disease.

In conclusion, there was greater degree of densification in the dorsal than the palmar aspect in all regions of distal third metacarpal bone in non-lame showjumpers, which reflects the loading pattern in this population of sports horses.