Veterinary session

Standing computed tomography (CT) is becoming increasingly available and used in equine lameness diagnosis. The distal aspect of the limb is one of the most frequently examined regions. The hoof wall can be affected by several pathologies and diseases, it is therefore paramount that the CT appearance of the hoof wall in healthy horses is described. There is available literature on the thickness of the layers of the hoof wall measured on radiographs and magnetic resonance images, but similar results have not been published for CT measurements.

The main objective of this study was to establish a reference range in Thoroughbred racehorses and showjumper sports horses for the thickness of the hoof wall and its layers at different measurement sites on CT reconstructions. I also aimed to investigate any association between age, breed, and size of the horses and the results obtained at the different measurement sites.

Computed tomographic reconstructions of 30 Thoroughbred racehorses and 29 showjumpers, all free from lameness, were analysed. On sagittal and transverse CT reconstructions, the entire width of the hoof wall, and the corium and the keratinised layer were measured. In the sagittal plane, measurements were obtained at proximal, middle, and distal measurement sites. In the transversal plane, measurements were taken medially and laterally. We established a reference range from the measured values in the two groups. We used a two-sample independent t-test and Mann-Whitney test to explore possible differences between Thoroughbreds and showjumpers. Furthermore, we applied a paired t-test and a Wilcoxon test to examine differences between the medial and lateral sides of the hoof and between the left and right legs of individuals. In addition, we looked for a correlation between the horse's body weight and the hoof wall's full thickness using a generalized linear model.

Showjumpers had significantly higher values of keratinised layer, corium and hoof wall measurements. The medial side was significantly thicker for hoof wall and corium measurements. In the case of the keratinised layer, the lateral side was thicker in Thoroughbreds and also for the pooled data of Thoroughbreds and showjumpers. There was no statistically significant difference in the keratinised layer thickness measured on the medial and lateral sides in showjumpers. No statistically significant difference was detected between the left and right limbs. We could demonstrate only a marginal effect of bodyweight, but it did not have a significant effect on the total hoof wall thickness.

The reference ranges and other results established in our study will help evaluation and accurate interpretation of CT images of clinical cases and will serve as a reference for further research.