TDK conference 2024

There are published radiographic reference ranges for dorsal hoof wall thickness, but reference ranges for computed tomographic (CT) measurements have not been established and no comparison between radiographic and CT measurements have been made. Radiodense markers have been used to highlight the dorsal hoof wall on radiographs, but to our knowledge, measurements obtained with and without markers have not been compared.

Our main objective was to compare radiographic, CT and anatomical measurements of the dorsal hoof wall thickness and the dorsal hoof wall to the palmar length of the distal phalanx (DHWDP) ratio. We also aimed to compare measurements obtained on radiographs with or without radiodense markers. We hypothesised that there would be significant difference between radiographic and CT, but not between CT and anatomical measurements and that radiographic measurements obtained with and without a marker would not be different.

A total of 60 limbs were included. First 30 cadaver limbs were evaluated. Lateromedial radiographs with and without markers, and sagittal CT reconstructions were obtained. Feet were sawed in the sagittal plane and photographs were acquired. To expand the data pool, images of further 30 forelimbs from horses that had undergone foot radiography and CT were added. The thickness of the dorsal hoof wall was measured at three standard locations. The palmar length of the distal phalanx was also measured and the DHWDP ratio calculated. A Wilcoxon signed rank test or paired t-tests were performed to compare measurements of different modalities.

Radiographic measurements were significantly greater than CT measurements at all measurement sites when analysing the pooled data of 60 feet (p<0.01). In cadaver limbs, at the proximal and distal measurement sites, CT and anatomical measurements were not significantly different, but radiographic measurements were significantly greater than both CT and anatomical measurements (p<0.01). At the middle measurement sites, all modalities were significantly different from each other. For the DHWDP ratio, all modalities were significantly different from each other (p<0.01). When comparing radiographs with and without a marker, the proximal and middle measurements were significantly greater in feet with a marker (p<0.01); the DHWDP ratios were not significantly different.

In conclusion, the significant difference between CT and radiographic measurements indicates that radiographic reference ranges for dorsal hoof wall thickness cannot be applied to CT studies. The use of dorsal hoof wall markers results in greater dorsal hoof wall measurements than measurements obtained on plain radiographs, which should be considered if sequential radiographs with and without a marker are compared.