Prevalence of radiographic changes in front feet and metacarpophalangeal joints of South African endurance racehorses

Abstract

If the number of events alone is considered, endurance riding is the fastest growing Fédération Equestre Internationale (FEI) discipline and the second most popular FEI discipline. To the author's knowledge, no studies have been published investigating the prevalence of radiographic changes in the front feet and metacarpophalangeal joints of endurance racehorses. The current study followed an observational design and aimed to provide point prevalence and distributive data of radiographic changes in South African endurance horses. Radiographs were obtained from 100 horses competing during the 2018-2019 racing season. Radiographs included 7 standard views of each distal forelimb. Data analysis of the front feet revealed a large proportion of horses showed bilateral signs of dorsopalmar hoof imbalance; an abnormal digital axis, with a hyperextended proximal interphalangeal joint being the most common abnormality. Osteoarthritis of the proximal and distal interphalangeal joints was only observed in a few horses. Interestingly, the hoof-distal-phalanx-ratio of the majority of horses was more than 25% but none of these horses showed any other signs of chronic laminitis, indicating that hoof-distal-phalanx-ratio might not be a reliable indicator of chronic laminitis in this population of horses. Ossification of the ungular cartilages was observed in the majority of horses, either present at one or both distal phalanges. Descriptive data analysis of the metacarpophalangeal joints showed that a large proportion of horses displayed radiological signs of metacarpophalangeal joint osteoarthritis, with the majority being bilateral. Knowledge about the prevalence of specific radiographic changes would enable equine practitioners to better evaluate and manage horses that are affected and will act as a basis for further studies in South African endurance racehorses. The current study provides insight into radiographic changes and their prevalence in the distal front limbs of South African endurance racehorses. Although no correlations were made with age, speed or number of competitive kilometres competed, the current study may serve as comparison for future research.