Radiological differences in tissue characteristics between uneven feet in foot lame horses

Abstract

Reasons to perform study: An important feature of foot conformation is unevenness, as this has been reported to lead to early retirement of elite horses from a warmblood population. The aim of this study was to compare radiological differences between uneven feet to improve our understanding of the mechanism behind this asymmetrical development. Material and methods: A complete set of good quality radiographs of both distal forelimbs was objectively compared for a group of 121 ‘foot lame’ horses that had been admitted to a privately owned and a university equine hospital for MRI of one or both front feet (2003-2010). Statistical software was used to test for a significant radiological difference between the upright and the weak foot (p<0.05). Results: It appeared that 60% of the horses were lame at the upright and 40% at the weak foot. In 84% of the horses the navicular bone had a significantly more radiolucent, osteoporotic structure and in 80% a more pronounced dorsal border of the navicular bone (NB) in the upright compared to the weak foot (p<0.05). Moreover, in 88% of the horses a significantly more radiodense, pronounced deep flexor tendon (DDFT) was found in the upright foot (p<0.05). Conclusions: It appeared that the navicular bone showed a more osteoporotic structure in the upright foot, while the DDFT appeared more compact, both indicating a chronically too low loading period. In contrast, the advanced enthesophyte formation on the dorsal navicular border in the upright foot points towards a chronically too high proximal navicular ligament loading compared to the weak foot. Practical relevance: There obviously is a need to adopt horse management systems that prevent uneven feet to develop certainly at the growing, young age, thus to expose distal limb tissues to a balanced biomechanical loading towards their performing, adult age.