Comparison of pathological lesions in navicular bone (os sesamoideum distale) and analysis of remodelling capacity in warmblood and coldblood horses.

The problem of navicular bone lesions is better understood in warmblood horses. The aim of our research was to compare pathologic lesions of navicular bone of different types of horses divided into age groups. An extra goal was to compare radiographs with anatomical status of navicular bone dissected from the hoof capsule. The study group included 161 horses, out of which 100 individuals were warmbloods, and 61 - coldbloods. In total 280 navicular bones were analysed. The flexor surface, distal border fragments, enthesophytes and the process of obliteration of nutrient foramina were analysed. Some navicular bones were also subject to histology test. A greater tendency for the obliteration of nutrient foramina was observed in coldblood horses than in warmbloods. This fact can be explained as increased remodelling, covering the phenomenon of closure of synovial invaginations and canaliculi within the navicular bone. As a result, the synovial groove disappears and blood vessels cannot enter the distal border. New bone formation on the distal border is more frequently observed in coldblood horses. The development of enthesophytes both on the distal and proximal borders depends to a large extent on the age of horses of both types. Warmbloods, however, are more prone to have the lesions located on the flexor surface, leading as a consequence to deep erosions. They might be found even in very young horses in the form of grooves crossing the sagittal ridge. The frequency of lesions varies depending on the type of the horse. Post-mortem analysis of navicular bones helped interpret radiographs in a more precise manner.