Meeting Abstract

88.2  Sunday, Jan. 6  Regional pressure changes in the digital cushion under vertical load in elephants and horses. WARNER, S E*; HENRY, V; HUTCHINSON, J R; Royal Veterinary College; Royal Veterinary College; Royal Veterinary College swarner@rvc.ac.uk

It is difficult to determine how externally applied locomotor loads affect internal foot mechanics, however the digital cushion (DC) in terrestrial animals is commonly associated with distributing and thus reducing pressures as a result of locomotion. Considering that the DC of horses is relatively small and rigidly confined compared to the DC of elephants, we used these two extreme, specialized morphologies to compare regional changes in (DC) pressure under load, focusing on forefeet. We hypothesized that under similar loads, pressures would vary with location and be greater in horse feet. We used standard invasive blood pressure monitoring equipment to measure cadaveric DC pressure in four locations under vertical loads representing 0%, 30%, 60% and 100% body weight (BW) in 6 adult specimens of mix-breed horses and 6 Asian elephants. We found that internal pressures increased under load and varied with location (p < 0.05). Surprisingly, under similar “standing” loads (mean ± SD; 27.8 ± 8.4 % BW and 29.6 ± 5.9 % BW), pressures were higher in the elephant DC (median ± IQR; 4.3 ± 4.8 mmHg) than in the horse DC (3.8 ± 1.5 mmHg), although these differences were not statistically significant. Regardless, the heterogeneous internal pressures we observed support the inference that the DC acts more like a compressible solid than an incompressible fluid under vertical loading conditions. Considering that high pressures may be related to the development of pathology, determining how internal structures such as the DC respond to locomotor loading is essential to understanding foot health and pathology.