The influence of tissue hydration on equine hoof capsule deformation and energy storage assessed using finite element methods

Abstract

The mechanical properties of equine hoof horn are known to vary with moisture content and this property is sometimes utilised for interventions that attempt to reshape the hoof capsule. However, the relationship of moisture content modulation to the mechanics of the whole hoof is unknown. This study explores the effect of moisture variation on hoof capsule mechanics and, in particular, deflections and stored elastic energy variations in the hoof. A finite element model of the hoof was used. The hoof capsule tissue was modelled using finite elasticity with a heterogeneous transversely isotropic material relation, in which the elastic parameters were varied according to the moisture content of the tissue. The laminar junction and sole corium were modelled using an exponential Fung-type constitutive relation fitted to published data. The distal phalanx bone was modelled as a homogeneous isotropic material. Substrate interaction was modelled by contact with a rigid plate and loads typical of a trot were applied. Different scenarios were modelled where the moisture content of the hoof wall was varied from 40% to 100% of the fully hydrated case. Results demonstrated that hoof capsule deflections and stored elastic energy in the capsule increased monotonically with increasing moisture content. Stored energy in the laminar junction and sole corium remained constant. The mechanical behaviour of the hoof capsule is sensitive to variation in moisture content and this mechanism may provide a way to modulate impact energy transmission. Experimental validations of hoof models should control for moisture content to improve reliability.