Tuesday, February 16, 2010 by Duncan McLaughlin
We have all seen them, those insidious concussion rings that appear in the hoof wall following an endurance ride, gradually moving down with the growing hoof capsule. Sometimes they even manifest as horizontal concussion cracks. They look ugly and they scream: Damage! And then, there is all that long-term concussive wear and tear on joints leading to inevitable arthritic change. Not surprisingly, managing concussion is often considered the primary soundness issue for your endurance horse over his career.
But need it be so?
To answer this question, let’s first consider how the hoof functions. Of course, as any internet search soon shows, there are about a bazillion or so theories on how the hoof functions and how to best manage and dress the hoof for optimal performance. For any one theory of hoof function you will soon find another in complete contradiction. However, all the different theories can be categorised into two basic models based on the distribution of weight through the hoof.
1. Whole Of Foot
Under this model, your horse's weight simply falls, via the skeleton, to the ground through all components of the hoof (wall, sole, bars, frog), which share in the distribution of that weight. The coffin bone is the load-bearing structure. Under this model, factors external to the hoof, such as the amount of daily movement, the living and working terrain, conformational traits, and the presence/absence of hoof protection, are considered to determine which hoof structures are trimmed or left untouched. The aim is to distribute weight across all hoof components, including the caudal hoof (digital cushion, ungual cartilages), to optimise correct coffin bone loading within the hoof in motion and at rest.
2. Lamellar Sling
Under this model, your horse's weight falls through to his coffin bone, which is in turn suspended in a 'sling' by way of the close interweaving of the epidermal (hoof wall) and dermal (inner hoof) lamellae. Under this model, the hoof wall is the primary weight bearing structure, and the focus is on angles and measurements of the hoof in isolation to both your attached horse and his living environment. Obviously this model is implicit in all farriery: attaching a shoe mandates the hoof wall as the only weight-bearing structure. Some vets and researchers also use this model. For example, the work of much-quoted laminitis researcher Chris Pollitt DVM is based on this model, which he describes as the 'lamellar corium - distal phalanx attachment apparatus'.
Most schools of barefoot trimming use methods based on the Whole Of Foot model. Rightly so - there is good reason to be skeptical of the Lamellar Sling model: