By: Laurie J. Blake with Kevin Alcock
An innovative approach to therapeutic shoeing
The clog is a horseshoe that’s not like any shoe you’ve seen before. It’s actually hard to describe it as anything other than “funky.” This specialized horseshoe created out of plywood and applied to the hoof using screws and adhesives was conceived to help with the mechanical challenges faced by horses living with chronic laminitis. Originally constructed of wood, the name “clog” seemed to fit, just like the iconic wooden shoes from Holland.
After a horse has foundered from laminitis, the coffin bone can rotate or sink in such a way that the bony column is no longer aligned. The damage to softer internal structures also causes the distorted growth of hoof wall, which compounds the mechanical issues faced by these horses. The key to creating healthy re-growth of hoof wall and minimizing further damage to the coffin bone is to alleviate these mechanical stresses through trimming. However, the distortion and damage can be so severe that trimming alone will not achieve the desired goals.
Some 20 years ago, Oklahoma veterinarian Dr. Michael Steward found himself facing problems with badly foundered horses on a regular basis, often without easy access to farriers skilled in these cases. Heart bar shoes and other traditional methods just weren’t working as well as he would have liked on some of these cases. He decided he had to try something new. After years of hands-on experience and studying radiographs of foundered horses, Steward saw a need for a therapeutic device he could apply himself.
Wood Shop Invention
Realizing that horses are creatures that have a natural instinct to keep moving and that movement greatly aids in blood circulation to the hoof, Steward created a shoe to eliminate the stresses of walking on a hoof wall that has lost structural integrity. The best place to create a prototype proved to be his wood shop. Very thick plywood was a material that could be easily cut and shaped into a useful device and modified quickly onsite using the horse for customized fitting.
Adopting a shape much like that of the hull of a boat allows for ease of “breakover” in multiple directions for the hoof, but to achieve the desired rolling motion to the foot, very thick plywood was needed. This thick plywood had another benefit: the soles of severely foundered horses may prolapse (move downwards) and the bone can even penetrate the sole surface, so a groove or trough could be carved into the wood to create a concavity to accommodate this distortion.
Steward found that after he applied the clog shoes, horses could move around more easily with less discomfort, while giving them the protection needed. To help in supporting the coffin bone, he could pack dental impression material into the limited concavity of the sole for even more distribution of weight across the entire hoof.
Drywall screws were used around the circumference of the hoof as a method of fastening the shoe to the foot and acrylic adhesives were added to aid in the shoe-to-hoof bond. The acrylics also protected the shoe from being pulled off should the horse step on it with another foot.
Since then, the clog has evolved into many forms. An EVA (ethylene-vinyl acetate – the same material used to make “Crocs” shoes for humans) combined with a plywood support layer was developed by Steward along with Dave Richards, a farrier from North Carolina. Their collaboration used a fibreglass tape product called Equicast as an easier method of bonding the shoe to the hoof.
Richards had developed the Equicast product that worked perfectly with the clog, almost eliminating the need for screws and adhesives. Together they discovered that the consistency of the EVA allowed the horse’s own weight and individual patterns of movement to collapse the material into a shape most comfortable for each individual case. And, in a further clog innovation, Richards has bonded the EVA with leather instead of wood for cases that require a more forgiving material in contact with the hoof surface. Farriers and veterinarians are currently experimenting with this concept all over the world.
Throughout this evolution, an unexpected added benefit revealed itself: this design seems to be helpful in all kinds of lamenesses, from laminitis to navicular, and even to “unexplained” lamenesses. It has also become a useful tool as a gauge or template in discovering the optimum angles, breakover points, and even the best directional rollover for each individual hoof. The soft wood of the clog can reveal patterns of how the horse moves most comfortably. The formable material of the EVA proves even more useful, as it collapses under the weight of the horse and shows the most comfortable angle of stance.
With clogs being as thick as three inches, they can be used to create a three-dimensional pattern to follow when constructing a longer-term shoe out of more traditional materials such as steel or aluminium, which is very effective when dealing with a medial/lateral (inside/outside) imbalance. The clog can now also be applied, without screws, using Elastoplast medical tape for very short-term experimentation, or a fibreglass tape for longer-term applications. Since it’s so easily applied, the clog has become a favourite tool among veterinarians specializing in podiatry.
The clog shoe does have its drawbacks. Proper trimming of the hoof remains paramount in its correct use. The placement of the shoe is somewhat forgiving, but a detailed understanding of each individual horse’s anatomy is important to have before applying the clog. The screws can also be difficult to place in some cases, such as with horses with thin-walled hooves. You need the skilled experience of a farrier, proper radiographs, and a clear understanding of the issue with which you are dealing. Unfortunately, many farriers are reluctant to try the clog simply due to its radical appearance.
The clog is not a new idea by any means. Steward has admitted to reading about similar designs in farrier text books over 100 years old after he began researching the idea while dealing with laminitic cases in his own practice. With new materials and more farriers and veterinarians using and building upon this design, who knows what this funky horseshoe will teach us. In any case, it is another great tool in the farrier industry for making horses’ lives better.