While quality evidence-based research on trimming and shoeing techniques remains scarce, there’s no doubt it plays an important role in managing horses with orthopedic issues. In fact, we might underestimate its importance, said Maarten Oosterlinck, DVM, PhD, Dipl. ECVSMR, ECVS, at the start of his presentation at the 2018 British Equine Veterinary Association Congress, held Sept. 12-15 in Birmingham, U.K.
“Given the link between the external shape of the hoof capsule and its internal function, trimming and shoeing should optimize functionality and ultimately reduce stress, both to prevent injury and to treat established pathology (disease or damage),” he said.
Oosterlinck, of Ghent University’s department of surgery and anesthesiology of domestic animals, in Belgium, described six biomechanical points of focus for trimming and shoeing horses.
1. Optimizing Hoof Balance
Hoof balance, said Oosterlinck, is the static geometry of the hoof and its dynamic interaction with the ground—“the Holy Grail of farriery.”
“If the foot is balanced, we assume there will be the most even joint contact area and the lowest pressure,” he explained.
Horses can have side-to-side (mediolateral) or toe-to-heel (dorsopalmar) hoof imbalances.
Both result in excessive compression on one side of the coffin joint, said Oosterlinck, and over time can lead to cartilage degradation, increased stress on the lower limb’s soft tissue structures, and hoof capsule distortions such as flares, quarter cracks, and sheared heels.
Correction of these imbalances—both to prevent and treat the aforementioned issues—should be done gradually and should start with the trim. This usually includes trimming the longer side of the hoof so it visually lands flat and maintaining the widest part of the sole as the coffin joint’s center of rotation.
“Shoeing without proper attention to trimming is a missed opportunity,” said Oosterlinck.
2. Shock Dampening
The hoof’s natural shock dampening properties prevent vibrations during movement from extending past the fetlock, said Oosterlinck. Shoes, however, reduce this inherent dampening effect.
Different shoes have varying degrees of shock absorption, which can be an important factor when deciding on the best material for your horse. Oosterlinck said synthetic shoes have superior absorption than steel. Viscoelastic pads with or without sole filling might further enhance shock dampening, but they increase weight.
“Increased shock dampening may be particularly relevant in the treatment of osteoarthritis or subchondral bone injury,” he said.
He added that the effect of arena footing type and maintenance is probably more important for shock dampening than shoeing modifications.
3. Slip and Braking
The hoof slips naturally during ground impact to help dissipate energy and minimize stress.
“However,” said Oosterlinck, “there is a narrow safety margin: Too much slip results in instability and risk of falling; too little slip increases the risk of catastrophic injuries.”
So while some farriers reach for toe grabs and studs or calks to manipulate hoof slip on certain footings, Oosterlinck warns against their use—particularly on horses with collateral ligament injuries.
“It may be worth considering other modifications like tungsten pins, a concave shoe, etc.,” he said.
4. Pressure Distribution
In horses with lower limb injuries, farriers aim to redistribute pressure on the hoof to lower the amount of stress applied to the injury site. They might use egg bar shoes, for instance, to shift the center of pressure toward the back of the hoof. They might use wedges to shift it toward the side of elevation.
“Moreover, hoof wedges and egg bar shoes alter distal (lower) limb joint angles and forces acting on the flexor tendons,” Oosterlinck said. “A heel wedge and a toe wedge result in a decrease and an increase, respectively, of the strain in the deep digital flexor tendon and the suspensory ligament. This may be useful in the treatment of tendinopathies as well as flexural deformities.”
Changing the width of the shoe at any point around its perimeter can have similar effects, without causing the typical hoof capsule distortion observed with, for example, heel wedges, he added. In the case of cartilage/bone injury, farriers might be able to relieve the compression on the affected side by promoting sinking of that side of the shoe in a deformable surface. In case of collateral ligament desmitis, providing a wider base of support at the affected side can decrease tension. Anecdotally, widening the outer branch, for instance, while rolling or rocking the inner toe might help manage horses with bone spavin or upward fixation of the patella.
To shift pressure distribution toward the back of the foot in laminitic horses, Oosterlinck suggested applying Styrofoam pads or a beveled wooden shoe.
5. Promoting Breakover
Breakover is the moment the horse’s heel lifts off the ground and rotates over the toe during movement. Farriers might try to manipulate the stress associated with breakover in horses with osteoarthritis, navicular issues, laminitis, or some soft tissue lesions using methods such as wedge shoes, rolled toes, rocker-toed shoes, reverse shoes, set-back shoes, and more, said Oosterlinck.
The choice is “largely dependent on personal preference and characteristics of the individual case,” he said. “Overall, shoes aiming at promoting breakover reduce the moment arm (torque) of the vertical force on the coffin joint.”
6. Optimizing Hoof Mechanism
The hoof expands and contracts on landing and take-off, respectively, aiding in shock absorption and blood circulation. Shoeing restricts this movement, so “putting a shoe on should not be taken lightly,” said Oosterlinck.
To support the hoof’s natural mechanism, farriers might reach for alternatives to traditional steel shoes. One study’s results indicated that glue-on shoes, for instance, don’t restrict forelimb heel expansion as much as nailed shoes do, he said. They do, however, reduce heel contraction.
He said the Moerman shoe, which is split at the toe to allow for independent movement of both halves of the shoe, was recently found to allow a similar amount of heel expansion as in barefoot horses.
Base trimming and shoeing decisions on the biomechanics of the hoof-ground interaction, said Oosterlinck in closing. Tailor farriery techniques to the individual horse, its static and dynamic hoof balance, any diagnostic findings, riding discipline, and footing type.
“The goal should always be to find the simplest solution that meets the objectives,” he said.