Heel problems in horses can manifest with a variety of characteristics, including underrun heels, heel bruising and heel cracks. These problems often contribute to chronic or refractory lameness.

While a number of effective techniques for treating heel bruising and structural hoof wall failure have been described in the literature (2 to 8), many of these techniques require considerable skill and/or time to execute. This paper describes the assembly and use of a two-component, glue-on shoe to treat chronic heel problems using a heel cushioning technique. This system is simple to use and, in many cases, is highly effective as an augmentation or substitution for hoof repair or reconstruction.

No Nail Damage

Glue-on shoes provide a mechanism to attach shoes to the horse’s hoof in a non-destructive, non-invasive manner. Several different glue-on shoes are available commercially, and a method for attaching conventional aluminum shoes directly to the ventral surface of the hoof has been described.

In addition to minimizing the damage done to the hoof wall, adhesive bonding of horseshoes allows the load of the attachment system to be spread over a significantly greater area than  conventional nail-on shoes, providing a significant decrease in the load of shoe attachment per unit area on the hoof wall.

Materials And Methods

Glue-on shoes have been used successfully for the treatment of a variety of problems involving structural hoof wall failure in horses. They are also often used prophylactically with healthy hoofed animals to maintain hoof wall integrity for highly competitive horses that are prone to hoof wall damage.

Two types of glue-on shoes were designed at the Applied Polymer Research Laboratory of the New Bolton Center to meet the demand for a reliable glue-on horseshoe for highly competitive animals.

The Series II shoe is a two-component system that can be used to make any configuration of corrective or therapeutic horseshoe. The first component is an 8-by-12-inch by 3/16-inch aluminum plate that is permanently bonded to a 1/8-inch thick, high-performance polyurethane sheet. The second component is a polyurethane rim pad attached to an engineered fabric cuff (Figure 1).

FIGURE 1A. The Series II shoe system consists of a cuff (center) and a plate. The foot side of the plate (shown on the left) is made from polyurethane. 1B. The ground surface side of the plate is available as a plain aluminum surface (below), or with a polyurethane treaded ground surface (above). 1C. The polyurethane-treated plate is manufactured with a toe “step” that allows the breakover to be set back under the toe a variable amount. When the shoe is assembled for the heel cushion configuration, the cuff/rim pad should end at the cranial edge of the floated heel. The caudal third to half of the hoof is supported on the TriPink. Plates can be tapped for conventional traction studs, or drive in studs can be used.

Shoe Assembly

Assembly of this shoe using the heel cushioning technique is done as follows:

1. Trim the hoof normally to achieve the desired balance. One or both heels should be “floated” as necessary.

2. Hold the polyurethane side of the plate against the ventral side of the hoof and trace the outline of the hoof onto the clear protective release liner (Figure 2).

3. Trace the desired shoe onto the plate (Figure 3). For the heel cushion configuration, the shoe should be a bar shoe or a solid plate. If a bar shoe is used, the bar should be wide enough to cover most of the frog if both heels are floated. It  can be angled to provide preferential support to one heel if only one is floated.

4. Cut the shoe using a power orbital action jigsaw. The best blades to use are general purpose, bimetal blades with 6 to 8 teeth per inch. 

5. Cut the cuff/rim pad to fit the plate. The cuff/rim pad should end at the point where the float of the heel or heels begins (Figure 4).

6. Remove the clear protective release liner from the shoe/plate and the cuff/rim pad and assemble according to  the manufacturer’s directions.

7. Bond the special Velcro supplied with the sole packing to the sole surface of the bar. This provides an anchor for the sole packing. 

8. Apply the shoe to the hoof according to the manufacturer’s directions, with the following exceptions:

• Apply the adhesive to the hoof and shoe as per manufacturer’s directions, but allow the adhesive to set slightly before final application of the shoe to the hoof.
• Place a spacer of sufficient thickness to maintain the heel float under the shoe at the heels before the final stretch wrap is done (Figure 5).
• Keep the stretch wrap on the hoof longer (20-25 minutes) than recommended by the manufacturer.

9. Remove the stretch wrap. Do not remove the heel spacer until the packing material is mixed and ready. Once the heel spacer has been removed it is important that the foot not be allowed to bear weight until the  packing has been applied and has cured.

10. Mix the sole packing at a ratio to achieve the desired hardness. This material will set and cure quickly.  Remove the heel spacer and apply the packing by hand to the back of the shoe. Force the packing under the bar as tightly as possible. The packing should lift the shoe from the heel slightly and slightly elevate the heels.

Discussion

Floating or relieving the heels refers to the practice of trimming the hoof in such a way that provides a space between the heel of the shoe and the heel of the hoof once the shoe is applied. This may be done for one or both heels of a given hoof.

This technique has been used in some format for many years for the treatment of adverse heel conditions, including heel bruising, heel cracks, quarter cracks, underrun heels and sheared heels (proximal displacement of the heel, collateral cartilage and coronet).

When heels are floated to treat heel bruising or some form of structural heel wall failure, the goal is to isolate the heel tissue from direct trauma. When this procedure is used to treat sheared or underrun heels, the goal is to change the morphology of the caudal aspect of the hoof to improve symmetry or mechanical function.

FIGURE 2A. Trace the outline of the hoof onto the plate. 2B. Draw in the desired shape of the shoe. Cut out the plate using a jigsaw.

Floating techniques that completely isolate the heel wall from weight bearing exacerbate the stress differential between the cranial and caudal sides of a heel or quarter crack.

Finite element analysis of horses’ hooves suggest that the reduction of frog support that occurs when horses are shod with conventional open shoes results in stress concentration in the heel area. It is reasonable to assume therefore, that a technique that does not completely eliminate frog and heel support, but rather reduces and redistributes the caudal hoof load over these structures and reduces focal stress concentrators, may be a more desirable method for managing heel problems.

FIGURE 3. Some potential configurations of the Series II shoe include: 3A. Straight bar. 3B. Solid plate. 3C. Angled bar (shown on a treaded step toe plate) and a heart bar (not shown). 3D. The Series II glue-on shoe configuration on a Friesian with underrun heels and chronic heel bruising.

Floating Failures

Conventional methods of floating the heel often fail to achieve the desired result for a number of reasons. Dirt may become lodged between the shoe and the floated heel, making it more prone to direct trauma as well as limiting the ability of the displaced heel to drop.

In some cases, the cranial extent of the floated heel is insufficient (perhaps due to the need to limit the unsecured section of the shoe) to allow adequate flexibility of the wall.

FIGURE 4. A spacer is temporarily placed between the bar and the heels to maintain the space while the adhesive cures. FIGURE 5A. With the spacer removed, the 1/4-to-1/2-inch heel space is visible. Notice that the cuff/rim pad ends at the cranial edge of the floated heel. 5B. This is the space that is filled with the TriPink sole packing.

“Window” type shoeing, including “Z” bar shoes, mushroom shoes and three-quarter shoes completely eliminate contact of the heel with the shoe by removing the section of the shoe from these areas.

Unfortunately, these shoes do not protect the injured heels from repeated direct trauma from the ground. Often hoof asymmetry and structural wall failure are concurrent, with one contributing to the other. Therefore, treatment of one of these two conditions necessitates treatment of the other.

FIGURE 6. Two examples of uses for the heel cushion configuration. 6A. Treatment of heel avulsion. 6B. Augmentation of carbon fiber heel crack repair.

Best Alternative

Anomalous caudal hoof morphology usually improves when at least the caudal third to half of the hoof has some degree of flexibility and is not restricted by a shoe. This is probably why hoof symmetry often improves when horses  remain barefoot. When leaving the horse barefoot is not possible, the next best solution is to design a shoe that modifies the load bearing character of both heels by floating both heels simultaneously.

Unfortunately, floating both heels simultaneously significantly reduces the attachment area for the shoe and increases the likelihood of shoe loss. Although this situation will be markedly improved through the use of this shoe,  concern over shoe loss with both heels floated will not be totally eliminated.

The decision to float one or both heels on the same hoof should be made based on the propensity of the horse to lose shoes, the competitive level of the animal, and the severity of the problem.