Farrier Takeaways
- The heart-bar shoe should only be used by a farrier who understands its design, relationship to the mechanics of the foot and has had experience using it.
- The farrier must possess the skills to properly trim the foot when undertaking an application such as the heart bar.
- The general heart-bar shoe design mimics the solar surface of the foot, adding extra support to the digital apparatus and helps prevent the foot from collapsing, establishing a more stable platform and adding an option to transfer loading from a damaged structure, such as a quarter crack to the frog for a period of time.
The heart-bar shoe is arguably one of the most used and recognized therapeutic shoes in modern farriery. The late Burney Chapman popularized the use of the heart bar. The Lubbock, Texas, farrier reintroduced the shoe to the farrier industry, most notably at the 1984 American Association of Equine Practitioners Convention with fellow legend Dr. George Platt.
The shoe is not a modern concept but has been used for over 100 years, although the functions of the shoe may be different than it was back then. One of the first written accounts of the shoe is in Dollar and Wheatley’s Handbook of Horseshoeing in 1898 (Figure 1 top).
Example of frog plate inserts.
Since then, many excellent machine-made shoes are available to all farriers regardless of forging skills. Simply put, the heart-bar shoe can be made with a single piece of bar stock or purchased from the rack at a supply shop (Figure 2).
Today, the heart bar is used in a variety of ways for both the treatment of foot pathologies and to aid in sport on penetrable surfaces. But like any shoeing solution, the shoe should never be used without knowledge of anatomy and physiology.
My goal in writing this isn’t to provide instruction for use. Instead, my goal is to identify some considerations and challenges encountered by farriers when using this specific device. The use of a heart-bar shoe is not a simple application and should only be used by farriers who understand its design, its relationship to the mechanics of the foot and have had experience in using it.
The shoe itself only works through correct foot preparation — the trim must be correct. Like a building collapsing without a solid foundation, your work with a horse will fail without a proper trim. The shoeing package compensates for what can’t be achieved through the trim. So, the proper trim provides the foundation for whatever you decide to attach to the foot. You must understand this principle and possess the skills to properly trim the foot when undertaking an application such as this.
The Heart-Bar Shoe Design
The shoe is designed to give support to the caudal aspect of the foot and remove tension from the laminar junction by transferring load to the digital apparatus through contact on the frog providing arch support.
It is arguably the only horseshoe that supports the internal structures of the foot. If placed incorrectly and pressure is applied, the results can be catastrophic.
The heart-bar shoe provides you a range of options then for aiding veterinary treatment of numerous foot pathologies and injuries, and to aid in creating “flotation” on modern arena surfaces by creating a larger platform for keeping the foot on top of the surface.
Example of a machine-made heart-bar shoe.
The shoes can be made from various materials such as steel, aluminum and modern materials. There also is a range of weld-in frog plate inserts that can be added to a normal open-heeled shoe (Figure 3), allowing the heart bar to be fabricated on-site.
Once the shoe is shaped and fitted for the foot, it can be attached both traditionally with nails or glued on using modern acrylic and urethane-based adhesives. If frog contact cannot be achieved due to it being too deep in the foot, the frog plate can be built up with either leather or urethane polymer.
Mechanics of the Heart-Bar Shoe
The general heart-bar shoe design mimics the solar surface of the foot, adding extra support to the digital apparatus and helps prevent the foot from collapsing, establishing a more stable platform and adding an option to transfer loading from a damaged structure, such as a quarter crack to the frog for a period of time.
Frontal section diagram of unshod palmar foot mechanics.
Frontal section diagram of a peripheral shod foot with an open-heeled shoe.
Frontal section diagram of foot with frog support.
The shoe can also be used to re-establish correct foot function and im-prove vascular blood flow. Figures 4-6 above help illustrate these mechanics.
Options for Fitting the Heart Bar
This shoe can be fit in three common ways. The amount of frog contact needed to achieve the desired mechanics for a particular pathology or injury influences this decision.
Fit with positive frog pressure. This type of fit is usually used in the aid of treatment of chronic founder. When used for this pathology, you must fit with caution and precision. A veterinarian can assist the farrier by providing lateral-medial radiographs marked correctly to guide the fitting of the frog piece (Figure 7).
A radiograph used in determining frog plate placement.
A dorsal wall marker of known length needs to be placed just beneath the hairline of the coronary band. A second marker needs to be accurately placed at the tip of the frog. The precision is crucial so you know its position on the foot.
In this application, you must place the frog piece of an inch behind the true point of the frog, when viewed on a lateral radiograph this would line up between the point of insertion of the deep digital flexor tendon and the semi-lunar sinus within the distal phalanx (Figure 8).
Anatomical diagram of the correct position of frog plate.
The amount of pressure needed can be tested by lifting and bringing forward the opposite foot to assess whether the horse is comfortable, or if there is too much pressure or not enough. If the horse is reluctant to bear weight, trying to stay off that foot, the farrier will need to adjust the amount of pressure exerted by the frog plate.
It is recommended that you don’t use this method on a horse that is actively foundering or sinking as it could increase hydrostatic pressure within the foot. If the need arises where there is no choice, the pressure can be released with a form of dorsal wall resection. However, in modern farriery, it is uncommon for this use to be carried out as there are much easier and safer ways to deal with the foundered horse.
Using a passive fit. In this application, the frog rests on the plate, but no pressure is exerted by the frog plate. The plate acts as a resistance to the downward force of the digital apparatus offering arch support to a damaged hoof capsule or acceptance of load transfer off a damaged structure for a period of time, allowing the damaged area to repair. The shoe also aids in the stabilization of the coronary band. Some conditions in which this shoe and fit can be useful include:
- Hoof wall cracks.
- Avulsions.
- Sheared heels (uncomplicated by severe thrush, which makes the frog sensitive).
- P3 fractures.
- White line disease.
- Certain cases of low or negative
P3 angle. - Post hoof wall resection or surgery (such as a keratoma removal).
- Bilateral corns.
These are types of cases in which the application may be beneficial, but of course, it won’t be the one-size-fits-all solution whenever a veterinarian diagnoses any of these issues.
Using a negative fit. In this application, the frog does not directly contact the shoe plate until the foot is loaded. Again, the frog plate acts as a resistance pad for the digital apparatus and helps in the stabilization of the hoof capsule.
This fit has been useful in the mechanical management of unstable hoof capsules, weak and flat feet that need extra help by providing arch support. Any use of this shoe also can be enhanced by using a pour-in pad or impression material, which combines to spread loading over a greater surface area of the caudal aspect.
Lateral radiograph with heart-bar shoe fitted.
Example of a heart-bar shoe with impression material.
Problems from Incorrect Use
Unfortunately, as with any shoe package, they can be misused. If applied incorrectly, damage or discomfort may result. For example, if too much pressure is applied, atrophy and damage to the frog can occur. Further harm can be caused to the internal and sensitive structures of the foot, including P3.
I recommend working closely with the veterinarian to monitor progress however this application is used. This discussion should determine the best shoeing cycle term and have the client commit to this decision. If the shoeing cycle is too long, the positive mechanics of the shoe will be lost.
The heart-bar shoe can be an effective solution, but only if correctly applied. By better understanding the complexity of this device, you’ll be better prepared to discuss the use of a heart bar with the hoof-care team.
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