Hoof Cracks

Equine veterinarians routinely deal with hoof cracks and most, fortunately, are minor nuisances or superficial problems.

Typical appearance of a quarter crack in a dry, brittle hoof. These cracks can extend from the coronary band all the way to the sole (pictured) or only part way down. Involvement of the coronet implies a more serious crack and longer healing time. Note that the top of the crack is located at the end of the bearing surface of the shoe indicating that this horse needs more heel support.

Sometimes, however, hoof cracks can be persistent and serious. Occasionally they can lead to fatal complications.

The Grade 1 winner Bevo was euthanized following complications of laminitis. This 4-year-old New York Sprinting Circuit champion developed a quarter crack that was repaired. The crack was feared to be infected and the horse was transferred to a veterinary clinic where complications rapidly developed and the colt was euthanized 48 hours later. Bevo's trainer, Billy Badgett Jr. said, "He went so fast it was unbelievable."

Because most cracks are not as serious they tend to not merit intense concern, but perhaps a closer look is warranted, as is a review of their causes and their various treatments.

Causes, treatments

Hoof cracks are described by their location on the foot, toe, quarter or heel. Cracks are also sometimes categorized by their origin and/or extent. Cracks that originate at the coronary band are generally considered worse than other types because this disruption of the coronary band affects tubular horn formation and the healing process tends to take longer. Also the potential for introduction of infection into the hoof is greater with cracks and defects that interrupt the coronary band.

This horse has been shod with a "floated" lateral hoof wall and heel and the crack has been Dremelled-out to allow faster hoof growth. A rim pad supplies the wall support everywhere except under the crack. Often an egg bar or heart bar shoe is used in these situations as well.

Hoof cracks occur for a number of reasons.

"Direct trauma to the coronary band," writes Dr. James Rooney, "is a clear example of one cause of hoof cracks and this trauma can be from wire cuts or outside influences, from interference from another foot, or from treading by the same or another horse."

These are the causes that are most frequently thought of. A poorly shod horse that wings in front often develops medial quarter cracks on the opposite foot. A non-careful jumper that commonly raps a pole with the hoof can show occasional toe cracks.

No outside trauma

But what about those cracks that develop without the influence of outside trauma?

A discussion of these cracks with Rooney soon dissolves into an explanation of biaxial compression forces and a review of the role of the horseshoe in the development of hoof cracks.

This horse has relatively minor superficial toe cracks extending from the coronet to sole. These cracks do not extend deeply into the wall of the hoof and are usually not a problem.

As the unshod foot of a normal horse bears weight or is loaded, the quarters of the hoof expand outward. This expansion continues along the hoof wall to the heels. When the same horse is shod, the quarter is constricted from this natural outward movement by the nails and the hoof will bend outward instead of or near the last nail. This bending motion can cause tearing and bruising of the laminae along the line of the bend and all the way up the hoof to the coronary band. If the bending is severe enough or consistent enough then a crack will appear.

Rooney makes the point that, according to this theory, though, "crack" is not a correct term and these defects are really the failure of production of horn tubules in an area of bending damage.

Similar forces occur in the formation of toe "cracks" which are areas where the hoof is forced forward and, rather than be allowed to expand, the natural outward hoof bulging is restricted by the first nails in the shoe. According to this theory, however, most unshod horses should be free from cracks and most shod horses should suffer from these bending damage problems.

Fortunately this is not the case. Rooney speculates that there are many, many individual factors that determine which horses will develop cracks and which will not. He states, "some of these individual factors are: genetic (and other) influences affecting quality of hoof horn, frequency of trimming/shoeing, surfaces upon which the horse habitually moves, body weight and condition (more weight=more load=more movement of hoof wall), misplacement of nails, state of hydration of the hoof wall, conformational influences (contracted hoof, low heels), etc."

As most veterinarians and farriers would agree, equine veterinarians routinely deal with hoof cracks and most, fortunately, are minor nuisances or superficial problems.

More extensive toe cracks in this horse indicate possible deeper problems. Some horses have abnormalities to the surface of the PIII which perpetuate these cracks. Radiographs should be taken for evaluation. In addition to shoeing support, this horse may need dietary improvements (including vitamins, minerals), topical additives to return moisture to the coronet and growing hoof and environmental changes to reduce stress on the hard, dry ground.

Overall picture

A horse with a hoof crack should be given a physical examination focusing on the overall status of the horse including nutritional history and growth/development issues.

Young rapidly growing horses often go through growth spurts that can affect their conformation and lead to problems in weight bearing.

Drastic changes in weight can contribute to hoof stress as well. Deficiencies or excesses of vitamins and minerals may be a part of the problem and environmental issues should be considered. Is the horse standing in wet bedding and softening the laminae of the hooves? Is the ground dry and hard? Is the horse being worked on a surface that is causing trauma? The natural tendency is to examine a case of hoof cracks by looking at the feet first, but often the horse's history and general examination will yield useful information not found in the feet.

Even load

The next step is to examine the horse at a walk and trot. Imbalance and uneven loading is the principal cause of hoof cracks not caused by outside trauma.

The use of a video camera often will help one see the actual pattern of loading and unloading because the film can be slowed down enough to watch for subtleties of weightbearing that cannot be seen even by a trained eye. Balancing the foot so that loading occurs in a symmetric manner is the biggest step in preventing hoof cracks. Any observed interference trauma of loading imbalance noticed at this point can be factored into both the diagnosis of the crack and the treatment plan.

Radiographs

Radiographs are occasionally taken in cases of cracks that have no easily determined cause. Damage to PIII, especially the extensor process of that bone, or to areas below the coronary band can produce cracks at the surface. Trauma to the walls of PIII can also produce a sequestrum that can form persistent cracks.

The egg bar shoe with adjustable toe band is sometimes used to place compression force across a toe crack in an attempt to promote healing. The metal staple is also used by some farriers. It is driven into the hoof wall perpendicular to a crack to help seal the defect. Eventually, behavioral training and the unloading of uneven sole forces are seen as a better means of hoof crack therapy.

The standard AP, lateral and oblique views often do not show these areas of damage. Tangential views across the wall of PIII in the area of the crack may be needed to reveal the problem.

Planning treatment

Once the cause is found, whether it is trauma, uneven loading or environmental, a treatment plan is necessary.

Trimming the foot to unload the bearing surface of the hoof associated with the crack is the first step. The hoof can be shod with an egg bar shoe or other such shoe so as to give the foot adequate support while the contact area of the crack is trimmed back or "floated".

Many farriers choose to use "clips" to help hold the hoof capsule together and provide further support for the new tubular horn that is being produced to heal the crack. Perhaps this tendency should be re-evaluated in light of Rooney's comments about hoof expansion during weightbearing since clips will further restrict the hoof's natural outward expansion.

It is a dilemma since more restraint of the capsule is needed to heal the crack, but that additional restraint makes the hoof more likely to crack.

Other techniques

Over the years many other techniques have been used to help close hoof cracks.

Elaborate systems of grooving and cross-marking the hoof have been employed in attempts to keep the cracks from spreading up or down the hoof wall.

Some types of grooves made into the wall with a dermal drill attempt to redirect the loading forces to help close the crack. Lacing or suturing a crack was a popular procedure at one time and is still occasionally used today, though its merits are not generally accepted.

In this procedure, small holes are drilled through the superficial layer of the hoof at right angles to the crack. Small wire or umbilical tape is threaded through the holes and the crack is laced up and sutured together. Proponents of this technique feel that the laces give support and speed up healing. Opponents feel that there is no decrease in healing time and that drilling further weakens an already compromised area of hoof wall.

Some farriers use small steel clips that are driven across the crack to hold the wall together. These devices provide support but also weaken the wall.

Other approaches

The relatively recent development of a number of synthetic plastic, acrylic, and methacrolate-like products have added a variety of other approaches to treating cracks.

Application of these materials to a Dremeled-out and cleaned crack can provide stability to a hoof wall during the healing process. The lower edge of the crack is packed with a cushioned material and the bearing surface of the wall is coated with a harder more durable product. This allows the wall to bear weight but the crack to be unloaded.

Compressive materials packed on the sole surface also help with weight distribution and loading problems in some horses. Because of the many new products and their differences in set-up times, in hardness and in durability, considerable skill is needed for their application. Seek the services of an experienced farrier. Correct use of these products can help even the toughest cracks while incorrect use and application can increase the pressure on the crack and can, in some cases, trap infections in the hoof that can lead to very serious problems.

Balance, patience

Despite all the techniques available for treating hoof cracks and all the newer high-tech compounds and resins, almost all veterinarians and farriers agree that dealing with hoof cracks is an exercise in balance and patience.

Trim the foot to provide balanced support for the horse, remove the pressure on the crack, and allow the horse time to re-grow healthy tubules and heal itself. This important, though somewhat simplistic, approach is echoed by the writings of Dr. James White in White's Farriery and Compendium of the Veterinary Art.

In a "Dissertation on the Foot of the Horse," first published in 1809, he writes, "a hoof crack is, in fact, a breaking or fracture of the horn in its weakest part." This agrees with the bending concept suggested by Rooney. Treatment of cracks, according to White, should begin with the removal of "every hollow part (of the crack) completely, however far it may extend under the crust." Once every part of the crack is removed down to healthy horn tissue "a bar shoe should be applied and eased off the affected heel and quarter."

The hoof should be grooved and "a strap applied around the hoof for some time to restrict movement. The quarter where the crack is should be rasped away as thin as possible," according to White and "attention should be paid to the brittle state of the hoof by observing and correcting problems of nutrition, management and movement."

Simple details

Nearly 100 years and the treatment advice is still unchanged. Pay attention to simple details, balance the foot, unload the crack and, according to the century-old advice of the veterinary surgeon of the Royal Dragoons, "in this way, cracks may be always cured without difficulty." While not all cracks will be cured so simply, this approach certainly has stood the test of time.