Understanding Hoof Cracks
Hoof cracks can be as simple as something that merely irritates the observer from an aesthetic point of view to something so serious that the horse is dead lame and unable to perform. Hoof cracks come in a variety of types and sizes, and they originate from a variety of causes that can range from something as serious as laminitis to something as basic as repetitive exercise on hard surfaces or improper shoeing.
A full-length hoof crack extends from the ground to the coronary band.
The approach to treatment usually depends on the type of crack, degree of associated pain, work load, athletic endeavor of the horse, ease of application, expertise of the veterinarian and farrier, availability of repair materials, and the cost of the procedure, according to Bill Moyer, DVM, Professor and Head, Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, and Robert Sigafoos, CJF, Section of Sports Medicine, New Bolton Center, University of Pennsylvania. The two have collaborated to author a book, A Guide to Equine Hoof Wall Repair.
The good news in dealing with hoof cracks is that, today, farriers and veterinarians have some space-age compounds and tools available to treat what in the past might have been a catastrophic condition.
In their book, Moyer and Sigafoos have categorized hoof cracks according to the following:
Location--toe, quarter, heel, or bar.
Depth--superficial or deep. Superficial cracks rarely result in lameness and often can be cleared up quickly. Deep cracks that reach all the way to the sensitive inner structures can cause intense pain and lameness and might render a horse unable to perform. Deep cracks could require elaborate and costly procedures to remedy.
Length--complete (i.e., from coronary band to ground) or incomplete, which would be a shorter crack.
Origin--either starting at the coronary band and working downward or starting at the ground level and working up.
Fortunately, says Moyer, the majority of hoof cracks fit into the superficial category and are not painful. In many cases, they can be treated by rebalancing the foot through proper trimming, application of a full bar shoe, and rest.
However, when the crack produces pain and compromising lameness, it is another matter. With this condition, movement of the independent portion of the wall or inflammation at the site of the crack (or both) can cause pain so severe that the horse is unable to perform.
The goal of any treatment procedure is to stabilize the crack to alleviate discomfort and provide the hoof with a chance to heal.
Following are some of the specific causes of hoof cracks as enumerated by Moyer and Sigafoos:
Laminitis or deep digital flexor tendon contracture syndrome with subsequent wall separation.
Excessive horn growth.
Excessively wet or dry environmental conditions.
Pre-existing damage to the coronary corium and trauma or infection--bacterial or fungal.
Frequent shoe changes.
Improper shoeing or trimming of feet.
Repetitive exercise on hard surfaces.
Internal failure of the horny hoof wall, they point out, probably precedes the appearance of cracks on the outer surface.
Two characteristics often are present when serious hoof cracks are dealt with--they will be infected and sensitive tissue will be exposed once the damaged hoof wall has been removed. Hooves that are so afflicted are no longer sturdy, durable, or reliable.
The importance of durable feet, free of cracks, cannot be over-emphasized. No foot, no horse. It is as simple as that. Most of the horses one sees in the wild have very sound hooves, devoid of cracks.
This isn't something that just happens of its own accord. Horses equipped with feet so poor they caused lameness often were a predator's next meal. In the wild, it is a culling process through survival of the fittest. Horses with poor feet didn't live long enough to pass those genes on to other generations.
It is different in a domestic setting, where we can afford to be far more forgiving. No one is going to put down a top racing prospect or jumper because the animal has weak hooves. Instead, we call on experts in the field to treat, trim, and shoe the horse in such a manner that it remains sound. Of course, if we then use this horse as a breeding animal, we are guilty of passing the problem on to future generations.
To further understand how hoof cracks occur and why they sometimes are so serious, let's take a basic look at this complex appendage called the equine foot.
Understanding The Foot
The foot serves a variety of valuable functions for the equine. It supports the horse's weight, absorbs shock, provides traction, conducts moisture, and helps to pump blood. In addition, the hoof resists wear and has the capability of replenishing itself.
Noted the late O.R. Adams in his book Lameness in Horses:
"Good conformation of the foot is essential to normal activities of the horse. No matter how good the conformation of other areas, if the foot is weak, the horse is not a useful animal...To have good foot conformation, a horse must have reasonably good limb conformation, since the foot reflects poor conformation of the limbs.
"Much variation in quality of structure exists in the feet of horses. Ideally, the wall should be thick enough to bear the weight of the horse without excessive wear, resistant to drying, be pliable, and should have normal growth qualities. The sole should be thick enough to resist bruising and should shed normally. The bars should be well developed and the frog should be large, strong, and should divide the sole evenly, with its apex pointing directly to the toe of the hoof wall."
The hoof wall itself is modified cornified epithelium. It is composed of keratinized epithelial cells that are solidly cemented with keratin. The keratinized cells are arranged in tubules that run perpendicularly from the coronary band to the ground surface of the wall and parallel to one another.
The hoof wall is comprised of three layers. The outer layer is the periople and the stratum tectorium. The periople, which functions much like the cuticle of a human fingernail, extends about three-fourths of an inch below the coronary band, except at the heels, where it caps the bulbs of the heels.
The stratum tectorium is a thin layer of horny scales that gives the glossy appearance to the outside of the wall below the periople. One of its tasks is to protect the wall from evaporation. (The hoof wall is approximately 25% water.) The middle layer composes the bulk of the hoof wall and is the most dense portion.
The inner layer is the laminar layer that forms the epidermal laminae of the hoof. This layer is concave from side to side and bears about 600 primary laminae, each of which bears 100 or more secondary laminae on its surface. These laminae firmly attach the coffin bone to the hoof wall. These combined laminae bear much of the weight of the horse.
The ground surface of the hoof wall is divided into the toe, quarters, and heel. At the heel, the wall turns forward to form the bars that converge toward one another. The sole, comprising most of the ground surface of the hoof, conforms to the inner curvature of the wall and to the angles formed by the wall and the bars.
The structure of the sole is similar to that of the wall, with tubules running vertically as formed by papillae of the sole corium. These tubules curl near the ground surface, which accounts for the self-limiting growth of the sole and causes shedding. The sole is not designed to bear weight from the ground surface, but is designed to bear internal weight.
The frog is a wedge-shaped mass that occupies the angles bounded by the bars and the sole. The frog is divided into the apex, which is the forward most point; the base, which is the rear portion; and the frog stay, which is the central ridge. The frog is 50% water and is quite soft.
The walls, bars, and frog are the weight-bearing structure of the foot.
Serving as a junction between the laminae of the wall and the tubules of the sole is the white line.
Next we come to the corium. The corium is a modified vascular tissue that furnishes nutrition to the hoof. It is divided into five parts.
One of the most important elements of the foot is the coronary band. The coronary band is the combined perioplic corium, coronary corium, and coronary cushion. It is the primary growth and nutritional source for the bulk of the hoof wall. Injuries to this structure are serious and usually have a permanent effect. A hoof crack that results from serious injury to the coronary band might become a permanent affliction. No amount of notching, use of acrylic material, or stapling can heal some cracks that are the result of severe injury to the coronary band.
The blood supply to the foot is furnished by the medial and lateral digital arteries. The blood comes to the foot via the arteries with distribution of the nourishment it is carrying being handled by the capillaries. It then is returned by the veins.
With that basic and partial explanation of foot structure in mind, we should be better able to understand what occurs when a hoof crack develops.
How The Hoof Cracks
Among the primary causes of hoof cracks, next to injury, says Steve Mellin, a farrier who teaches an intensive one-year farriery course at Colorado State University, is foot imbalance. Improper foot balance, he says, often is implicated in quarter cracks, some of which are difficult to heal.
The good news, he says, is that fewer out of balance feet are being seen today than in the past. Educational courses for farriers, such as the one being offered at CSU, and instructional information from organizations like the American Farrier Association, he says, have been instrumental in teaching farriers about foot balance and the proper way to trim and shoe to achieve it.
One of Mellin's predecessors in the farrier department at CSU, Doug Butler, PhD, CJF, FWCF, who now works and teaches in the private sector, defined proper balance in a paper titled "Foot Balance," published in the American Youth Horse Council's Horse Industry Handbook. Following is a small portion of that dissertation:
"Balance," Butler wrote, "as it applies to horse shoeing may be defined as equal weight distribution around the center of gravity of the horse's limbs. It involves trimming the foot and fitting the shoe on the end of the limb. Perfect balance is rarely achieved. But the closer we get to it, the better chance we have for maximizing performance and sustaining soundness in the horse.
"Balance may be considered when a horse is standing or moving. Considerations of conformation or stance are called geometric or static balance. Considerations of movement or gait are called functional or dynamic balance. Geometric balance takes into account the horse's conformation and is the prime consideration that will provide for the needs of most horses. Functional balance deals with the alteration of foot movement and involves corrective shoeing.
"The horse's conformation, gait, speed, level of training (especially degree of collection), hoof length, shoe weight, head position and weight, and the rider's skill and weight or the load being pulled all may affect balance.
"Each time the horse is shod, the farrier should feel challenged to come closer to the ideal stance gait for that particular animal. At the same time, the farrier must place the minimum amount of stress on the limb. The object is to sustain soundness or return to it if the horse is lame. The hoof should be trimmed to land flat in movement if the joints are stressed, as well as to make a horse comfortable."
A major part of the problem in losing sight of hoof balance, Mellin believes, formerly rested with inadequately trained farriers. The European horse community, he says, has left this country behind in farrier science. In England, for example, he says, becoming a farrier involves enrollment in a five-year program.
First, the applicant must be sponsored by a practicing farrier before he or she is even accepted. Once accepted, the student undergoes two full years of rigorous instruction and practical experience. Along the way, the candidate must pass a number of tests. Failure to do so results in that person's seeking a new vocation. Once the two years of instruction are completed, the student must serve as an apprentice with his or her sponsor for three years before being qualified to hang out a farrier shingle.
However, Mellin says, this country is beginning to catch up to the Europeans and, as a result, problems with hoof cracks stemming from imbalance are not as common as in the past.
A form of foot imbalance that can cause a quarter crack, he says, can be viewed from the rear. The entire heel block on one side will be pushed upward.
Quarter cracks are most common in racehorses, but they can occur in any breed. Conditions, in addition to hoof imbalance, that contribute to quarter cracks include hoof dryness and disciplines that result in repeated concussions. Conformation also is often implicated.
The first step in treating a quarter crack that results from foot imbalance, says Mellin, is to level the foot and remove a portion of heel block that has been pushed upward. The results can be almost instantaneous. "If the horse is placed in a place where there is soft, moist footing," said Mellin, "the displaced heel block will often move down to its normal position within an hour."
Also a part of the remedy can be attachment of a shoe, with other portions of the foot absorbing weight and pressure until the heel block has returned to its normal position. From that point on, trimming or shoeing to achieve a balanced foot is imperative.
Getting a crack of any kind to disappear can involve a variety of remedies. If he is dealing with a toe crack, Mellin says, he will frequently attach a heavy shoe with toe clips on either side of the crack.
For the more serious cracks, he often will use a Dremel tool to clear the crack all the way to the white line. The crack then is filled with acrylic and staples are driven into the foot with one prong of the staple on each side of the crack.
The goal is to allow the hoof to grow out until the crack has disappeared, sort of like waiting for a human fingernail blemish to disappear by nail growth and regular trimming.
Just how long this takes will vary from horse to horse, with genetics, soil surface, moisture, and nutrition all being involved. One of the key factors in maintaining healthy feet that will not be prone to cracks, as well as stimulating hoof growth, is nutrition. Studies have shown that the hooves of horses on an optimum diet will grow up to 80% faster than those of horses on a subsistence ration. Rapidly growing hooves, generally speaking, are of higher quality and are easier to maintain than slower growing hooves. This also means, of course, that if a crack should occur in a rapidly growing hoof, the problem will likely be resolved more quickly than in a slow growing hoof.
Age also is a factor. The hooves of young horses grow faster and are more resilient than those of their older counterparts. Weather, too, can be a factor in hoof growth. Hooves grow faster in warm weather than in cold.
Moisture is also highly important in maintaining a healthy hoof that will be less likely to sustain cracks.
Butler puts it this way:
"Hoof moisture has been shown to have a direct effect on hoof quality. There is constant evaporation taking place from the hoof. Moisture must be replaced to compensate for this loss. Systemic water is transferred from the extensive blood and lymph supply of the sensitive structures to adjacent horn cells and they, in turn, transfer it to other horn cells.
"Environmental water from ground sources is also conducted throughout the hoof in a similar manner. Balance of the two sources of moisture is probably maintained through the principal of osmosis. When one source is insufficient, the animal depends more heavily on the other.
"Hoof quality may relate more to the hoof's ability to regulate moisture content than anything else, because as the moisture content of the hoof wall decreases, the hoof becomes harder and tougher. Commercial hoof dressings have not been shown to be helpful in increasing hoof moisture and improving hoof strength. Younger horses usually have softer hoofs than older horses. There is also a variation of moisture content between the young and old wall within the same hoof. This contributes to its biomechanics since the young wall of the heel and top is more flexible than the old wall of the toe and bottom."
Mellin concurs that water is superior to any hoof dressing in maintaining the correct moisture balance. A few years ago, he said, he conducted something of a test involving a group of 4-H youngsters enrolled in the horse project. He divided the 10 young horse project members into two groups. One group regularly applied hoof dressing to their horses' feet. The other group applied no dressing, but cleaned the hooves daily and at least once each day, led the horses through a water-mud area.
"By the end of that summer," Mellin said, "the five horses that were led through water and mud on a regular basis had twice the hoof growth than those that had hoof dressing applied. In addition, the water-mud treated horses had no hoof cracks."
The horses most at risk of developing hoof cracks as the result of improper care, he said, are box stall horses. He recommends that such horses have their feet cleaned thoroughly each day and that when that has been concluded, they be led through a wet, muddy area to give the hooves an opportunity to absorb moisture.
The thorough cleaning, he said, opens the entire bottom portion of the foot to air, thus making it untenable for bacteria that cause thrush, and the mud pack helps keep a healthy moisture level.
However, Ric Redden, DVM, a lameness specialist from Versailles, Ky., is quick to point out that too much water can be as detrimental to the hoof as too little. He is of the firm opinion that one of the reasons many racing Thoroughbreds have deteriorating feet, including quarter cracks, is because the hooves are kept too moist.
Excessive moisture, he maintains, causes the hoof walls to lose their strength. Excessive moisture, he adds, also causes deterioration of the matrix that holds the tubules together.
Whatever the cause--concussion, hoof imbalance, or hooves that are too dry or too wet--when a serious hoof crack appears that penetrates the sensitive layer, it is time for treatment procedures that often are far more complex than those employed for a superficial hoof crack.
Management of serious hoof wall injuries involves four stages, says New Bolton's Sigafoos. They include the following:
- Assessing the injury, including etiology and prognosis.
- Debriding the damaged hoof wall to remove all necrotic or damaged material.
- Planning the repair.
- Applying the repair.
In a paper published in the American Association of Equine Practitioners proceedings of 1995--"Polymeric Composite Repair for Acute and Chronic Refractory Hoof Injuries in Horses"--Sigafoos reported that a number of conditions should be given serious consideration in determining the proper approach to treatment of chronically infected or refractory hoof cracks:
"Factors such as radical hoof angle changes, excessive toe length and marked hoof asymmetry can produce cracks or other forms of catastrophic wall failure.
"Refractory (not readily yielding to treatment) toe cracks and dorsal submural erosive lesions will frequently result from chronic laminitis, presumably from a change in the mechanical characteristics of the hoof wall brought about by the compromise of the underlying vasculature. Radiographic assessment of a hoof that is affected with chronic toe cracks, submural erosive lesions, or wall collapse (dishing) can assist in the determination of a suitable method of trimming the hoof.
"The general condition of the hoof should be inspected for concurrent problems that may contribute to the instability of the injury. Factors such as underrun or sheared heels, wall separation, or focal proximal displacement of the coronet can contribute to the refractory nature of some types of hoof wall damage and usually can be repaired in conjunction with the primary injury."
There are two characteristics that these types of hoof cracks have in common, Sigafoos says. First, they often will be infected when you decide to repair them and, second, sensitive tissue will be exposed once the damaged hoof wall has been removed. Additionally, the formation of an abscess can result when cracks of this type are repaired, regardless of whether an infection or exposed sensitive tissue is present at the time of the repair.
A key element in successful hoof repair, Sigafoos believes, is careful hoof wall debridement.
"Careful hoof wall debridement is an essential part of hoof wall repair," he wrote. "All necrotic or separated wall must be removed until a competent and continuous junction of stratum medium to epidermal lamina is exposed around the border of the defect. If it is necessary to expose sensitive tissue during debridement, the borders of the defect should be enlarged to provide a boundary of healthy, cornified tissue at least 0.5 centimeters adjacent to the border of the defect. Failure to completely remove damaged hoof wall can compromise the integrity of the wall as an adhesive substrate, and it can trap moisture or exudate under the repair."
Normally, debridement is carried out with a Dremel tool that would fit the description of an over-sized dentist's drill. It can utilize a variety of burrs or cutting edges.
As already mentioned in the preceding discussion on construction of the equine foot, the coronet is always involved in hoof growth and repair and should be thoroughly examined before treatment procedures are implemented.
"The coronet should be inspected and palpated for cracks and focal areas of proximal displacement," Sigafoos advises. "These problems are best addressed by relieving the coronet immediately distal to the affected area. This is done by cutting a one-centimeter wide, half-round horizontal notch just distal to the coronary groove, using a Dremel tool and ball end carbide burr. This notch follows the arc of the coronary groove and is cut as close to the coronary corium as possible."
The goal here is to relieve pressure on the coronary band so that normal hoof growth can once again begin.
Sigafoos then launched into a discussion on planning and designing the repair. A key ingredient in the approach is proper drainage:
"Repair design depends on the location, type, and severity of the hoof wall injury, as well as the amount of wall loss following debridement. Regardless of the type of injury, drainage should always be established for repairs that involve any section of the hoof that has been debrided proximal to the level of the sole.
("Distal access drains are used for the treatment of hoof cracks. These drains usually have a proximal and distal port, with the distal port protected by a bolt and screw.")
"Adhesives must not be applied to the tissue within the debrided cavity, regardless of whether or not infected or sensitive tissue was exposed during debridement."
Sigafoos then discussed hoof crack repair via the fabric lacing approach which also involves the application of adhesive acrylic material:
"Infected or acute hemorrhagic hoof cracks can be effectively repaired by reducing and stabilizing the injury using a fabric lacing technique. Fabric lacing provides a method for repairing injuries in which insufficient surface area or hoof wall thickness is available for the conventional type of lacing repair. This technique is particularly suited for repairs of heel cracks that occur in the extreme caudal aspect of the heel as well as avulsion (tearing apart) injuries involving the coronet when minimal thickness of cornified tissue is present. Drainage for hoof crack repairs is established by bridging the laced area with acrylonitrile-butadiene-styrene (ABS), which is bonded in place to cover the abaxial (situated out of or directed away from the axis) side of the repair. Once the repair is completed, holes can be drilled into the ABS to form a drain."
The lacing technique features the application of layers of fabric that are saturated with adhesive and positioned over the defect. Once the adhesive has cured, the fabric on either side of the crack is drilled and laced.
Making the procedure possible has been the development of high-performance acrylic adhesives and a variety of structural engineering fabrics for reinforcement.
"High-performance acrylic adhesives offer excellent adhesion to the hoof wall, high impact strength, and good flexibility," says Sigafoos. "Additionally, this chemistry can be used with a lightly contaminated surface because of the low-viscosity monomer (methyl methacrylate) that acts as a solvent to displace contaminants away from the substrate."
Included among the space age fabrics that are available for hoof repair are E fiberglass, S2 fiberglass, Kevlar (aramid), Vectran (liquid-crystal polymer), Spectra (ultrahigh-molecular-weight polyethylene), and carbon fiber fabric.
Sigafoos gives the following assessment of the qualities of each:
"E fiberglass is the least suitable of the structural fabrics for most types of hoof wall repair. This fabric will frequently fracture when used on adult horses.
"S2 fiberglass offers a low-cost alternative to other structural textiles and has excellent adhesive compatibility with high-performance acrylic adhesives. S2 fiberglass can be used alone for repairs that are subject to minimal stress and abrasion, or in conjunction with other, tougher fabrics as a laminate to improve adhesion.
"Kevlar is a high-tensile, high-modulus fabric, but has poor abrasion resistance and is difficult to wet out with acrylic adhesives. If Kevlar is used for hoof wall repair, it should always be used as the axial layer in a laminate with a more abrasion-resistant fabric.
"Spectra offers the greatest tensile strength and fatigue and abrasion resistance of all the hoof repair fabrics commonly used. It is usually used as the moist abaxial layer in a hoof wall repair to enhance strength and abrasion resistance. Spectra has poor adhesive compatibility and will not form a covalent bond with acrylic adhesives.
"Carbon fiber fabric offers high-tensile strength and tensile modulus at the cost of poor impact strength. Carbon fiber fabric has excellent adhesive compatibility with acrylic adhesives and can be used in conjunction with other fabrics to improve adhesion and strength of hoof wall repairs. It is an excellent fabric to use when a minimal amount of hoof wall surface area is available for bonding, such as when a heel crack is repaired. Carbon fiber can be used as middle or axial layer in a laminate and should be protected with an abaxial layer of a more abrasion-resistant fabric."
Following are specific steps taken by Sigafoos when using acrylic adhesives to repair a serious hoof crack:
First, the defect is thoroughly debrided. When that is completed, the normal hoof wall surrounding the defect is sanded lightly and cleaned with a free-flowing acetone rinse.
A thin layer of adhesive then is applied directly to the hoof wall surrounding the defect. This layer is applied immediately after the two components of the adhesive have been mixed. If a fabric lacing technique is used, two sections of fabric are saturated with adhesive and positioned over the defect so that the edges are aligned over the center of the defect in an upper to lower direction. This stage of the repair is allowed to cure for 15 to 20 minutes.
Following the cure cycle, the fabric is drilled and laced using 18-gauge stainless steel wire. A small strip of one-sixteenth-inch thick ABS is cut to form the covering over the opposing sections of fabric and is bonded in place.
Two to three layers of fabric are cut to overlap the repair as much as possible on both sides of the laced area. These fabric layers are saturated with adhesive and bonded in place. The type and number of layers are dictated by the location of the injury, but in most cases, the most abaxial layer should be Spectra fabric, with the axial layers composed of carbon fiber or S2 fiberglass.
Installed at the bottom or distal end of the crack is a removable bolt. Ongoing treatment involves removing the bolt daily and flushing the area with 2% iodine.
The next question is this: Does the procedure indeed work? Results recorded at New Bolton Center indicate that it does.
Nineteen horses which were admitted to the Center had acute hemorrhagic or chronic refractory hoof cracks that were repaired through the use of a fabric lacing technique. The results were considered favorable if the horses were able to return to training or competition.
Eleven cases (58%) were able to return to competition or training with complete cessation of lameness. One horse did not improve and was retired. Three cases were lost to followup. Four cases were broodmares not included within the competitive group. Two of these mares became sound following the repair and two did not. The two broodmares which remained lame were foundered.
In most of the cases, the defects closed and stabilized or disappeared. One case involved damage from a wire cut with a significant injury to the coronet. Although the horse became sound and returned to training three months after the initial repair, the injury never became sufficiently stable without composite reinforcement.
Following are Sigafoos' concluding comments concerning the procedure:
"Maintaining the stability of hoof wall defects is an important step in returning horses to competition. Three considerations are essential for successful repair of hoof wall injuries. The first of these is complete debridement of the defect. Even small areas of necrotic or damaged hoof tissue left under a repair will promote continued breakdown of the hoof wall and can be a potential source of infection.
"The second is the establishment of drainage. Any defect that has been debrided proximal to the level of the sole must have drainage. The third of these is repair design. A successful repair will treat the original injury as well as any other concurrent defects that may contribute to the hoof wall instability.
"In most cases, soundness will return immediately or within five to seven days following the type of repair described herein. Hot-water foot soaks can help to decrease lameness and can begin eight to 12 hours after the repair has been performed.
"Complete closure and elimination of the defect will not always occur and is not essential for the animal to return to competition. Some horses may need to have defects reinforced indefinitely."
Another dimension to this type of hoof repair is added by Tracy A. Turner, DVM, MS, Dipl. ACVS, College of Veterinary Medicine, University of Minnesota. In a presentation at the 1996 AAEP meeting in Denver and in a paper published in the proceedings, Turner outlined an approach that involved impregnating hoof repair material with antibiotics to facilitate earlier repair and more rapid healing.
"Techniques have been devised to repair the hoof wall integrity by utilizing various acrylic materials. These techniques work well in the normal hoof, but it is commonly believed that whenever there is the possibility of infection or when sensitive tissue is exposed, acrylics should not be used because infection can either develop or be exacerbated.
"However, because it has generally been accepted that acrylic repairs are contraindicated, because of microflora that is trapped under the acrylic, which makes the disease worse, or because of the exothermic (heat) reaction caused by the materials, which leads to further damage of the wall or abscessation, these cases are usually not repaired with acrylics and have a much longer healing time."
Turner and his associates hypothesized that if hoof acrylic could be impregnated with antibiotic, the antibiotic would leach out of the material and this would work to prevent infection and abscesses.
The researchers carried out three studies to evaluate the approach. The final study involved a clinical trial with 18 horses. The cases included 14 hooves affected with white line disease, 10 hooves with non-healing hoof cracks and defects, and one horse with a hoof wall avulsion.
The feet were cleaned and debrided in standard fashion. The wall was prepared for acrylic repair, then medicated acrylic was applied to the exposed inner horn and along the junction of normal hoof wall and exposed horn. A second layer of non-medicated hoof repair material was used to cover the medicated acrylic and fill the entire defect.
Turner had this to say, in part, about the results:
"The medicated hoof acrylic repair was left in place until the hoof grew out. The material had to be replaced in two cases. In each case, no exacerbation of disease was noted. In fact, in the cases of white line disease, it was thought that these cases resolved faster. In the cases of non-healing defects, the defects healed and grew out in each case. The horse with hoof wall avulsion was able to become weight bearing on the hoof earlier than had been expected.
"This study shows that antibiotics can be incorporated into hoof repair materials and this antibiotic will elute out at therapeutic concentrations.
"One problem was noted. The addition of the antibiotic powder does appear to slow the curing process of the acrylic. Additional time is required for it to cure before additional layers are applied. Failure to allow it to cure may cause premature loosening of the repair.
"We have shown that the impregnation of antibiotic powder into the hoof acrylic can be very beneficial as a treatment method for some diseases of hooves."
As was stated at the outset--hoof cracks can range from the benign to the catastrophic. The good news is that many of these cracks can be prevented by proper trimming and shoeing, a solid nutritional program, and providing the correct amount of moisture for the hoof. Of equally good news is the fact that when a serious hoof crack appears, often due to injury, space-age materials and techniques are available to assist in the healing process.
Yet, even this good news is leavened by the fact that serious injury to the all-important coronary band can result in a hoof defect that will be with the horse for life. Many of these serious injuries can be prevented with proper fencing (elimination of barbed wire, for example) and the removal of other hazards that can cause foot and hoof injuries.
The old adage of an ounce of prevention being worth a pound of cure applies to hoof cracks, especially those emanating from injury to the coronary band.
About the Author
Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.
POLL: University Equine Hospitals