Hoof Wall Repair

Being a farrier is an ancient calling. From the time man domesticated the horse, removed it from its natural habitat, changed its diet, and put it to use in competitive endeavors on a variety of surfaces, hoof care has become a critical aspect of equine ownership.

For 2,000 years or more, man has utilized horseshoes to protect the equine foot from undue wear and injury, but of even more importance has been regular trimming and proper nutrition. Research has shown that horses on a proper diet will have larger, stronger hooves than will animals on a restricted diet.

Despite the best of care, there will still be some horses which will have hoof problems. Figuring prominently in this group are racehorses, but all sport horses are more susceptible than the average pleasure riding mount. The reason is the stress and demand placed on the hooves of horses which run at speed, jump, or stop quickly.

While some of the old tried and true methods of hoof repair remain in vogue and are as effective today as they were hundreds of years ago, the modern-day farrier has space-age materials to lend assistance in repairing stubborn hoof injuries that his or her predecessors couldn't even dream about.

Bill Moyer, DVM, professor and head of the Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, and Robert D. Sigafoos, CJF (Certified Journeyman Farrier), Section of Sports Medicine, New Bolton Center, University of Pennsylvania, have collaborated to author a recently published book, A Guide To Equine Hoof Wall Repair. This text outlines step-by-step procedures in utilizing some of the new space-age products. The book is published by Veterinary Learning Systems of Trenton, N.J.

Before taking over his present duties at Texas A&M, Moyer was on the staff at New Bolton Center and worked with Sigafoos, the staff farrier, to develop techniques for using space-age substances such as polymethylmethacrylate (an acrylic adhesive) and synthetic fiber materials.

Use of the these materials has been particularly effective, says Moyer, in dealing with hoof cracks, especially those of the quarter and heel region. The procedure is known as fabric lacing repair for hoof wall injuries.

In one study involving Moyer and Sigafoos at New Bolton Center, 19 horses were admitted with severe hoof crack problems that were of a severity that the horses were lame and unable to perform. In each case, the damage was repaired by using a fabric lacing technique.

To be considered a favorable result from the procedure, the horse had to be able to return to training or competition. Of the 19 horses involved, 11 (58%) were able to return to competition or training with complete cessation of lameness. One horse did not improve and was retired. 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 that remained lame were foundered. Three cases were lost in follow-up.

In most cases, it was reported in the findings, the defects closed and stabilized or disappeared.

Hoof cracks, Moyer says, are categorized according to the following:

  • Location--toe, quarter, heel, or bar.
  • Depth--superficial or deep.
  • Length--complete, which would be from the coronary band to the ground, or incomplete, which would be a shorter crack.
  • Origin--either starting at the coronet and working downward or starting at ground level and working up.

The depth of the crack is significant. If it is superficial, the problem might be relatively minor and might not cause the horse any discomfort. Conversely, a deep crack that reaches all the way to the sensitive inner structures can be extremely painful and compromise the horse's ability to perform.

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 and fabric lacing repair might be the most desirable approach. The goal of the treatment is to stabilize the crack to alleviate discomfort and provide the hoof with a chance to heal.

Before discussing the repair procedure, however, it might be helpful to determine just what causes cracks in the first place.

What Causes Hoof Cracks?

Following are some of the causes of hoof cracks as outlined 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; underrun heels; pre-existing damage to the coronary corium from trauma or infection (bacterial or fungal); frequent shoe changes; improper shoeing or trimming of feet; repetitive exercise on hard ("fast") surfaces.

Two characteristics are often 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.

Management of hoof wall injuries involves four stages, reports Sigafoos. They are: 1) assessing the injury (including etiology and prognosis); 2) debriding the hoof wall to remove all necrotic or damaged material; 3) planning the repair; and 4) applying the repair.

In a paper published in the AAEP Proceedings of 1995, Sigafoos reported that a number of conditions should be given serious consideration in determining the proper approach to treatment.

"Factors such as radical hoof angle changes, excessive toe length, and marked hoof asymmetry can produce cracks or other forms of catastrophic wall failure," he reported. "Refractory 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, dorsal 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."

A key element in successful hoof repair, reports Sigafoos, is careful hoof wall debridement. This means that all of the necrotic or separated wall must be removed.

"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 for infection," he says.

Normally, debridement is carried out with a tool that would fit the description of an oversized dentist's drill. It can utilize a variety of burrs or cutting edges.

The Repair Process

The fabric lacing repair process, says Moyer, begins with a proper trimming of the feet. "There is no point in treating a crack on an unbalanced foot if the imbalance remains in place," says Moyer.

There is a key point to bear in mind before repair begins, Moyer warns. If there is infection as part of the injury, the wound must not be sealed unless drainage is provided. It is best, he says, first to clear up the infection, then repair the hoof.

The key ingredient in the fabric lacing repair process is an acrylic adhesive (polymethylmethacrylate) that adheres to the hoof wall in such a manner that it literally becomes a part of the hoof for up to six months and grows out with it.

Another strong point of the acrylic material, says Moyer, is that once it is set, it can be shaped and trimmed, and even takes nails readily. The material sets up (cures) quickly and, after curing, is pretty much unaffected by weather or external moisture. The curing process is normally complete within about 24 hours.

There is a downside to this seemingly miraculous substance. The technique can be expensive and the procedure can be time consuming. Plus, it requires meticulous preparation and a favorable environment.

The repair procedures also try a horse's patience, but it is best to avoid local anesthesia, according to Moyer. It is important, he explains, that the veterinarian and farrier are aware of any sensitivities in the foot. Horses which are hard to handle can be administered sedatives or mild analgesics.

Moyer and Sigafoos list these important points for veterinarian and farrier to follow before beginning a fabric lacing repair technique:

  1. Always trim the foot first.
  2. Avoid nerve blocks when possible.
  3. Always start with a clean hoof. After sanding, clean thoroughly with acetone and a wire brush.
  4. Do not leave any undermined wall in place. All unconnected hoof wall should be removed.
  5. Be aware that repairs will grow out with the hoof wall and usually do not need to be removed. The material can be trimmed much like a hoof wall.
  6. Tape the coronary band to keep it clear of the resin. The material is difficult to remove from hair and can appear unsightly. (However, they add, to their knowledge, the material causes no adverse effects to the coronary band.)
  7. Always deposit a sample of the first batch of resin in a discardable container to make sure the materials are being properly mixed.
  8. Use appropriate safety techniques--wear protective gloves, eyewear, etc., and use the acrylic only in a well-ventilated area.

Use of fabric lacing repair to deal with a complete quarter crack is described by Moyer and Sigafoos like this:

Using a drilling instrument, such as a Dremel tool, explore the crack, making sure the hoof wall next to the crack is not undermined and, more importantly, that there is no infection. Next, a generous area on either side of the crack is sanded.

Following this procedure, a stepladder effect is created by burring four to six notches perpendicular to the crack in the hoof wall for horizontal stability.

It is at this point that cleanliness of the hoof wall is imperative so the adhesive will weld to it. Moyer recommends cleaning the area with a wire brush and rinsing it with acetone. Next, the area must be dried. A heat gun or hair dryer can facilitate this portion of the process.

The acrylic adhesive is now spread over the entire sanded and cleaned area of the hoof, with the material smoothed out with a tongue depressor or other discardable device.

It is important at this stage that the acrylic has an opportunity to cure. One method to make sure this part of the procedure works well, as imparted by Moyer and Sigafoos, is to wrap the area in polyethylene and secure it in place with adhesive bandaging material. This type of covering poses no binding problems because the acrylic adhesive won't adhere to polyethylene.

Again, a hair dryer or heat gun can be used to accelerate the setting process. Moyer and Sigafoos recommend allowing 5-15 minutes for this stage of the curing process, then removing the polyethylene.

The next step is to lightly sand the repair and prepare a piece of synthetic fabric that will match the size of the overall patch area. The fabric is soaked with acrylic adhesive and placed over the patch area. Additional acrylic is placed over the patch until the patch is entirely covered and no longer visible.

Once again the hoof is covered with polyethylene and allowed to set. The only thing left in the process, once the poly-
ethylene is removed, is to lightly sand the area, but that is for aesthetic purposes only.

The hardened acrylic will literally become a part of the horny capsule. As the hoof grows, the patching material "grows" along with it. When all works well, the crack is completely stabilized and the new hoof growth is without blemish.

The entire repair procedure requires approximately 30-45 minutes.

Because the acrylics on the market are hard, yet resilient, a shoe can be placed on the hoof and nails driven through the acrylic in the same fashion as through the hoof wall.

Heel Crack Repair

Repairing a heel crack that is located just below the coronary band, but does not reach ground level, utilizes much the same technique as the complete quarter crack, but with another twist--the use of two small brass plates and wire.

Moyer and Sigafoos explain it like this:

Once again the drilling instrument is used to clean and widen the crack with a cutting burr. Then, two drill holes are placed three-eighths to three-fourths of an inch on either side of the newly created trough, with each pair of holes directly opposite each other.

The two plates, cut from brass shim stock, should be slightly longer than the exposed trough and about one-fourth inch wide. Holes are drilled in the plates to correspond to the holes that have been drilled through the hoof wall.

Next comes 22-gauge stainless steel wire, which is inserted through the holes in the hoof wall, then through the brass plates on either side. The wire is then pulled tight while the horse puts weight on the foot and the ends twisted to hold it firmly in place.

The reason for the brass shims, says Moyer, is that without them the wire suture would pull through the hoof material. When the plates have been wired into place, the acrylic and fiber material are applied in the same manner as with the complete quarter crack. The repair procedure takes 1-1 1/2 hours.

Again, Moyer says, the brass plates can remain in place and will simply grow down, along with what is hoped to be a healthy hoof.

Hoof Wall Loss

A problem that veterinarians and farriers face frequently is a quarter crack with hoof wall loss. The repair procedure for this type of injury, as described by Moyer and Sigafoos, is only for cracks that occur on the bottom of the foot and run upward--not for incomplete cracks that begin at the coronary band.

Once again, the first step in the procedure is to trim the hoof and explore the crack.

This time, two holes are drilled approximately one-half inch apart on either side of the crack. The drill holes are through the bottom of the hoof and just outside the white line. The points of exit of the two holes should approximate those normally achieved when driving shoe nails.

A synthetic suture--a thin shoestring can be the suture of choice--is inserted in the far hole on one side and threaded to the near hole on the other side; then in near-to-far fashion with the other two holes. The suture is tightened and secured with three knots. The knots are saturated with cyanoacrylate adhesive to ensure security and a shoe is nailed to the foot.

After attaching the shoe, the application of acrylic and the synthetic fiber patch are used to cover the area. Once the acrylic has cured, the final product can be treated a though it were a normal hoof.

Infected Crack Repair

There is a final procedure that Moyer and Sigafoos have discussed in their book and in person, but it is a procedure that Moyer holds in reserve as something of an emergency effort.

This procedure involves placing a patch over an infected hoof crack. The ideal treatment of the infected crack, Moyer emphasizes again, is initial stabilization with open drainage. Once the foot is cleared of infection, he says, and the exposed tissue is cornified, the resin can be safely applied.

However, he admits, there are some cases in which a patch over an infected area is required, such as "...if it's Thursday and the horse is entered in a $250,000 race on Saturday."

The preparation steps are identical to those described in dealing with a quarter crack that has hoof wall loss and needs to be sutured at the bottom. When the suture is in place, the area is packed with a water-soluble material, such as Play-Doh or clay.

Placed on top of the clay layer is a plastic drain that extends from the top to the bottom of the problem area. The acrylic resin is then applied liberally over the drain. After the resin has cured, the Play-Doh or clay and the plastic drain are removed and the cavity that remains is flushed with an antimicrobial solution.

A shoe is then placed on the hoof. One of the reasons for the shoe is to help protect the opening at the bottom from contamination. Moyer also suggests that a gauze sponge or cotton be placed in the cavity under the shoe.

Repairs Other Than Cracks

There is another problem area where the new space-age materials can be used imaginatively--underrun heel and long toe. The underrun heel and long toe problem occurs when the angle of the heel is at least five degrees lower than the angle of the toe. What has happened in many cases is a breakdown of the heels, leaving the horse with a longer than desired toe and little heel support.

The solution is to use acrylic adhesive to reconstruct the hoof wall in such a manner that it is evenly loaded.

If carried to an extreme, the horse winds up with a complete prosthetic hoof wall, including heels, bars and buttresses, to which a conventional shoe can be nailed.

In the early stages of the procedure, all damaged and separated horn is removed from the hoof. After cleaning and properly preparing the foot, the acrylic resin is applied to the hoof walls in such a manner that a section of new hoof is created, only this time with the correct angle and bearing surface.

Moyer says the newly constructed hoof can be shod 15-30 minutes after the final application of acrylic resin. He recommends that a bar shoe be used.

Following reconstruction, he says, the horse can resume all normal activities in approximately two hours, but it is a good idea to limit environmental exposure for 12 hours.

On subsequent shoe resets, he says, the repair can be trimmed and the foot shod as if normal hoof wall were in place. Whether further reconstruction is necessary is determined by the direction and quality of new horn growth.

The approximate time needed for this repair procedure is estimated at 60-90 minutes.

Much has remained the same in the care and treatment of equine feet through the years, but the advent of new space-age materials has definitely given the farrier and the veterinarian major assistance in their efforts to keep performing horses sound.

About the Author

Les Sellnow

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.

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