Friday, December 07, 2012

On the Case: Wrapping Up a White Line Disease Rebuild

 A Series of Case Reports from The Hoof Blog

Lameness-specialist veterinarian Mark Silverman, left, and creative-thinking farrier Ernest Woodward, right, have opened the Southern California Equine Podiatry Center outside San Diego, California. The Hoof Blog asked them to share this case, which is somewhat more practical and more economical than many hoof repair treatments. 

To accomplish it, you need to know and understand the products used and their properties in order to select the right fabric, adhesive and/or impression material to insure the success of the job.

Silverman and Woodward are perhaps more cerebral about their case management than a lot of other vet-farrier duos. They really do reinvent the wheel with each case--or at least it seems that way. They are scrupulous about documenting their work and are very generous to share it as they do.

Some people’s approaches to a case are limited by what they already know how to use; others are limited by the economics of an owner or the environment the horse will experience. Brand loyalty, ease of ordering materials, supplies on hand and just plain personal preference all affect the choice of solutions.

Referral work brings in yet another limitation: coming up with a treatment that can be maintained and, in the case of a shoe, reset by another farrier who may or may not be present during the treatment and who may or may not be familiar with or motivated to learn about adhesives, foots casts, glue-on shoes, dental impression material and composite matrices.

The case Silverman and Woodward present is based on a standard hoof wall rebuilding technique that has been in use since the 1980s. But we have a choice of many more materials today, and the trick is understanding and selecting materials and when/how/where to use the chosen ones.

1. The case on arrival for treatment referral to Southern California Equine Podiatry Center. The horse’s white line disease damage was extensive and focused at the dorsal and lateral portion of the foot (right front shown). The farrier who cares for the horse had been fighting to keep a protective shoe in place; as you can see, he had been getting increasingly creative to provide needed protection for the foot. The horse's regular veterinarian had debrided the hoof wall. SCEPC was asked to treat the disease and stabilize the foot--but leave the shoeing to the horse's regular farrier.

Silverman and Woodward’s sample case illustrates some updating and refinement of that technique but, moreover, it illustrates the synergistic process between the team and the horse’s regular vet and farrier. They created a best-case scenario by allowing the horse’s regular farrier to go on shoeing the horse more or less normally; he could still select the shoe style and size of his choice, and nail it on, even clinch the nails.

Dr. Silverman explains:
The single most important process in treating white line disease is debridement (removal) of the affected wall, which exposes the infected region to light and oxygen. It appears to stop the progress of the disease and is critical to a successful outcome.

2. Treatment began with a thorough chlorine-dioxide soak, further debridement, wall sanding and covering the wall defect with a thin layer of dental impression material enhanced with copper sulfate.

While the damage from white line disease does not appear to progress proximal to the last centimeter or two of the hoof wall below the coronet, the damage can extend around the complete circumference of the wall.

In my opinion, the reason the disease does not affect the most proximal portion of the wall is related to the blood supply and elevated oxygen levels in the wall around the coronary papillae.

When debriding, it is important to follow contaminated tracks all the way to healthy tissue. Fungidye 2X liquid can be used as both a penetrating treatment and as a dye marker to reveal subtle tracts that require exploration.

3a. Materials for "bridge building", hoof repair style: (left to right): tongue depressor for mixing, copper sulfate crystals, chopped fabric, trimmed fabric, roll of fabric. Top: Equilox adhesive was used in this case; other PMMA adhesives should be suitable (follow manufacturers' recommendations).

If only a small amount of wall needs to be debrided, the area is simply left open to the air and, following a chlorine dioxide soak, the shoe is reset (after correcting any balance or support issues). In some recent cases we are using ozone gas therapy instead of chlorine dioxide soaking, as this avoids saturating the foot before a rebuild.

It is very important to avoid weightbearing on the tissue deep to the stratum medium, especially at the toe. If bending forces challenge the deep tissue of the hoof, it will be pinched and the horse will become uncomfortable.

This situation required building a synthetic wall that would bridge the gap at the weightbearing surface and allow the placement and nailing of a shoe.

3B. The green of the copper sulfate creates a guacamole effect when the chopped fibers are mixed with the adhesive.

After thorough wall preparation, a base layer of extra-soft dental impression material (DIM), heavily treated with copper sulfate, was placed as a thin barrier over the exposed deep tissues. The DIM acts as a buffer for the next layer, a more rigid fiber-reinforced “bridge” across the defect. Finally, a nailable adhesive-impregnated fabric “collar” protects the repair and stabilizes the foot.

The “bridge” is only needed if a significant (one-third or more) portion of the weightbearing surface of the hoof wall is compromised. The bridge should only cover the lower portion of the debrided section of hoof wall, leaving the more proximal portion exposed to air.

The bridge is a paste-like mix of acrylic with fabric “chop” fragments added for strength. Once the bridge mix has been applied, cured and is properly shaped, a two- or (occasionally) three-layer laminate of composite cloth (usually Poly/Vectran®) is placed around the hoof circumference, including over the bridge, to add strength and provide the nailing surface.

4. Marker guidelines on wall help with cuff alterations in later steps. The greenish filled-in surface that you see is the "bridge", an overlay of reinforced acrylic over medicated DIM. The bridge will be partially cut away to expose the proximal portion of the diseased area. The top layers of adhesive-impregnated woven fabric have yet to be placed at the time of this photo.

Once the outer cloth layers have also cured, windows are cut into the repair site using previously-placed black marks on the hoof wall as guides. Window drilling penetrates to the underlying dental impression material. Layers of repair material--outer fabric, inner bridge and DIM--are removed at the proximal margin of the defect to allow topical treatment and air access to the exposed area.

We will often sand the black marks away, for cosmetic reasons, after cutting the windows. If we had elected to use an additional ozone gas therapies, we can even gas the affected region with the shoe and the rest of the repair in place. This would not be possible with a chlorine dioxide soak.

One added note: the copper sulfate added to the dental impression material and adhesive generally comes in a coarse granule. We find we have better results when this is ground to a fine powder, almost talc-like in consistency. This makes for more even distribution and better absorption.

After both debridement and reconstruction sessions, this horse was handed back to the regular farrier for shoeing. He was able to nail his shoe of choice onto the foot, and could nail right into the cuff.

5. The finished foot, with windows cut so air can get to the white line defects. the marks on the wall will be sanded off and the horse's regular farrier will be able to nail a normal shoe on the foot. The green specks on the outer layer are copper sulfate granules.

This description is an update of the adhesive-and-cloth hoof repair technique pioneered by Rob Sigafoos during his tenure at the University of Pennsylvania’s New Bolton Center.

Adhesive wall repair or wall replacement uses many of the same materials and principles used in gluing shoes, but addresses a different set of challenges, both for the materials themselves and for the professionals hoping to simultaneously treat an infection or condition of the hoof as well as repair a defect.

Wall repair or replacement also can integrate adhesive-saturated fabric--both whole strips and tiny fragments--into the treatment to reinforce the adhesive.

In terms of cost, a glue-on shoe used in this process would have cost $75 for a pair of shoes, since ideally both feet would to be done for the sake of symmetry. Adhesive and consumables like gloves would cost another $20.

This technique used a few dollars worth of dental impression material, $5 in cloth, and $20 in glue for a total of about $30. This is an illustration that hoof repair is not always an expensive process. What is expensive is the time and effort it takes to become competent and knowledgeable in the process and to learn the alternatives that are available to suit the case at hand.

From a standpoint of colleague consideration, the shoe on this horse can be replaced or reset by any farrier, which is not the case with a glue-on shoe.

Familiarity and skill in the use of materials and consideration of colleagues and owners are the keys to success. Creative solutions can be found for cases of all shapes, sizes, environments and budgets.

--written by Fran Jurga

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