Friday, February 18, 2011

No Farrier, No MRI: Diagnostic Imaging Sessions Begin With Careful Un-Shoeing

If you’re a farrier or horse owner who is new to equine MRI, you might be surprised to learn that most horses couldn’t have an MRI without the help of farrier skills.

That’s because horses that are shod must have their shoes removed before the MRI process can begin. This could be done before the horse leaves home, but it is usually done at the vet clinic where the MRI will be done, since the horse may need to be trotted or lunged as part of the diagnostic process.

An MRI session begins long before the horse's limb is scanned. It begins with an exam and the removal of both front or hind shoes, if the horse is shod.
For advice on the gentle art of shoe removal, Hoofcare + Lameness went to one of the world’s best authorities, Dave Duckett FWCF. A former farrier instructor at the national schools in Great Britain and Ireland, Dave is an undisputed expert analyst on the fine points of shoeing and unshoeing a horse, as his many world championships and other titles attest.

Duckett reminds us that a lame horse that is having an MRI may have some resistance to standing on three legs during shoe removal. It may also resent having its hoof walls tapped with the hammer to cut the clinches. For this reason, it may be safest to do the work at the vet clinic.

  Pulloffs should be used from the heel forward, gently removing the shoe without harming the hoof wall, but it is best to remove the nails with a creased nail puller. (Michael Wildenstein file photo)
Normally, a farrier might rasp off the clinches and an apprentice would go to work loosening the nails and then wrenching the shoe off the foot. With the shoe will come the nails, but farriers know full well that some may break. It may not happen often, but nail fragments can remain in the foot.

When and if this happens on the day an MRI is scheduled, the fragment will need to be found and removed, since any metal might disturb the magnetic function of the scanning system.

There are many reasons that nails break off. Duckett remarked that nails commonly corrode and break in the feet of horses that have been standing in urine-soaked bedding or manure-filled pens. The longer a shoe has been on, the more likely the nails are to break on any shoe, he added.

The design of the shoe itself can cause a nail to break off; the shape of the nail hole may be wrong for the size or style of nail that was used, so the nail fractures under the head. If the nail hole is too small, the edges of the hole shear the side of the nail as it passes through, weakening the shank, increasing the likelihood of fracture, and possibly creating soft steel dust particles that are carried up into the hoof wall. “The shoe doesn’t give, the nail does,” Duckett said, “and it usually fractures under the head.”

Cross-section of toe nails in foot, showing clinches (Michael Wildenstein file photo)
Duckett also warned about machine-made shoes that are hot fit, then quenched before nailing. This hardens the steel of the shoe around the hole, so the soft steel of the nail is likely to shear more as it passes through.

The constant expansion and contraction of the horse’s foot causes stress to the nail inside the wall, and can also lead to nail fatigue and even breakage, usually on the inside heel or both heels, according to Duckett.

It's safer to cut the clinches and pull the nails through the wall rather than rasping the clinches off and thinning the hoof wall of a horse that may already be lame. (Michael Wildenstein file photo)
So, instead of rasping off the clinches, or even just bending them back, the clinches should be cut off; this can be a challenge for someone not accustomed to finding the clinches in a recently shod foot, especially on the inside wall.

Creased nail pullers allow careful remove of each nail; the jaws can get down into the crease of the shoe. (Michael Wildenstein file photo)
Once the clinches are cut, each nail should be gently pulled through the foot with the creased nail pullers with a continuous pull, not a yank. Vet clinic farriers quickly learn to count their nails, check each one for its full length, and keep them in a little tray or cup to account for each foot’s nails.

Duckett pointed out that some clinches, if not cut, will break off occasionally and be lost inside the foot. This can be an inconvenience if a horse is scheduled for an MRI. He said that an experienced farrier will be able to pop a nail into the old hole and extricate the lost bit of metal.

The unshod foot will be cleaned and examined. As Hallmarq’s Nick Bolas pointed out, metallic dust can also be created by a rasp or by rust from shoes or the horse’s environment.

And that just won’t do for a horse that has a date with a huge magnet. Any sort of metal residue on the hoof wall or inside needs to be removed before the scanning begins.

Nail holes can be flushed with a cleaner—I fully expect a special product to enter the market any day now! A product like Life Data Labs’ Hoof Disinfectant is probaby found in most farriers' trucks and will do the job.

  Even the tiniest artifacts show up and can be magnified in an MRI scan. In this image, you can see a few glitches along the hoof wall. (Hallmarq MRI image)

Working with Hallmarq Veterinary Imaging Systems, Hoofcare + Lameness came up with these tips for horse owners, clinics and farriers for pre-MRI hoof prep:

1. Owner: ask the vet clinic who will be pulling the shoes. Some owners may prefer to schedule a farrier appointment and make sure that the horse's regular farrier does the work. The owner should make sure that this farrier knows what s/he is expected to do so the correct tools will be on hand. It is most convenient to have the work done at the clinic.

2. Owner: Make sure that a farrier with Hallmarq MRI prep experience will be doing the work so that the procedure described above will be followed. The horse owner may also need some supplies. Some owners may prefer to leave the shoe pulling to the farrier working at the vet clinic.

3. Owner: Make an appointment for the horse to be re-shod after the Hallmarq MRI is completed; this can be done at the vet clinic if the farrier is accustomed to working there or makes arrangements in advance. If a diagnosis is expected that might affect the shoeing, delay the re-shoeing in expectation of changes to be made.

4. Owner: Consider the use of padded boots like Soft-Ride Equine Comfort Boots during transport to and from the clinic if the horse is sore without shoes. At the very least, cover the feet with vet-wrap or duct tape to keep them clean. If the horse is traveling to the vet hospital, the feet with be cleaned again but remove any caked-on mud and debris and comb out any feathers and the mane and tail to make sure no metal is hidden in any of the horse's hair.

5. Owner: Do not use hoof polish, gels, sealers or any topical medications on the horse’s legs for 24 hours before the scheduled appointment. 

6. Owner: Don’t clip the pasterns unless directed to do so by the veterinarian or Hallmarq MRI technician. The vet clinic staff will usually clip any hair that is in the way.

7. Clinic: Clean the shoes with a wire brush and rinse under running water to remove any dirt and manure. Store them in a plastic zipper-top bag and mark them with the horse’s and/or owner’s name. Sometimes a veterinarian or consulting farrier will ask to see the shoe that was removed from a lame foot to check how the horse “wore” the shoe. Always be careful to properly dispose of nails.

8. Owner: After the shoes are removed and the feet are clean is a good time to take record-keeping photographs of the horse’s feet.

9. Owner: A horse with its shoes newly removed may be a little sore so give plenty of time to load and unload from trailers. If using a commercial service to pick up the horse, make sure they are aware of this. Farriers: make sure that owners or trainers know that this mild soreness after unshoeing is a specific side effect and not part of the horse’s larger lameness issue. Depending on clinic policy and arrangements made in advance, owners should be prepared to receive a partially-unshod horse after the MRI is complete.

10. Clinic, owner, farrier: Education is critically important to the success of the horse’s MRI scan. Learning how to properly use farrier tools and which farrier procedures are considered Best Practices in the preparation of a horse for MRI scanning is a new area where we all have a lot to share and learn from each other.

A carefully unshod horse whose clinches were cut (not rasped) and whose nails were removed with a creased nail puller is a welcome sight to the farrier who will be re-shoeing the horse; if he or she needs to re-use the nail holes, the wall won't be rasped away and if the shoes are re-used, it is not likely to be twisted in the heels. (Gary Huston photo)
In this age of MRI, Hallmarq recognizes that farriers are both needed in this important first step in preparation of the horse for MRI, and that farriers will be involved throughout the process of caring for the horse during its rehabilitation from the lameness that the MRI should help diagnose. For this reason, Hallmarq Veterinary Imaging is dedicated to including farriers in education programs and studies.

Content and photos © 2011 Hoofcare Publishing

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