There isn't much time in the busy farrier's life to chat with his brethren of the forge. On the road before daylight, driving endless hours, and arriving home late at night after a hard day's work doesn't leave much time for socializing. However, the annual American Farrier's Association (AFA) Convention not only lets farriers get together for a good time, but allows them to compete in various "smithing" skills and to sit in on lectures and demonstrations from industry leaders.
Below are synopses of some of the lectures given to the AFA members during the convention.
Diagnosing Palmar Hoof Pain
More than one-third of all chronic lamenesses in the horse occur in the palmar (lower back) region of the hoof, noted Tracy Turner, DVM, MS, Dipl. ACVS, of the University of Minnesota. Lameness in this area can include hoof wall cracks, sole bruises, vascular disease, tendonitis, synovitis, thrush, problems with the coffin bone (third phalanx), and problems in the navicular region. But, instead of zeroing in on a horse "having navicular" when there's pain in this area, it's important for your veterinarian to determine the exact cause of your horse's trouble in order to alleviate his discomfort.
"The first step in developing a logical approach to treatment of palmar hoof pain is accurate assessment of the pain and careful evaluation of hoof structure that may predispose the horse to or cause the pain," said Turner. "Four diagnostic tests should be performed: Hoof tester examination, distal limb flexion, hoof extension wedge test, and palmar hoof wedge test (see images below right). A positive response to any of these is important, but a negative response is equivocal and does not rule out any problem."
While most people are familiar with hoof tester and limb flexion tests, the hoof extension test is a little different. For this test, the horse's toe is elevated with a small block while someone else holds up the opposite limb. The horse is trotted away after 60 seconds and his gait is evaluated.
The palmar hoof wedge test is performed by placing the block under the back two-thirds of the frog and forcing the horse to stand on that foot as with the toe wedge. Turner said the test can be modified so that the wedge is under only one heel.
While "blocking" or using local anesthesia is often performed on a lame horse, there are problems with distinguishing the exact area affected by the block. For example, said Turner, horses injected in either the distal interphalangeal joint or the podotrochlear (navicular) bursa region, which aren't connected, can result in similar pain relief. The structures these two areas have in common are the navicular bone, the impar ligament, and the collateral sesamoidean ligament (proximal suspensory ligament of the navicular bone).
Turner said horses with palmar foot pain can be divided into five groups:
- Horses with navicular region pain that's desensitized by distal interphalangeal joint analgesia and bursa analgesia as well as palmar digital analgesia;
- Horses with distal interphalangeal pain that's desensitized by distal interphalangeal joint analgesia as well as palmar digital analgesia, but not bursa analgesia;
- Horses which are not desensitized by distal interphalangeal joint analgesia but are desensitized by bursa analgesia and palmar digital analgesia;
- Horses which are improved by distal interphalangeal joint analgesia or bursa analgesia but aren't made sound, but are sound after palmar digital analgesia;
- Horses which are not desensitized by either distal interphalangeal joint analgesia or bursa analgesia, but are desensitized by palmar digital analgesia.
Turner said injecting the navicular bursa should be done using radiographs and adding contrast media to "prove the limits" of the block. This is necessary because the bursa can be difficult to inject and it is in close proximity to other synovial structures such as the distal interphalangeal joint and distal tendon sheath, both of which could cause pain and be blocked if the injection is misdirected or "leaks" to other structures.
Recently, said Turner, a method for examining the navicular region by using ultrasound to look up through the bottom of the horse's foot was introduced. Other diagnostics include scintigraphy, radiography, thermography (heat imaging), and an assessment of hoof balance.
For evaluating hoof balance, 11 measurements of each foot are made, said Turner, including seven of hoof length. These include medial and lateral heel lengths, medial and lateral quarter lengths, dorsomedial and dorsolateral toe lengths (to either side of the center of the toe), and sagittal toe length (straight down the middle). These measurements are plotted on a graph to give the general shape of the foot. Other measurements include the frog's length and width at their longest and widest points, hoof circumference immediately below the coronary band, and hoof angle (using a hoof gauge). The horse's body weight also is determined using a weight tape or scale.
"The University of Minnesota has had an ongoing prospective study of these findings," said Turner. "So far, about 54% of the (heel pain) cases are affected by navicular region pain and 46% by other sources of palmar heel pain. Clinical signs for these two groups have shown interesting differences."
The study shows that distal limb flexion has been positive in 100% of the navicular region pain cases and only positive in 88% of horses in the palmar heel pain group. Hoof tester examination, which is considered a cardinal sign of navicular problems, was positive in only 54% of the horses with navicular region pain, compared to 65% of those with palmar heel pain.
The frog wedge test was positive in 79% of the palmar heel pain horses, whereas the toe wedge was positive in 64% of navicular region pain horses and only 43% of horses with palmar heel pain.
Scintigraphy (bone scan) was positive in only 62% of the navicular region pain horses, indicating that pain was present without scintigraphic changes in the other 38%. Also, 20% of the palmar heel pain horses had a positive bone scan, indicating that the navicular bone might be involved in a complex problem of heel pain.
In conclusion, Turner said that a thorough examination of a horse affected by palmar foot pain gives a more precise diagnosis. Treatment then should be based on the diagnosed source of the pain.
Hoof and Limb Anatomy
Equine hooves and limbs are complex and highly evolved for speed, and Mitch Taylor, Certified Journeyman Farrier and proprietor of the Kentucky Horseshoeing School, firmly believes that a farrier cannot shoe a horse to his best advantage without thoroughly understanding the anatomy involved. "Especially for pathological and therapeutic shoeing, I don't think you can properly shoe the horse and visualize what's going on without knowing basic anatomy of the horse and extensive anatomy of the digit from the fetlock down," he said.
During a two-hour presentation involving step-by-step dissection of multiple equine lower limbs, Taylor discussed hundreds of fine points of equine anatomy to further educate attendees about the dynamic balance of forces and support structures. "The grouping of equine muscles at the proximal end of the limb provides a long lever arm with powerful drivers," he explained. "The long lever provides a longer stride per unit of muscle work than in the animal with relatively shorter legs."
Some of his points included:
- "The deep digital flexor, superficial digital flexor, and extensor muscles are slack until just before the foot hits the ground," he explained. "When the foot flips up, things tighten up. The leg is pre-loaded by this with the joints in close contact. Otherwise, we'd have a lot of injury and bone chips."
- The superficial digital flexor tendon (SDFT) is very flat, and easier to tear than the thicker, rounder deep digital flexor tendon.
- The SDFT attaches to the first and second phalanges (P1 and P2). This keeps the pastern joint from subluxating, so P1 and P2 function as a single bone throughout most of the stride.
- "The fetlock is stabilized with ligaments that give it more strength than the bones it's made of," Taylor explained. "The proximal sesamoidean ligaments must have an equal and opposing force to keep (sesamoid) bones together and stable for suspension. Often we do dissections from racehorses and sometimes we see sesamoids pulverized, but rarely do we see torn sesamoidean ligaments without bone fracture."
- Tendon laxity can be very detrimental to the horse. "This can be likened to pulling out a stuck truck slowly vs. taking up eight to 10 feet of slack with one jerk," he said.
One of the more unique aspects of Taylor's presentation was his setup for loading and unloading dissected limbs so attendees could see the action of different hoof and lower leg structures during weight bearing from different angles. He loaded a dissected limb up to 2,000 pounds multiple times, demonstrating that, "Under load, the sole drops, P3 (the third phalanx or coffin bone) shifts down and backward, and the space from the top of P3 to the top of the hoof capsule increases (in other words, the entire bony column shifts downward within the hoof capsule)," he said. "The majority of bone movement is in the first 200-300 pounds of load."
Shoeing the Arabian and Half-Arabian Show Horse
With shoeing standards strictly regulated by the International Arabian Horse Association and the United States Equestrian Federation for the Arabian and Half-Arabian show horse, knowing the legal limits for shoes, pads, hoof packing, and overall hoof length can mean the difference between a winner and a disqualified horse. Bob Parks, Certified Journeyman Farrier, a well-known farrier of Arabian show horses since 1978, did a live demonstration at the American Farriers Associations' Convention on how to shoe the horse so that he can legally perform to the best of his ability in English pleasure, country English pleasure, hack, and English park classes.
Parks, who was a member of the 1988 and 1990 USA Farrier's Team, said that his goal is to produce a nice, open trot with as much animation as possible. The horse should move in a bold fashion and should have enough confidence in his own movement that he knows he is not going to rock back when he plants his foot.
Length of the hoof, measured from the ground to where the coronary band becomes firm, is of prime consideration. Regulations state that the hoof should be no longer than 4 1/2 inches including shoe and pads. When trimming, Parks likes to take off as little foot as possible to be within the regulations. He shoes with a blunt toe, trying to develop vertical depth and mass to the foot, so the horse can get his foot off of the ground quicker. The blunt toe quickens breakover and mimics the shape of the coffin bone, preventing distortion of the hoof wall.
Adding mass to the foot increases animation and Parks likes to increase the mass by 10-30% if possible to give the horses he shoes an advantage in the show ring. If the horse will tolerate it, he prefers to use an electric belt sander rather than a file to smooth the outside of the hoof, because it is faster and removes less foot. He starts the year off using an 80-grade sandpaper since the foot is not as cosmetically pleasing after a winter season without competing. He then might use a 100-grade, and during the show season he uses between 120- and 150-grade sandpaper to just clean and smooth the foot.
He emphasized the importance of shoeing within regulations. "Too much weight can cost a national championship," he said. Shoes are allowed to weigh up to 14 ounces, not including pads or rivets. If bands are used, they are included in the overall weight as well as their bolts and rivets, and must be attached to the shoe. In addition, nothing welded to the shoe (bars, clips, etc.) can extend below the ground surface of the shoe to increase performance.
Pads must either be made of leather or plastic and are not included in the weight. Any combination of pads can be used to obtain the overall desired length; however, pads cannot be bonded together or have foreign material between them. Performance-enhancing materials, such as lead, under a pad can lead to a suspension of the owner or trainer. Hoof packing must be made of any normal, accepted material such as foam rubber, oakum, pine tar, silicone, etc.
Parks mentioned that horses which have been shod often will stand better for trimming and shoeing. And for one who shoes 160 horses year-round, a well-behaved horse is much appreciated.
True to tradition, this year's AFA convention offered the valuable continuing education farriers need in order to improve their shoeing work. Look for these attendees to help raise shoeing standards to new levels in the future.
For more information on the American Farrier's Association, visit www.americanfarriers.org.
--Kimberly S. Herbert, Sarah E. Evers, and Christy West
About the Author
POLL: University Equine Hospitals