- May 1, 2007
Shoes are usually removed during the acute stage of laminitis because they concentrate weight on the hoof wall and laminae. An alternate way to support the foot is crucial in the acute stage--let the horse stand in sand, or use Styrofoam or impression material in the bottom of the foot to let the whole solar surface bear the weight of the horse. The toe can be beveled to move breakover back and decrease leverage pressure. It is important to get X rays of the feet during the acute stage; this gives a baseline to compare against later, if and when damage progresses.
Stephen O'Grady, DVM, MRCVS, a professional farrier with Northern Virginia Equine in The Plains, Va., has dealt with laminitis for many years. "If the owner wants to know when to shoe the horse, my criteria is that first the horse must be past the acute stage and relatively comfortable," O'Grady says. "He also needs to be off (or on minimal) medication. Third, the horse needs to have had no further radiographic changes for at least 10 days to two weeks. That means the foot is stable. In the chronic stage we can deal with it mechanically by trying to correct rotation of the coffin bone or any displacement."
Logic points at realigning the coffin bone by reducing heel height; this helps extend the weight-bearing surface in the heel area and moves the base of support further back (a heel usually grows down and forward). However, trimming the heel increases tension on the deep digital flexor tendon (which wraps under the heel and attaches to the coffin bone). Thus, it is necessary to elevate the heels (with a shoe or wedge) to compensate for loss of heel horn height, since muscles and tendons have become shortened and pull against the laminae.
"The foundered horse is bearing all the weight on the toe of the bone (the tip, or apex), so the object of shoeing is to put the coffin bone back in alignment so he's bearing weight on the whole bottom of the bone," explains O'Grady. "If we lower the heels, the bone has better relationship with the ground, but this tightens the tendon, and we have to raise the heel back up to relieve that stress.
"The laminitic foot has more growth at the heel and minimal growth at the toe, with abnormal growth patterns," he continues. "The bottom of the foot is generally a flat plane. If we trim the rear part of the foot, from behind the widest part of the foot back to the heel, we create two planes. If you put a flat shoe on the foot, so it's resting against the heel you just trimmed, the toe will be off the shoe, with space between the toe and the shoe. This unloads the toe, so you take care of that problem as well."
The air space at the toe can be filled with impression material.
Scott Morrison, DVM, of Rood and Riddle Equine Hospital in Lexington, Ky., says there are several ways to aid the laminitic foot using different types of shoes, once the horse is no longer in the acute phase. "Gluing them on is best, since you don't want to drive nails into an inflamed, compromised hoof," says Morrison. Glue-on shoes allow the farrier or veterinarian to adjust the angle of the shoe in relation to the bone, to make the coffin bone as level as possible in relation to the ground.
When trimming the heels, necessary elevation can be achieved by using a shoe that contains a wedge (thicker at the heels), and placing the breakover back at the tip of the coffin bone. "Glue-on shoes allow you to move the breakover back; put the shoe where you need it to change the area that's bearing weight," explains O'Grady.
Glue-on shoes are ideal for realigning the coffin bone, especially if the foot does not have enough hoof wall or sole to accomplish this positioning by traditional trimming and shoeing methods.
Morrison says the guideline is to keep the breakover behind the diseased laminae. "If the toe area is affected, I try to keep the breakover behind the toe. Looking at the foot from the side, I drop a plumb line from the front of the coronary band to the ground, and try to keep the breakover at that point, unloading the majority of the diseased laminae. In most shoes for treating laminitis, breakover is an important feature, along with sole support. A third feature is some type of heel elevation, such as a small wedge, to decrease the pull of the tendon," explains Morrison.
Attaching "rails" to a shoe is another method of heel elevation. (Rails are pieces of metal that are generally narrower than the shoe web, that widen toward the heel. These can be added to shoes or there are rail shoes available.)
A horse with a rotated coffin bone bears most of his weight on the toe. The purpose of shoes is to move weight bearing to the part of the foot that has not been adversely affected and is capable of bearing weight. "You want to get the weight off the sole," says O'Grady. "That's why we trim the heels and fill the shoe with impression material--to use the whole back part of the foot to bear the weight, getting the weight off the toe," he says. By enhancing breakover, the foot can leave the ground easier (the weight doesn't have to move as far forward to break over), diminishing the pull of the tendon on the coffin bone at that point of the stride.
Morrison says if there's a lot of rotation, shoeing mechanics might not be able to resolve it, especially if the tip of the coffin bone has penetrated the sole. "With some, we cut the deep digital flexor tendon (tenotomy) to take most of the rotational force off the coffin bone," he says. Whether these methods work will depend on how long the bone has been rotated.
"If the coffin bone has been out of position a long time, the tip of the bone may be damaged and infected," says Morrison. "Then prognosis is poor for getting that horse walking sound again. But if we deal with it early and the bone is still healthy, prognosis is good for getting the horse pasture sound or for light use. I've had a lot of horses in which the bone had penetrated the sole that we've seen early and used tenotomy that people are riding again."
Getting to them early and treating them effectively makes a difference in outcome. "Once there is a lot of bone disease or damage, this is a chronic source of pain," says Morrison. "In chronic cases where the bone has rotated, our goal in shoeing and tendon treatments is to relieve compression of the sole beneath the coffin bone. Sole tissue at the toe becomes very thin where the bone is compressing it. In our efforts to get the horse to grow more sole at the toe and get the coffin bone back to normal relationship with the ground, we monitor feet with radiographs at each shoeing, to make sure we are gaining sole," he says.
"Once a horse has had chronic laminitis, the laminae are never as strong as in the healthy foot," says Morrison. "So for the rest of the horse's life you may have to use some kind of special shoeing or trimming to give him easy breakover and sole support."
O'Grady says the final step in creating a corrective shoe is to fill the solar surface (inside the boundary of the shoe) with some kind of impression material. "This gives support to the whole foot and increases the surface area that now has ability to bear weight. You fill that opening so it all helps carry the load," he says.
The goal is to reduce pain by changing the forces on the laminae, ideally limit further damage to the laminae, and facilitate better circulation within the foot--which, in turn, will help produce better sole and horn growth.
Tia Nelson, DVM, a farrier and veterinarian from Helena, Mont., says, "The foot is so dynamic--changing so quickly in a laminitic situation--that it's difficult to keep everything exactly where it needs to be. Also, there are many people who are not going to have a farrier come to reevaluate the hoof every two to three weeks, or every two to three days during an acute situation.
"There are things that work, such as the Equine Digit Support System, developed by Gene Ovnicek," she says. "I think this is the kindest and most user-friendly horseshoe for foundered horses, and tailor-made for each horse. I don't use it myself because I make my own (version), but it's basically the same. I just buy a sheet of 1.5-inch blue-board Styrofoam insulation and make 30 to 40 pairs of shoes from that. You cut it to the shape of the bottom of the foot and tape it on with duct tape. This material conforms to all the contours of the bottom of the foot."
Nelson is reluctant to put regular shoes on a foundered horse until she is confident there is good reattachment of the bone to the hoof wall and rotation is being solved. "If the laminae are in trouble and we put a shoe on the hoof wall, we have transferred most of the weight to the hoof wall, which is vulnerable," she says. But if a horse is stable and no longer in pain, and there is good hoof growth and reattachment of hoof wall to coffin bone, she will put shoes on the horse--recognizing that it's vital to make sure the feet never get very long. The lever effect of a long toe is always detrimental. You want the coffin bone and pastern angle close to the same, and you have to back the toe up to do this.
"The shoe is placed well under the foot, with the support back at the heels, and a good breakover located not more than one-third of the length of the foot ahead of Duckett's dot (which is usually about three-eighths of an inch behind the point of the frog)," notes Nelson. "I cut the heels down significantly to continue derotating the coffin bone. You can radiograph the foot to figure out where the bone is, but you can learn to read the hoof wall to determine where it is," says Nelson.
Realigning the Coffin Bone
A radiograph shows the farrier or veterinarian how much the bone has rotated and how to trim the foot and/or apply shoes at the proper angle to put the coffin bone in better relationship with the ground surface. "We don't always want it parallel, because in some cases if it's too parallel to the ground, the bone sinks down when weight is placed on it," says O'Grady. "You aim for better weight bearing on the whole solar surface of the bone rather than just the tip."
After shoes are first applied, the horse is generally confined to a stall for three weeks, then he can be given short periods of hand walking. Shoes should be replaced every four to five weeks, with the rails or wedge lowered at each reset as the hoof wall grows and the coffin bone gradually comes back to normal position. Usually rail shoes are only needed for the first few shoeings, but the glue-on shoes are continued until the hoof wall has regrown enough to maintain the alignment with trimming and conventional shoeing, says O'Grady.
He reviewed records on 75 horses with significant coffin bone rotation--more than 10 degrees--and severe lameness, in which glue-on shoes and rails were used. At first reset, five weeks after these shoes were applied, lameness was decreased and the horses showed no pain with hoof testers. There was increased sole thickness and notable hoof growth at the toe in all the horses. By the third reset, the hoof wall and sole growth were enough that trimming and conventional shoeing could keep the coffin bone in proper alignment. O'Grady says few horses with chronic laminitis ever return to their former level of athletic use, but all the horses treated in this study became comfortable enough to return to some level of use or to pasture soundness.
Early attention by your veterinarian and farrier to a laminitic horse can help the horse be more comfortable, prevent or arrest coffin bone movement, and offer a brighter future for the individual's soundness. To be successful, the owner must frequently and constantly monitor the newly foundered horse, and she must be willing to keep the horse's feet shod or properly trimmed for the remainder of his life.
MANAGING THE WHOLE HORSE
Tia Nelson, DVM, a farrier and veterinarian from Helena, Mont., says treating laminitis is always case dependent: "As a veterinarian, I treat more than just their feet. I look at feed to find out why the horse is chronically foundering. Typically this is not a one-time episode (such as getting into the grain bin). Usually the horse has some sort of metabolic problem, such as insulin resistance, equine metabolic syndrome, or Cushing's that needs to be identified first. If you don't try to find the underlying cause, you'll be chasing yourself in circles trying to solve it."
Insulin-resistant horses often respond to a diet low in nonstructural carbohydrates along with careful and attentive hoof care. Many of them can stay barefoot and comfortable. But if their feed is high in soluble carbohydrates, they can remain chronically tender. "You can knock yourself out using the most fantastic shoes, but if you don't address what is constantly inciting the low-grade or chronic laminitis, you will be frustrated," says Nelson. "If the horse is overweight, I strongly recommend weight loss, to take some of the stress off the feet." --Heather Smith Thomas
About the Author
Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.
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