Saturday, May 21, 2011

A "Natural" Approach to Navicular Disease

This article was first published in EQUUS magazine.


A group of researchers, farriers and other experts argue that restoring basic hoof function and getting a horse moving again are the best ways of addressing navicular problems. 



Joey, a handsome sorrel Quarter Horse, was a standout in the Houston Police Mounted Patrol unit. “We’d had Joey since 1996 and he was the very best horse we had,  able to go into any dangerous, high stress situation and lead other horses in tactical formations,” says Officer Greg Sokoloski, who trains the patrol mounts.  Four years ago, however, the gelding’s place on the force was in jeopardy. After initially showing soreness in his left front foot, Joey began to move like a horse in pain, taking progressively shorter strides and landing toe first. Rest and medication had no effect, and, finally, x-rays confirmed bone changes consistent with the chronic heel pain known as navicular disease.

Joey was outfitted with a wedge shoe that lifted the heel of his left foot, reducing pressure on the sore area. He was also put on stall rest for several months and eventually returned to light work wearing the wedge shoe. But even after 10 months, he wasn’t getting any better. It looked like navicular syndrome would claim yet another horse’s career, forcing Joey into retirement.


Navicular syndrome has a well-earned reputation as a problem that is difficult to resolve. The condition, characterized by localized pain in the heels of the forefeet, exacts a heavy toll: chronic lameness, loss of usefulness and—in the worst cases—progressive deterioration that may make euthanasia the only option.

Not surprisingly, countless studies and thousands of research dollars have been devoted to understanding and solving navicular disease. As part of that effort, some experts have been investigating whether so called “natural” hoof care, a philosophy that stresses the importance of trimming and lifestyle over shoeing, can alleviate navicular pain.

Natural hoof care advocates take a fundamentally different approach to navicular syndrome. Rather than utilizing eggbar shoes or other corrective footwear, they believe that trimming the hoof to return it to a more natural state is a better solution. Of course, no one treatment works in every case of navicular syndrome. Because of the many variables in each individual situation, one horse may respond well to conventional treatment of medication and egg bar shoes and another won’t. But what is certain is that if the conventional treatments always worked, there would be no interest to trying a natural approach to begin with. Here’s a closer look at what the new direction in navicular treatment entails.


Science goes alternative

When it comes to the treatment of navicular disease, the aim of both traditional therapeutic shoeing and barefoot trimming is to decrease pressure on the painful areas in and around the navicular bone. The methods they use to achieve this however, stand in stark contrast to one another.

Adherents of therapeutic shoeing typically look to “stand the horse up,” meaning they increase the angulation of the foot by raising the heels through the use of devices such as wedges, pads, and eggbar shoes. This is done to decrease pressure on the navicular bone from the deep flexor tendon, and to protect the rear third of the foot from environmental pressure.

Natural hoof care advocates disagree with this protocol and believe it actually makes things worse in the long run – even though it might provide relief temporarily. They assert that it is critical to lower the heel, get the frog, bars and sole all sharing in the load bearing, and get the horse moving heel first. They believe this method not only decreases pressure on the inflammed areas that cause the pain of navicular disease, but also helps the horse develop a healthier foot overall.

While some find it easy to discount such “alternative” assertions, they become much harder to disregard when a scientific heavyweight throws his support behind them. Enter Robert M. Bowker, VMD, PhD, of the Equine Foot Laboratory at Michigan State University (MSU). Bowker has spent the last decade delving into the physiology and biomechanics of the equine foot, and his findings have led him to believe that barefoot is the way to go in the treatment of navicular disease.

“You have to look at what the tissues inside the foot experience,” says Bowker, “and when you raise the heels, you are decreasing the load bearing surface area of the foot – similar to when a woman wears a high heeled shoe. This actually increases the biomechanic stresses – the force per unit area – on the inside of the foot, so you have made the situation worse, not better.

“The reason why horses with navicular often appear sound when you raise the heels is that you have shifted the focal point of the load to a new area that is not inflammed – but this is a temporary, symptomatic fix and precludes any possibility of healing. In my experience, it is only a matter of time before that new area becomes inflammed and painful, so these horses eventually go downhill again.”

Physiologically correct barefoot trimming is better, Bowker believes, because it takes the opposite approach to traditional therapeutic shoeing. “When you take a horse barefoot,” he states, “you gradully lower the heels, which increases the surface area of loading on the bottom of the foot and allows the frog, bars and sole to share in the load bearing. These factors drastically reduce the pressure inside the foot – like taking a woman out of high heels and putting her into a running shoe.”

Bowker’s work has shown that you don’t even have to increase the surface area that much to decrease the loads inside the foot significantly. As he explains, “Although I never published it, I did an experiment in my lab in which we used pressure sensitive film to test the load on the foot with differing amounts of surface area in contact with the ground. First we had the [unshod] horses stand on the film on a cement block so that it was mainly the walls of the foot that were in contact with the ground – similar to what we typically see with peripheral loading devices [shoes]. Then we moved the horses onto a rubber mat which was fairly hard, but conformable enough to allow the other parts of the solar surface of the foot to partially share in the load bearing. The surface area increased, but not by all that much – it didn’t even double – and yet the pressure inside the foot decreased to one quarter of what it had been.”

Decreasing that pressure inside the foot allows it to heal, adds Bowker – something that conventional wisdom has considered impossible in horses with true navicular disease. “The degree to which a horse can heal depends on how much damage there is,” Bowker states. “If the navicular disease has been going on for ten years, the impar ligament and the other soft tissue around there are probably so destroyed that even if they did heal, they would still not be anywhere near normal function. However, healing can and often does take place in horses treated through barefoot trimming – I’ve seen it on radiographs.”

As an example, Bowker describes the case of a horse that was brought to him five years ago. “At that time,” he recalls, “it had navicular and the radiographs showed the beginning of ossified cartilages – not good. We gradually lowered the heels, and over time, that ossification resorbed significantly. Recent radiographs show that there is a 3-5 millimeter shrinkage from when I first saw it – and that’s a very good thing. Meanwhile, the horse has been fine and the owner’s been riding it all this time.”

Numerous other cases in which horses treated with barefoot methods have achieved long-term comfort and soundness have convinced Bowker that barefoot does more for the horse than merely relieve symtoms. However, he realizes that it isn’t going to be the right choice in every case. “It depends on what your goals are and what time frame you are looking at,” he says. “If you have a horse show this weekend and you need that horse to appear sound, you have to go with the traditional methods because barefoot is a longer term approach and it isn’t going to do that for you. However, if an owner is truly interested in helping the horse, I would definitely prefer to see them try the barefoot route.”


Trim as treatment

           
In addition to increasing the load-bearing area on the bottom of the foot, Bowker’s work has demonstrated that physiologically correct barefoot trimming does something else that traditional therapeutic shoeing cannot do: it helps the digital cushion and lateral cartilages – internal support structures typically weak and underdeveloped in horses with navicular disease – to become healthier and more robust. Such improvement is desireable for the treatment of any foot-related problem, for as Bowker explains, “When those structures are strong and healthy, they are more able to provide support and dissipate impact, so once again, the force per unit area on the tissues on the inside of the foot decreases.”

Bowker’s research has revealed that when a foal is born, the lateral cartilages and digital cushion at the back of the hoof are soft, fatty and thin, but under natural conditions they will gradually thicken and strengthen over time to accommodate the growing horse’s increased body weight. These mature structures, he says, are essential to the support, protection and overall function of the foot. For these structures to develop properly, several factors must be in place:

  • the horse’s foot must be trimmed (or wear on its own) in a way that provides optimal balance and allows natural function, e.g. expansion and contraction; proper breakover; frog, bars and sole sharing in weight bearing
  • the feet must have plenty of movement over firm terrain
  •  the horse must land heel first to provide the back part of the foot with the pressure necessary to stimulate development.

Unfortunately, says Bowker, some farriery and horsekeeping practices—specifically shoeing before feet reach their full size, restricting the activity of youngsters, housing and working horses primarily in soft footing, and improper trimming—inhibit the development of the lateral cartilages and digital cushion. The result is full-grown horses with “baby” feet that are vulnerable to pain, particularly at the back where there should be a robust, fibrous digital cushion to provide protection. Tellingly, Bowker says, “The lateral cartilages of horses with navicular disease have three to four times less mass, [than a healthy horse] even though as foals they all have the same amount.”

Complicating the issue is the fact that when the back of the foot is sore due to navicular disease or other sources of pain, the horse will often land toe first, which creates a vicious circle because toe first landing does not provide the heel pressure necessary for developing the digital cushion and lateral cartilages. This is another reason why natural hoof care advocates disagree with the traditional notion of “protecting” the back of the foot from environmental pressure.

The good news is that an adult horse with poorly developed internal structures isn’t necessarily destined for a life of lameness. Bowker’s research also indicates that the internal structures of an mature horse’s foot can become thicker, denser and more supportive when the foot’s natural form and ability to expand, contract and land heel first are restored. The treatment is to work towards achieving what Bowker calls the “physiological trim” (see sidebar). “To do this trim,” says Bowker, “you need to be trimming frequently and keeping the toe short – that means backed up, not thinned from below – between the frog apex and the hoof wall, and keeping the frog and bars on the ground.”

Exactly how this is done depends in part on the terrain where a horse works. As barefoot expert Pete Ramey explains, “The bars and frog should be in a support role at impact. To achieve this, the horse must be comfortable enough to impact the ground heel first, and the shape of the foot must be such that the frog and bars bear much of the initial impact force. These two simple goals create a wide range of ‘correct’ trims for various situations. For instance, on a horse that lives and works in yielding or rocky terrain, the bars and frog might be considerably recessed within the ‘cup’ of the foot and still provide adequate support and frog/bar function. In contrast, a horse that lives and works on hard, flat terrain might need longer bars and a protruding frog to achieve the exact same support. Always remember that as these decisions are made, comfort and heel first impact are top priorities. Any trimming decision that yields a voluntary toe first impact will work against the navicular horse.”

Making the necessary changes, however, can backfire if done too quickly, says Ramey. “The hardest and most important part of trimming a horse with navicular is achieving a heel-first landing and thus the frog pressure required to finish developing the lateral cartilages and digital cushions,” he notes. “However, if you leave a navicular horse’s frog on the ground, and the inner structures of the foot are still weak and undeveloped, the frog may be so sensitive that the horse tiptoes in motion. This will get you nowhere.” 

Trimming in stages is usually the answer, says Ramey. “Often we have to leave the heels a little longer for a few months when we’re treating a navicular horse. As the longer heels sink into footing, they reduce the pressure to the frog to a level where the horse can comfortably bear weight. This reduced pressure allows us to start making progress with digital cushion development.”

The addition of boots with foam insoles can greatly speed up this process, says Ramey. “In the real world, a foam boot insole is often the only surface that many of these horses will actually land on with the back of the foot. Any other surface causes too much pain, and horses will land on their toes. This makes the pads a very important place to start. Progress cannot begin until the horse is voluntarily loading the frog.”

“Getting this right takes some tinkering,” he continues. “Often a foam insole alone does the trick. However, if the heels are very contracted and the frog is deeply recessed between them, I tape a frog-shaped pad to the insole to dampen the vibration to the inner structures. If, instead, the frog is protruding, I might cut the frog shape out of the insole to reduce pressure for a while. Continued exercise in the pads rapidly develops the inner structures and, in my experience, soon the pads and boots are no longer necessary.”


What shoes can do for breakover

Natural hoof care advocate Gene Ovnicek, a farrier with 40 years of experience, agrees that trim is a key factor in alleviating navicular pain, and adds that how the horse’s heels are shaped also influences the breakover point, the part of the toe that leaves the ground last when a horse picks up his foot. A natural breakover point—as opposed to one dictated through trimming or shoeing—is crucial to normal hoof function and the prevention of navicular problems, says Ovnicek.

 “Most domestic horses have only a moderately functional foot,” he says. “This is because what many of us consider a normal foot is actually a distorted one. Breakover is a big part of that.” An unshod hoof, Ovnicek explains, wears naturally to the level of the sole and the toe develops a smooth, beveled surface, which starts behind the leading edge of the hoof wall close to the tip of the coffin bone. This beveled surface reflects and contributes to the horse’s natural breakover point. On a shod horse the beveling is limited only to the shoe surface. A forced, unnatural breakover of a shod hoof, he says, requires extra effort and will leverage the hoof wall to “a dish in the dorsal wall that is often times unnoticed from one shoeing to the next.”

Despite the general emphasis in natural hoof care on going barefoot, Ovnicek believes that, at least during initial treatment, shoes sometimes offer the best way of facilitating a breakover point that puts less stress on the foot and helps make a navicular horse more comfortable. “We’ve found that breakover is a huge factor in relieving the strain to get a horse be able to pivot over the top of his foot,” he says. “It’s great if you can do that when a horse is barefoot, but it can be difficult because you’re limited by how much you can immediately reduce breakover on a bare foot. If a horse has distorted hoof wall and a thin sole, you have to be particularly careful about making changes quickly because there is not a lot to work with, and therefore you may not get the comfort necessary to get such barefoot horses functional on day one.” 

Ovnicek’s goal is to eventually allow a horse to go without shoes. But, he says, “Horses with proper breakover, whose frogs are on the ground, and who are landing on the back of the foot are going to have basically normal function, regardless of whether they are shod or unshod. The barefoot horse is going to have better function—by function I mean a solid, well developed frog, healthy bars and suitable sole quality, all pain free and able to perform on a hard, abrasive surface—but the shod horse, especially if the foot is compacted with dirt, can have function that is almost as good.” 

That means you can put away your hoof picks: The experts agree that a shod hoof packed with “clean” (free of manure) dirt is more supported and, in the end, healthier, than a shod hoof picked clean.
Like Ramey, Ovnicek puts great effort into getting a navicular horse comfortable and moving, noting that when this is accomplished the transformation can happen fairly quickly. “We most often succeed in a very short time simply by putting these horses in a sound state and back to work, and then allowing that to work in our favor,” he says. He explains that work is critical for both shod and unshod horses, because the internal components of the foot rely on the stimulus of exercise to stay healthy and function optimally. But in any case, he says, “If a horse has badly distorted feet—the heels are curled under, the bars are crushed in---just trimming all of that distortion and getting the feet back on the ground provides tremendous relief right away.”

Ovnicek adds that getting the horse comfortable and moving doesn’t necessarily mean a horse will be completely sound within two to three months because other problems, such as adhesions of the tendons and ligaments, can develop to compensate for hoof-distortion issues.

Faced with the possibility of retiring one of his best mounts, Officer Sokoloski sought permission to take a new approach to treating Joey’s navicular syndrome. Sokolski had been studying barefoot trimming and got the okay to see if that would help Joey – even though the veterinarians at the teaching hospital had told him that going barefoot would make Joey’s condition worse. Sokoloski pulled the gelding’s orthopedic shoes and trimmed his hooves to shorten the toes and bars, which put his frog in contact with the ground and encouraged a heel-first landing. “Two weeks later, I was riding him,” says Sokoloski. “Two weeks after that, we were riding him in one of the biggest, most unruly protests we’ve had to deal with, and we were sure glad to have him.”

Joey was back in action, but he improved even further when a barefoot trimmer suggested putting him in boots with foam insoles that cushioned his still-sensitive heel region until his hoof structures could recover fully. Before long, Joey’s feet were better able to bear up on the hard, paved surfaces that police horses tend to encounter daily—even without his boots.

Today, four years after Sokoloski was told that Joey’s navicular disease meant he could no longer be ridden, Joey is busy and happy giving riding lessons in Columbus, TX. “He was still doing great with his feet, but he was getting old and we had a lot of young horses on the force we needed to get out there, so we did retire him in February, 2007. Still, we were sure grateful that the barefoot hoof care made it possible for him to work not only regular patrol, but an additional 46 special events, parades, protests, and dignitary assignments after we had been told he would have to retire in 2005!


SIDEBAR: PHYSIOLOGICAL TRIM

Many barefoot trimmers use the principles that Dr. Bowker has described as the “physiological trim”. The goal of this trim, Bowker explains, is to “allow the foot to dissipate energy with maximum efficiency, while at the same time providing maximum support.”  To achieve this, Bowker outlines these basic principles:


-  The frog should be in contact with the ground. This usually means that very little if any frog tissue is removed during a trim.
-   The bars should be weight-bearing and just a millimeter or two below the level of the hoof wall in moderate footing.  Most horses will require little if any trimming of the bars.
-   The live sole should not be “lowered” or removed. The sole should share in weight bearing, along with the frog and bars, when the horse is standing or moving on a conformable surface.
-   The toe should be short (backed up, not thinned from below), with approximately 1/3 of the hoof in front of the true apex of the frog, and 2/3 behind the apex.
-   The toe should be beveled to facilitate breakover.
-   The coffin bone should be slightly higher (2-5 degrees) in the back.
- Horses should be kept barefoot whenever possible; if shoes are necessary for certain events or activities, remove them afterwards. Hoof boots may be a suitable replacement for shoes for some activities, and can also help during the transition to barefoot.
- All changes aimed at achieving this or any trim should be made gradually.

In addition, Bowker recommends that horses be kept on a surface that has enough give to conform to the solar surface of the foot (engaging all structures in weight-bearing), but enough firmness to provide beneficial pressure/stimulation to the frog, bars and internal structures of the foot. Many find pea gravel very suitable to this purpose, and even adding it to small areas of a large pasture or paddock can make an appreciable difference.


 SIDEBAR

Defining the terms


The terms "navicular disease" and "navicular syndrome" often are used interchangeably, but researchers generally have come to agree that the former is the more accurate description for the condition that produces some or all of these clinical signs in affected horses:


• chronic, progressive lameness in one or both forelimbs
• short or shuffling gaits, often with a toe-first landing
• sensitivity to hoof testers on the central third of the frog
• relief from pain when a nerve block is applied to the palmar digital nerve serving the forelimb
• frequent shifting of body weight when standing
• resting the affected foot on the toe (“pointing”).


Traditionally, the term navicular disease has been used to refer to degenerative changes in the navicular bone that have been confirmed by X rays. But experts disagree on what radiographic evidence constitutes significant changes. Furthermore, many horses with “classic signs” of navicular changes may not demonstrate lameness at all. Improved imaging techniques, such as MRIs, are allowing much more specific diagnosis of foot pain that was once labeled navicular, such as tendonitis of the deep digital flexor tendon where is runs under the navicular bone, but navicular syndrome is still often the label given to heel pain with no other discernable cause.

Thanks for reading! If you would like to be notified when new articles are added to this blog, just click the "follow" button on the upper left part of any page.