California Riding Magazine • February, 2009

Understanding the
Signs of Laminitis

by Dr. Kim Sergent

Laminitis - this dreaded condition of the feet can range from mild to severe and even proceed to the point of euthanasia of your beloved friend. Understanding the signs and getting immediate help from your veterinarian can often reduce the severity and help shorten its course. Unfortunately, this age-old disease is still common and only partially understood which makes successful treatment sometimes difficult.

The Signs

A horse that is reluctant to move and then appears all over “stiff” is one of the most common descriptions that I hear. It is this general “stiffness” that makes people wait to call their vet, meanwhile more damage is occurring within the foot. As the symptoms increase, one might see a change in posture from standing square to one where the front feet are out in front (and sometimes one foot farther out than the other as there is usually one that is worse) with hind feet forward and under the body. You may also see a horse that shifts weight back and forth on the front feet. The horse will often have difficulty picking up and holding up one or both front feet. This is due to pain in the down foot and not wanting to support the extra weight as the opposing limb is lifted. Most folks think the affected foot is the one that they are unable to pick up. You may or may not detect heat in the feet. Although I am primarily talking about the front feet (which is the most common scenario) laminitis has been known to affect all four feet. If you are unsure but you know something isn’t right I urge you to get the horse seen immediately by a veterinarian and let a professional guide you.

The Cause

Actually there are multiple conditions that are risk factors for developing laminitis. Infections of the gastrointestinal tract, uterus, lungs and the lining of the lungs (the pleura); colic; metabolic diseases including Cushings and insulin resistance; overweight horses; carbohydrate overload (for example, getting too much grain); toxins and certain drugs; concussion on the feet (hard work on hard ground or overloading one leg due to injury to the opposite limb). Though at first glance these conditions appear unrelated, the common thread is an inflammatory response. This inflammatory response then targets the laminae of the feet (more on anatomy in a moment). Microscopic changes occur almost immediately after a causative event and 24 to 72 hours later the first symptoms appear. If you know the horse was overfed grain or got out and ate green grass all night get the horse seen as soon as possible before he becomes symptomatic.

The Anatomy

The main bone in the foot is called the coffin bone or P3 (for third phalanx). The deep digital flexor tendon runs down the back of the limb, down the back of the foot and attaches to the mid bottom of the coffin bone. P3 is suspended within the hoof by fingerlike or leaf-like projections called laminae. There are sensitive laminae (which contain nerves and blood vessels) adhered to the coffin bone and there are insensitive laminae, which are attached to the inner hoof wall. These projections are interlocked all around the hoof. Each of the approximately 600 laminae have hundreds of little secondary laminae which act like super strong Velcro allowing support of the entire horse. As the hoof grows out the bonds release and continue down the foot to reattach, while new cells from the coronary band replace the old ones.

The Disease

Once laminitis starts, the laminae become inflamed and edematous (full of fluid). The attachments pull apart, typically, at the toe first. Sometimes this is as far as the disease progresses but often the coffin bone pulls away from the hoof wall and begins to rotate. This puts the front of the bone, which is normally parallel to the hoof wall at a steeper angle than the front of the hoof. The deep digital flexor tendon pulls on the bone further due to the location of its attachment. Rotation can involve only a few degrees or can progress to the point where the tip of the coffin bone goes through the sole. All of it is painful to the horse. Sometimes all the laminae give way and the entire coffin bone sinks (these are termed “sinkers”). Occasionally, both rotation and sinking occur together. Sinkers have a much poorer prognosis than do those that rotate although either group may need to be euthanized eventually (five percent of all cases).

The Exam and Treatment

The exam done by a veterinarian will include a physical, taking a history, feeling the pulse in the vessels supplying the foot, feeling for heat in the feet, observing the horse at rest for posture and weight shifting and watching the horse walk and turn. Once the diagnosis is made, a blood sample for baseline complete blood count and chemistry may be taken. Radiographs should be taken as a baseline to determine if there is rotation or sinking of the bone. With radiographs, various measurements can be taken to tell you how serious the laminitis is. Underlying problems such as Cushings, insulin resistance, and other feed related issues need to be addressed immediately.

There are numerous treatments that are available and what works for one horse may not work for the next. Analgesics to reduce pain and inflammation are at the top of the list. These are given systemically and some are applied topically to the area of the arteries supplying the foot. Vasodilators are also used to increase blood flow to the foot. Again, systemic and topical vasodilators are used. Studies continue to find new and hopeful treatments for this devastating disease.

The other very important factor is taking care of the feet. Styrofoam pads that are taped on are a good first choice to cushion the feet but have to be replaced frequently. Many horses don’t want to pick up their feet, so this can be quite a chore. There are boots that can be used and shoes or pads that can be taped on as well. The bottom line is that if one thing doesn’t seem to work there are usually other things to try. Confinement to a stall to reduce movement and therefore further trauma to the foot is always warranted. The stall should have deep bedding or soft supportive footing, (i.e. sand).

Be prepared for setbacks and continued involvement of your farrier and veterinarian. It is a frustrating disease for all and it takes time to resolve all the associated problems, so keep your chin up and have patience!

For more info call All County Equine Services (A.C.E.S.) at 619-659-3532 or visit www.acequine.com.