Laminitis: A debilitating disease of the foot
Laminitis is a painful condition of the equine foot in which there is inflammation and necrosis of the laminae. Understanding the anatomy of the foot helps shed light onto this terrible disease. To make things simple, the equine foot is essentially composed of the hoof wall, the laminae, and the coffin bone (also known as P3 or the distal phalynx). In the normal horse, the hoof wall and P3 are parallel; held together by the glue that is the laminae. With laminitis, there is failure of the laminae and the "glue" weakens allowing the bone to move away from the hoof wall. You may hear that a horse has "rotated" or "sunk". These terms are used to describe the type of movement that P3 has made once laminitis has occurred. The movement of P3 is irreversible. If laminitis is identified early on, aggressive treatment is initiated to stop movement of P3 and re-stabilize the foot.
Laminitis is characterized by symptoms of acute foot pain. It can affect one or all feet. Horses with foot pain often have a "tender footed" walk or look like they are walking on glass. In severe laminitis, they stand with a rocked back stance as they try to get weight off of their toes. They may also lay down for long periods of time since standing on their feet is painful. Examination of the foot reveals an increased digital pulse and sensitivity to hoof testers at the toe.
The list of underlying causes of laminitis is long. We generally split the list into 3 categories: traumatic, metabolic, or toxic.
Traumatic causes of laminitis include excessive concussion or exercise on hard surfaces. It may also occur when a horse sustains a non-weight bearing injury in the opposite limb and they stand for long periods of time on the non affected limb (eg Barbaro, the racehorse, who fractured a leg and then was euthanized for laminitis of the opposite limb).
Metabolic causes include PPID (see previous post) and Equine Metabolic Disease. High circulating internal steroids and abnormal utalization of sugar and carbohydrates predispose these horses to laminitis. Toxic causes include diarrhea, grain overload, high fever, and retained placenta. In these conditions, bacteria release endotoxins that affect the entire body.
In acute laminitis (when symptoms are immediately identified), treatment is aimed at quieting the inflammation with use of stall rest, anti-inflammatories, and ice therapy. The vet and farrier work best as a team by taking weight off of the toe and providing frog and sole support. BEST RESULTS are achieved when treatment is instituted within the first few hours of clinical signs. Treating the underlying illness may also be addressed (especially when metabolic or toxic causes of laminitis are identified). Once the disease becomes chronic or recurrent, prognosis for an athletic future becomes poor. Therapeutic shoeing is the cornerstone of management at this point. Providing support to the back of the foot, improving break-over at the toe, and possibly raising the heel can prevent additional relapses.
The take home is that early, prompt treatment of laminitis can greatly improve prognosis. Once the disease become chronic, it becomes much more difficult to alleviate pain and prevent further breakdown of the laminae.