Single screw may treat acute laminitis

Kathryn Carmalt, a fourth-year veterinary student, is involved in developing a new technique for horses with laminitis.

It’s 2 a.m. and I’m in search of an ice machine in the physiology lab at the Western College of Veterinary Medicine (WCVM).

No, it’s not for refreshments after a long day’s work or even in celebration: ice is one of the standard treatments for laminitis in horses, more commonly known as founder.

Veterinarians use the ice to fill recycled intravenous (IV) fluid bags or special boots that are secured around a horse’s hooves. In suspected cases of laminitis, these boots have to be changed every two hours as the ice melts because the cold temperature has been proven to retard the degeneration of the lamellae (sensitive tissues) in the horse’s hoof.

Any student who works in the WCVM’s Large Animal Clinic for any amount of time is bound to find themselves searching for that same ice machine in the hopes of preventing and/or treating this very serious disease.

When a horse founders, the lamellae that bind the hoof wall to the underlying coffin bone become inflamed. During this very painful process, the coffin bone loses support on the front of the hoof. Since it can’t counteract the pull that the deep digital flexor tendon is placing on it, the coffin bone begins to separate from the hoof wall and rotates within the hoof — or sinks.

What many horse owners may not be aware of is that that disease’s inflammation stage is of a limited duration, typically lasting about 24 hours. If a clinical team can control or reduce the inflammation with medication or ice, they can possibly prevent the coffin bone’s rotation from occurring.

Unfortunately, there’s no standard treatment protocol for laminitis: equine specialists even debate the value of using ice to treat laminitic horses beyond 24 hours.

During one of these late-night icing sessions, I couldn’t help but think that there had to be a better way to treat these horses. All of the current treatments for laminitis are medical in nature, but the problem is quite physical. The bone is rotating within the hoof, so why not stop it mechanically? Why not physically prevent it from rotating — similar to what’s done when stabilizing a fracture?

The novel therapy for laminitis involves placing a screw through the hoof wall.

Those questions led to an idea that has grown with the support and knowledge of equine surgeons Drs. David Wilson and James Carmalt along with other veterinarians at the veterinary college.

This summer, we’re investigating the possibility of preventing coffin bone rotation in cases of acute laminitis by placing a single screw through the hoof wall and engaging the bone —preventing the rotation in the disease’s acute stages. After 48 to 72 hours — once the initial inflammation has subsided — the screw will then be removed.

What complicates things is that the causes of laminitis are as variable as its treatment.

As a large animal internal medicine specialist, Dr. Katharina Lohmann has seen her fair share of laminitis cases associated with colitis, retained placentae and sepsis — a potentially life-threatening complication of a bacterial infection.

Sometimes laminitis is caused when a horse has to bear excessive weight on one limb to “off load” the weight on an injured leg. This was the scenario for 2006 Kentucky Derby winner Barbaro: the racehorse was eventually euthanized after developing laminitis months after he fractured his left hind limb in the 2006 Preakness Stakes.

These days, a growing number of laminitis cases are linked to metabolic diseases such as equine Cushing’s disease and metabolic syndrome.

What should owners know about these conditions?

“One thing owners can do is to recognize the relationship between horses being overweight and having metabolic syndrome — and [those] horses foundering,” says Lohmann.

“It’s hard sometimes, but horses shouldn’t be terribly overweight and horses that are older and showing signs of Cushing’s [disease] should be treated for that condition.”

She adds that recognizing the links between these conditions and laminitis can go a long way to help prevent at least some forms of this very serious disease.

A single screw through the hoof wall engages the bone, to prevent rotation in acute cases of laminitis.

For the forms of laminitis that can’t be avoided through preventive measures, we hope to provide a method that will help veterinarians to mitigate the long-term damage done to the foot associated with rotation of the coffin bone.

So far, the outlook is promising. We have performed biomechanical testing at the University of Saskatchewan’s College of Engineering and proven that a single screw in the coffin bone is strong enough to withstand the forces likely to be placed upon it by the deep digital flexor tendon.

Additionally, we’ve developed and tested a technique in normal, live horses. The animals tolerated the screw placement procedure without showing undue discomfort post-operatively: these horses could be managed without the levels of painkillers that are usually necessary in clinical laminitis cases.

The screws could also be removed (while the horses were standing) without desensitizing their feet — a further indication that the presence of the implant was well tolerated.

We need to do more development and testing, but for a surgeon like Wilson who sees numerous cases of laminitis, this new technique could be a significant advance in treating the disease.

Hopefully, it could also mean fewer late-night “ice runs” for veterinary students like me at the WCVM.

Kathryn Carmalt of Saskatoon, Sask., is a fourth-year veterinary student who was part of the WCVM’s Undergraduate Summer Research and Leadership program in 2014. Kathryn’s story is part of a series of articles written by WCVM summer research students.