No Foot, No Horse: Surgical Conditions of the Equine Foot

By Garrett Metcalf, DVM

There is a wise old saying, “No foot, no horse,” and that is absolutely true. Horses of all breeds, disciplines, and sizes must have healthy feet, or they will suffer from poor performance, chronic pain, or, worse, succumb to diseases of the foot. Several medical conditions require surgical treatment within the hoof wall of the horse, and this article will highlight the most common conditions that necessitate surgical intervention and specialty farrier care.

Foot Abscesses

Foot abscesses are a very common issue that nearly every horse may experience at some point in their lifetime. While abscesses are often minor issues that can be easily corrected by a farrier or veterinarian, allowing access to the abscess for drainage, they can also be debilitating and sometimes serious. Abscesses are localized pockets of infection that find their way into the sole or white line of the foot. These abscesses often form due to structural abnormalities in the foot, trauma leading to bleeding under the sole, improper hoof care that creates abnormal forces on the foot, or, of course, the old hot nail.

For example, trimming the foot without relieving enough sole pressure can overload the sole, leading to bruising and setting up an abscess. Other common foot abnormalities that lead to abscessation are laminitis and club feet. These conditions can cause tearing and stretching of the white line, allowing bacteria and moisture to enter deeper into the foot. In some cases, this can destabilize an already unhealthy foot, leading to a life-threatening situation. Deep abscesses that go untreated for days or weeks can continue to invade and dissect through tissue planes, forming larger abscesses. These large abscesses may require surgical intervention to prevent spreading and to eliminate the infection completely.

Pedal Bone Osteitis

The pedal bone, or coffin bone, is unique compared to other bones in the horse. It is a porous bone that is intimately attached to the foot capsule and sole. The bone and the hoof tissue have a high blood supply due to the vast amount of metabolic energy required to keep the foot supplied with nutrients. However, when the hoof is diseased or compromised by conditions like laminitis or infection, the blood supply can be jeopardized, leading to disaster. The resulting condition may be an infected portion of the coffin bone, or sequestration of bone.

Bone sequestrums occur when bone lacks blood supply and becomes infected by bacteria that thrive on dead tissue. While sequestrums are generally treatable, the coffin bone is unique in that it lacks an outer soft tissue coating called periosteum. This membrane typically provides blood supply and supports healing with progenitor cells and stem cells. The absence of this layer in the coffin bone leads to poor healing, a more delicate blood supply, and increased vulnerability to infection.

Treating an infected portion of the coffin bone requires aggressive action to prevent further spread and destruction. If infection spreads, it can damage the blood supply to the bone and hoof, weakening the bone to the point of fracture under the horse’s weight. The first step in treatment is aggressive surgical debridement or removal of infected tissue and bone. This is followed by aggressive antibiotic therapy using both local delivery methods (such as antibiotic beads, pastes, or ointments) and systemic routes. Regional limb perfusions, where antibiotics are delivered to the affected limb via blood vessels, may also be used. Additionally, proper support for the remaining hoof is essential, which requires the expertise of a skilled farrier.

Quittor

Quittor is a chronic deep infection within one of the collateral cartilages of the coffin bone. The collateral cartilages, which are attached to the coffin bone’s wings, are often referred to as “side bone” on x-ray films. Lacerations, puncture wounds, trauma, and abscesses can lead to infection in the collateral cartilage. While quittor might seem like a minor issue to most, it is often much more serious than it appears. This infection can smolder beneath the surface, not fully resolved until the infected cartilage is removed.

The diagnosis is typically straightforward, as there is often a draining tract with swelling, heat, and proud flesh over one of the collateral cartilages. However, the challenge lies in locating and removing all of the infected tissue. A hoof wall resection, or a window cut in the side of the foot, is often required to access the infected tissue and allow drainage and local treatment. Quittor can be challenging and may require multiple surgeries to clear the infection. After the hoof wall resection, a specialized shoe may be needed to protect the foot and help stabilize it until the hoof grows out to cover the defect.

Keratoma

Keratoma is a benign, tumor-like growth that arises from the hoof wall or laminar tissue of the foot, known as keratin. Keratin is the same material that makes up our hair and nails. This growth expands between the foot wall and the coffin bone, leading to pressure necrosis and damage to the coffin bone. Keratomas typically form at the toe region of the foot and are thought to be triggered by trauma to the hoof tissue.

The most common signs of a keratoma are recurring foot abscesses in the same location, accompanied by localized lameness. X-rays, CT scans, and MRIs can help diagnose the presence of a keratoma. Often, the growth is well-formed enough to be visible on x-ray, but advanced imaging may be necessary for a definitive diagnosis.

The only treatment for a keratoma is surgical removal through the hoof wall. This requires a hoof wall resection, performed with either an oscillating saw or drill bit, to remove the hoof wall without damaging the coffin bone. The keratoma typically appears as off-white, crumbly tissue that is easily removed from the surrounding healthy hoof wall. After surgical removal, a specialized shoe is required to protect the foot and allow access to the surgical site for continued treatment and to prevent infection.

Coffin Bone Fractures

Coffin bone fractures can occur in several patterns, some more serious than others. These fractures are typically categorized as either articular or non-articular, depending on whether or not the coffin joint is involved. Non-articular fractures are generally less serious and can heal without major surgery. These fractures are often stabilized with a special shoe and casting tape applied around the foot to make the hoof itself act as a splint for the coffin bone.

Articular fractures, which involve damage to the coffin joint, are far more serious. Any fracture involving a joint threatens the health of the joint and requires surgical reconstruction as soon as possible to prevent debilitating arthritis. The difficulty in treating these fractures lies in the foot’s structure; the bone is located inside the hoof, making it challenging to access. However, techniques exist that allow surgeons to place screws into the coffin bone through small resections of the hoof wall to stabilize fractures. This option is only viable when the fracture pattern and location are suitable.

Street Nail

A street nail surgery is used to treat deep penetrating injuries to the frog or sole of the foot, which can lead to infections in the coffin bone, navicular bone, and surrounding soft tissue structures. This procedure is necessary when a metal object, such as a nail or screw, penetrates and infects these vital structures. The surgical “window” allows for flushing of the synovial structures and removal of damaged or infected tissue.

Success of this procedure is greatly improved with the use of an arthroscopic camera, which can be placed in the navicular bursa or coffin joint, depending on the area affected by the puncture. The arthroscope allows for better visualization and more thorough flushing of debris and infection from these tight spaces. A special shoe called a hospital treatment plate is then applied to protect the foot while keeping it clean and accessible for further treatment.

Conclusion

As you can see, there is a common thread running through these hoof conditions: infection and the need for specialized farrier care. Successful treatment of these conditions requires close collaboration between the veterinary surgeon and farrier. While surgery on a horse’s foot is challenging and sometimes limited, many conditions can be successfully treated with the right surgical intervention and post-operative care.