No Foot, No Horse

By Dr. Garrett Metcalf, DVM

There is a wise old saying no foot no horse and that is absolutely true. Horses of all breed, discipline and size must have good healthy feet or they will suffer poor performance, chronic pain or worse succumb to diseases of the foot. There are several medical conditions that require surgical treatment within the hoof wall of the horse and this article will highlight the most common conditions that require surgical treatment 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. Abscesses are often minor issues that can be easily corrected by a farrier or veterinarian getting access to the abscess to allow drainage but they can be rather debilitating and sometimes rather serious. Abscesses in general are localized pockets of infection that found its way into the sole or white line of the foot. These abscesses often form because there is some structural abnormality of the foot, trauma that led to bleeding under the sole or improper hoof care that has led to abnormal forces being applied to the foot and of course the old hot nail. For example trimming of the foot without relieving enough sole pressure can lead to overloading the sole and in turn sole bruising setting up for an abscess. Other common abnormalities of the foot that leads to abscessation are laminitis and club feet. These two conditions can cause tearing and stretching of the white line and allow bacteria plus moisture to enter deeper into the foot which in some cases can further destabilize an already unhealthy foot, leading to a life threatening situation.  Deep abscess that go untreated for days or weeks can continue to invade and dissect through tissue planes leading to larger abscesses. These large abscess sometimes require surgical intervention to keep them from spreading and to eliminate the abscess all together.

Pedal Bone Osteitis

Pedal bone or the coffin bone is a very unique bone compared to others in the horse. The coffin bone is a rather porous bone that has intimate attachment to the foot capsule and sole. The bone and the hoof tissue has a very high amount of blood supply rightly so because of the vast amount of metabolic rate energy it uses to keep the foot supplied with nutrients. Whenever the hoof is diseased or compromised from laminitis or infection the blood supply can be compromised as well spelling disaster. The disaster that can ensue from these conditions is an infected portion of the coffin bone or sequestration of bone. Bone sequestrums are when bone lacks blood supply and is also infected by bacteria that thrive off of dead tissue. Bone sequestrums are generally rather treatable conditions because once removed the bone can heal but the coffin bone is not the same as other bones in the horse. The coffin bone lacks an outer soft tissue coating called periosteum. Periosteum is a very robust membrane outside of almost all bones that provide blood supply and support healing with progenitor cells and stem cells. The uniqueness of the coffin bone without this important layer leads to poor healing, a more delicate blood supply and makes is more prone to infectious insults.

Treatment of an infected piece of the coffin bone requires aggressive steps in order to prevent spread and destruction of the rest of the coffin bone.  Further spread into the coffin bone can lead to further damage to the blood supply to the bone and hoof as well as weakening the bone to the point of fracture under the weight of the horse. Aggressive surgical debridement or removal of infected tissue and bone is the first required step to reduce the amount of infection present in the foot. Secondly is aggressive antibiotic therapy using local delivery methods and systemic routes of administration. Local antibiotic delivery is by means of antibiotic beads, pastes or ointments and by means of regional limb perfusions. Regional limb perfusions are 20-30 minute treatments where antibiotics are delivered to the affected limb via blood vessels in that limb. The antibiotic is held in the limb by a tourniquet above the application site to allow higher concentration of the drug to enter the target tissue or region of the limb. Lastly is proper support of the remaining hoof while still maintaining access to the infected areas to allow local treatment. This step cannot be overlooked and requires the work of a talented farrier to make it possible.

Quittor

Quittor is a chronic deep infection within one of the collateral cartilages of the coffin bone. The collateral cartilages are attached on both wings of the coffin bone and are often referred to on x-ray films as side bone. Lacerations, puncture wounds, trauma and abscesses of the foot can lead to infection of the collateral cartilage. To most people quittor doesn’t sound like a big deal and seems like it would be easily addressed with a few days of antibiotics but that is not the case. This infection deep in the foot can be like a smoldering fire that cannot be put out until the infected cartilage is removed. The diagnosis is usually straight forward because there is often a draining tract with swelling, heat and proud flesh centered over one of the collateral cartilages. The difficulty lies in finding and removing all of the infected tissue not to mention that you have to go through the hoof wall to get there. A hoof wall resection or a window cut in the side of the foot is often needed to access the infected tissue, allow drainage and local treatment at the same time. Quittor can be rather difficult and sometimes require multiple surgeries in order to get the infection cleared up. After the hoof wall resection is made often a specialized shoe will be needed to help protect and keep the foot stable until the hoof grows out the defect in the hoof wall.

Keratoma

Keratoma is a benign tumor like growth that arises from the hoof wall or laminar tissue of the foot called keratin. Keratin is what makes up our hair and nails. This growth continues to expand between the foot wall and the coffin bone leading to pressure necrosis and damage to the coffin bone. This abnormal keratin tissue is usually located at the toe region of the foot and is thought to be triggered by trauma to the hoof tissue. The most common signs of a keratoma are reoccurring foot abscesses in the same location and same foot, plus lameness that are localized to the foot. X-ray, CT and MRI can be used to diagnose keratoma formation within the foot. Often the keratoma is well formed enough to be seen with x-ray but sometimes advance imaging is necessary to make the diagnosis.

The only treatment and cure for a keratoma is surgical removal through the hoof wall. This requires a hoof wall resection with either an oscillating saw or drill bit to removal the hoof wall without damaging the coffin bone. A keratoma has an often distinct appearance by this off white crumbly type tissue that is often easily removed from the surrounding healthy hoof wall. After surgical removal a specialized shoe is needed to protect the foot and allow access to treatment of the surgical site to prevent infection.

Coffin Bone Fractures –

There are many different patterns or ways that a coffin bone can be fracture and some are more serious than others. To keep it simpler we break them down into articular or non-articular meaning do they enter the coffin joint or do they not.  Non-articular coffin joint fractures generally are much less serious and can be healed without major surgery. Often times non-articular fractures are stabilized with a special shoe and casting tape placed around the foot to make the hoof itself the “splint” for the coffin bone nestled inside the hoof wall.

Articular fractures of the coffin bone are a much more serious problem because of the damage that is done to the coffin joint. A fracture into any joint is a serious threat to the health of the joint and requires surgical reconstruction as soon as possible to keep the joint from developing crippling arthritis. The trouble again with any surgery on the foot is that the bone is inside the foot making it difficult to access. There are techniques to place screws into the coffin bone through small hoof wall resections to allow stabilization of coffin bone fractures. It does require the right fracture pattern and location to make this surgical treatment a plausible option.

Street Nail

A street nail surgery is used to treatment of deep penetrating injuries that occur at the frog or sole that leads to infection of the bottom of the coffin bone, navicular bone and closely related surrounding soft tissue structures. Street nail procedures are often needed when a metal object such as a nail or screw penetrates and infects the one of the vital structures of the bottom of the foot. This window allows flushing of the synovial structures and removal of damaged/infected tissue. This procedure success is greatly improved with the use of an arthroscopic camera placed in the navicular bursa or coffin joint depending on what area the puncture wound involves. The arthroscope allows better visualization and more thorough flushing of debris and infection out of these tight spaces.  Again this surgery cannot be successful with the application of a special shoed called a hospital treatment plate shoe that allows access to the bottom of the foot while keeping the foot clean and protected.

As you can see there is a pretty clear pattern to these hoof conditions: infection and the need for specialized farrier care. In order to be successful in treating these conditions the veterinary surgeon and farrier must work hand in hand to provide the best care for the horse. Although performing surgery on the foot of a horse is challenging and sometimes limited, it is often possible to have successful outcomes with a variety of different conditions.