As every horse owner knows, the horse’s foot is a very complicated structure. It may not look it from the outside, but within the hoof wall are many elements and sensitive structures that form the foot. A penetrating injury to the sole of the foot should be treated as an emergency.
The horse’s foot consist of a tough outer hoof capsule (hoof wall) that encases and is connected to sensitive laminae which in turn nourish and support the pedal bone (also called the coffin bone) within the foot.
The sole is made up of horny tissue and is similar to the hoof wall but it lacks the rigidity and strength of the hoof wall. The sole joins the hoof wall at the white line; this is where the internal sensitive laminae become insensitive around the base of the hoof wall.
The frog consists of firm but rubbery tissue which acts as the cushion and helps to spread the weight of the horse.
Within the foot are the sensitive sole and laminae, digital cushion, pedal bone, navicular bone, tendons and lateral cartilages.
Penetrating injuries are caused by foreign objects, such as a misplaced shoeing nail, a nail in your horses bedding, out in the field, or on the floor while being exercised out on the road. Other sharp objects such as flint stones, glass, needles, wood splinters and wire, etc can all penetrate the sole causing serious injury.
The location of a penetrating injury can be the difference between life and death. Wounds that occur at the back three quarters of the foot are the most serious. Injuries involving the navicular bursa and/or the coffin joint, can result in infection (septic arthritis) if prompt action isn’t taken which can be life-threatening. The further away from the hoof wall an injury occurs, the higher the risk of damage to the coffin (pedal) bone. Infection of the coffin bone (osteitis) causes areas of the bone to die and erode away.
If your horse is quite lame, you are unable to remove the cause of the injury, or you think deeper structures within the foot are affected, call your vet immediately! These injuries can be life-threatening and need to be treated as soon as possible. While you are waiting for your vet to arrive, apply a poultice to the affected foot to prevent further contamination.
If you find anything in your horse’s foot you should remove it immediately so that your horse doesn’t tread don it again causing further deeper trauma to the structures within the foot.
With wounds that do not involve any deeper structures, the foot should be cleaned and poulticed to ensure any bacteria is cleared from the site of injury. If however, your horse becomes lame within the next 24-48 hours following injury you should call your vet immediately as this is likely to indicate infection or damage to deeper structures has occurred and your horse will need to be treated as soon as possible.
Simple infections to sensitive tissues under the sole can be drained; your vet will cut a hole in the sole where the original wound occurred to allow any pus to drain out of the affected area. This is usually followed by repeated poulticing to draw out all of the infection. Once the infection has resolved, the hole that is left will need packing, usually with iodine soaked swabs but this will depend on size, shape and location of the hole, and bandaged to ensure infection doesn’t return while the hole heals up. If the infection does not clear up a bigger, deeper hole may need to be made.
If the infection is deep seated, your vet may need to remove a much larger area of the sole to ensure complete drainage of pus and removal of infected and damaged tissue. If the pedal bone is affected, your vet will need to cut deep into the foot to remove any damaged bone. Radiographs will be needed to ensure all the affected tissue and bone has been removed. Where extensive amounts of sole are cut away, your horse will require a special metal hospital plate attached to the shoe so dressings can be kept in place and kept clean while your horse is recuperating.
A penetrating injury to the navicular bursa will require surgery immediately. The navicular bursa and coffin joint will need to be flushed under general anaesthesia, so your horse may need to be referred to a clinic that specialises in surgical procedures like this. Where infections involve soft tissues at the back of the foot, extensive removal of damaged tissue may be necessary.
In all circumstances, if your horse isn’t up to date with their tetanus vaccinations, your vet will administer a tetanus antitoxin injection which will provide your horse with immediate protection against tetanus. Tetanus, caused by Clostridium tetani, is an environmental bacteria and is commonly found in soil, therefore foot injuries are at particular risk from the disease.
Antibiotics will be given to some cases of deep infection and to all cases of penetrating injuries in order to combat bacterial infections.
The prognosis for simple infections to sensitive tissues under the sole is generally good and horses usually respond well to drainage and poulticing. Every horse is different, but small holes in the sole can heal up uneventfully within a few weeks.
Where infection persists, prognosis is guarded and will depend on how the horse responds to treatment.
Recovery from more complicated deep penetrating injuries where extensive surgery has been required can take many months, with return to soundness being a long process. In some cases, the bacterial infection within the hoof cannot be controlled and euthanasia may be the only option due to prolonged, severe lameness. Recurring infections are common in horses that have had previous infections. In addition, in cases of severe lameness there is the risk of laminitis occurring in the other limb due to weight overload which will affect the prognosis.