THE horse’s hoof wall and sole form a tough protective layer around the internal structures of the foot. However, they can be pierced if the horse steps on or collides with a sharp or pointed metal object, particularly nails or wire.

Such injuries are not very common but if they do arise, they can result in severe damage to the pedal and navicular bones, the deep digital flexor tendon and the surrounding soft tissues.

Severe lameness results and, even with aggressive treatment, not all horses will survive or be able to return to their prior level of athletic performance.

Of particular risk are injuries to the middle third of the sole and frog.

The reason for injuries in this area being especially problematic is due to the fact that the distance from the surface of the frog to the underlying bones, coffin joint, tendon and navicular bursa is only a couple of centimetres.

The navicular bursa is a small fluid-filled sac-like structure that lies between the navicular bone and the tendon within the hoof. If it gets infected it has very limited ability to heal itself, much like a septic joint, and ongoing lameness may result.

So, if a horse stands on a nail that passes straight up through the middle of the frog, it can readily contact and damage these structures, as well as introducing dirt and bacteria deep into the foot. The direction of penetration is also important, as a nail that enters towards the edge of the hoof may initially appear to have caused less damage.

However, when it is being removed it is important to note the path that the tip followed, as frequently it is found to have headed towards the centre of the foot.

Once the object is removed the relatively soft tissues under the sole tend to collapse, making it subsequently very difficult for the vet or farrier to see in what direction the object was headed. Sometimes the object may become dislodged before it’s noticed, making diagnosis even more difficult.

NOTICING LAMENESS

Affected horses tend to go suddenly and dramatically lame: typically they will either hold their foot up completely when attempting to move, or they will only briefly touch their toe to the ground when taking a step. A wound containing a nail or other object may be visible in the foot once it’s picked up.

The digital pulse in the affected foot will be stronger than normal. If the initial injury was unnoticed and infection has set in the horse is likely to be extremely painful on the affected limb and there may be swelling or discharge at the coronet or pastern.

If a horse steps on a nail and is sore for a day or two but then appears to recover it’s easy to assume that the injury was minor and the horse is on the road to recovery. However, occasionally the initial injury will have introduced some bacteria deep into the foot and infection develops over a period of 48-96 hours.

If this is the case the horse will suddenly get much more painful a few days later. Treatment is more difficult in these cases as irreversible damage may have been done to the foot by the time the infection can be brought under control.

FIGURE 2: The same area as in figure 1 within the hoof. The navicular bursa runs along the back of the navicular bone and the coffin joint is between the navicular and pedal bones. Photo Karen Dunne

VETERINARY ATTENTION

Veterinary treatment should always be sought urgently if you have any suspicion of a penetrating hoof injury. Your vet may x-ray or scan the foot to check for internal damage and to see if there are any foreign objects left in it.

The horse will also require pain relief, antibiotic therapy and possibly an anti-tetanus treatment. Fluid samples can be collected from the coffin joint and navicular bursa to check for the presence of infection. The latter procedure may be performed under x-ray or ultrasound guidance.

If infection is found within these hoof structures, flushing and surgical treatment under a general anesthetic is usually necessary to give the horse the best possible chance of a good recovery. For these reasons your vet may wish to admit the horse to an equine hospital to facilitate specialised treatment and aftercare.

It may be necessary to cut a hole in the sole of the foot to allow the infected tissue to drain and be removed. If this is the case the horse will need be remain in hospital for several weeks of ongoing treatment, typically with customised shoeing input from an expert farrier.

What do to if your horse stands on a nail