The equine hoof is a very complex structure as you can see in the diagram, and houses not only bone, but tendons, connective tissue and has a very specialised blood supply.
The hoof wall and sole itself is a very strong and supportive structure, however it is easily damaged under the right circumstances and can have substantial effects of soundness and may even carry a life threatening prognosis.
We occasionally see horses and ponies that have suffered puncture wounds to the sole, and although the reflex action is to pull out for example a nail and hope that everything will be ok. Here we will discuss what implications this could have for your horse and how best to approach such a situation.
Puncture wounds commonly occur through the sole of the foot, and can heal alone and not cause any damage at all but can also range to being a serious life threatening injury depending on the location and how deep the object has penetrated. Not only can the objects be obvious that puncture through the sole such as nails and wire, but can include wood splinters, glass, etc.
Where the foreign object penetrates is of great importance as it can give clues as to which structures could be affected and it is important to establish this. Many punctures result in bruising and potentially a secondary infection without affecting deeper structures, but infections of deep structures such as the coffin bone, coffin joint, navicular bone/bursa, digital tendon sheath, or collateral cartilages will often require more care and treatment.
In general puncture wounds around the wall will not affect the sensitive hoof structures, and the further away from the wall the more likely that deeper structures will be affected. Towards the heel you will most likely hit the digital cushion which is a soft connective tissue structure designed to absorb concussive effects of the hoof landing. Most commonly we see objects penetrating into the frog and the central sulcus, which can be the most serious as the navicular bursa, tendon sheath or coffin joint can all be affected. Therefore puncture wounds to the central region of the foot should be treated as an emergency.
If you find a nail or another foreign object in your horses foot it is important to try not to panic and leave the object in place as long as you are sure it will do no further harm. The reason we say this, is because it is far easier to analyse the depth and what structures have been affected if we can visualise this. Call your veterinary surgeon, this way you can seek expert advice and ensure you are doing the right thing. The vet may recommend that the offending article is to be pulled out immediately or if they are concerned may offer a visit.
If you have already pulled the foreign object out, we recommend poulticing the foot to help draw out any infection.
Often with puncture wounds such as nails we like to take an x-ray of the foot to see the extent of damage. If there is penetration of deeper structures or an extensive infection then further treatment may be required. If the navicular bursa or coffin joint is infected then it will require emergency referral to a specialist to enable the joint to be flushed out under general anaesthetic.
Other investigations that can be carried out are fistulograms (if the foreign object has already been removed we inject a dye that will show up on x-ray into the puncture site), MRI and CT imaging. These are mostly carried out at referral centres.
Lameness often occurs within 24-48hours after injury and if infection sets in the lameness will get worse over time as the hoof is a space limited structure and swelling and infection is not accommodated for.
We also have to think about the vaccination status of your horse when they have a penetrating wound. The risk of tetanus is always present as the bacteria (Clostridium tetani) is naturally in the environment. So if your horse is unvaccinated in this instance tetanus anti-toxin may be of importance, and although is not the same as a vaccination can help prevent this fatal outcome.
Prognosis for minor puncture wounds is very good, and 95% of cases result in recovery.
If you find yourself in this situation please do not hesitate to call your veterinary surgeon, if only for advice.