by Dr Luke Wells-Smith BVSc
Equine Veterinarians Australia ( EVA)
While injuries to the coronary band range in severity, prompt attention may prevent any ongoing issues with lameness.
Horses are prone to injuring themselves in a variety of different ways, with varying degrees of severity. The limb appears to be a part of the equine anatomy that is commonly injured and as the hoof is at the end of the limb it can be subjected to damaging circumstances. Wounds in the horse, particularly of the lower limb, can be difficult and time consuming to treat, which can be especially true for injuries of the coronary band and hoof capsule. Essentially an extension of the skin, the hoof heals in a very similar fashion, however with a few important differences.
The Four Phases of Healing
Inflammation: This is characterised by pain, heat, swelling and redness. As the hoof is a rigid structure, there is little room to accommodate swelling.
Debridement: Removal of dead and contaminated tissue from wounds to allow for drainage is necessary, however as there is no area to drain debridement is difficult in the hoof capsule.
Repair: Wounds to the skin heal from the outside to the inside but skin and hoof wall differ in structure and wounds to the coronary band heal from top to bottom (proximal to distal).
Maturation: Over time, as they heal, wounds finally organise their structure to resemble the original tissue. In the hoof this is called keratinisation - the hardening of the hoof tissue and this is a form of maturation.
The coronary band is responsible for the production of the hoof capsule, which is made up of small tubules, similar to tiny hairs all stuck side by side, that create a rigid and strong structure to protect the internal, sensitive structures of the foot. The hoof tubules are then attached to the coffin bone by lamellae, similar to tiny fingers that all link together, forming a tight bond. This tight bond is essential in keeping the hoof capsule, which is continually growing at approximately 10mm per month, attached to the coffin bone. The sole and frog is produced by the solar (sole) and frog corium, therefore wounds to the coronary band rarely cause defects on the solar surface.
Coronary band injuries can range from mild to severe and abrasions can occur in cases where the horse has fallen on a hard surface, such as a gravel road or concrete wash bay. Wire wounds are another common cause of coronary band injuries - depending on how tight and for how long the wire has been wrapped around the affected area will have a profound effect on the outcome. Chronic injuries to the heel bulbs can occur from the hind feet over-reaching or from sharp objects such as corrugated iron. Severe quarter cracks can extend into the coronary band causing damage to the soft tissue structures Other times the hoof can be simply torn away from the coronary band (hoof avulsion) by blunt trauma, such as kicking a sharp, solid object like a steel fence post.
The majority of coronary band injuries are relatively minor, however there is the potential for other soft tissue structures to be involved. The coffin joint is located very close to the skin surface and coronary band, therefore it is important to rule out any possible penetration into the joint capsule. The collateral ligaments and collateral cartilages are also close to the coronary band and skin surface. In wounds involving the coronary band, hoof wall and solar surface of the foot, investigation of the coffin bone, navicular bone and associated ligaments, along with the deep digital flexor tendon, may be required. For these reasons, any wound to the coronary band should be evaluated by a veterinarian and a farrier. X-ray and ultrasound may also help evaluate any damage to these structures, allowing the best possible treatment plan to be formulated.
Treatment depends entirely on the cause of the injury, the structures involved and the time from initial injury. Superficial coronary band abrasions, once evaluated by a veterinarian, can be cleaned and bandaged with a topical dressing that includes Silver Sulphadiazine (ie Flamazine).
Abrasions caused by over-reaching should be treated as above, however these horses should have the toe of their hind feet shortened. This can be achieved with a trim and, if the horse requires shoes, it should be shod with side clips or no clips. If shoes with toe clips are used, the shoe cannot be set far enough under the foot to prevent it striking the bulb again. X-rays of the hind feet can help the farrier and vet determine how much toe can be removed and where the shoe should be positioned.
Horses with old injuries to the coronary band, which have healed with a scar and a hoof wall defect, can develop an ongoing lameness. These can be treated by removing the hoof wall from the bottom of the hoof (sole junction) up to the coronary band, in the area of the coronary band scar.
Right: A cast can provide a great environment for healing, reducing the chance of scar tissue formation.
Far right: A septic collateral cartilage of the foot
was potentially caused by an over-reaching injury.
Right: A severe hoof avulsion (where the hoof was pulled away) one week after the injury.
Far right: The same hoof three months after the initial injury. Photographs by Dr Luke Wells-Smith.
Deeper lacerations to the coronary band are best stitched (sutured), however, if not stabilised appropriately, the suture line tends to break down. A cast can provide a great environment for healing, reducing the chance of scar tissue formation, the breakdown of a suture line and a subsequent hoof wall defect once healed.
Horses with old injuries to the coronary band, which have healed with a scar and a hoof wall defect, can develop an ongoing lameness. These can be treated by removing the hoof wall from the bottom of the hoof (sole junction) up to the coronary band, in the area of the coronary band scar. The foot is then cast for stability.
Veterinarians have had success with this technique so far in eliminating the hoof wall defect and the associated lameness. Severe wounds involving many different structures of the foot can be complicated to treat, however the foot has a great healing potential. Horses that have lost a large percentage of their hoof mass can heal incredibly well, however they need to be treated in an appropriate manner and undergo a rehabilitation process that may take in excess of 12 months.
In many cases the hoof wall itself is damaged during the injury, therefore it is important to have the farrier and veterinarian working together to formulate a treatment plan. Therapeutic shoes and techniques may be required, particularly in the severe cases, to successfully treat injuries to the coronary band and hoof wall.
Another factor to take into consideration is that whenever dealing with an injury to the foot, it is important that the horse is up to date with its tetanus vaccination. Bacteria that cause tetanus live in the soil and the hoof structure can provide a perfect environment for the bacteria to start producing the tetanus toxin.
While coronary band injuries can be a serious condition in the horse many of these injuries can heal with great success through the diagnosis and treatment formulated by the veterinarian and farrier.
ABOUT THE AUTHOR - Dr Luke Wells-Smith BVSc
Luke has been a farrier for 10 years and an equine veterinarian for the last 3 years. He currently works for the Equine Podiatry and Lameness Centre in Muswellbrook, New South Wales where he diagnoses and treats lameness conditions in the horse on a daily basis and has a keen interest in laminitis and navicular syndrome. www.equinepodiatry.com.au
For more information on Equine Veterinarians Australia (EVA) go to: www.eva.org.au