The coronary band is the junction between the hair-producing skin of the horse’s lower leg and the hoof wall.
The coronary band serves as a lifelong cellular proliferation zone, producing cells called keratinocytes that mature and then ultimately die to form the horn of the hoof wall. The coronary band is estimated to be responsible for 70% of hoof growth. The constant addition of these keratinocytes at the coronary band causes the hoof wall to grow downwards, past the bones of the hoof, to reach the ground. The average rate of hoof growth is 6mm/8mm per month and is influenced by lots of extrinsic as well as intrinsic factors.
Did you know?
Hooves completely regenerate every eight to 12 months.
Coronary band injuries
Injuries of the coronary band are all too common. They often result from overreach injuries, entrapment of the hoof or injuries caused by fencing or wire.
Lacerations
Lacerations that extend from the pastern region through the coronary band toward the back of the foot are the most common coronary band injuries. These so-called ‘heel bulb’ injuries generally occur when horses step on one another’s feet. But horses also sustain similar injuries when their feet become entangled in wire in their paddocks or when their feet get caught under fences or doors. When hacking, litter and sharp rocks put horses at risk for coronary band injuries.
Horses that overreach when performing their gaits are particularly at risk for coronary band and hoof wall injuries of the front feet. Certain disciplines also predispose to these injuries, with jumpers suffering a large number due to moving at high speed with lots of twisting and turning.
When your vet arrives, they will first want to determine the depth of the injury and whether any debris has been caught in the wound. The depth is critical, as deeper wounds can affect the coffin joint or pastern joint. Injuries deep enough to damage those structures can result in long-term lameness and the development of other complications, such as osteoarthritis, that affect soundness. Some horses who sustain wounds deep enough to damage bone structures and tendons must be euthanised.
After the vet has assessed the severity and depth of the wound, they usually wash the injured area with a povidone-iodine or iodine scrub and sterile water and remove any remaining debris or unhealthy tissue surrounding the wound.
If the wound is clean and less than six hours old, it might be suitable for suturing. However, as this is a very mobile area, a foot cast will also be required to minimise movement until the wound and coronary band are healed, which usually takes about three weeks.
Wounds more than six hours old or very contaminated are cleaned, covered with a hoof bandage, and allowed to heal on their own. If the wound is extremely contaminated, veterinarians might administer systemic antibiotics or even opt to clean and debride the wound in surgery.
What to do if you notice a coronary band injury?
If your horse sustains a coronary band laceration you should call a vet as soon as you notice the wound. While waiting for the vet to arrive, you can gently wash the wound with water, apply a clean gauze bandage to the injured area, and place the horse in a clean stable to await treatment.
Avulsion injuries
Avulsion injuries create wounds that pull the hoof from the lower limb. Hoof avulsion injuries occur when a horse’s foot is cut through the entire coronary band and hoof capsule, usually after it has been caught under an object.
Vets treat these injuries by removing the damaged hoof wall and cleaning the wound. They then work with the horse’s farrier on a long-term treatment plan. The general principle of treatment is that the area under the damaged wall is trimmed shorter than the rest of the foot so that it doesn’t bear any weight. This gives the damaged area time to heal properly. A shoe will be applied to compensate for that section of the hoof’s inability to bear weight. These support shoes spread the load of the horse’s weight allowing the horse to stand on the undamaged portions of the foot while the damaged aspects heal.
The supportive shoes used to treat hoof avulsion injuries are constructed with either a single bar placed diagonally across the shoe or a pair of bars that cross each other diagonally from one side of the shoe to the other, forming an ‘X’ configuration. The severity and location of the injury dictate whether a single bar or an ‘X-bar’ shoe is applied to the injured hoof.
Secondary issues
Hoof cracks often occur secondary to coronary band lacerations or avulsion injuries. Farriers treat hoof cracks resulting from coronary band injuries by using clips to secure shoes to the hoof wall. Farriers and vets might have to use acrylic compounds, staples, or wire lacing to close very severe cracks and support the outer hoof wall while new hoof material develops.
As healing takes place, farriers perform follow-up treatments such as trimming the hoof and replacing shoes.
Outcome of coronary band injuries
Most horses that sustain coronary band injuries recover complete soundness under appropriate immediate and long-term care. However, there will almost always be a hoof defect at the site of the injury.
Horses with injuries that do not involve damage to the coffin bone or pastern joint are usually very likely to return to their previous athletic soundness. However, even shallow injuries can result in some long-term effects if they involve a large portion of the coronary band.
Abscesses
Aside from injuries, abscesses are also common causes of coronary band damage.
Abscesses generally drain from the bottom of the horse’s foot, but when horses’ hooves are extremely hard, such as during periods of hot, dry weather, abscesses are more likely to track up the hoof wall, generally between the sensitive and nonsensitive lamina of the hoof, and break through the softer coronary band.
To treat a coronary band abscess, the owner (in discussion with their vet and farrier) will probably need to clip the hair at the break-out site, wash the wound daily, and apply an antibiotic ointment to the area.
Coronary band dystrophy
Coronary band dystrophy (properly termed pemphigus) refers to a disorder that causes the tissue at the top of the hoof wall to weaken or waste away. Several diseases can affect this area but with coronary band dystrophy the horse’s hair above the coronary band sticks out straight instead of laying down against the skin. There is crusting, scaling, redness, and ulceration of the tissue.
A hard band of tissue develops at the coronary band, and the hoof wall stops growing, causing the growth rings on the dorsal hoof wall to be tightly packed. The crusting and scaling extend down the hoof wall and can even involve the frog. An ulcerous condition called canker can develop, and some horses become lame.
The disease usually occurs in heavier breeds of horses, like Warmbloods.
A biopsy is the best method of diagnosing the condition, but biopsy sites are difficult to heal, so the diagnosis is usually made with an exam given by your veterinarian. If coronary band dystrophy is diagnosed, prednisolone, a strong steroid given orally, is often part of the treatment, as the disease is believed to be immune-mediated.
Antibiotics are usually used to treat potential low-grade infections, and an NSAID may be prescribed for pain.
Treatment also involves removing shoes from your horse and clipping the hair at the coronary band. Your horse’s heels should be trimmed on the same plane as the frog, and all loose and unhealthy tissue should be removed with a rasp.
Cleaning the area daily and applying a cortisone ointment usually is an effective treatment. If canker is involved, treatment of the diseased tissue with cryotherapy is usually needed.
Although the condition usually heals with treatment, the treatment is time-consuming and requires huge commitment on the part of the owner.
Did you know?
Whole body vibration has been shown to increase hoof growth.
Final thoughts
The coronary band is a small but crucial structure in maintaining our horses’ soundness. Whilst most injuries to this region are simply unlucky, we can seek to protect the area by keeping paddocks clean, maintaining fencing and stable doors and walls and using overreach boots wherever necessary.