The coffin bone is the primary bone within the horse’s foot. The hoof capsule encases this bone like a body in a coffin (hence the name coffin bone). The laminae within the foot are the soft tissue structures that firmly attach the coffin bone to the hoof wall. Laminitis, in its simplest terms, is inflammation of the laminae that attach the coffin bone to the hoof capsule. This inflammation decreases blood flow to the area of the laminar attachments. Local alterations in blood flow may be the result of a variety of systemic illnesses, such as grain overload, colic, retained placenta, etc. Whatever the source of the disease, laminitis usually causes crippling pain in horses and is potentially devastating to horse owners.
In some instances, the laminar attachments become so compromised that the coffin bone and hoof capsule actually separate from each other. If the normal pull of the deep digital flexor tendon exceeds the strength of the remaining laminar attachments, the bone may rotate downward away from the hoof wall. Veterinarians consider the disease chronic if rotation occurs or if the condition lasts for more than several days.
Most treatments for laminitis focus on improving blood flow to the foot, alleviating the pain associated with this condition, halting disease progression, and re-establishing a functional relationship between the coffin bone and hoof wall. Veterinarians often use vaso-dilating agents such as acepromazine, isoxsuprine, pentoxyphyline, and nitroglycerin in hopes of improving blood flow. Phenylbutazone (Bute) commonly relieves pain and decreases inflammation in laminitic horses. A variety of recommended shoeing and trimming techniques attempts to decrease the amount of tension on the coffin bone and redistribute pressure on the hoof’s weight-bearing surfaces.