Bruising on the solar surface of the foot usually is caused by direct injury from stones, irregular ground, or a poorly fitting shoe. Horses with flat feet or either thin or dropped soles are predisposed to bruising, usually at the toe or around the periphery of the sole. Bruising in the caudal sole at the buttress (the angle between the wall and the bar) is termed a corn. Bruising commonly occurs with no abnormalities present on the keratinized sole, although solar changes may be present ranging from some red staining of the inner solar epidermis (due to minor hemorrhage) to the palpable presence of serum either under the solar epidermis or seeping through it. If untreated, the affected area can become infected (ie, a subsolar abscess). Persistent, nonresponsive bruised sole dorsal to the apex of the frog suggests possible distal displacement of the distal phalanx secondary to laminitis.
A “corn” is most common in the forefeet on the inner buttress and can be caused by 1) the heel of a shoe improperly placed (heel of branch bent excessively toward frog); 2) a shoe left on too long, causing pressure on the buttress; or 3) shoes fitted too closely at the quarters or too small for the foot. Corns are described as dry (only mild bruising), moist (serous exudate present), or suppurative (infected or abscessed). Bruising may be associated with lameness, depending on the severity. When the foot is raised and the solar surface freed of dirt and loose horn, a discoloration, either red or reddish yellow, may be noted. Pressure on the affected area with hoof testers usually causes varying degrees of discomfort, again depending on the severity of the lesion.
Treatment of sole bruising is intended to remove pressure and protect the bruised area. In horses predisposed to corns, proper shoeing with branches that fit well on the hoof wall at the quarters and heels (and extend to the caudal aspect of the buttress) will decrease the incidence of lesions. In horses predisposed to bruising due to dropped soles, application of a wide-webbed shoe beveled on the solar surface (made concave relative to the solar surface) to avoid solar pressure will help protect the sole. Additionally, a pad can be placed on the foot to protect the sole. In horses with painful corns, the affected heel can be unweighted by trimming the wall and insensitive sole to minimize contact with the shoe until healed; a bar shoe can also help disperse pressure away from the trimmed area.
If the bruise/corn is suppurating, ventral solar drainage, usually established with a hoof knife, is usually adequate to allow healing. If the affected subsolar area is large, the abscess can usually be addressed by establishing small areas of drainage (~1 cm in diameter) at opposite sides of the affected area (established by probing), followed by lavage with saturated Epsom salt solution via either a 14-gauge catheter or teat cannula attached to a 60-mL syringe, repeated daily or every other day until healed. This is usually more effective than foot baths or application of poultices. The sole should be covered until the solar surface is covered by tough epithelium (horn). Parenteral antibacterial therapy is of questionable value unless cellulitis is present proximal to the coronary band.