A keratoma is a benign growth between the hoof wall and the pedal bone inside the foot. The growth starts from the horn producing cells, usually originating from the coronary band growing downwards to the toe.
The exact cause is unknown but some cases can be linked to chronic irritation or infection in the shape of slow abscesses or direct hoof injury. Injury to or inflammation of the coronary band is also thought to be a possible cause.
There may not be any visible signs of the keratoma on the outside of the hoof but a bulge on the hoof wall can be present. There is often an inward deviation of the white line visible on the bottom of the foot. Lameness can develop, due to the pressure of the keratoma. Often this presents as an intermittent lameness. Other clinical signs may involve a foot abscess at the location of the keratoma and possible sensitivity to hoof testers.
Further investigation will include taking X-rays of the foot. This might show the location of the keratoma and how far it has advanced. The keratoma can sometimes be visible as a semicircular defect in the pedal bone. Other options for further diagnosis can be a biopsy of the keratoma to identify the growth and in difficult cases MRI can be a helpful tool.
Surgery is required to remove the keratoma. This can be done either standing or under general anaesthesia. The hoof wall is removed to gain access and the growth is excised. Complete removal is important because the keratoma can return if it is not completely removed. The wound is packed with gauze soaked in iodine and bandaged up completely to keep the wound clean with support of a special shoe. Your horse will require antibiotics and pain relief after the surgery. Further management will include box rest and regular bandage changes. The foot will be bandaged until a hard layer of horn has formed over the area. Following this the horse will have to remain in clean, dry conditions until the wound has completely healed over. The complete process can take many months because the hoof wall grows only about ½ cm each month. With patience and careful management the prognosis is usually good.
Photo source: “Adams’ Lameness in Horses”, fifth edition, Ted S. Stashak, 2002, 720 - 722