Knowledge about hooves
Hufkrankheiten

Keratoma - understanding a rare, under-researched disease of the horse's hoof

4 Min. Lesezeit

What is a keratoma and what do horn cracks have to do with it?

Keratoma

The keratoma is a rare, so far under-researched disease of the horse's hoof which still poses many puzzles in veterinary medicine.

A keratoma is an excessive accumulation of horn cells (keratin) between the hoof wall and the coffin bone. The pillar shape arises because the hoof grows from top to bottom and so the proliferated cells are also pushed downward. As a result, the white line on the underside of the hoof is also deformed at this spot: where the keratoma reaches the ground, the white line is curved inward.

But beware: a deformed white line does not always automatically mean that there is a keratoma! The white line can also be deformed by an abscess or simply by a small stone.

Only on an X-ray image can a keratoma be diagnosed with certainty. Because at the location of the keratoma the coffin bone - the lowest bone in the hoof - is eroded and therefore visible as a notch or hole on the X-ray.

Causes

Keratomas do not occur too often in horses and consequently are not very well researched either. Therefore, expert opinion is divided on exactly how keratomas develop. Specifically, there are different views on what came first: the keratoma or the eroded coffin bone. Some say that the keratoma develops first and then presses on the coffin bone, causing the bone to be eroded. Others say that, conversely, the notch in the coffin bone is what first leads to the development of the keratoma (because the hoof fills the "hole" with additional horn cells) and the coffin bone must therefore have already been damaged before.


In any case, the following causes can lead to irritation of the wall dermis or to erosion of the coffin bone and thus to keratomas:

  • injuries to the coronet
  • persistent or frequently recurring pressure on the horn capsule, e.g. by kicking the box door or incorrect shoeing (pricking or hammering the clips too hard)
  • abscesses
  • conformation faults and the resulting imbalances are also discussed

Horn cracks

Keratomas are often associated with horn cracks. Horn cracks can both be the cause of a keratoma or have the same cause as it. A deep horn crack, i.e. a fissure through the hoof wall down to the dermis, can develop due to high tensions in the horn capsule (e.g. with overly long or unbalanced hooves). This destabilises the horn capsule, and the constant motion can irritate the dermis and consequently lead to the formation of additional horn material - a keratoma develops.

A horn crack can also happen because there was an injury at the coronet and scar tissue has now developed there. Since the hoof wall is formed by a cell layer at the coronet, this layer can also be affected by the scar tissue and therefore produce horn of a different kind. As a result, both a keratoma and a horn crack can develop - both triggered by the scar at the coronet.

Note: a horn crack should not be confused with other cracks on the hoof; see also our article on "Brittle hooves".

Treatment

Keratoma

Many keratomas are incidental findings and cause the horse no problems. In this case no treatment is necessary.

Sometimes keratomas, however, also cause lameness because they exert pressure on sensitive tissue in the hoof. In these cases a vet will advise the surgical removal of the keratoma. Caution is warranted here, however: since with a keratoma there is already damage to the coffin bone (which cannot be repaired even with surgery), the keratoma often returns. This procedure should therefore be carefully considered.

On the other hand, keratomas can often lead to recurring abscesses/hoof ulcers, because the horn material there is softer and therefore more susceptible to bacterial colonisation. As a result, the coffin bone can be further attacked and eroded by the abscesses, causing the keratoma to grow larger over time. To avoid this, with a keratoma scrupulous hygiene and a balanced hoof capsule must be ensured, so that no micro-cracks develop and no bacteria can enter.

Author: Nathalie Kurz

Images: Janina Gottwald

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