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?


The keratoma is a rare, as yet under-researched condition of the horse's hoof that still poses many mysteries in veterinary medicine.

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

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

A keratoma can only be diagnosed with certainty by means of an X-ray. This is because, at the location of the keratoma, the coffin bone — the lowest bone in the hoof — has been eroded and is therefore visible as a notch or hole on the X-ray.

Causes

Keratomas do not occur very often in horses and are accordingly not particularly well researched. As a result, there is disagreement in the professional world about exactly how keratomas develop. Specifically, there are differing views on what came first: the keratoma or the eroded coffin bone. Some believe that the keratoma develops first and then presses on the coffin bone, causing the bone to break down. Others believe that, on the contrary, the notch in the coffin bone is what leads to the development of the keratoma in the first place (because the hoof fills the "hole" with additional horn cells), and that the coffin bone must therefore already have been damaged beforehand.


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

  • injuries to the coronary band
  • persistent or frequently recurring pressure on the hoof capsule, e.g. from kicking the stall door or incorrect shoeing (nail bind or hammering the clinches too tightly)
  • abscesses
  • malpositions and the resulting imbalances are also being discussed

Horn cracks

Keratomas are often accompanied by horn cracks. Horn cracks can either be the cause of a keratoma, or they can share the same cause as it. A deep horn crack — that is, a fissure through the hoof wall to the corium — can arise from great tension in the hoof capsule (e.g. in overly long or unbalanced hooves). This makes the hoof capsule unstable, and the constant movement can irritate the corium and consequently lead to the formation of additional horn material — a keratoma develops.

However, a horn crack can also occur because there has been an injury to the coronary band and scar tissue has formed there. Since the hoof wall is formed by a layer of cells at the coronary band, this layer can also be affected by the scar tissue and may therefore produce horn of a different kind. This can, on the one hand, cause a keratoma to develop, and on the other hand a horn crack — both triggered by the scar on the coronary band.

Please note: a horn crack is not to be confused with other cracks on the hoof; see also our article on "Brittle Hooves".

Treatment


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

Sometimes, however, keratomas do cause lameness because they exert pressure on sensitive tissue within the hoof. In these cases, a veterinarian will advise surgical removal of the keratoma. However, caution is required here: since a keratoma already involves damage to the coffin bone (which cannot be corrected even with surgery), the keratoma often returns. This procedure should therefore be carefully considered.

On the other hand, keratomas can frequently lead to recurring abscesses/hoof ulcers, because the horn material there is softer and therefore more susceptible to bacterial infestation. As a consequence, the coffin bone can be further attacked and eroded by the abscesses, causing the keratoma to eventually grow larger. To avoid this, meticulous hygiene and a balanced hoof capsule must be maintained in the case of a keratoma, so that no microcracks form and no bacteria can enter.

Author: Nathalie Kurz

Images: Janina Gottwald

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