(b) Treatment of Low Cracks (Plantar Cracks).—These cracks, occurring principally upon the hoofs of unshod horses, are the result of excessive stretching and bending of the lower border of the wall. Insufficient rounding of the wall with the rasp is largely responsible for them. An exciting cause in shod horses is the use of too large nails in shoes that are punched too fine.
Every coronary crack becomes in time a low or plantar crack, and this has an important bearing upon the prognosis, because a renewal of the coronary crack will be followed by a low crack.
In order to remove these cracks it is sufficient merely to shoe the horse. Upon shod horses they may be prevented by using properly punched shoes and thin nails. The lower border of the wall near the crack should be relieved of pressure by cutting out a half-moon-shaped piece of horn. To prevent the crack from extending farther upward we may burn a transverse slot at the upper end of the crack, in as far as the leafy layer of the wall, or cut such a slot with a small hoof-knife.
2. Clefts.
An interruption of continuity of the wall, at right angles to the direction of the horn-tubes, is called a cleft.
Clefts may occur at any part of the wall; yet they occur most often upon the inner toe and inner side, as a result of injury from sharp, improperly placed heel-calks ([see page 173]). However, suppurating corns, or other suppurative processes situated at the coronet or which find their point of escape at the coronet, may from time to time lead to separations of continuity and the formation of horn-clefts.
Fig. 222.
Hoof with clefts of the toe and side wall.
Horn-clefts, though the result of lesions which are often very injurious and interfere with the use of the horse, are of themselves not an evil which can be abolished or healed by shoeing, although, in many cases, proper shoeing would have prevented them. A horn-cleft is not a matter for consideration by the shoer until it has grown down so far that it comes within the region of the nails.