Quarter cracks are longitudinal fissures in the hoof occurring near the heels.  They can generally be attributed to improper shoeing, or to overall neglect of the foot.  In addition quarter cracks can be caused by allowing the horse to stand on hard floors for extended periods of time; or when the frog, sole and bars have been pared away and the heels weakened.  This condition may also be caused by springing the shoe off at the heel and putting the weight of the horse on the wings of the coffin bone.  These causes lead to a dry and inflexible hoof, which results in the cracking of the hoof. 

In trimming a hoof with a quarter crack, reduce the wall, especially at the heels, as much as the safety of the foot will permit.  The next step is to remove the contractile disposition of the hoof by rasping it at the quarters.  After this open both sides of the crack with a knife so that friction of the fractured parts cab be avoided.   Then rasp or cut out the bottom of the crack so that no part of it will bear upon the shoe.  After the wall has been lowered trim the frog if it projects below the bottom of the foot.  By doing this the frog will aided in growing wider and assist the foot in expanding.  When the cracks occur well back at the heels I sometimes find it necessary to protect the weak parts by applying a bar shoe. 

When the crack occurs opposite the wings of the coffin bone, level the foot and shorten the toe as much as can be done conveniently.  If cracks happen on both sides, shoe with a three quarter tip.  File or rasp the wall on both sides of the crack, from coronet to ground surface as thin as safety will permit.  If the foot is sore and tender, apply a high quality foot salve to relieve the stress on the affected area.  A new growth of horn may also be stimulated by keeping the hoof moist with cold-water bandages around the coronet.  Remove the shoes every three weeks in order to prevent excessive growth of horn.  By following these instructions, quarter cracks may easily be cured and the horse regularly worked.