Sandcracks are vertical cracks that develop in the hoof wall. They either start at ground level and extend upwards, or, more seriously, start at the coronary band and grow downwards towards the bearing surface of the hoof wall. Many horses develop superficial sandcracks and never become lame. However, sandcracks can reach into the sensitive layers of the hoof wall or extend into the coronary band, and in those more serious cases, infection can develop resulting in acute lameness. Fissures that originate from the coronary band are generally caused by a defect in the band which results from a wound to that point; the quality of hoof produced at this site is poor, adn when this grows down the hoof a verical crack is formed.
Large wounds, bruises or infection breaking out at the coronary band cause a horizontal crack which extends partway round the hoof wall. These rarely cause any trouble until they grow down to near the ground surface, when the section of hoof below the crack may break off. This can cause shoeing problems until the defect has grown out. A permanent sandcrack is formed when the coronary band is damaged. Thus when the cells that produce the horn are damaged they are unable to produce horn to heal up the crack that has occurred. Cracks that extend from the ground surface upwards are caused by an unbalanced or overgrown foot. The unequal forces acting on the foot cause separation of the horn tubules, which extends up the foot until the bond between tubules is stronger than the separating force.
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An infected crack must be trimmed out, and all evidence of infection removed. Antibiotic treatment, both local and systemic, will probably be needed, together with daily dressing. Once the horse is sound, the defect can be stabilised by filling the trimmed-out crack with a synthetic resin and fixing it with staples or wire lacing.
Another method of fixation is to build up a fiberglass pad over the filled crack. Small screws are used to secure the pad to the hoof wall on each side of the crack.