Have you ever noticed that mysterious notch at mid-toe in the white line region (the connection between the hoof wall and sole that has no nerves or blood vessels) of your horse's foot and wondered what it is? This shallow notch comes in different shapes, sizes, and textures and might or might not extend to the outer hoof wall or up to the coffin bone. According to Lisa Lancaster, MSc, PhD, DVM, of Lancaster Veterinary Services, in Denver, Colo., the purpose and relationship of the toe "crena" to toe wall health is relatively unknown, as no formal research has been conducted about it, but she presented her theories at the 6th International Equine Conference on Laminitis and Diseases of the Foot, held Oct. 28-31 in West Palm Beach, Fla.
Not every horse has a crena on his foot (and on many horses it comes, goes, and evolves), so theories as to its existence include:
The old belief that it's a man-made injury, likely caused by unskilled farriers;
- It's a coffin bone notch, or "toe stay," for hoof stabilization that prevents twisting of the coffin bone; or
- It's a vestigial remnant of a similar looking cleft found in the coffin bone of pre-horse species fossils.
In the limited crena research Lancaster has performed, she collected 18 feet from Quarter Horses euthanized for reasons unrelated to the feet and found that 15 of them had toe crenas on the sole surface. In five feet the crena extended up to the level of the coffin bone. Upon microscopic examination of the crena tissue at the coffin bone level, she determined it had "the histologic (microscopic) appearance of the laminar wedge found in chronically laminitic feet."
Lancaster noted that when the crena exists at both the sole surface and bone level the "laminar wedgelike" tissue appears to disrupt the normal laminar interface that should secure the coffin bone to the hoof wall. Does this mean there are biomechanical similarities between the crena structure and the fragile laminar wedge? Obviously, she said, more research is needed to determine whether the crena is a marker of toe wall health or if this hoof characteristic could be used as a possible prognostic indicator in laminitic horses. As a precautionary method, she suggested owners, veterinarians, and farriers might want to monitor this region on the toe if a horse is undergoing laminitis treatment or other hoof rehabilitation.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.