Sesamoid Injuries

Jim Hamilton, DVM

Sesamoid injuries are most common in race horses presumably due to speed and over extension of the fetlock joint. In 2 year olds, early signs of stress can be seen radiographically as wide channels running through the sesamoid bone termed "sesamoiditis". This channeling may be due to increased blood supply demands by the bone in response to increased "pounding".

As the work load increases, the channeling in the bone represents weak zones and puts the bone at higher risk of fracturing. The bone fractures most commonly in three different places:

and uncommonly

"Apical" fractures carry the best prognosis because they are easy to surgically remove and "basilar" fractures carry the worst because they cannot be removed and tend not to heal completely (even with 9-12 months rest).

The other associated problem can be injury to the sesamoidian ligaments, sometimes called the "XYZ" ligaments. These ligaments originate at the base of the sesamoids and run down the back of the pastern. They attach to either the long or short pastern bones. Unfortunately, injury to these ligaments also carries a poor prognosis because they are slow to heal and the body often deposits calcium into the ligament which weakens them predisposes to re-injury.

My suggestion is to take radiographs of the fetlock. Include an A-P, both obliques, lateral and flex lateral views. If they are clean, then an ultrasound evaluation of the sesamoidian ligaments is indicated. What to do then will depend entirely on which problem you have! I'd be interested to hear the results!

e-mail Dr. Jim Hamilton, DVM
Southern Pines Equine Associates