PrintDistal tarsal osteoarthritis is known by many different names—bone spavin, jack spavin, blind spavin, juvenile spavin and occult spavin—but regardless of what you call it, the lower hock is the most common site for arthritis in a performance horse.
Several different options for treatment exist, including laser therapy, surgery and—the most recent innovation—ethyl alcohol injections. But how do you choose which one is best for your horse?
The lower hock joints, made up of the tarso-metatarsal and distal intertarsal joints, are low motion joints, meaning that they don’t have to be able to move in order for the horse to perform. However, those two joints take a lot of torque as a result of the work that we ask our equine friends to do. While in some instances, poor conformation, under-conditioning or overtraining are to blame for lower hock pain, in most cases it comes as an aside to a carefully managed training program.
Unlike upper hock joints, which need freedom of movement in order to function, the focus of treating the lower hocks is generating long-term comfort and relief from pain rather than continued motion and flexibility. That is why treating lower hock disease often involves, whether intentionally or inadvertently, fusing the joints in order to relieve the pain.
Searching For Alternatives
James Carmalt, M.A., VetMB, MvetSc., FRCVS, Dipl. ABVP, ACVS, an associate professor of large animal surgery at the University of Saskatchewan (Canada), is currently working with a team of researchers to determine the success of using ethyl alcohol injections in the tarso-metatarso and distal intertarsal joints to relieve the painful effects of osteoarthritis.
“A colleague and I were sitting around in the office one day trying to come up with the areas of research that were most important and needed work done, and we came up with laminitis first, then bone spavin and then colic,” recalled Carmalt, who credits his colleague for the idea to inject ethyl alcohol into the joint.
“I would love to claim ownership for the idea, but it was actually Dr. Ryan Shoemaker who read about spinal cancer treatments in people and noted how ethyl alcohol was being injected into the spines of terminal patients to kill the nerves, allowing people a decent last few months. It was he who pursued the idea.”
In the 1980s and early ’90s, horses with lower hock joint problems were often subjected to injections of sodium mono-iodoacetate (MIA), which was extremely painful. Many of the horses suffered from lameness for 24 to 48 hours following the procedure, and some even experienced severe soft tissue damage and progression of arthritis in the proximal (higher up) hock joints. Shoemaker thought injecting ethyl alcohol into the joints would help fuse the joint without the pain and suffering associated with MIA.
Not long after the research began in 2007, Shoemaker, DVM, MVSc, Dipl. ACVS, went into private practice and left the project with Carmalt, who currently oversees 34 horses, 11 of which were in the original study.
“So far the horses I’ve worked with have only required a single injection, and the majority were sound following the procedure,” said Carmalt. “I remain cautiously optimistic.”
As news of the procedure began to spread, other veterinarians started experimenting with the injections. Scott Ander-son, DVM, used his sister-in-law’s Appendix Quarter Horse for his first patient.
