Osteoarthritis of the distal (lower) hock joints (bone spavin) is a common performance problem in sport horses. At the 2009 American Association of Equine Practitioners (AAEP) convention, held Dec. 5-9 in Las Vegas, Nev., Chris Bell, DVM, discussed fusion of the tarsometarsal (TMT) joint by injection with ethyl alcohol.
Historical attempts to fuse these small joints using mono-iodoacetate resulted in severe soft tissue damage, progression of arthritis in more proximal (higher up) hock joints, and persistent pain. Bell, who is a resident in large animal surgery at the Western College of Veterinary Medicine, at the University of Saskatchewan, noted that ethyl alcohol creates effective cartilage destruction and fusion within four months with limited complications.
He stressed that a full lameness exam with radiographs and intra-articular anesthesia should be conducted prior to considering this technique. Injection of radio-opaque dye into the TMT joint ensures there is no communication upward with the proximal intertarsal and tarsocrural joints. Dye confined only to the TMT joint can then be aspirated out and replaced with ethyl alcohol.
The clinical trial Bell described involved 16 horses. At three to six months post-treatment some horses became a little sore, and then they rebounded as the joints fused. At six to 12 months after treatment, all had their hock-associated lameness resolved, along with radiographic evidence of fusion. At one year, all were pain-free, with 12 of the 16 returning to their intended athletic use.
Bell explained the advantages of this procedure: It takes less than 90 minutes, involves inexpensive materials, and can be done on site in the field using a simple technique that is well-tolerated by most horses. A treated horse can return to work immediately due to the pain-blockading effect that alcohol creates on local nerves.
Disadvantages include the need for contrast radiography that could diffuse into undesirable areas (a vein, other joints), thereby confounding radiographic interpretation. Careful positioning is necessary to obtain useful radiographic results. And, cases of advanced OA might limit needle access into a joint. Veterinary follow-up for years following is critical, since OA can develop in higher hock joints as joint morphology changes with fusion.
Bell reports this technique is not applicable to a young horse or those with only mild to moderate osteoarthritis.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.