Carpal spavin is a degenerative form of osteoarthritis located at the junction of the medial splint bone (the inside part) and the second carpal (knee) joint. Not only does this result in crippling lameness, but quality of life issues often lead to euthanasia of affected horses. At the 2009 American Association of Equine Practitioners (AAEP) Convention, held Dec. 5-9 in Las Vegas, Nev., Spencer Barber, DVM, Dipl. ACVS, of the Western College of Veterinary Medicine, presented a joint fusion technique for managing carpal spavin.

In western Canada where he practices, Barber sees this problem mostly in Quarter Horses and Arabians. These horses usually have at least a year's duration of severe lameness that is apparent at a walk. The horse is reluctant to flex his leg, and the lower inside aspect of the carpus has a "rounded-off shoulder" appearance. There is radiographic evidence of narrowed joint space, bone dissolution along the top of the splint bone, and proliferative new bone growth. Treatment response to NSAIDs or intra-articular injections is short-lived; these horses cannot be ridden. If left untreated, this condition results in 80% of affected horses being euthanized within three years.

The study involved 12 horses, three of which had bilateral carpal lesions (in both knees). The arthrodesis (fusion) surgery involves a drilling technique to damage cartilage and underlying subchondral bone, with the intent of creating a bony fusion that immobilizes the joint. Postoperative pain is limited, although exercise is restricted for three to six months with the horse confined to a paddock or stall.

Barber explained that radiography does not always correlate well with clinical response since spot fusion in the joint immobilizes the area to alleviate pain, yet might not be evident on radiographs. By 90 days post-surgery, six of 12 horses were pain-free, five had slight pain, and one had moderate pain. Horse owners thought their horses could return to work in a mean time of six months. In fact, eight out of 12 horses returned to their original athletic activity, with the other four horses ridden and considered sound. All owners subjectively felt that the surgery was successful