by Mark Hurtig
Dept. of Clinical Studies,
Ontario Veterinary College
Guelph, ON, N1G 2W1
The Art of Treating Equine Joint Disease:
new surgical technique saves horses

With the emphasis on healthier and more active lifestyles, competitive sports are attracting people well into their later years. Horse owners are expecting the same of their mounts. Many hard working hunt, dressage, and three-day event horses can be highly competitive in their late teens and early twenties. Injuries, however, are a fact of life for both people and horses. This is particularly true for those involved in competitive sports. Often these injuries occur early in life and are career-limiting. Now, with specialized mosaic arthroplasty techniques, the rehabilitation of many competitive horses with previously untreatable joint injuries is possible.

Joint injuries are a major cause of economic loss in the horse industry. Even a small cartilage injury in a critical spot can end a successful career. While the knee is the most problematic site for the human runner, injuries in the equine carpal (knee) and fetlock joints in the front limb are limiting for the horse. Cartilage in these high motion joints does not heal in adult horses. Medications in the glucosamine sulfate, non-steriodal anti-inflammatory and hyaluronate families are ineffective treatments for the kind of cartilage and bone injury that we often see in competitive horses.

Another approach to joint injury is to resurface the site with a graft. Synthetic materials and crude cartilage grafts have been tried, but both types were easily damaged
and had problems with attachment to the underlying bone. In human orthopedics, grafting is relatively successful in difficult cases where a tumor or injury has destroyed all or part of a joint. These large grafts are sometimes harvested from another part of the same joint as an autograft, or as an allograft from an organ donor program.

A more recent innovation in sports medicine is using small cylindrical autografts to resurface a symptomatic cartilage defect, in the manner that small tiles make up a mosaic. With our comparative orthopedic research group at the University of Guelph this technique, called mosaic arthroplasty, is being refined by Dr. Anthony Miniaci, an orthopedic surgeon at Toronto Hospital (Western Division).

We deliver the grafts to precisely drilled holes in the damaged area as small cylinders, like dowels, in an evenly spaced pattern. Our research has shown that a group of three larger diameter grafts (4.5 or 6.5mm) was more successful than a group of smaller diameter ones (2.7mm). The smaller grafts were fragile and the bony portion of the graft healed poorly. Larger grafts were easier to position to reconstruct complex, curved contours.

Accuracy of graft delivery is essential in areas where the cartilage is thin, such as in the equine carpus (knee). We must exactly match the levels of graft and host cartilage, otherwise mechanical damage and loosening of the graft result.

The greatest advantage of mosaic arthroplasty for horses is that the entire procedure can be done arthroscopically with out the need for a large incision. As a result, previously untreatable injuries in the carpus, fetlock, hock and stifle are now potentially treatable. Some investigations involving allografts are also underway. Allografts, taken from another recently euthanatized or slaughtered horse, have the advantage of being an exact match for the damaged site, but do have the potential complication of immune rejection.

Through our research we have developed specialized mosaic arthroplasty techniques; and with the help of Smith and Nephew Endoscopy adapted instruments for the horse. Preliminary results in the equine carpal joint are encouraging and, like Dr. Miniaci, we are offering mosaic arthroplasty to carefully selected patients in our surgical practice. The people and horses that are most likely to benefit are those with small, focal, joint cartilage injuries. Patients with chronic, longstanding injuries, osteoarthritis and unstable joints are unsuitable candidates for this technique.

Horses with small focal injuries are the most suitable candidates for mosaic arthroplasty, a grafting technique proving useful in halting debilitating joint disease. Dr. Mark Hurtig and his team of researchers have adapted for horses leading-edge surgical techniques used in human athletes.

Longer-term studies and clinical trial are beginning. The success of cartilage transplantation in controlling joint disease in horses is of significant interest. Reducing the cost of treating chronic joint disease, which includes anti-inflammatory and intra-articular medication, as well as lost training days and lost winnings, would mean real saving to the horse owner.

The researchers would like to acknowledge the generous support of the Ontario Ministry of Food, Agriculture and Rural Affairs (OMAFRA) and the Morris Animal Foundation.

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Updated: October 2005.