Horses’ knees are like human ones, and that’s good news for both species.
It means that continuing research at Colorado State University aimed at helping horses with osteoarthritis–missing cartilage–also is applicable to humans as well, said Dr. Wayne McIlwraith. That’s significant, because nearly 21 million Americans suffer from osteoarthritis. After heart disease, it’s the second leading cause of long-term disability in the United States.
McIlwraith, a surgeon and director of the Equine Sciences Program at Colorado State’s College of Veterinary Medicine and Biomedical Sciences, has worked for the past 12 years on horses with osteoarthritis–cartilage loss that causes bone to rub against bone, producing pain and loss of movement.
"Naturally occurring clinical conditions in the horse, as well as our models, simulate the human situation a lot better than earlier models did," McIlwraith said. "For example, osteoarthritis can develop in a horse in one-tenth the time that it takes to develop in humans."
Prior to 1995, McIlwraith and a team at Colorado State’s Veterinary Teaching Hospital conducted clinical research, identified and learned to treat a number of conditions and tested various medications designed to treat arthritis and osteoarthritis in horses.
The team recently has adopted a procedure developed by Dr. J. Richard Steadman of the Steadman-Hawkins Foundation in Vail for use on humans. Called "microfracture," Steadman’s technique involves punching small holes in the subchondral bone beneath the knee cartilage near a joint surface injury, which tends to cause cartilage growth.
"Our research group has done a long-term study (on horses) showing the (microfracture) technique is superior to the conventional treatment of scraping down to bleeding subchondral bone," McIlwraith said. "More repair tissue is produced, but the quality of the tissue still is not that of normal quality repair tissue."
Meanwhile, the Colorado State researchers have a second project: identifying proteins called "growth factors" that will promote the growth of sturdy new tissue.
"The microfracture technique itself is helping horses," McIlwraith said, and added that the work has changed the way he operates on horses and has changed the way Steadman works on human knees. As a result of McIlwraith’s studies, Steadman scrapes a defect differently and allows weight bearing in his patients sooner, for example.
McIlwraith presented his findings on microfracture to human orthopaedic meetings in Europe and North America in 1998.
"The response in both those instances has been for human orthopaedic surgeons to feel that they now have sufficient justification to be using the technique," he said.
Work over the past three years has been funded by National Football League Charities and the Charles Koch Foundation. Future research is leading, according to McIlwraith, in several directions:
*A project with Neocyte Joint Venture involves culturing cartilage cells from a young animal, seeding them onto a scaffold and implanting it in an injured joint.
*A project with Atrix Laboratories of Fort Collins is investigating a polymer that could deliver growth factors to a healing joint.
*Working with Oratec and the Steadman-Hawkins Foundation, a radio frequency probe is being evaluated to see if it can help "weld" cartilage.
*Gene therapy, which involves finding a gene and using a virus to carry it into joint cells where it can produce the desired effect, is being carried out in collaboration with researchers at the University of Pittsburgh.
*The development of synovial fluid (which lubricates joints) and serum markers to indicate early deterioration in cartilage is under way with several European collaborators.
McIlwraith is satisfied with progress so far.
"Our plan was to get more cartilage by using the microfracture technique," he said. "Now our goal is to identify those growth factors critical to healing, so we’ve been doing immunohistochemistry to look at what growth factors really are present. That process is continuing."