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A bowed tendon specimen (centre) with a core lesion (red circle) compared to the normal tendon (above) from the opposite leg.

Injury research brings together horses and athletes

February 26, 2009

Horses and humans are at the forefront of research exploring the benefits of platelet-rich plasma therapy, writes Ellen Harvey. However, many questions remain, including whether it might ultimately prove better than stem cell therapy.

What does a top American football player have in common with a racehorse? The answer is becoming clear in research being conducted with performance horses at Cornell University.

When Pittsburgh Steelers wide receiver Hines Ward suited up for this year's Super Bowl after spraining his kneee just two weeks earlier, he may have had a horse to thank for a faster than expected recovery.

Ward was the recipient of platelet-rich plasma therapy (PRP), in which a small amount of blood from an injured person or horse is extracted and placed in a filtration system to separate red blood cells from platelets. A teaspoon or two of the product is injected at the site of an injury to boost healing.

While research on PRP is ongoing, there is a free exchange of information among researchers with both human and equine applications.

PRP has the potential to dramatically increase prospects for equine athletes to remain in competition without the need for expensive and risky surgery.

One of the major researchers in the field, Dr Lisa Fortier, of Cornell University, says there is a great deal of interplay between human and equine research in this subject.

"Horses are actually a very good model for human diseases. That's why our data is published in the Journal of Orthopedic Research, which is a human journal," she says.

"They're (horses) highly athletic, their joints are about the same size as humans, the data you get is objective - not someone saying they feel better or they don't."

Fortier notes that researchers in both human and equine orthopaedics are working closely in the area referred to as Biologics.

"There's a strong interest in all biologics right now; you have something that's autogenous, derived from your own body, so there's no risk of disease transmission, immune rejection," Fortier says.

"The idea of a biological repair rather than injecting a steroid or a different hormone is very appealing, so lots of people have been working hard in biologic regeneration in general, in humans and equines.

"Platelets are the body's natural store of a bunch of growth factors. That is their design in your body - to go to the site of injury, degranulate and release all these growth factors to help tissue healing.

"They've been using platelet-rich plasma in dentistry for decades to help (jaw)bone so that implants have a place to stick in better. It's also been used in different forms of plastic surgery, all forms of oral maxiofacial surgery to help skin repair.

Dr Lisa Fortier
"We know that the growth factors in platelets help tendon and cartilage and muscle and bone heal. So the concept for musculoskeletal repair in general is very appealing.

"In horses, they suffer from tendonitis, bowed tendons, quite commonly, and in human athletes it's usually shoulder or Achilles or sometimes cruciate ligaments (in the knee) and usually those require some sort of surgery.

"We're trying to take damaged tissue, whether it's strained or torn, and regenerate new tissue using platelets. We have a new biologics group, the Biologic Orthopaedic Society, which is a combination of veterinarians and MDs. It's the first organisation devoted solely to biologic orthopedics.

PRP is commonly used for elbow tendonitis, shoulders and Achilles tendons.

"It's gaining strength in plantar fasciitis in people. In horses, we mainly use it for tendons and suspensory ligaments, but we also use it for cartilage repair.

"In horses, our big issue is not so much getting them back to their level of athletic performance; the problem is keeping them from reinjuring that site. When the tendon heals, it heals less elastic, more stiff and prone to re-injury."

Fortier noted that there are still many questions in need of an answer through continued research.

"One of the biggest issues with platelet-rich plasma is that the product that you get is very variable depending on what manufacturer you use. There is no standard platelet-rich plasma," Fortier says.

"You are using the horse's blood, but there are at least 25 different ways to get the platelet-rich plasma, that's not standard and not controlled by the FDA (US Food and Drug Administration) yet. Maybe we'll find out there isn't just one way to get there.

"Maybe you need one for tendon, a different one for ligament; lots of variables. One of the goals of this biologic orthopaedic group is to get all of us together, compare the machines we use, the products that we use, the applications we use them in and the outcome. For instance, how many people get redness, soreness and pain after injections? It could be related to the machine you use."

Fortier says the PRP therapy that helped Hines Ward is becoming more common among vets who care for equine athletes.

"Anybody who does high-end equine athletes would have a machine," Fortier says. "Some machines might be a couple hundred dollars, an application would probably be $2500 for making the platelet-rich plasma and injecting it as well.

"The big question we're trying to sort out as well - is it as good or better, or not as good, as stem cell therapy? There are several companies in the US that are growing stem cells for horses and then they inject back into the tendon and ligament.

"That is much more costly because you have to take the stem cells out of the horse, grow them and then inject them back in. We don't know if that's better (than PRP), we can put it in tendons and ligaments, but to put it in cartilage you need to be at a surgical facility. With stem cells you need to grow them in a lab; the plasma rich, you're concentrating them and putting them back in, so that's less expensive."

Fortier says that some of the biggest success stories have been with middle-aged horses - seven to nine-year-olds - and specifically jumping horses.

"Rio Rouge is one that comes to mind," says Fortier. "He had a several month long history (of lameness), got platelet-rich plasma and went back to jumping. I'm very pleased with how the middle-aged horses are responding. The younger ones have time to get better; it's the middle aged ones that have a harder time healing."

Many other research questions remain, she says.

"We're trying to figure out if we need different types of platelets for acute versus chronic injury. In people, if you have a chronic injury, it can be six to eight months by the time a diagnosis is made. Some of these middle-aged horses have been lame and the scar tissue is already there.

"In the acute injury, we're trying to get the torn tissue to heal properly the first time, without forming scar tissue. There's white blood cells also in platelet rich plasma and white blood cells can cause tissue damage - it's inflammation.

"A big question right now is do you want white blood cells or how much do you want? If you have a lot, you're going to create inflammation and do you want that to help an acute or chronic injury? Presently, we think we do not want more inflammation in an acute injury and maybe do in an old one because the scar tissue is already there if you want to kick start the healing process again."



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