Joint approach

New Zealand-born Dr Wayne McIlwraith is a world authority on equine joints. He has performed surgery on more than 10,000 horses. He talks to NEIL CLARKSON about yearling x-rays and what US research is telling us about the racing careers of horses with joint issues.

A United States study proves that some problems showing up in pre-sales x-rays of thoroughbred yearlings significantly reduce the odds of the horses making it to the racetrack.

However, the research also shows that some issues revealed in x-rays appear to have no bearing on later track performance. Another linked study also reveals that 50 per cent of assessed yearlings had some radiographic issues, which veterinarians refer to as radiographic change.

The findings are arguably a victory for both sides in the argument over pre-sales x-rays, now a key element in the top-tier sales at Karaka. Buyers can rightly argue that certain radiographic changes clearly point to a reduced likelihood of a horse succeeding on the track. Sellers now have clear evidence that certain issues showing up in x-rays are unlikely to affect careers.

A key player in both studies was Dr Wayne McIlwraith, a New Zealand-born veterinarian who is Professor of Surgery and director of the Equine Orthopaedic Research Laboratory at the College of Veterinary Medicine and Biomedical Sciences at Colorado State University.

Dr McIlwraith says the term "radiographic change" was chosen carefully, with veterinarians keen to avoid the use of terms such as problems and lesions.

Dr Wayne McIlwraith, with a student.
Dr Wayne McIlwraith, with a student. "A lot of the problems we see in thoroughbreds
are management caused," he says.

" 'Change' suggests something that people would consider deviating from normal. It doesn't imply that it is significant."

Indeed, the studies have shown, among other things, the definition of what is natural variation is wider than many originally thought. The studies centred on about 1200 thoroughbred yearlings offered for sale at Kentucky's Keeneland sale, the biggest of its type in the US.

A repository for pre-sale x-rays of yearlings was introduced at Keeneland in July 1996. Its operation is much like that at Karaka, where a standard set of x-rays of each horse's key joints are held for viewing by veterinarians.

Dr McIlwraith says the introduction of the repository was a sensible move, and not just because of buyer demand. "Prior to the repository, if you were looking at a horse and it was going to go for a lot of money, you would get a vet at Keeneland to x-ray the horse. A good horse might have been x-rayed 20 times."

The next issue was interpretation of the x-rays. "Of the 1200 yearlings (in the study), 50 per cent showed some radiographic change that some vets would have turned around and got excited about."

It was found that some horses were being passed over by buyers on the basis of these interpretations. This, points out Dr McIlwraith, is not beneficial for buyers or sellers. The problem is not just centred on the seller potentially missing out on the best price. "A buyer could miss on a great horse. No-one wants to see a horse they passed over win the Kentucky Derby two years later."

The 6800-strong American Association of Equine Practitioners saw the need for a study, and funding was obtained. The first part centred on quantifying the extent and types of changes found in the x-rays of yearlings.

The source of these x-rays was a major equine veterinary practice in Kentucky, which was able to provide sets of joint x-rays for more than 1000 thoroughbred yearlings offered at Keeneland sales between 1993 and 1996 - before the introduction of the repository. In the horses, there was variation in the number of joints examined because of what was considered current at the time period. There were 1162 horses subjected to radiographs - this included front fetlocks in 1127, the hind in 1102, carpi in 1130, tarsi in 1101, stifles in 660, and forefeet in 300. All the joint x-rays were read again and the data collated into a detailed series of findings. The findings are too detailed to include here, but can be summarised as follows:

The prevalence of radiographic change is, of course, only part of the equation. The next task was to explore the early racing careers of the horses to determine whether concerns over x-ray findings translated into a poorer track career - or no track career at all.

Dr McIlwraith says it was a time-consuming and challenging task for the study team. "The follow-up is really hard. It was a big undertaking."

The end result was a list of radiographic changes that clearly impacted on racing performance. But equally important, says Dr McIlwraith, it turned up a list of radiographic changes that were shown to have no apparent affect on race performance.

Overall, 946 (81%) of the yearlings started in at least one race during ages 2 or 3. The most significant radiographic changes that were considered to affect performance were palmar supracondylar lysis of the third metatarsal, spur formation on the sesamoid bones, and disease in the inside of the carpus.

The odds of starting a race when age 2 or 3 years was three times lower with those changes compared to a yearling that did not have those changes. Yearlings with fragments in the hind fetlocks also were less likely to start a race as were yearlings with spur formations in the hind sesamoid bones. Of equal value in this study was identifying several changes that did not affect performance - particularly, flattening, concave defects and fragments in the fetlock joints.

Conversely, the study also raised concern about some x-ray findings not previously considered a problem.

The study went some way towards reducing the level of paranoia among those selling horses over the findings of veterinarians.

"The vet is in a good position now to give the positives and negatives."

Dr McIlwraith, who at times attends sales as a consultant available to give second or third opinions on x-rays, says the question asked more and more of him is, "if this causes a problem, can you fix it?"

"It's a good, positive trend."

Dr McIlwraith says there is still scope for more research. "We did not answer all questions, but we did all right," he says of the studies.

So what did the study show about race performances? As indicated above, 946 horses (81%) of yearlings went on to start in at least one race when aged two or three.

However, the odds of horses whose x-rays raised specific joint problems had a 57 to 69 per cent chance of starting - considerably lower than the 81% across the whole sample group.

Dr McIlwraith says most of the radiographic changes fall within the category of developmental orthopaedic disease, and within the realm of Osteochondritis Dissecans (OCD).

"I tell people that OCD is like human heart disease. We all have levels of predisposition to it. If we have bad genes, we have to be careful about our diets. OCD is a bit like that."

Dr McIlwraith says he knows of several mares that had three OCD foals in a row. Some stallions, he says, are known to throw OCD offspring.

Horse joints are, by their nature, fragile. Thoroughbreds are bred for speed. When galloping, they have only one leg on the ground at one time, and the load going through the knee has been calculated at 4000 pounds.

"They have to do a lot of work on those little legs."

At Keeneland, all pre-sales x-rays must be taken within a fortnight of the sale. Some owners x-ray yearlings months before the sale and, if required, arrange arthroscopic surgery to remove bone fragments or correct some problems. In such cases, a letter outlining the surgery is placed on file in the x-ray repository.

Dr McIlwraith suspects the incidence of OCD in New Zealand could be quite a lot lower than elsewhere, and research to confirm this could ultimately be a smart marketing move for the country's thoroughbred industry.

The reason, he suggests, is because management of stock is better here. "A lot of the problems we see in thoroughbreds are management caused," he says.

In many parts of the world, including Kentucky, horses spend much more time in stables than in New Zealand. In Kentucky, for example, mares and foals are let out from stables for exercise in large pastures. Mares, he says, will sprint across the paddocks and young foals try to keep up. The result can be sesamoid fractures - a problem rarely seen in young New Zealand stock.

Another advantage in New Zealand is that more of their nutrition comes from grass. Overseas, many horses live on a wide range of heating feeds. "Some are getting more than they need." Some sellers are intent on getting their yearlings as big as possible for sales. "If you increase their calorie intake you will increase the incidence of OCD."

On the whole, he says, New Zealand management is excellent in comparison with many other parts of the world. Germany, for example, has a major colic problem among its warmbloods, mainly caused by the high percentage of grain in the horses' diets, and the fact that many spend up to 23 hours a day in stalls.

Dr McIlwraith says experienced equine veterinarians are well qualified to assess pre-sales x-rays, armed with their own knowledge, the study findings, and a clear knowledge of what is required of the horses in both training and racing.

Equine vets are well aware that pre-sale assessment of bloodstock is one of the most important services they offer the thoroughbred industry.

X-rays are a crucial part of this, because they can give early warning of potential career problems.

Dr McIlwraith qualified as a veterinarian from Massey University in 1970. He worked in a mixed veterinary practice at Darfield, in Canterbury, for two and half years before leaving for Peru to fulfil his passion for climbing. He worked in England in 1973 and 1974 before climbing in the European Alps for three months.

He was rapidly coming to the view that the ultimate challenge would be equine surgery, which saw him heading to Ontario Veterinary College. He completed his surgical residency and PhD at Purdue University, in Indiana.

"I was looking to come back to New Zealand when I finished my PhD."

Fate, however, was to intervene. Dr McIlwraith was hired as Assistant Professor of Surgery at Colorado State University's College of Veterinary Medicine after the sudden death of O.R. Adams, author of Lameness in Horses, in 1979.

The position fulfilled his desire for an academic career, and also kept him near mountains. For his first 15 years at the university he was a surgeon. He became Professor in 1986.

Dr McIlwraith has operated on about 10,000 horses, and developed many of the keyhole surgery techniques now used in equine joint surgery. Even now, he still operates on about 400 horses a year.

He was asked to take over the Equine Sciences Programme in 1994 and ended up developing its orthopaedic research programme.

He was awarded an honorary Doctorate of Science from Massey University in 2003, the first veterinary graduate to receive such an honour.

Dr McIlwraith knows better than most what the osteoarthritis in his hip means - a result of a climbing fall. He believes he is on track for hip replacement surgery, which is likely to end his climbing career.

"I'm pretty lame," he admits.

He and his wife are regular visitors to New Zealand - probably even more so in the future now that they have bought a piece of seaside real estate near Kaiterteri, in Nelson.