|This horse has "bowed" it superficial digital flexor tendon; the tendon protrudes, or bows out, at the back of the leg. This is the most common debilitating tendon injury suffered by racehorses and requires a long layoff for recovery, although new treatments are shortening the time lost from training. (Photo: Dr. Barak Amram/VetMoves)|
The research was led by Bryan O'Meara, who is in the final year of a three year clinical training scholarship funded by The Horse Trust. O'Meara carried out the research at Donnington Grove Veterinary Surgery in Newbury, under the supervision of epidemiologist Dr Tim Parkin from University of Glasgow.
Tendonitis is one of the most common musculoskeletal injuries in racehorses, with a prevalence of 11-30%, according to earlier research.
O'Meara examined the clinical records and racing histories of 400 racehorses who had been treated for superficial digital flexor (SDF) tendonitis injuries over a five year period from 2003 to 2008.
The race records of horses affected by tendon injury were compared with 400 matched control horses that had never suffered SDF tendon injuries. The controls were horses training in the same establishment at the time of injury and of the same age and sex as the case horse.
The Horse Trust-funded research looked at the performance of the racehorses in races before and after treatment for the injury, and at the performance of the control horses before and after the treatment date. The Racing Post Rating (RPR), which is published by the Racing Post (a British racing newspaper with charts) after every race, was used as a measure of performance.
O'Meara found that there was no significant difference in RPR before and after the treatment date in case and control horses.
This result is unexpected as in vitro studies have found that healed tendon tissue has reduced elasticity properties due to the presence of scar tissue. This suggests that a horse with a healed SDF tendon would need to work its muscles harder to compensate and would therefore be expected to have lower performance.
O'Meara said more research is needed to back-up his finding that performance isn't significantly affected by tendon injury.
"It could be that using Racing Post Rating to measure performance isn't sensitive enough to pick up a change in the horse's performance," said O'Meara. "However, it's encouraging that there's no marked change in performance after a horse has recovered from a tendon injury. These findings show that there's no need to give up on a horse that has a tendon injury--they can still come back and perform well, or can be used for other, less demanding riding activities."
The Horse Trust-funded research also found that there was no significant difference between case and control horses when returning to racing and completing three races. Only after completing five races, or three years post treatment, was a significant difference found between case and control horses. This finding is a step towards developing a more accurate assessment of tendon-treatment outcome after five races or three years post-treatment is a better indicator of the outcome of treatment.
"At the moment, some tendon treatments state their success as the percentage of horses that return to racing after treatment. However, we've shown that there's no significant difference between case and control horses at this time," said O'Meara. "At the moment, there are a myriad of treatments available to treat tendonitis. Hopefully this finding will be used in further research to learn which treatments are most effective."
O'Meara's research also found a link between SDF tendon injury and the racehorse competing at its maximum performance level: the case horses were significantly nearer to their pre-injury maximum performance level in the race immediately before injury (compared to matched controls), suggesting that they were competing nearer their individual maximum performance level when the SDF tendon injury occurred. (Note: this statement is not explained but would seem to suggest that either the level/class of the race or the distance perhaps was the best the horse had done in its career when the injury occurred.)
Editor's note: Information in this article was provided by The Horse Trust, a British charity that funds equine research and promotes education about horse health and welfare. Hoofcare Publishing likes to support The Horse Trust whenever possible. The research described in this article was published in the May 2010 edition of the Equine Veterinary Journal and is available online as a downloadable PDF file: "An investigation of the relationship between race performance and superficial digital flexor tendonitis in the Thoroughbred racehorse".
Readers should keep in mind that the study included only British racehorses and that the majority of British racing is done on grass. Race distances, conditioning schedules and training methods also vary in Great Britain from methods used in North America and some other countries. But the results are interesting, no matter where you live!
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