For The Good of the Horse: Dubai Symposium 1996

 

His Highness General Sheikh Mohammed bin Rashid Al Maktoum in his opening remarks at the Dubai International Equine Symposium summed up the purpose of the meeting in six words: For the good of the horse. He arranged for an unprecedented gathering of the world's experts to discuss the health and problems associated with soft tissues. As important as the formal lectures, however, was the opportunity for veterinarians from all over the world to meet and exchange ideas about how to best care for the horse. As the week unfolded, it became apparent that Sheikh Mohammed had just that in mind.

"Tendons and ligaments are very important, and we're very happy to see the world's experts gathered here in Dubai and sharing their knowledge about this mysterious problem," said Sheikh Mohammed. "It is important to have a meeting like this to focus on soft tissues.

"With the new technologies and surgeries, you will have more understanding and ideas for the future. I'm very happy also for all of you here because when you go home, you will have a little more knowledge of the care of the horse."

Sheikh Mohammed also made the announcement that a symposium on respiratory problems in the horse will be held in Dubai next year.

Mike Hauser, DVM, MS, head of the Dubai Equine Hospital, said before the symposium that Sheikh Mohammed's purpose for hosting the event was to share and create ideas and offer a timely addressing of the problem of soft tissues. After the symposium, he said the gathering "satisfied Sheikh Mohammed's goals."

While the exchange of ideas was the purpose of the meeting, the hospitality surrounding the event goes beyond mere adjectives. Held in conjunction with the Dubai World Cup, the richest Thoroughbred race in the world, the symposium offered delegates an opportunity to not only learn while present, but to form associations and friendships that could lead to enhanced future communications between practitioners and among countries.

A hard-bound, four-color, 430-page proceedings was available at the symposium for delegates to take home as a reference. And even though the lure of the city was palpable, the 450-plus delegates were first and foremost in Dubai to share, listen, and learn.

The Emirates Auditorium at the Holiday Inn Crowne Plaza in Dubai was the site of the symposium. Security was tight, but not distracting, for the opening ceremony attended by Sheikh Mohammed, who is Minister of Defense of the United Arab Emirates and Crown Prince of Dubai. The four days of lectures covered topics ranging from scintigraphy, tomography, and ultrasound to ligament and tendon injuries and treatments.

Update On BAPN

Bowed tendons are the bane of many athletic horses. Research has shown that once a horse bows--where the tendon stretches, tears, or becomes damaged--there is a great likelihood that that same tendon will again be injured after the first problem is healed. This is because when tendon fibers heal, they form scar tissue that is not as elastic as the original tissue, thus shortening the tendon and forming an area of scar that won't stretch as much as before.

BAPN, which is derived from the seeds of the wild sweet pea, has the unique ability--if administered correctly--of preventing cross-linking between collagen fibrils when the tendon is healing. So instead of a mesh-like formation of scar tissue in a tendon, the fibrils can heal in a normal, parallel pattern. This allows the tendon to be more flexible and less likely to suffer from repeat injury once the horse is returned to training. The tendon also doesn't have the classic "bowed" appearance because the scar tissue has been controlled.

In November of 1993, BAPN (beta-aminoproprionitrile fumarate) was in the early stages of research to gain FDA approval for equine use. Bill Davis, MD, a human vascular surgeon in Arizona who had worked in preliminary research with the drug in humans, saw the potential for its use in horses. He enlisted the aid of Ron Genovese, VMD, a racetrack practitioner from Cleveland, Ohio, who had seen thousands of tendon problems in his career and was familiar with ultrasound examination of tendons.

Genovese used BAPN on his first horse in May of 1991, and research has been continuing apace since that time. He said the group is hopeful that BAPN will receive FDA approval in 1997.

An early success story of the project involved Onion Roll, the 1992 Ohio Thoroughbred champion sprinter. After the horse suffered what Davis termed a "horrible bow" on April 7, 1993, he was included in the BAPN study. Following about six months of treatment, Onion Roll ran in a $4,000 claiming race going two furlongs at Thistledown on Sept. 27. Not only did the horse win the race, but he equaled the world record for the distance of :20 4/5 set in 1945. Davis said that an ultrasound examination of the horse after the race showed that the tendon was "clean."

Although Onion Roll was ready to race after only six months, most horses need about nine months of treatment and rehabilitation before they are ready to resume competition.

The key to using BAPN, noted Genovese, is veterinary supervision of the tendon as it is healing. It is necessary to monitor the tendon with ultrasound, and manage exercise to promote proper healing. One of the major causes of failure that Genovese remarked upon was that the tendon often looks "healed" on ultrasound, but that other assessments need to be conducted before the horse resumes hard work if the tendon is to be able to withstand competition. (More on BAPN will appear in The Horse in upcoming months.)

Soft Tissue Injuries

In Hauser's paper on the treatment of acute soft tissue injuries, he stressed that early diagnosis was important, as was appropriate intervention times for invasive procedures and rehabilitation periods. He said soft tissue injuries should be considered medical emergencies, especially when tendons or ligaments are damaged.

"Graduating degrees of controlled stress with proper increments of calendar days and activity types and levels that are linked to follow-up evaluations are also integral to a favorable response to a treatment plan," he noted.

He stated that following early diagnosis by physical examination and imaging modalities--particularly diagnostic ultrasound--emergency medical treatment should be promptly administered. Included in that treatment are medications aimed at reducing the inflammatory response at the site of injury.

"Both steroidal and non-steroidal anti-inflammatories, antihistamines, enzymes, DMSO, and diuretics are used systemically," he noted. "With distal extremities, local application of ice, poultice, topical medications including DMSO, and cooling preparations further inhibit the inflammatory cascade. If the transitory effects of the medication are coupled with a cessation of exercise challenge, there will be improved anatomical appearance of the affected structure."

He said that a common error made by horse owners, trainers, and some veterinarians is attempting to continue training, showing, or racing in the presence of clinically apparent tendon or ligament injury.

"Many times favorite leg paints or other topical medications are relied upon to 'hold' the tendon from receiving further damage while training continues," he stated. "This is a dangerous procedure and is seldom successful. The amount of damage usually increases and performance ultimately decreases or lameness occurs and training must be discontinued."

Imaging Soft Tissues

Norman W. Rantanen, DVM, MS, Diplomate ACVR, who coordinated the symposium, discussed the principles of magnetic resonance, computed tomography, ultrasonography, and scintigraphy in imaging soft tissues. He said diagnostic ultrasound remains the method of choice for equine soft tissue imaging.

"Its success over the last 13 years in detecting tendon and ligament injuries provided a major breakthrough in diagnosis and treatment of the injured equine athlete," he said.

One of the major reasons for this degree of acceptance has been the development of machines with varying frequencies to image different structures. Also, the equipment is portable and can be taken to the horse in the field. Various imaging heads and frequencies allow imaging from the tissues just below the skin's surface to 30 cm in depth. He noted that lower-frequency sound waves penetrate deeper into the tissues, but the trade-off is poorer resolution because the crystals used to create low frequency sound beams are physically larger and are more difficult to focus. Conversely, higher-frequency sound waves offer better resolution due to smaller crystal size, but provide less penetration.

He said the sound beam must be focused at 90 degrees to the tendon or ligament fibers. Because the major ligaments are more-or-less parallel to the skin surface, the structures are usually imaged successfully.

One notable exception to successful imaging, noted Rantanen, is the deep digital flexor tendon as it passes palmar to the navicular bone.

"Because the dense hoof structure will not allow sound penetration, it is not possible to direct the beam to the tendon at 90 degrees, therefore it cannot be successfully imaged."

Although it takes extensive anatomical knowledge and skill to evaluate soft tissues with ultrasound, even the horse owner can look at an ultrasound image over the veterinarian's shoulder and see that patterns of fibers are either parallel or mottled, see "dark spots" where there are holes in the structure, or notice where there are disruptions in the normal pattern of the tendon or ligament.

Newer ultrasounds have the ability to determine area of circumference and to calculate an approximate percentage of fiber damage. This more accurately allows the veterinarian to monitor progress of an injury.

Magnetic resonance imaging (MRI) in the horse has been limited to cadaver specimens to this point for two main reasons--the existing MRI scanner shape is not conducive to equine imaging since it was designed for humans, which means there are size and weight limitations for the tables that hold the patient that preclude adult horses. Also, the equipment is cost-prohibitive for most veterinary practices other than teaching institutions. Rantanen noted that he feels MRI could have potential in examining tendons and ligaments of the horse.

At this conference, MagneVu company introduced the first MRI system designed for veterinary use. The portable unit weighs approximately 120 pounds and is available to licensed veterinarians only. The technology differs from the standard MRI scanning in that a small magnet is used to oppose the tissues in standing, tranquilized horses. Rantanen felt that because of the limited depth of penetration of the portable system, its initial value will be in scanning extremities, especially within the hoof.

Computed tomography (CT) uses conventional X-ray beams to produce images, but a series of detectors replaces the film. Sequential "slices" or images of the area of interest are obtained. The data is collected by the detectors, passed through a computer, and the images are seen on a monitor.

CT is particularly useful in imaging the equine skull, neck, and extremities. Rantanen said CT has had limited, but successful, use in equine imaging, but has become an integral part of small animal imaging. Initial equipment costs are high, therefore most machines are in large teaching hospitals. Horses also have to be anesthetized to undergo scanning.

Nuclear scintigraphy is becoming more readily available outside veterinary teaching hospitals. While scintigraphy is often thought of as a means to determine location of bone remodeling, it can be used for a variety of other structures.

"There are three phases during which different information can be obtained during imaging," noted Rantanen. "The vascular phase can be imaged immediately after injection (of a radioactive isotope that is read by the system) to determine the blood supply to an area. This is a short phase and lasts only a few minutes. The blood pool or soft tissue phase overlaps the vascular phase and is present when the isotope concentrates in the areas of hyperemia of the soft tissues. This phase is longer than the vascular phase and images of soft tissues can be made up to 20 minutes or more (after injection). The bone phase occurs after two to five hours of delay to allow the labeled product to be incorporated into the bone."

While scintigraphy often will allow location of the site of injury, it will not provide a diagnosis.

Thermography is yet another method of imaging soft tissue, and was addressed by Tracy Turner, DVM, MS, Diplomate ACVS, of the University of Minnesota. He described thermography as a pictorial representation of the surface temperature of an object.

"It is a non-invasive technique that measures emitted heat," said Turner. "A medical thermogram represents the surface temperatures of skin, making thermography useful for the detection of inflammation. This ability to non-invasively assess inflammatory change makes thermography an ideal imaging tool to aid in the diagnosis of certain lameness conditions in the horse."

He noted that non-contacting thermography that detects infrared radiation is the most accurate. (For more on thermography see page 43.)

Surgical Treatment

Larry Bramlage, DVM, MS, Dipl. ACVS, of the Rood and Riddle Equine Hospital near Lexington, Ky., said there is no treatment that universally solves a horse's tendon problem.

"The difficulty is that injury to the tendon results in fibrosis, which further compromises the functional performance of the tendon in its weight-carrying activity," noted Bramlage. "Even if one can attain a return to normal by surgical treatment, normal was inadequate to prevent injury at the horse's first episode. Therefore, an improvement over the normal anatomy is required to prevent recurrence, and this is seldom possible. Therein lies the difficulty in treating tendinitis."

One surgical method that is aimed at trying to improve a horse's chance to return to competition is tendon and ligament splitting. When these structures contain isolated pockets of blood or serum, "splitting" allows surgical drainage, reduces scarring, and speeds healing.

Another method advocated by Bramlage to improve a horse's chance at recovery from tendinitis (superficial digital flexor tendon, or "bowed" tendon) is the superior check ligament desmotomy.

"The rationale behind check ligament desmotomy is to transect (cut) the superior check ligament hoping to improve the mechanics of tendon rehabilitation by reducing tendon tension and lengthening the check ligament somewhat to increase the usable length of tendon-check ligament segment," noted Bramlage.

In a study of superior check ligament desmotomy in Thoroughbreds with bowed tendons, he found that there was a 71% chance of returning the horse to racing, and a 58% chance of the horse racing in the same class (but the average earnings per start will decrease with the increase in age and the injury). In Standardbreds, this surgical technique, combined with tendon splitting when appropriate, resulted in a higher degree of return to function and successful racing.

Many other topics relating to soft tissue were covered, and some will be addressed in upcoming issues of The Horse.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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