Medical Messengers--British Equine Veterinary Association
The annual meeting of the British Equine Veterinary Association provided a wealth of information on topics ranging from tendons and ligaments to muscle diseases, from disorders of the back to conformation. Sue Dyson, MA, VetMB, PhD, DEO, FRCVS, president of BEVA and a member of the Centre for Equine Studies at the Animal Health Trust in Newmarket, England, noted that, "The specialist and workshop sessions provide an excellent forum for broad discussion with participation from the audience as well as the speakers. This provides a wonderful opportunity for dissemination of knowledge and opinion. In both these and the main sessions there should be attractions for both basic practitioners and the more scientifically minded."
BEVA was founded in 1961 with primary roles as "the prevention and treatment of injury and disease of the horse, its general well-being, and the advancement of equine veterinary science."
There are many diseases and health problems that are familiar to horse owners and practitioners working on horses throughout the world. There also are debates on subjects such as therapeutic options and equine dental technicians.
It has been proposed in the United Kingdom that non-qualified people who wish to perform dental manipulations such as removal of wolf teeth, temporary cheek teeth, and in certain cases permanent cheek teeth, undergo a period of training following a syllabus produced by the British Equine Veterinary Association and the Royal College of Veterinary Surgeons. Such people then would be subjected to a rigorous examination. If their level of expertise was satisfactory, they would be certified as equine dental technicians by the Royal College of Veterinary Surgeons.
"It is hoped that by creation of this group of approved dental technicians it will discourage non-qualified people from carrying out such interferences, thus ensuring that the welfare of the horse is preserved," noted a release from BEVA.
These approved dental technicians will have to carry out manipulations under the direct supervision of a veterinary surgeon, in a clinic where appropriate radiographic and anesthetic equipment is available to "remedy any possible sequelae of such procedures."
Annular Ligament Injuries
Professor Jean-Marie Denoix, considered the foremost equine veterinary diagnostician in France, opened the BEVA congress with a paper on injuries of the palmar annular ligament (located just above the fetlock). Denoix, who has a particular interest in imaging, showed spectacular slides of the anatomy of the region in normal and compromised horses. Denoix is head of the equine department at the veterinary school in Alfort, France.
In his experience, he found that in 3,500 ultrasound examinations of horses between 1989-96, about 230 had a variety of different pathological conditions involving annular structures located at the dorsal or palmar aspect of different joints (see images). He said he has seen many cases of synovial effusion in this area of the fetlock, and that the superficial and deep digital flexor tendons can be pushed apart by this excess fluid.
"The clinical appearance of horses is not definitive to let you know which structures are involved and how," said Denoix. "Mostly, we use ultrasound for diagnosing this problem. MRI (magnetic resonance imaging) also is used."
He said damage in this area of the fetlock can interfere with the swing phase of a horse's stride, so it can be an injury that limits a horse's athletic ability. Denoix noted that there also are annular ligaments in the carpus (knee) and tarsus (hock) that can be injured.
Aging, Training, Injury, And Tendons
Carol Gillis, DVM, of the University of California, Davis, noted that previous studies have shown 53.9% of racehorses on pre-race inspection had tendinitis. She encouraged veterinarians to use ultrasound to note changes in size, echogenicity, and tendon pattern in tendons of horses in training, especially those coming back from injury.
In her research, she found that after horses reach two years of age, their sex, weight, and increasing age had no effect on tendon structure cross-sectional area, echogeniticy, and fiber pattern of the tendon. She did verify that larger tendons take larger loads before they strain, a testimony to horsemen who look for good tendons in sound, young horses.
She also determined that there is an increase in tendon size with training of young Thoroughbreds, and that echogenicity changes, meaning that the tendon does change with training. However, the decrease in echogenicity might be because of an increase in non-aligned collagen (the main supportive protein in skin, tendon, bone, cartilage, and connective tissues). Collagen normally is linearly aligned in rows, rather than haphazardly or with fibers crossing over one another. Therefore, tendons respond to training by increasing in cross-sectional area and in density.
She noted that with young horses in training, an increase in tendon size of more than 15% could indicate a high risk of tendon injury or re-injury.
Ron Genovese, VMD, a practitioner in Ohio, has overseen much of the field testing of a product known as BAPN (or BAPTN, beta aminopropionitril fumarate) in treating superficial digital flexor tendon injuries (bowed tendons) in racehorses. Studies were undertaken at various locations across the United States to obtain FDA approval of the drug, and that approval is expected early in 1998. Field trials on various breeds of horses were conducted at the University of Pennsylvania, Michigan State, The Ohio State University, University of Virginia, and Texas A&M.
Genovese noted that with a carefully supervised and regulated system of exercise following BAPN treatment, injured tendons tended to have improved (decreasing) cross-sectional surface areas upon evaluation, a reduction in hypoechoic fiber bundles, and improved parallel alignment of scar tissue in comparison to untreated tendons.
With regard to performance, Genovese noted that in moderate and severely injured horses, those treated with BAPN were 37% successful (racing at a level equal to or better than before injury) and 57% failures, with placebo groups having no successful horses and 71% failures. (For further reading on BAPN see The Horse of September 1996, page 31.)
The Equine Back
"It would be nice if we could define back pain like lameness (with grades to determine severity), but it is not possible," noted Professor Leo B. Jeffcott, Dean, Professor of Veterinary Clinical Studies, Department of Clinical Veterinary Medicine, University of Cambridge.
Most of the back pain horses experience is chronic, he said, although there are secondary back problems that do alter the way the horse moves. However, if the back problem is secondary, helping the back without treating the primary cause of pain will not cure the horse.
He said it is of critical importance in working with these lame, sore horses that the attending veterinarian knows the conformation of the horse, the use of the horse, and the ability of the rider. Then, a thorough clinical exam is performed, using imaging to assist in diagnosis.
Joyce Harman, DVM, who owns an equine holistic practice combining acupuncture, chiropractic, herbal medicine, and homeopathics, said when a horse starts to lose biomechanical function in the back, it puts a strain on the lower legs--ankles, knees, hocks, and stifles. She has found if you treat the back and spine, then the lower leg problems clear up.
Jeffcott noted that a single problem or site is uncommon in lameness situations, "Usually multiple problems account for poor performance."
Denoix said that in studies of the axial skeleton of the horse with elastic used to simulate muscles, he was able to demonstrate that the main flexible area is the lumbosacral junction. He noted that some horses had five degrees of flexion, while others had 20 degrees of flexion. He said using ultrasound transrectally will allow a practitioner to see the intervertebral discs and possible areas of concern. He said in some cases he can identify fusion in the spine, which would predispose the horse to pain. He said back problems caused by lesions usually can be seen with radiographs.
There was agreement that back problems caused by bone also could cause associated muscular soreness. Harman noted that the "violent" manipulations done to horses' joints and spines in the name of chiropractic caused damage, and that, "If you take a joint past its normal range of motion, you can cause long-term damage."
Professor Michael Nowak of Germany discussed imaging in diagnosing back pain. He said the most common diagnostic tools are X rays, scintigraphy, thermography, and ultrasound. He agreed with other practitioners that having a thorough exam, especially under saddle doing what the horse normally does in training or competition, is important in diagnosing the areas involved with lameness, soreness, or poor performance. He said the future should hold improved ways to use the above-mentioned diagnostic tools, with possibly the inclusion of magnetic resonance imaging (MRI).
Role Of Saddle/Rider In Back Pain
"A saddle is a rigid structure that connects the dynamic structures of the horse and rider," said Harman. "The fit and position of the saddle affect the movement of the horse and the ability of the rider to communicate his/her wishes to the horse."
Basically, Harman said saddles are a "necessary evil" for riding and competition. She said in her experience, saddle fit is a major contributor to poor performance syndrome. When a correctly fitted saddle is used and the resultant back pain is removed, she has found performance problems disappear, often rapidly.
Being a veterinary acupuncturist, Harman also noted that a saddle sits on from one-third to one-half of the bladder meridian, which is a major acupuncture meridian for the body.
The saddle should rest behind the shoulder blades and sit squarely in the center of the back, noted Harman. The tree needs to fit across the withers, and the panels need to contact evenly on the back. The tree needs to be wide enough to give support, with the gullet allowing the saddle and rider's weight to stay off the horse's spine. The seat needs to be level.
She said all saddles, no matter the manufacturer or cost, should be inspected. Manufacturing defects occur in saddles, such as twisted trees, uneven padding, or even broken trees.
She said using pads does not prevent pressure points, calling it the "Princess and the Pea Syndrome." Often, adding pads under a saddle increases the pressure across the withers. If pads are to be used, then the pads should be fitted to the horse with the saddle, instead of just fitting the saddle to the horse without taking the pads into consideration.
Another problem Harman pointed out was that horses change shape with fitness, amount of work, and the season of the year. She said veterinarians need to pay attention to saddle fit as a possible cause of not only back pain, but many of the obscure lower leg lameness and uneven gaits seen in performance horses. "The origin of many of these begins with altered function of the back under the saddle," she added.
Research has shown the pressures under a saddle often exceed capillary closure pressure by three-fold. She said that on 80% of horses, the left shoulder is farther back and more muscled, with the right shoulder farther forward and less muscled. Therefore, you get pain associated with the left rear quarter of the saddle. This occurs because the saddle "twists" due to the horse's back being not the same shape on each side, but the saddle being made as if the horse's back is even.
The rider has a direct effect on the horse's back. Tension or pain in the rider can show up as tension or resistance in the same place on the horse--i.e., the rider's right shoulder to the horse's right shoulder. Computerized pressure data have shown that a good rider, no matter his or her weight, will place less pressure on the back of the horse than a poor rider. (Harman said that a trained eye can detect about 80% of what the computer records.) Rider imbalance can turn a well-fitted saddle into one that is painful for the horse. Rider balance problems can mimic saddle fit problems, said Harman. The rider must be in the center of the saddle to distribute that weight evenly on the horse's back.
Harman also noted that the stirrup bar placement was incorrect on some saddles, forcing the rider into an awkward position for the athletic endeavor attempted. One specific saddle, the half-tree exercise saddle for racehorses, is especially known for causing back pain, said Harman. She said just taking the exercise saddle and placing it back behind the shoulder blades instead of on top of the withers could eliminate many of the back soreness problems associated with training.
A major cause of economic loss to the horse industry is muscle pain, said Harman. "Muscle disease is less common than muscle pain, and most (horses with muscle pain) are interpreted as having training or behavior problems," she added.
Harman described a "circle of muscles" that allows the horse to move as nature intended--allowing the back to lift, the hindquarters to engage, the neck to telescope, and the sternum to rise. If a horse is not elastic or has muscle pain, then the back and neck are hollow, the sternum drops, and this "stiffness" prevents normal movement of joints, which means the horse overuses its legs.
"Clients can be our best teachers for individual horses," said Harman. The owner's observations are critical in letting the veterinarian know when the horse has a problem, what makes the problem better or worse, and what the rider notices during exercise.
Signs of pain include objection to being saddled, being slow to warm up or leave the starting gate, being difficult to shoe, having a "bad" attitude, resisting work, bolting or running away, swishing the tail, pinning the ears, ginding the teeth, or biting. Again, she pointed out that many "behavior" problems are associated with muscle pain, and when the muscle pain is taken away, then the "bad" behavior stops.
A horse's conformation and its stance are two different things, she pointed out. She said if you walk a horse forward and stop, then move him forward again and stop, many won't stand square. They just aren't built for standing comfortably with the same amount of weight on all four feet.
A veterinarian should observe the horse at a walk and jog to look at tracking (foot placement), back motion, tail position, and symmetry of motion. With the horse on the lunge line, the veterinarian should observe freedom of movement, stiffness (often worse in one direction), and back/neck position in both directions.
Under saddle, the horse should be compared to his movements when he was lunged. The veterinarian should observe the rider (skill, weight, type of bit used) and check saddle fit.
Palpation is a critical part of the examination. The muscles and joints are palpated thoroughly, feeling for any loss of normal motion, asymmetry in motion, and tension or pain.
"Palpation skills are enhanced by learning acupuncture and chiropractic approaches for treating horses," said Harman. "The information gathered by specific palpation allows the practitioner to make a diagnosis and prepare a treatment plan. A light touch often reveals more than a heavy touch, and much practice is needed to develop the light touch."
The healthy muscle is soft when relaxed, and has spring or resilience. A painful muscle is tight, ropy, or spongy, even when relaxed. There is little spring or give in the injured muscle.
Harman pointed out that the term "subluxation" has caused a rift between chiropractors and veterinarians, but only because there are different meanings assigned to the same word. The traditional veterinary definition of a subluxation is an incomplete or partial dislocation. The chiropractic definition is an alteration of normal dynamics, anatomic, or physiologic relationships of contiguous articular surfaces.
Treatment must take in the whole horse, no matter the specific location of the pain. Harman said the most consistently effective therapies available to treat muscle pain are acupuncture and chiropractic, either combined or separately. Massage and physical therapy also can be used for muscle pain relief and prevention of muscle injury and spasms in the future.
Harman and others on the muscle disease program noted that no physical therapy should be given to a horse without a veterinary diagnosis.
Here is a problem you might never hear about, but apparently it is more common than practitioners previously thought. Aortoiliacofemoral thrombosis is a blockage or plug in the large saphenous vein in the hind leg of horses. Clinical signs often follow exercise, and they can be moderate to severe, noted Dyson. Usually these clinical signs are preceded by a history of loss of performance. Signs include hindlimb stiffness that could be one or both legs, stumbling, repeated knuckling at the hind fetlock, distress and sweating over the body with the affected limb remaining cool, and stamping of hind limbs.
She said in a survey of 28 specialist equine veterinarians from around the world, eight had not recognized a case of aortoiliacofemoral thrombosis. The remaining 20 veterinarians had diagnosed 44 cases of the problem, all of which were confirmed by ultrasound.
"There was a profound domination of male horses (20 stallions, 16 geldings)," said Dyson. "There was no particular breed incidence. Racehorses and other competition or pleasure horses were similarly affected. There were nine breeding stallions.
"Nine of the horses were less than five years of age; 19 between five and 10 years of age; 10 between 10 and 15 years of age, and six of 15 years of age or older," she added. "Seven horses had exhibited clinical signs for less than seven days, several for only a few hours prior to diagnosis. Ten horses had shown symptoms for more than one week and up to one month, while the remaining 27 horses had a longer history of compromised performance. Thirteen of the 44 had no palpable abnormality, but partial vessel occlusion was seen on ultrasound."
In breeding stallions, she noted a history of slowness to cover mares, pain after covering, and failure to ejaculate. There was lameness in these stallions after covering mares, and sometimes the stallions would lie down.
She said treatment rationale was based on pain relief and the use of anti-inflammatory drugs, platelet inhibitors, anthelmintics, fibrinolytic agents, and vasoactive and anticoagulant drugs.
Twenty-nine of the 44 horses underwent treatment, and three were allowed to live untreated. Two horses returned to their former athletic function with apparent resolution of clinical signs. Eleven horses improved, but clinical signs persisted. Twelve horses showed no response to treatment or deteriorated, and an additional four were euthanized. The three untreated horses remained symptomatic if exercised.
Dr. Astrid B. M. Rijkenhuizen of Utrecht University in the Netherlands reported on a surgical technique using a human Fogarty thrombectomy catheter for removal of thrombi to restore blood flow. She had two cases which were treated successfully.
"Based on this study and the human literature, it seems that the results of surgery depend on the localization of the obstruction, the extent of the obstruction, the length of history, and medical therapy," said Rijkenhuizen.
Dr. Bill Davis, a human surgeon (who also is one of the people responsible for bringing BAPN to the horse industry), said aortoiliacofemoral thrombosis is usually a problem of older people. He discussed the various treatment regimens and surgeries that have been tried over the years to correct this problem in humans, and said there could be some correlation in humans to folic acid deficiency. He also mentioned the possibility of using balloon angioplasty or vein bypass surgery in horses.
Stephanie J. Valberg, DVM, of the University of Minnesota, is one of the world's leaders in research on exertional rhabdomyolysis (ER), or tying-up. She said ER is a common cause of poor performance in most equine breeds. There have been many proposed causes of ER, including lactic acid build-up, electrolyte imbalances, hypothyroidism, vitamin E and selenium deficiencies, over-exertion, heat exhaustion, metabolic myopathies, abnormal calcium regulation, and more. Valberg said one of the reasons for the confusion regarding ER could be that by applying the term tying-up to all horses with muscle cramping, specific subsets of exertional myopathies have gone unrecognized.
Using a protocol that includes complete blood counts and serum chemistry, serum T3 and T4, renal fractional excretion of electrolytes, histochemical and biochemical analysis of frozen muscle biopsies, and exercise testing, a classification system for tying-up recently has been developed.
Sporadic ER is due to extrinsic factors affecting muscle function. These include generalized and focal muscle strain (over-exertion), exhaustion syndrome in endurance horses, and electrolyte imbalances.
Recurrent ER appears to be due to intrinsic muscle defects. At least two specific, likely heritable, defects are recognized in particular breeds:
1) a polysaccharide storage myopathy, characterized by an abnormal polysaccharide and abundant glycogen in muscle fibers, and persistent elevations in serum CK;
2) abnormal intracellular calcium regulation characterized by intermittent ER and increased risk for generalized anesthetic myopathies.
She is suspicious that calcium imbalances could have a great deal to do with recurrent ER. She noted that very often it was the nervous, faster fillies who were more prone to ER episodes than their slower, less nervous counterparts. There is a question of whether extra calcium in muscles might make the horse run faster, but too much could cause the horse to exhibit ER. Valberg also said there seemed to be a pattern of inheritance, and researchers at the university will be conducting breeding studies to see if this theory is true.
About the Author
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.