Mike Scott, DVM, MVSc
Diplomate, American College of Veterinary Surgeons
Moore & Company Veterinary Services Ltd.
Calgary, Alberta, Canada
www.mooreandco.com

Introduction
I am a veterinarian specializing in equine surgery, and I work at Moore & Company Veterinary Services in Calgary, Alberta. I graduated from the Western College of Veterinary Medicine (WCVM) in Saskatoon in 1993. Following graduation, I completed a 1 year internship in Large Animal Medicine & Surgery at the Ontario Veterinary College. I was then fortunate to be admitted to a Large Animal Surgery Residency program at the WCVM. I completed my residency training in 1998, and became board certified by the American College of Veterinary Surgeons in 1999. Today most of my work involves equine surgery, lameness diagnosis, and diagnostic imaging. It is a pleasure and an honor to give this presentation at the Horse Industry Association of Alberta Horse Breeders and Owners Conference.

Mike Scott

Dr. Mike Scott graduated from the WCVM in 1993. He then completed a one year internship in large animal medicine and surgery at the Ontario Veterinary College at Guelph. In 1997, Dr. Scott completed a three year residency in large animal surgery at WCVM, and attained a Master Veterinary Science degree. Two years later, he became a board certified large animal surgeon. Dr. Scott has been Moore & Co.'s surgery specialist for seven years. He is particularly interested in orthopedics, arthroscopy, diagnostic imaging, lameness diagnosis, and sports medicine. Dr. Scott has been instrumental in the implementation of Nuclear Scintigraphy at Moore & Co.

Dr. Scott is the past president of the Western Canadian Association of Equine Practitioners for the 2004-2005 year. He has published scientific articles on research projects such as; the development of intra-osseous regional perfusion techniques for treatment of orthopedic infections, congenital Hypothyroidism and Dysmaturity of Foals, Microvascular Free Tissue Transfer Techniques for Wound Repair, Measuring incidence and Prognosis for Osteochondrosis in Draft Horse Breeds.


This presentation is intended to provide horse owners with a brief summary of some aspects of equine veterinary medicine in which recent advances have been made. It is by no means a complete list of areas with important advances, in fact it is a biased list. I will be discussing topics which I am somewhat familiar with, some topics which I think are important, and some topics which I think are interesting. In covering 10 different subjects in one presentation it isn’t really possible to go into great detail. I hope to provide a glimpse into some of these subjects and to emphasize one or two points about each topic that I think are of value for anyone with an interest in horses.

1. Nutrition for the Equine Athlete
There have been significant developments in the last decade in our knowledge of equine nutrition and in the options available for feeding horses. Feed companies employ knowledgeable veterinarians and nutritionists to develop new products, and produce a wide variety of new feed options in the competition for market share. Horse owners should strive to gain a basic level of understanding of equine nutrition in order to understand the options available and to select appropriate feeding options for the types of horses they are feeding. Feed programs should vary according to the age and breed of horse, the management, and type of work being done.

On many occasions I ask owners what they are feeding their horse, and all too often they list the names of the supplements they are feeding, barely mentioning the concentrates and often forgetting about the roughage portion of the diet. This response illustrates a lack of understanding of basic equine nutrition and an over-emphasis on the products receiving the most promotion and advertising (i.e. supplements). The components of an equine feed program include water, roughage, concentrate, salt, and vitamin and mineral supplements. An overall review of equine nutrition would require and entire presentation on its own, which can not be done here. In this context I will mention the basic components of the diet and discuss some concepts on feeding for athletic performance.

An important concept in nutrition is caloric intake. Calories are the basic units of energy supplied in the feed, which the horse uses for building and maintaining tissues and the production of energy. The scientific definition of a calorie is the amount of energy required to heat 1 gram of water by 1 degree Celsius. If the horse is growing or working hard, it requires more calories than the sedentary adult. The calories in the diet are supplied primarily by the roughage and concentrate the horse eats, not by the salt, minerals, and supplements. The calories in the feed are provided at varying levels by the carbohydrate, fiber, protein, and fat in the feed. Fats are the most calorie dense, followed by carbohydrate and lastly protein. Protein provides the lowest level of calories, so when concentrates are designated as 12%, 14%, or 16% protein this gives little information as to the caloric density of the feed and is a poor measure for selecting a concentrate ration on its own. Protein is a necessary component of the diet and is important for growing horses, debilitated horses, and lactating mares but it is not the most important consideration for normal healthy adult horses.

Much of the calories in the traditional horse diet come from carbohydrates in the roughage and concentrate. Carbohydrate can be subdivided into soluble and insoluble carbohydrate. Soluble carbohydrate is essentially starch, which is rapidly digested by the mammalian digestive system and absorbed as simple sugars. Insoluble carbohydrate is the indigestible plant fiber found in roughage. It can not be digested by the typical mammalian digestive tract. Unlike the human, the horse is able to use this material because it has a large colon and cecum which functions as a fermentation system. Trillions of bacteria living in the fermentation system of the hindgut can digest the insoluble carbohydrate, breaking it down into smaller components that can be absorbed by the horse.

The horse has a limited ability to digest and absorb hydrolysable carbohydrate (starch) in the small intestine. Large concentrate meals may result in excess starch reaching the large intestine. This not only reduces the efficiency of feed use, but also increases the risk of digestive disturbance as the excess starch is rapidly fermented in the large intestine producing excess gas and acid. Oats are approximately 50% starch, while corn and barley range from 60-65 %. Normal digestion of the starch produces glucose, which is needed for the production of muscle glycogen, the main fuel used during exercise. Providing some starch in the diet of the athletic horse is important for maintenance and replenishment of glycogen reserves. However, feeding excessive levels of starch leading to hindgut fermentation results in lactic acid accumulation in the gut, excess gas production, colonic acidosis, and increased incidence of colic. It has been shown that feeding more than 2.7 kg of oats per day is associated with increased risk of colic. In addition to risk for colic, a total ration high in grain usually results in horses spending a lot of time with nothing to eat, which is the single most significant factor in the development of gastric ulcers.

There are several strategies that can be used to reduce the risk of digestive disturbance related to heavy grain rations, such as those fed to racehorses. Limit the size of the meal to avoid “starch bypass” to the large intestine. Energy concentrates should make more use of non-starch carbohydrates (e.g. beet pulp) and vegetable fats. Use of these alternate energy sources allows reduction of levels of starch in the diet to a safer level, while maintaining or increasing the total amount of energy consumed. A suggested upper limit for starch intake in a single meal is between 2 and 4 grams starch/kg body weight. If oats are 50% starch, for a 500 kg horse this would be a maximum recommended amount of 2 kg.

The addition of fats to horse rations is now commonplace. Commonly used forms of fat include vegetable oils (canola, corn, soy), rice bran (18-22% fat), and flax meal (40% fat). Vegetable oils contain approximately 3 times as much digestible energy as oats. The addition of fats to the ration can be beneficial for several reasons. It allows the amount of digestible energy in the ration to be increased without increasing the total carbohydrate intake. This is advantageous for horses that are at high levels of exercise and for horse that are in poor condition. Suggested upper limit of oil supplementation is about 500 g per day (about 2 ½ cups) divided into about 2-3 feedings which would provide 1.7 MCal per day or about 16% of daily energy requirement. This is a maximal level; feeding of oil should be introduced gradually beginning at ¼ cup per day.

The feeding of fats in the diet may help prevent exertional rhabdomyolysis or “tying up”, and also calm horses that “wash out” prior to competition. Typical racehorses are consuming 30 Mcal of digestible energy per day, much of it from starch. Consumption of 5-8 kg of grain per day contributes to increased incidence of tying up episodes, and it seems that high calorie, high starch diets make the horse more nervous and high strung. A diet lower in starch and higher in fat and fermentable fiber will result in a calmer horse and reduces the incidence of tying up. One recommendation for horses in intense work that are prone to these problems is a diet where 20% of digestible energy (DE) is from starch and a minimum of 20% of DE is from fat
Feeds such as soya hulls and beet pulp are non-starch carbohydrates composed of highly digestible fiber. Beet pulp is readily digested, has a higher energy value compared to hay or other less digestible fiber, and increases the digestibility of the hay portion of the diet. Beet pulp can be substituted for grain in the ration in order to further reduce the risk of digestive upset, gastric ulceration, tying up and washing out that can affect some horses on a high grain diet.

2. Colic Surgery
For most horse owners the concept of their horse undergoing colic surgery is frightening and something they would rather not think about. Most horses will never require colic surgery, but enough do that it has become a regular part of what we do at our hospital. As equine veterinary medicine has gained experience in this area, numerous improvements in techniques and treatments have resulted in improved survival rates and better outcomes. It makes sense for horse owners to have some basic understanding of colic and its treatment in case their horse is unfortunate enough to have this problem at some time.
When is colic surgery indicated? When we are evaluating a horse with colic, we examine many different parameters including the history, the type and age of horse, the temperament of the horse and its apparent pain tolerance, physical examination findings, rectal examination findings, ultrasound exam findings, and lab work. We consider all the information provided by our exam, but there are really 3 main parameters that we rely on to decide what to do. These 3 main indicators are (1) ongoing signs of colic, (2) elevating heart rate, and (3) physical abnormality in the abdomen. If the horse is continuing to show signs of pain despite administration of painkillers, this indicates that there is something significantly painful going on and surgery may be needed. If the heart rate is going up, this indicates that the horse is experiencing continued pain and/or the horse is going into shock (compromise of the circulatory system function that is not usually seen with mild colic). If we can tell from rectal examination or ultrasound examination that there is a significant physical abnormality such as intestinal twist or severe distension, surgery is more likely necessary so that we can try and correct the physical abnormality.
Diagnostic ultrasound examination of the abdomen is a relatively new procedure in the evaluation of colic. It has become one of the most important aspects of our workup, and has significantly increased the accuracy of our diagnosis. Using ultrasound, we can evaluate regions of the abdomen that can not be felt with rectal palpation. We can often tell if there is intestinal displacement, intestinal distension, normal or abnormal anatomy of the small intestine, large colon, spleen, kidney, and liver, or abnormal or increased fluid in the abdominal cavity. It can allow us to quickly identify significant abnormalities, leading to earlier surgical intervention and a greater chance of success.

Early diagnosis and improved surgical and post-operative techniques have significantly increased our success rates with colic surgery over the last decade. We can now quickly and reliably identify which horses need surgery, and we can usually tell if the problem is just bad or really bad (there are no good colics!). Some problems such as a large colon displacement have a good prognosis for survival, whereas others such as a small intestinal strangulation have a poor prognosis. Determining this in advance helps owners decide whether the risk and cost of surgery is justified. Small intestinal strangulation is one of the most severe surgical emergencies. Usually by the time we are in surgery the small intestine has been twisted long enough that it has been damaged due to lack of blood supply. In order for the horse to survive, the dead small intestine needs to be cut out and the intestinal tract needs to be reconstructed. These horses are usually in severe shock and are very sick. The anesthesia and surgery are much more difficult, and the horse is much more sick after the surgery and has more complications. The long term survival rates for such cases is approximately 40%. Large colon disorders such as displacement or impaction have a better prognosis. The horse is often not in shock, and the intestine is usually all viable. The surgery may involve opening and emptying the colon, but does not require removing gut and reconstructing what is left. The long term survival rates for such cases is approximately 80%.

Early and accurate diagnosis is a key in determining the outcome of severe colic cases. Horse owners should have a basic understanding of the types of colic and what signs indicate that surgery may be needed. Many owners and trainers have access to painkillers, including phenylbutazone and flunixin (Banamine). Giving the horse 2 grams of phenylbutazone orally in the early stages of a colic episode is a reasonable treatment, as this will not be enough to mask the signs of a severe case. If flunixin (Banamine) is used, it should only be given at half the regular dose if surgery is an option (only 5 cc for a regular horse). Flunixin (Banamine) is a potent painkiller, and can mask the signs of severe colic enough that it can be difficult to determine if surgery is needed delaying treatment and decreasing the prognosis.

3. Skeletal Development & Bone Adaptation
Modern horse breeding and management practices are harming our horses, and resulting in horses that are weaker and more prone to injury than they should be. From the selection of breeding stock based on paper pedigree and money won to overfeeding, I believe that many aspects of how horses are currently bred, raised, and trained are harmful to both individuals and breeds. Horses have been domesticated for thousands of years. For the majority of that time their primary purpose was for work, rather than companionship and entertainment. Veterinary medicine was crude, and for most horse owners it probably made more sense and was more of a necessity to replace a chronically sick or injured horse than to treat it. The result of this “survival of the fittest” life meant that the horses that stayed healthy and sound were more likely to be bred and pass on their genetics resulting in selection for these traits. Today, the “survival of the fittest” selective pressure is reduced, horses are selected for breeding for reasons other than health and fitness, and many physiologic weaknesses are becoming commonplace. When genetic predisposition is coupled with unfavorable training and management, illness and injury is more likely to result.

This theory can be applied to many aspects of equine health and management, from psychology and training to hoof care and farriery. One area that we can see the result of these factors is skeletal development and skeletal injury. Horses that are born with weak bone, conformational faults, or developmental orthopedic conditions such as osteochondrosis dessicans (OCD) are already prone to skeletal injury and disease. Even horses that are born with normal skeletons can be weakened or damaged by management conditions that do not favor proper skeletal development. Bone is a dynamic structure and constantly changes in response to force through 2 primary mechanisms:

1. Bone Modeling – Appears to occur only in the juvenile horse. New bone can be either added or taken away. Bone can become longer, thicker, or heavier or different in shape

2. Bone Remodeling – removal of old or damaged bone and replacement with new mineral. Bone remodeling occurs throughout life, but typically does not result in overall change in the amount of mineral.

Given that bone modeling occurs only in the juvenile skeleton, the greatest opportunity to create bone that can withstand the rigors of future athletic use is during the growth period, usually from 0 to approximately 2 years of age. The skeleton needs to be stressed in order to develop to meet future demands. All the minerals and supplements in the world will make no difference to the horse that can not exercise enough to stimulate his skeleton to develop properly. This does not necessarily mean that young horses should begin rigorous training at an early age, but it does mean that they should have moderate amounts of exercise of sufficient intensity at an early age. Limiting the ability of a horse to exercise on its own will predispose the horse to a weakened skeleton. If the skeleton is insufficiently stressed, a lack of bone development or bone resorption will occur. If the skeleton is over-stressed, injury will occur. It has been shown that a maximal effect on bone mass can occur with 36 cycles of loading at 0.5 Hz per day (Lanyon 1884). This means that for the young horse short periods of exercise with as little as 36 strides at the appropriate intensity will condition the bone for future loading at that intensity. The level of intensity is important; bone trained by trotting will develop for trotting, bone trained by galloping will develop for galloping. Depending on the type of work the horse is destined to perform, it would probably be advantageous to allow the young developing horse opportunity to begin short periods of this work at an early age.

These considerations are important in the training of horses destined to be elite athletes, but they can also be relevant for anyone raising or buying young horses or horses that were once young. If the young horse is “babied” it will not develop properly. If it is overfed, overprotected, and confined to a stall or small corral for much of the time, it will not develop properly. The young horse needs to be able to run, gallop, and play. It needs to be able to spend time with peers where they can fight and play and behave like horses. Not only will this result in normal psychological development, it will result in normal skeletal development. This sounds like common sense, but all too often it does not occur. Many foals, weanlings, and yearlings are kept in stalls or small corrals for much of the time. Often individuals destined for yearling sales spend several months leading up to the sale kept in stalls, overfed, separated from peers, and exercised on walkers or in other ways that promote muscle development but not optimal skeletal development. Management of young horses in this way will predispose them to injury and lameness in the future.

4. Navicular Disease
The dreaded “N” word is most certainly ingrained in the minds of horse owners, such that even mentioning it during an examination can bring tears to the eyes of some. This degenerative condition of the foot is also referred to as navicular syndrome, podotrochleosis, or caudal heel pain. In my experience, when there is more than one name for a disease it usually means that we don’t really know what is going on, and that has been the case with navicular disease. To some extent, this uncertainty is decreasing with improvements in diagnosis, research, and treatment.
Navicular disease is a chronic forelimb lameness associated with pain arising from the navicular bone and structures closely associated with it. It has historically been considered a single disease, but given the variety clinical presentations it is likely that there are a number of different conditions that give rise to pain in this area. The most important initial diagnostic test in making this diagnosis is the palmar digital (PD) nerve block. This test involves injecting a small amount of local anesthetic solution around the palmar digital nerves, which provide sensation to the back half of the foot. If the lameness is reduced following this procedure, it indicates that the source of pain and lameness is originating in the back half of the foot. In the past (and to some extent the present) this was the extent of the diagnostic work-up, and the horse was pronounced to have navicular disease. It is certainly not this simple, in fact it is anything but. Recent research is showing us that there are a variety of injuries and chronic degenerative processes that can be present in the navicular region, causing pain in this area. In a recent study, 199 horses that responded to a PD nerve block were examined. All of these horses had no visible abnormalities seen on radiographs of the foot. Magnetic resonance imaging (MRI) examinations of the feet were performed, which will show features of soft tissue as well as bone. Deep digital flexor (DDF) tendonitis was the most common injury (59%) with primary injury in 65 horses (33%) and a further 27 horses (14%) having lesions of the DDF tendon and the navicular bone. Seventeen percent of horses had injury to multiple structures. Desmitis of the collateral ligament (CL) of the coffin joint was the second most common injury (62 horses, 31%) with primary injuries in 30 horses (15%) and a further 32 horses (16%) that had CL desmitis in conjunction with other injuries. Seven horses simply had trauma to the short pastern bone and coffin bone (Dyson 2005). This study and other similar research using modern imaging techniques are revealing that navicular disease is in fact a variety of diseases or injuries. Using nuclear scintigraphy, we have been finding similar results with some horses having definite navicular bone abnormalities, some horses having soft tissue injuries, and many horses having a combination of both.

In the diagnosis of lameness, radiographs can be cost effective and highly diagnostic but can also be very misleading. Appropriate radiographic diagnosis requires high quality images and a high degree of knowledge and experience. In no area is this more true than in the diagnosis of navicular disease. There are countless examples where horses have obvious lameness in the navicular region and have normal radiographs, as well as horses that are sound and yet have obviously abnormal navicular bones. The recent introduction of digital radiography has helped improve the accuracy of diagnosis in this area, as digital radiographs tend to be of higher quality and show more detail than film images. A high quality series of radiographs is the second most important diagnostic procedure in the diagnosis of navicular disease, but these images must be properly made and interpreted. If the images appear normal, this does not rule out the diagnosis. If there is an obvious abnormality, this information is usually helpful in making the diagnosis. If the images show subtle or equivocal abnormalities, additional diagnostic testing is usually indicated.

How can this knowledge help treat these horses? Well, an accurate diagnosis is not always a necessity but is certainly an advantage in deciding how to treat a disease. If we can determine that a horse with heel pain actually has a collateral ligament injury and can find no significant evidence of degeneration of the navicular bone, then this horse should be treated with rest and has a reasonable chance of recovery. In this situation, attempts at keeping the horse in work with corrective shoeing and anti-inflammatory medications will probably not work and could exacerbate the injury. If we can determine that the horse actually has an abnormal, degenerate navicular bone then the prognosis for recovery with rest is poor and it makes sense to treat the horse with corrective shoeing and medications that may alleviate his pain and allow him to continue working. In the previously mentioned study, 71% of horses with trauma of the coffin or pastern and approximately 30% of horses with DDF tendon injury or CL desmitis recovered with appropriate rest. Horses with combination injuries where the navicular bone was involved or primary navicular bone abnormalities had a poor prognosis.

Navicular disease is a source of frustration for veterinarians and horse owners because it is difficult to treat. Often attempts at treatement have been palliative, masking the signs of the disease to allow the horse to continue working for a period of time. Many horses do not respond to treatment or only respond for a while. Many of these difficulties remain, but there have been some recent improvements or advances. More accurate diagnosis is helping identify which horses should be rested and which one will be unlikely to respond to rest. Improvements in foot care and modifications in trimming and shoeing is usually the starting point for treatment of all cases. For horses with inflammation of the navicular bone and coffin joint, periodic injection of the coffin joint with anti-inflammatory medication is often used. Injection of the navicular bursa is becoming a more frequent treatment. In cases where there is evidence that the abnormality involves the DDF tendon and the flexor surface of the navicular bone, treatment of this area specifically may yield good results where other treatments have not. In some cases, shock wave therapy has given temporary relief and has been useful as an adjunctive treatment. A relatively new treatment option is systemic administration of the drug tiludronate (Tildren). Tiludronate is one of a group of drugs called bisphosphonates, which are used in to treat people with metabolic bone diseases such as those associated with certain types of cancer. Bisphosphonates, such as tiludronate, are used to normalise bone metabolism via inhibition of bone resorption. Areas of increased bone resorption and formation are typical lesions in a diseased navicular bone. In a recent randomized, controlled, blinded study 73 horses with navicular disease were evaluated. Horses were categorized as recent (lame less than 6 months) or chronic cases. Some of the horses were treated with the drug, and some were treated with a placebo. When the horses were evaluated 2-6 months following treatment the horses in the treatment group showed significant improvement, with the horses with more recent lameness showing the best results. (Denoix 2003)

5. Nuclear Scintigraphy
Commonly referred to as a “bone scan”, nuclear scintigraphy is an exciting new imaging modality that provides a unique method of evaluating the musculoskeletal system. This technique has been in existence for over 10 years in veterinary schools and large equine hospitals in the United States. We began using this technique at our hospital 2 years ago. Scintigraphy is used to evaluate the musculoskeletal system for injury, using a radioactive marker called technetium99. At our clinic, we obtain the technetium99 from a local human hospital where they perform the same examinations on human patients. The technetium99 is administered to the horse and allowed to distribute into the skeleton, and after a few hours the horse is scanned with the gamma camera, a large radiation detector with an attached computer. The technetium99 will accumulate in the skeleton in higher levels in regions of increased bone remodeling activity, which can indicate areas of injury. The main difference between this technique and other imaging methods is that it will highlight the metabolic activity of bone, rather than the anatomy of the bone.
Nuclear scintigraphy is very useful for evaluation of injuries or lameness where the diagnosis has not been clear with other imaging methods, where the source of lameness can not be localized because it is high up the leg, where there is subtle lameness or reduced performance that can not be localized to any specific location, or where there may be multiple sources of pain or injury. It is also has the potential to be very useful for pre-or post-sale evaluation and for evaluation high performance equine athletes prior to periods of intense competition, as it can identify subtle signs of developing or potential injury. This procedure is routinely performed on human patients worldwide, and is safe and non-invasive. The technetium99 is a 3-4 cc intravenous injection, and the scan is performed with the horse standing and moderately sedated. The process takes approximately 4 hours for image acquisition, and 2-3 hours for image evaluation. The horse is kept in an isolation stall for 48 hours after isotope administration in order for the radioactivity to disappear, so the whole process requires a 3 day hospital stay.

Scintigraphy is highly sensitive, detecting subtle bone activity the signs of which would never be visible on an x-ray. Because of these differences, it can identify areas of injury that can not be visualized with x-rays or ultrasound due to location, or areas of injury where there is nothing to see because the damage has not resulted in an obvious physical chance such as a fracture, bone chip, spur, or bone proliferation. Examples of the types of injuries identified include stress fractures, pelvic injuries, spinal injuries, chronic ligament injuries, and arthritis with no visible radiographic evidence. In addition to identifying subtle lesions in the lower legs, it is the only imaging modality currently available that allows us to evaluate the entire spine of the horse because radiographs can not penetrate the wider portions of the horse’s body sufficiently. Scintigraphy does not replace other more traditional imaging methods - usually once an area of suspicion has been identified on the bone scan, additional imaging with x-rays or ultrasound is also performed in order to look for concurrent physical evidence.

7. Joint Therapies
In the pursuit of the wide variety of modern equestrian sports, horse owners ask their horses to perform athletic feats that can result in injury to their joints. Injury to cartilage, ligaments, the lining of the joint (synovial lining) and the bone underlying the cartilage results in joint inflammation. Joint injury and inflammation may lead to arthritis, which may be permanent and progressive. Traumatic arthritis is a common reason for reduced performance and lameness in the horse.

Once serious injury to a joint has occurred, complete healing of the injury is often not possible. Because of this, the goals of treatment typically consist of reducing the symptoms of the disease, slowing or stopping the progression of the disease process, and enhancing healing as much as possible. A variety of options are available to try and reduce the signs of arthritis and treat joint injury and disease including rest or alterations in training, various forms of physiotherapy, surgery, and administration of medications. Medications may be given intravenously, intramuscular, or intra-articular (injected directly into the joint). Joint injection is one of our most valuable options for the treatment of joint disease, but should be used appropriately.

I frequently hear horse owners and trainers use the term “maintenance” or “he just needs a little maintenance” when joint injection is discussed. I believe that the concept of “maintenance” is an over-simplification of a serious situation. Joint injection is not “maintenance”, it is the treatment of disease. If it is needed, it usually indicates that the horse has a problem, and by injecting the joint and keeping the horse in work it is possible that the problem will worsen in the long term. This may be an acceptable or necessary risk, but before this treatment is used horse owners should inform themselves about why the treatment is recommended, the types of medications that may be used and their effects, the long term prognosis, and potential adverse effects or side effects.

The two most commonly used medications for the treatment and/or prevention of arthritis are steroids and hyaluronate. Hyaluronate is essentially a large, complex sugar molecule. It is a naturally occurring substance which is synthesized by the lining of normal joints and found in the joint fluid and cartilage. It has important functions in the lubrication, nutrition, and maintenance of structures within the joint.
The exact mechanisms by which the hyaluronate injections benefit the arthritic joint are not yet fully understood. The description of the product acting as a lubricant, and that the purpose of treating a joint with hyaluronate is to improve lubrication is certainly an over-simplification. When it is injected into a joint or intravenously, it stimulates synovial cells within the joint to produce more hyaluronate, which may help to normalize the environment within the joint. Components of injected hyaluronate, and naturally produced hyaluronate are used for maintenance of joint cartilage. Probably the most important action of injected hyaluronate is its ability to reduce inflammation within the joint.
For the treatment of mild joint inflammation or as a preventative treatment, intravenous injection of 40 mg of hyaluronate is commonly used. The duration of benefit from such treatment is unknown, since it depends on the severity of the horse’s problems and the intensity of work. A commonly used program would be the treating the horse once every 8 weeks during the busy time of year, with timing of treatments to correspond to athletically demanding events. Typically the cost of intravenous treatment with brand-name hyaluronate product costs approximately $100-$150. Horse owners should beware of “generic” products, which are usually of unknown content, unknown concentration, untested, and of unknown efficacy and safety.

For the treatment of inflammation localized to a specific joint or for treatment of more severely affected cases, injection of the joint with hyaluronate alone or in combination with steroids is often used. Again, the duration of action is dependent on the severity of the condition and the intensity of the workload. In general, if the duration of benefit is less than approximately 6 weeks then I think alternatives should be considered. As a general rule, I choose to use hyaluronate or hyaluronate & steroid combination in “high motion joints” such as the fetlock, knee, or coffin joint as this is optimal for improving joint health and longevity. In “low motion” joints such as the small lower joints of the hock joint complex, I choose to use steroids alone as they are the most potent anti-inflammatory medications we have and are less expensive. Treatment of these joints with hyaluronate has not been shown to be more effective and adds to the cost of treatment. In addition, in treatment of these “low motion” joints enhanced longevity is not as much of a concern as simply reducing pain and discomfort.

The costs of joint injection vary depending on the number of injections and the concentrations of drugs used. A single joint injection with steroids may cost approximately $75, whereas injection of a large joint such as a stifle with a combination of 40 mg of hyaluronate, steroids, and antibiotics (to protect against infection) may cost approximately $300.

A common misconception is that medications such as glycosaminoglycan (Adequan) or hyaluronate are “good” for joints, and that steroids are “bad”. This is an over-simplification and is not correct. Certain steroids, such as those with medium strength and duration of action are beneficial for overall joint health in the inflamed joint. Other steroids, such as the strongest long-acting varieties, may be associated with accelerated joint degeneration when used repeatedly in horses that are asked for continued athletic effort. When a horse requires frequent joint injection in order to perform at the expected level, it is likely that continued joint degeneration will result in an eventual decrease in the effectiveness of the treatment. This result is a combination of factors including the medication, the disease process, and the stresses placed on the joint rather than the medication alone. Managing the horse so that joint injections are used judiciously rather than with abandon is a good policy for the horse owner and veterinarian to work towards.

Recently, products advertised as “oral” hyaluronate have become available. These products fall into the vast, unregulated and confusing circus of products called “nutraceuticals” or “supplements”, which are not bound by the same standards of testing for safety and efficacy as drugs. Many supplements lack quality research to support their use and show little to no efficacy in clinical trials. There is no current good research to suggest that oral administration of hyaluronate is effective for the treatment of joint disease in the horse. Given the fact that the hyaluronate molecule is an extremely large sugar molecule, I expect that when it is administered orally it is digested and broken down into simple sugars, rather than absorbed intact. Further research in this area is needed and will likely be forthcoming.

6. Joint Surgery
Joint surgery is an increasingly common aspect of modern equine veterinary medicine, and continued advances are being made. In the past, joint surgery usually involved cutting open the joint capsule (arthrotomy) to allow access to the interior, for the removal of bone chips or cartilage fragments or to access small fractures within the joint. This procedure usually resulted in significant damage to the joint, and resulted in pain, post-operative morbidity, and scar tissue formation which impaired future joint function. Approximately 20 years ago minimally invasive arthroscopic surgery began to replace arthrotomy. The use of arthroscopy allowed much better visualization and assessment of the interior of the joint, significantly less tissue trauma, decreased pain and morbidity, faster healing, and better post operative function. Techniques for arthroscopy have continued to advance, with improved equipment and application to virtually all joints of the limbs.
Although arthroscopy is most often used for situations where there is a known injury within a joint, it also has great usefulness as a diagnostic procedure. There are many situations where there is an injury within a joint which is not apparent on radiographs. We can localize the source of the lameness to a given joint but the diagnosis is not clear. The injury may be damage to cartilage, damage to ligaments within the joint, hidden fractures, or generalized joint inflammation. Arthroscopic exploration of the joint can often make a definitive diagnosis when imaging modalities can not.

A common situation that occurs in athletic horses, particularly racehorses, is that a joint injury is identified or suspected but is not promptly treated. Reasons for this may include incomplete diagnosis, desire to keep the horse in work, cost concerns, of fear that the horse will not recover well from surgery. In the majority of cases in which we are performing arthroscopic surgery, we are almost too late. Injured cartilage or damaged bone within the joint causes chronic inflammation, release of debris within the joint, production of degradative enzymes, scarring, pain, and joint degeneration. Injection of an injured joint with steroids in order to keep the horse in work can accelerate the process of joint degeneration. Performing arthroscopic surgery relatively soon after joint injury will have a much more successful outcome, can prolong the working lifespan of the horse, and may be the most cost-effective treatment option in the long term. A series of videos will be presented to illustrate these concepts.

8. Shock Wave Therapy
Shock wave therapy (SWT) is a relatively new treatment modality used for the treatment of various musculoskeletal injuries. This treatment is performed using a device that generated a low frequency, high amplitude, high energy pressure wave that is directed into the tissues using a handpiece. Despite what may be implied by the name, it does not involve an electrical shock. The energy created by the device is a pressure wave, similar in concept to a wave in the ocean. A wave in the ocean can travel long distances without dissipating, carrying potential energy. This energy is expended when the wave encounters something with a different density than water, such as the beach. The effect of this energy transmission can be mild or tremendous depending on the size (amplitude) and energy of the wave. Shock wave therapy devices create a high amplitude waveforms which are directed into the body to deliver their energy at a targeted location. There are essentially two categories of devices. One type creates an impulse that radiates outwards from the handpiece, spreading out into the tissues. This type of treatment is most correctly referred to as “radial pulse pressure therapy” or RPPT. The other type of device creates an impulse that converges towards a focal point within the tissues, concentrating its energy release at that point. This type of treatment is properly referred to as “focused shock wave therapy” or FSWT. Consumers should have an awareness that there are different types of SWT and why their veterinarian may recommend a certain type.

How does shock therapy work? The short answer to this question is “we don’t really know!”. The technique was originally developed for the treatment of people with bladder or kidney stones. In order to treat a person, the device was carefully positioned against the skin aiming at the stone within the body. The device was activated, and as the waves passed through the soft tissues (which are mostly water) to the stone, the energy of the wave was released against the stone like a wave crashing on the beach. This would cause the stone to fragment into pieces, allowing it to be passed in the urine and eliminating the need for surgery. As this treatment became routine, other tissue effects were noted such as improvements in tissue healing. Further research was performed, leading to the application of shock wave therapy for treatment of various musculoskeletal injuries in humans such as tennis elbow (epicondylitis), plantar fascitis of the foot, and shoulder tendonitis. It has been used for these and other similar chronic injuries in humans for approximately 10 years, primarily in Europe. Based on a variety of experimental studies conducted in animals and humans, it seems that SWT has several effects. It seems to relieve pain, perhaps by affecting nerve conduction. It seems to decrease inflammation by increasing the production of the body’s own anti-inflammatory chemical mediators. It seems to improve healing by inducing the increased development of new blood vessels in the area of injury. One of the must recent areas of research in the human field is the use of FSWT for the treatment if impaired blood flow in the heart muscle due to coronary artery disease. Preliminary results have shown that following a course of relatively mild, non-invasive treatment patients had decreased symptoms, improved heart muscle blood flow, increased development of new blood vessels in the heart muscle, and decreased need for medication. (Fukumoto 2006). In the horse, recent work has shown that SWT improves healing of injured tendons by increasing new blood vessel growth and improving circulation (Kersh 2006).
We are still learning how to use shock wave therapy appropriately in our equine patients. The most important requirement for success with this technique is an accurate diagnosis. If we do not really know the nature of the injury or where it is, it is unlikely that we will be successful in treating it. The shock wave therapy impulses are only effective in a very small area, and therefore we need to know the location of the injury in order to treat it. Based on our own experiences and published reports of others it can be appropriate for treatment of suspensory ligament injuries, flexor tendon injuries, certain types of arthritis, certain joint injuries, collateral ligament injuries in the foot, and some back problems. In general, it is most appropriately used for chronic injuries. In most cases we will treat the horse 3 or 4 times at approximately 2 week intervals and then assess the response.

9. “Regenerative Medicine”
The concept of “regenerative medicine” is a relatively new, and holds promise as a new frontier for the treatment of many ailments. Along with this promise comes interest, excitement, and the potential for exaggeration and misinformation. Perhaps the most important point to realize about this topic is at this time the currently available treatments are all relatively un-proven and should be considered experimental.

When tissue is injured, it heals or tries to heal using various types of tissue repair such as the formation of granulation tissue, the growth of new blood vessels, and the formation of scar tissue. This normal tissue healing can be called reparative healing. Regenerative healing involves replacement or restoration of the damaged tissue with new tissue that has the same physical and functional characteristics as the original. Bone is naturally capable of regenerative healing; it heals by forming new bone which is ultimately remodeled and adapted to its environment such that it becomes the same as the original. Other tissues are not so capable. Regenerative medicine involves manipulating tissue or biological components of tissue during the healing process with the goal of regenerating the injured tissue to its pre-injury state, or as close as possible.

Many musculoskeletal injuries result in poor functional repair which predispose horses to ongoing lameness or significant risk of re-injury. Damage to cartilage heals poorly, and damage to tendons and ligaments often heals by the development of scar tissue which is not as strong as the original tendon. There is currently much interest in the use “tissue engineering” treatment methods to avoid these adverse consequences. These strategies involve one or more of the following approaches (a) a scaffold, (b) growth factors, and/or (c) a cell source.

The biological scaffold concept involves adding non-cellular tissue components to an area of injury that will facilitate the growth of more organized, more functional, more “normal” tissue. “A-cell” is a commercial preparation of collagen derived from porcine tissue. It is purified and processed into sheets or a powder. In theory, when this material is placed into injured tissue it provides a scaffold for new cells to move into the site of injury more rapidly and in a more organized manner that they would on their own. This should diminish the development of excessive scar tissue and accelerate the healing process. We have used this product for the treatment of injured tendons and ligaments with some apparent success, although long-term follow-up is lacking.

The growth factor concept involves adding biological chemical messengers to injured tissue to stimulate improved healing responses. These factors include proteins, hormones and other substances that occur naturally in the body. All body and cell functions are orchestrated by a symphony of such chemicals, some of which we are coming to recognize and understand. One example of this concept was previously described, the use of IRAP for the treatment of joint inflammation. Another example is the use of concentrated blood plasma for the treatment of injured tissues. Blood taken from the horse is processed to create a concentrated sample containing growth factors (platelet rich plasma or PRP). This is then placed into sites of tissue injury, theoretically resulting in desirable effects such as increased cell migration or division, increased development of new circulation, decreased scar tissue formation, and more rapid or complete healing.

The cell source concept involves adding new living cells to an area of injury, and today the focus is on stem cells. For several years now stem cells and stem cell research has been the focus of reports in the news media, and for good reason. The potential use of stem cells for the treatment of injury and disease holds great promise for human and veterinary medicine because, in theory at least, such treatment could truly be regenerative. Current research is investigating stem cell therapies for repair of heart muscle damaged after heart attack, paralysis due to spinal cord trauma, brain injury due to neurodegenerative disease such as Parkinsons, and a wide range of other afflictions.
So what is a stem cell and what makes it so special? When an embryo is developing, it is initially just a ball of cells that repeatedly divide, resulting in the growth of the ball. Initially all of the cells appear the same, and do not appear to have specific features or functions. Once a certain size is reached, some of the cells begin to differentiate into tissue types, such as those that will form the nervous system or those that will form the musculoskeletal system. This process of differentiation is a key concept. As growth and differentiation occurs, the embryo becomes a fetus with recognizable physical components such as a body, a heart, an eye, etc. This process continues to birth and beyond, so that eventually most of the cells forming the individual are differentiated and have specific functions such as nerve cells, muscle cells, skin cells, and almost all the cells making up the body - almost all the cells. Within the body, some cells remain in an undifferentiated state and these are called stem cells. They are undifferentiated, and retain the magical capability of differentiation. In the right environment, they can transform into muscle cells, nerve cells or any other cell type that might be appropriate. We are now developing the capability of finding these cells, culturing them, and using them for treatment if disease. Stem cells can be obtained from embryos, but in human medicine at least this procedure has met with ethical and political obstacles. Stem cells can also be found in the tissues of the adult body, such as the bone marrow, fat tissue, peripheral blood, and others. In theory, these cells could be isolated, cultured, and implanted back into the body to help treat injury or disease. However, reality is not usually as simple as theory and much work still needs to be done before such theoretical treatments become reality.

In equine veterinary medicine, there are currently two examples of “stem cell therapy” that are being used clinically. Neither one is really what it claims to be, and good research showing their benefits is lacking. One of these treatments is the use of autogenous bone marrow transplants and the other is the use of cells derived from fat tissues (a commercial preparation from a company called “Vet Stem”).

Autogenous (meaning from the self) bone marrow transfer has been used for the treatment of equine tendon and ligament injuries as well as enhancing fracture healing. In the treatment of tendon and ligament injuries, the process involves harvesting liquid bone marrow from the sternum and injecting it into the region of injury. The injected product is primarily blood and the cellular components of bone marrow, a few of which are stem cells. To suggest that it is the small population of stem cells that are resulting in any benefit is a leap of imagination, but it appears that there may be some benefit to the procedure. The stem cell concentration in equine bone marrow is approximately 1 in 5000 to 1 in 10,000 cells (Vidal 2006) If there are approximately 5,000 000 total cells per ml of bone marrow, this means that there are approximately 500 stem cells/ml. In experimental stem cell studies, 10 to 70 million stem cells were used for effective tissue repair (Muschler 2002). This means that using pure bone marrow in this way would require 20 liters of bone marrow to obtain a significant stem cell population, not a practical technique. Despite this apparent limitation, this technique may still have merit. In one report, 100 horses were treated for suspensory ligament injury using autogenous bone marrow injections (20-30 ml). After 6 months, 84% were sound and had returned to full work (Herthel 2003). These results are superior to horses treated with rest alone, which typically have a 15-70 % chance of returning to soundness depending on the severity of injury.

The use of fat derived stem cells for the treatment of injury is another method currently in use. This technique involves harvesting a sample of fat tissue from the horse, which is then separated into cellular and non-cellular portions. The cellular portion is then injected into the site of injury in tendon, ligament, or joint. This cellular fraction is composed of all the nucleated cell components of the tissue sample, of which about 1 in 100 is thought to be a stem cell (Dahlgen 2006). Using this technique, approximately 5 – 10 million cells are obtained of which approximately 50,000 – 100 000 should be stem cells, approximately 10 times that obtained with bone marrow. This stem cell fraction is still far below those shown to be necessary in experimental studies. Reported results from uncontrolled studies on the treatment of tendon and ligament injury with this method claim 70% return to performance (Dahlgren 2006). These results require substantiation with additional studies.
The idea of regenerative medicine is exciting and holds great promise. This novelty and excitement has led to the rapid establishment of treatment techniques and commercial products. Veterinarians and horse owners should be aware of these developments and consider these treatments when the need arises, but should use caution when accepting unrealistic claims and should investigate the facts before expecting miracles.

10. Veterinarian Specialization.
Perhaps one of the most significant changes that is occurring in equine veterinary medicine is the development of veterinary specialty training and the increasing availability of specialists. Many horse owners have been used to having a familiar, regular veterinarian that has served them and their horses well and was expected to handle all aspects of their horse’s care. This model has worked well, particularly in more rural areas where even finding an equine veterinarian can be difficult. However, modern veterinary medicine progresses at an astonishing pace, and is becoming increasingly complex. The volume and complexity of veterinary medical knowledge now available is such that veterinary schools are moving to “stream” students into large animal or small animal disciplines so that they have some hope of obtaining a working level of basic knowledge by the time they graduate. Horse owners are demanding an ever increasing level of service from veterinarians, from management of complex medical problems for geriatric patients to embryo transfer to surgical repair of broken legs to complex diagnostic imaging such as advanced diagnostic ultrasonography and medical resonance imaging (MRI). It is simply not possible for any one veterinarian to have a high degree of knowledge in all areas. Veterinarian specialization is providing horse owners with the ability to access cutting-edge treatments for their horses if they seek it.

Veterinarian are required to hold a license to practice in the province in which they work, and are subject to the bylaws and regulations of their professional organization. One of the bylaws states that no veterinarian can claim to be a specialist unless they have advanced specialty training. Veterinarians obtain specialty training by completing a residency in their chosen specialty and then passing the specialty board examinations. A residency program usually involves 4 to 5 years of additional study ending with a challenging series of examinations. Once the candidate has completed the residency training and passed their examinations they are “board certified” and have earned the right to be called a specialist. There are currently a variety of specialty boards, including the American College of Veterinary Internal Medicine (ACVIM), the American College of Surgery (ACVS), the American College of Veterinary Opthalmology (ACVO), the American College of Theriogenology (ACT – specialty in reproduction), the American College of Veterinary Radiology (ACVR), the American College of Veterinary Dentistry (ACVD), and many others. Specialists are not the ideal veterinarians for the provision of most regular veterinary services. A long term relationship with a good general practitioner is invaluable, as this person can be relied upon for routine health care and will be there in times of need. In situations where a horse has a condition that its regular veterinarian may be uncomfortable treating, unfamiliar with, or lacks the resources and equipment to treat, referral to a specialist may be a good option. In the last 5 years there has been an exponential increase in the number of board certified equine specialists practicing in Alberta, which should benefit referring practitioners, horse owners, and most importantly our horses.

References:
Dahlgren et al. Use of adipose-derived stem cells in tendon and ligament injuries. Proc Am Coll Vet Surg. 2006. 151-153.
Denoix et al. Tiludronate as a new therapeutic agent in the treatment of navicular disease: a double-blind placebo-controlled clinical trial. Equine Vet J. (2003) 35 (4) 407-413.
Dyson et al. Lameness associated with foot pain: results of magnetic resonance imaging in 199 horses (January 2001 – December 2004) and response to treatment. Equine Vet J. (2005) 37 (2) 113-121.

Fukumoto et al. Extracorporeal cardiac shock wave therapy ameliorates myocardial ischemia in patients with severe coronary artery disease. Coronary Art Dis. 2006 Feb;17(1):63-70.

Herthel. Diagnosis and Management of Lameness in the Horse. Saunders 2003. p 674

Kersh et al. The evaluation of extracorporeal shock wave therapy on collagenase induced superficial digital flexor tendonitis. Vet Comp Orthop Traumatol. 2006;19(2):99-105.
Lanyon et al. Static vs dynamic loads as an influence on bone remodeling. J Biomech 1984; 17(12): 897-905.
Muschler et al. Connective tissue progenitors: practical concepts for clinical applications. Clin Orthop Relat Res 66-80, 2002.

Vidal et al. Cell growth characteristics and differentiation frequency of adherent equine bone marrow-derived mesenchymal stroma cells: adipogenic and osteogenic capacity. Vet Surg 2006 35 (7) 601-610.

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