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World experts discuss tendons and ligaments
DUBAX ZNqFERNAT?X9
BQUXNE SYMP 9 Dr. Michael Hauser (right) with Dr. Dan Hawkins (left).
WORLD EXPERTS DISCUSS TENDONS AND LIGAMENTS
some problems experienced by his racehorses. Sheikh Mohammed has spared no expense in his quest for world recognition for Dubai as a horse racing center. He hired people to work with veterinary officials of every major racing country to set up conditions in Dubai so that horses can be quickly and easily imported and exported for racing purposes. This made it possible for the Dubai World Cup winner, Cigar, to be shipped into Dubai a few days before the big race and then back home shortly afterwards. Cigar won $2.4 million in
William E. Jones, DVM, PhD
On March 27, 1996, several hundred of the world's leading veterinary experts on equine tendons and ligaments met in a very unorthodox setting to discuss their favorite subjects. Prominent racetrack veterinarians from Kentucky to South Africa, as well as university professors and researchers, converged on Dubai, one of the United Arab Emirates (UAE) for a meeting called by His H i g h n e s s Sheikh Maktoum bin Rashid A1 Maktoum, ruler of Dubai. I was extremely happy to be one of those in attendance. The unusual meeting was conducted under the guidance of His Highness General Sheikh Mohammed bin Rashid A1 Maktoum, Minister of Defense of the UAE and Crown Prince of Dubai, no stranger to Thoroughbred horse people, and an avid owner of some of the best racehorses and the most lavish stud farms anywhere. These men were the organizers of the Dubai World Gold Cup Race held during this veterinary conference at Nad al Sheba Racecourse, in Dubai. To make Dubai a world-class racing center has been a long-time goal of Sheikh Mohammed, who likes to be involved in the details of his equine endeavors.
148
He hires the best people he can find, but he wants to be involved. In fact, he was the one who decided the First Dubai International Equine Symposium should be on the subject of tendon, ligament and soft tissue injuries. He knew from personal experience that these were the most trouble-
Dinner at the Dubai World Gold Cup Race. (left to right) Dr. Ron Genovese, Dr. Bill Moyer and John Porter.
JOURNAL OF EQUINE VETERINARY SCIENCE
that race, and his trainer knew it was well worth the trip. The A1 Quoz Stables, near Nad al Sheba, is a part of Sheikh Mohammed' s plan to bring world-class racing to Dubai. It sets standards that even Kentucky and Ireland can look up to. It has the best equipment and facilities anywhere. To top it off, Sheikh Mohammed has built a $15 million veterinary hospital nearby which is more lavish than any in the world. It has the very latest equipment and is staffed by the most professional people that could be found. The hospital is run b y Michael L. Hauser, DVM. Chief surgeon is Carlos C. Cervantes, DVM. The Dubai International Equine Symposium was organized and conducted by Dr. Norman Rantanen, under the direction of Dr. Hauser. Dr. Rantanen is world renowned for his expertise in veterinary diagnostic ultrasound, he has examined the best horses around the world and has been a mentor for many of the veterinarians who treat the tendons and ligaments of the greatest racehorses in the world. Drs. Hauser and Rantanen worked together in a practice in Lexington, Kentucky, a few years ago. Sheikh Mohammed opened the Symposium with words of encouragement to the assembled clinicians, researchers and delegates, expressing his .desire to help improve the status of veterinary care for racehorses and specifically the diagnosis and treatment of tendon and ligament injuries. He announced that the Symposium would be held again next year, on the subject of the respiratory system and its pathologies as found in the racehorse. Dr. Julie Wilson set the stage for the discussion about racehorse tendon, ligament and soft tissue injuries on the track, using data from three sources: 1) injury reports from racing regulatory veterinariansm The Racing Injury Reporting System; 2) the Illinois Racing Board database; and 3) the Canterbury Downs (Minnesota) database. She
Volume 16, Number 4, 1996
showed that the most common type of Thoroughbred racetrack injury was bowed, rebowed or ruptured tendon occurring, on dirt tracks, at a frequency of 0.941 per 1000 starts, 0.580 on turf. She pointed out that scrutiny of databases of racing injuries suggest that many factors may play a role in the etiology of these injuries, and that there are distinct differences in the frequency of injuries between racetracks. She said, "Soft tissue injuries are overshadowed by fractures in racing Quarter horses and are much less frequent in Standardbreds." While many experts were there to teach and enlighten, the highlight of the Symposium, in my opinion, was the p r e s e n t a t i o n s of Dr. R o n a l d L. Genovese, who is known as the tendiniris guru of the veterinary profession. Originally learning to use diagnostic ultrasound from Dr. Rantanen, Dr. Genovese went on to develop a system of sonographic evaluation of tendon damage and repair during the healing phase. He has been involved with Dr. Virginia Reef in a study of a promising new drug for the healing of tendon injuries in racehorses. Together, they have developed an intricate procedure for treating and monitoring injured tend o n s - - a system, still being refined, which promises to save the careers of many racehorses when owners and trainers have the patience to follow their recommendations. Dr. Reef described the trials which showed the drug, beta-aminoproprionitrile fumarate (BAP-F), to bring about quicker, stronger healing of tendons, when used with the appropriate exercise regimen. Dr. Genovese has been looking at ter/dons with ultrasound for the past decade, and has saved most of the images. Although he has a busy racetrack practice, he has taken time over the years to carefully study these tendon images before, during and after the healing process. He has compared the tendon images of those horses that went on to successfully race and those that
suffered re-injury of the tendon. Through careful measurements and analyses of the injured areas in tendons, and by comparing changes over time, Dr. Genovese has learned to assess the strength of an injured tendon with some degree of accuracy. He feels that the more quantitative he can become in his assessment of tendon damage, the more successful he will be in prognosis. Injuries to the Superficial digital flexor tendon are the most common type of "bowed tendon." The tendon has long microscopic strands of collagen running parallel to the cannon bone. This collagen has a certain amount of crimping so that it can stretch when the horse sustains a heavy force during weight bearing at fast speeds. Continual heavy stretching, which occurs during the training and racing of every horse, eventually takes much of the crimp out of the collagen, and then it begins to pull apart. In the very early stages of tendon damage, Dr. Genovese explained, there is some capillary damage so that edema begins to accumulate in the tendon. This causes a slight enlargement in the diameter of the tendon which can be detected with careful study of a sonogram. This is done by capturing the ultrasound image on a computer screen and drawing a line around the outer edge of the tendon with a computerized marking device. Computer programs are available which will quickly calculate the area within the drawn circle. This area is then compared to the area of the opposite (normal) tendon, at the same level. This means that both tendons should be examined with ultrasound in a thorough examination. Dr. Genovese has found that it is important to get images from 7 regions, or zones, of the tendon from the accessory carpal bone to the fetlock, some 25 to 27 centimeters. The tendon is first divided into three major zones (1, 2, and 3) from proximal to distal. Zones 1 and 2 are each divided into a and b, and zone 3 is divided into a, b and c. This allows determination of the
149
length as well as the width of the tendon lesion, or the total extent of the swelling. While it is possible to see the tendon image on cross-section, the true severity of the injury is confirmed on longitudinal view and scored for future reference. In this view, the disarray of the collagen fibers can be observed. As healing progresses, the strength of the repaired tendon can be assessed by determining the extent of fiber alignment, over time, in the injury zone. The formation of new collagen will occur in all tendon injuries over time, but the simple addition of more collagen does not improve tendon strength of itself. Tendon strength comes from the alignment of the fibers in the direction of the force applied to it. The strongest healed tendon is the one with the new fibers aligned parallel to the cannon bone, as in the normal tendon. Research has shown that the proper alignment of these fibers occurs when stretching of the tendon occurs. This emphasizes the importance of controlled exercise during tendon healing. One of the problems in tendon healing is that as collagen fibers are produced by the cells in the tissue, they are rapidly cross-linked in a position which may not be parallel to the cannon bone. Once cross-linking has occurred, it is a long, difficult process to regain the former alignment which provides the most strength. This is the place where the new drug is helpful. BAPN is injected into the tendon in the injured area. This drug interferes with crosslinking of the fibers during their healing, allowing them to align themselves with the forces brought about by controlled exercise. Once the fibers are aligned, and the effects of BAPN wear off, cross-linking occurs between the fibers, adding the strength needed to avoid re-injury. The new drug is not yet on the market, but it is hoped that it may be available sometime next year. Drs. Genovese and Reef have developed their tendon rehabilitation program around the concept of controlled
150
exercise during healing. They recognize from the outset that the success of their rehabilitation depends on the cooperation of the trainer and the horse. Some trainers will eventually tire of the wait and go back to their old methods of handling bowed tendons, and push too much exercise too soon to the horse. Sometimes the horse cannot be controlled enough to limit the exercise to an appropriate level. For example, the amount of strain an excitable, energetic horse puts on a tendon while being hand walked may be quite a bit more than a quiet horse being hand walked. The amount of tendon strain during healing is critical. It must be enough to stimulate proper alignment of the fibers, but not enough to tear the delicate new fibers. In fact, the appropriate exercise is so critical during rehabilitation that Drs. Genovese and Reef have defined 7 exercise levels which their patients should progress through over the course of healing. A zero level would be stall rest. This is where therapy for most horses with tendon injuries begins. The first exercise level (EL-l) is hand walking, walking on a mechanical walker or treadmill walking. The type of exercise in the second level (EL-2) includes swimming, ponying, light lunging at the trot or trotting under saddle for no more than 5 to 10 minutes.Exercise at this level for the Standardbred would be walking (only) in a jog cart. Surprisingly, turning a horse out in the paddock provides a relatively heavy amount of exercise, and is considered level three (EL-3) in this rehabilitation program. The temperament of the horse should be carefully considered before allowing free paddock exercise, according to Dr. Genovese. The next step up (EL-4) involves hacking (walk, trot, canter) for 15-20 minutes, 3 days per week. The return to race training (galloping) is considered to be the next level (EL-5). Breezing is the next level (EL6), and the final level (EL-7) represents maximum athletic activity for all breeds.
Dr. Genovese explained the most critical aspect of their rehabilitation program, "It is important in the management of tendon healing to relate sonographic changes with the exercise level of the horse. The injured tendon may be healing as expected, but if the exercise level recommended, or in place, is too excessive, there will be a greater risk of relapse. Therefore, any sonographic evaluation must be correlated to the exercise level the horse is performing at the time of examination." The healing rate of each tendon injury is a little different from all others. It is impossible to set a time frame for healing and progressively increasing exercise level that is appropriate in all cases, according to Dr. Genovese. This is why he has developed a system of measuring the healing progress quantitatively. In addition to measuring the cross-sectional area of the lesion and the total lesion volume, Dr. Genovese uses a fiber alignment grading system, giving every lesion a score of 0-3, with 3 having the lowest percent of aligned fibers, or the greatest amount of damage. He also finds it useful to calculate the sum of the cross-sectional areas of th'e tendon in all zones, along with calculation of the cross-sectional area of the injured portion of the tendon. This allows ca!Culation of the total percent of hypoechoic fiber tracts (injured tissue). He dubs this "%T-HYP." The initial ultrasound examination becomes the baseline by which subsequent healing is measured. "The %THYP must show significant improvement from the baseline, and for maximum chance of success should be equal to or less than 10%," Dr. Genovese said. "Horses with tendon injuries that are slight might only reduce from a 5% or 6% to a 2% or 3% for example. In this instance, this level of reduction is an acceptable evaluation. More extensive tendon injuries will have a relatively greater reduction, but for optimal chance of success, should be reduced to the 10% range."
JOURNAL OF EQUINE VETERINARY SCIENCE
Others who evaluate a lot of tendons, especially surgeons, often place less emphasis on the percent of h)~poechoic area, believing that the size of the h y p o e c h o i c lesion in the sonogram may not accurately reflect the amount of damaged fiber tracts. For example, an initial blood clot in the tendon may take up more than 10% of the cross-sectional area in the principal zone of injury, but after tendon splitting surgery-- where the blood and debris is removed-- the hypoechoic area becomes significantly smaller, and the percent of hypoechoic area is much less. In this case, the sonographic difference may be significant, but the actual number of injured fiber tracts has not really changed. The rehabilitation involves at least three critical ultrasound evaluations. The first, of course, is to measure and define the baseline injury. The second is to evaluate the extent of healing prior to advancing to level 3 exercise, where paddock freedom often results in a rebow. Generally this second examination takes place 16 weeks after injury. The third ultrasound examination usually takes place just prior to putting the horse back into training. Dr. Genovese' s studies have shown that there must be at least a 50% improvement from the baseline evaluation before exercise level 5 (light training) begins. "The fourth critical sonographic evaluation time of tendon injury management is actually a group of examinations and are referred to as 'in training sonographic monitoring,'" Dr. Genovese explained. "These evaluations are made preceding EL changes at the training level, such as advancement from EL-5 to EL-6, and preceding advancement to EL-7. Once racing starts, frequent sonographic monitoring between races, especially between the first 4 or 5 races, can provide data to determine tendon sonographic stability or instability." Most racetrack practitioners attending the symposium were impressed with
Volume 16, Number 4, 1996
the Genovese/Reef system of evaluation of tendon injuries and the use of it in rehabilitation. It will take a long time to educate the majority of trainers to the benefits of such a system, but I believe that eventually the standard for tendon rehabilitation will center around a system of tendon injury quantitation similar to that discussed at this Symposiu~n. Dr. Larry Bramlage discussed the surgical remedies available for bowed tendons, specifically tendon splitting and superior check ligament desmotomy. He feels that both surgeries are indicated in many cases, and they help to improve the prognosis for eventual return to racing. While Drs. Milos Chvapil and William M. Davis explained the histologic details of tendon healing, and provided considerable hope that the new drug Bapten will augment the healing process, Dr. Roy Pool presented a rather pessimistic picture of what occurs after severe tendon rupture. In his opinion, while scar tissue can fill the experimentally-created gap or the core lesion o f spontaneously occurring tendinitis and while scar tissue can remodel and mimic the architecture, it probably never reclaims the original mechanical properties. He was also pessimistic about the helpfulness of tendon splitting surgery. Other types of soft tissue injury were discussed. Dr. Leo Jeffcott brought some new information about the diagnosis and management of back problems.He emphasized that diagnosis of back problems is notoriously difficult and always requires a thorough and systematic examination. Dr. Bill Moyer discussed soft tissue injuries of the foot, emphasizing that precise diagnosis and assessment of damage can be difficult because the affected tissues are often obscured from view via their position in a horny capsule. The correction of problems usually requires attempts at altering the causative factors, reducing inflammation and pain, and providing support
with correct or corrective shoeing. Dr. Dan Hawkins captivated the audience with his discussion of the physical examination of the musculoskeletal system. He said that the diagnostic aids and technical procedures that greatly assist diagnosis are diagnostic regional nerve and intra-articular blocks, radiography, ultrasonography, scintigraphy, and locomotion analysis. These ancillary diagnostic aids confirm and expand information obtained by physical examination and clinical history. The combined information contributes to an accurate diagnosis and an effective therapeutic plan. Diagnosis was the major emphasis of the Symposium, with treatment taking a decided back seat. This was probably because most of the new developments have recently come in the area of diagnosis. Dr. Norman Rantanen captivated the audience with his explanations of the principles of magnetic resonance, computed tomographic, ultrasonographic and scintigraphic imaging of the soft tissues of the horse. The newest technique on the horizon for veterinary diagnostics is magnetic resonance imaging(MRI). "Because MRI provides diagnostic information regarding soft tissue and bone, it has potential value in examining the tendons and ligament s of the horse," he said. There is technology being developed to allow using a small remote magnet for MRI imaging by MAGNEVU, a California-based company. This technology differs from the standard MRI scanning in that a small magnet is used to oppose the tissues in standing, tranquilized horses. The system is very portable and makes for ideal equine imaging. Dr. Tracy Turner seemed to convince the entire group that thermography definitely has a place in diagnosis of soft tissue problems of the horse. He also e f f e c t i v e l y illustrated how scintigraphy can be used to diagnose specific types of soft tissue problems.
151
BQUXNE SYMP 9 Dr. Michael Hauser (right) with Dr. Dan Hawkins (left).
WORLD EXPERTS DISCUSS TENDONS AND LIGAMENTS
some problems experienced by his racehorses. Sheikh Mohammed has spared no expense in his quest for world recognition for Dubai as a horse racing center. He hired people to work with veterinary officials of every major racing country to set up conditions in Dubai so that horses can be quickly and easily imported and exported for racing purposes. This made it possible for the Dubai World Cup winner, Cigar, to be shipped into Dubai a few days before the big race and then back home shortly afterwards. Cigar won $2.4 million in
William E. Jones, DVM, PhD
On March 27, 1996, several hundred of the world's leading veterinary experts on equine tendons and ligaments met in a very unorthodox setting to discuss their favorite subjects. Prominent racetrack veterinarians from Kentucky to South Africa, as well as university professors and researchers, converged on Dubai, one of the United Arab Emirates (UAE) for a meeting called by His H i g h n e s s Sheikh Maktoum bin Rashid A1 Maktoum, ruler of Dubai. I was extremely happy to be one of those in attendance. The unusual meeting was conducted under the guidance of His Highness General Sheikh Mohammed bin Rashid A1 Maktoum, Minister of Defense of the UAE and Crown Prince of Dubai, no stranger to Thoroughbred horse people, and an avid owner of some of the best racehorses and the most lavish stud farms anywhere. These men were the organizers of the Dubai World Gold Cup Race held during this veterinary conference at Nad al Sheba Racecourse, in Dubai. To make Dubai a world-class racing center has been a long-time goal of Sheikh Mohammed, who likes to be involved in the details of his equine endeavors.
148
He hires the best people he can find, but he wants to be involved. In fact, he was the one who decided the First Dubai International Equine Symposium should be on the subject of tendon, ligament and soft tissue injuries. He knew from personal experience that these were the most trouble-
Dinner at the Dubai World Gold Cup Race. (left to right) Dr. Ron Genovese, Dr. Bill Moyer and John Porter.
JOURNAL OF EQUINE VETERINARY SCIENCE
that race, and his trainer knew it was well worth the trip. The A1 Quoz Stables, near Nad al Sheba, is a part of Sheikh Mohammed' s plan to bring world-class racing to Dubai. It sets standards that even Kentucky and Ireland can look up to. It has the best equipment and facilities anywhere. To top it off, Sheikh Mohammed has built a $15 million veterinary hospital nearby which is more lavish than any in the world. It has the very latest equipment and is staffed by the most professional people that could be found. The hospital is run b y Michael L. Hauser, DVM. Chief surgeon is Carlos C. Cervantes, DVM. The Dubai International Equine Symposium was organized and conducted by Dr. Norman Rantanen, under the direction of Dr. Hauser. Dr. Rantanen is world renowned for his expertise in veterinary diagnostic ultrasound, he has examined the best horses around the world and has been a mentor for many of the veterinarians who treat the tendons and ligaments of the greatest racehorses in the world. Drs. Hauser and Rantanen worked together in a practice in Lexington, Kentucky, a few years ago. Sheikh Mohammed opened the Symposium with words of encouragement to the assembled clinicians, researchers and delegates, expressing his .desire to help improve the status of veterinary care for racehorses and specifically the diagnosis and treatment of tendon and ligament injuries. He announced that the Symposium would be held again next year, on the subject of the respiratory system and its pathologies as found in the racehorse. Dr. Julie Wilson set the stage for the discussion about racehorse tendon, ligament and soft tissue injuries on the track, using data from three sources: 1) injury reports from racing regulatory veterinariansm The Racing Injury Reporting System; 2) the Illinois Racing Board database; and 3) the Canterbury Downs (Minnesota) database. She
Volume 16, Number 4, 1996
showed that the most common type of Thoroughbred racetrack injury was bowed, rebowed or ruptured tendon occurring, on dirt tracks, at a frequency of 0.941 per 1000 starts, 0.580 on turf. She pointed out that scrutiny of databases of racing injuries suggest that many factors may play a role in the etiology of these injuries, and that there are distinct differences in the frequency of injuries between racetracks. She said, "Soft tissue injuries are overshadowed by fractures in racing Quarter horses and are much less frequent in Standardbreds." While many experts were there to teach and enlighten, the highlight of the Symposium, in my opinion, was the p r e s e n t a t i o n s of Dr. R o n a l d L. Genovese, who is known as the tendiniris guru of the veterinary profession. Originally learning to use diagnostic ultrasound from Dr. Rantanen, Dr. Genovese went on to develop a system of sonographic evaluation of tendon damage and repair during the healing phase. He has been involved with Dr. Virginia Reef in a study of a promising new drug for the healing of tendon injuries in racehorses. Together, they have developed an intricate procedure for treating and monitoring injured tend o n s - - a system, still being refined, which promises to save the careers of many racehorses when owners and trainers have the patience to follow their recommendations. Dr. Reef described the trials which showed the drug, beta-aminoproprionitrile fumarate (BAP-F), to bring about quicker, stronger healing of tendons, when used with the appropriate exercise regimen. Dr. Genovese has been looking at ter/dons with ultrasound for the past decade, and has saved most of the images. Although he has a busy racetrack practice, he has taken time over the years to carefully study these tendon images before, during and after the healing process. He has compared the tendon images of those horses that went on to successfully race and those that
suffered re-injury of the tendon. Through careful measurements and analyses of the injured areas in tendons, and by comparing changes over time, Dr. Genovese has learned to assess the strength of an injured tendon with some degree of accuracy. He feels that the more quantitative he can become in his assessment of tendon damage, the more successful he will be in prognosis. Injuries to the Superficial digital flexor tendon are the most common type of "bowed tendon." The tendon has long microscopic strands of collagen running parallel to the cannon bone. This collagen has a certain amount of crimping so that it can stretch when the horse sustains a heavy force during weight bearing at fast speeds. Continual heavy stretching, which occurs during the training and racing of every horse, eventually takes much of the crimp out of the collagen, and then it begins to pull apart. In the very early stages of tendon damage, Dr. Genovese explained, there is some capillary damage so that edema begins to accumulate in the tendon. This causes a slight enlargement in the diameter of the tendon which can be detected with careful study of a sonogram. This is done by capturing the ultrasound image on a computer screen and drawing a line around the outer edge of the tendon with a computerized marking device. Computer programs are available which will quickly calculate the area within the drawn circle. This area is then compared to the area of the opposite (normal) tendon, at the same level. This means that both tendons should be examined with ultrasound in a thorough examination. Dr. Genovese has found that it is important to get images from 7 regions, or zones, of the tendon from the accessory carpal bone to the fetlock, some 25 to 27 centimeters. The tendon is first divided into three major zones (1, 2, and 3) from proximal to distal. Zones 1 and 2 are each divided into a and b, and zone 3 is divided into a, b and c. This allows determination of the
149
length as well as the width of the tendon lesion, or the total extent of the swelling. While it is possible to see the tendon image on cross-section, the true severity of the injury is confirmed on longitudinal view and scored for future reference. In this view, the disarray of the collagen fibers can be observed. As healing progresses, the strength of the repaired tendon can be assessed by determining the extent of fiber alignment, over time, in the injury zone. The formation of new collagen will occur in all tendon injuries over time, but the simple addition of more collagen does not improve tendon strength of itself. Tendon strength comes from the alignment of the fibers in the direction of the force applied to it. The strongest healed tendon is the one with the new fibers aligned parallel to the cannon bone, as in the normal tendon. Research has shown that the proper alignment of these fibers occurs when stretching of the tendon occurs. This emphasizes the importance of controlled exercise during tendon healing. One of the problems in tendon healing is that as collagen fibers are produced by the cells in the tissue, they are rapidly cross-linked in a position which may not be parallel to the cannon bone. Once cross-linking has occurred, it is a long, difficult process to regain the former alignment which provides the most strength. This is the place where the new drug is helpful. BAPN is injected into the tendon in the injured area. This drug interferes with crosslinking of the fibers during their healing, allowing them to align themselves with the forces brought about by controlled exercise. Once the fibers are aligned, and the effects of BAPN wear off, cross-linking occurs between the fibers, adding the strength needed to avoid re-injury. The new drug is not yet on the market, but it is hoped that it may be available sometime next year. Drs. Genovese and Reef have developed their tendon rehabilitation program around the concept of controlled
150
exercise during healing. They recognize from the outset that the success of their rehabilitation depends on the cooperation of the trainer and the horse. Some trainers will eventually tire of the wait and go back to their old methods of handling bowed tendons, and push too much exercise too soon to the horse. Sometimes the horse cannot be controlled enough to limit the exercise to an appropriate level. For example, the amount of strain an excitable, energetic horse puts on a tendon while being hand walked may be quite a bit more than a quiet horse being hand walked. The amount of tendon strain during healing is critical. It must be enough to stimulate proper alignment of the fibers, but not enough to tear the delicate new fibers. In fact, the appropriate exercise is so critical during rehabilitation that Drs. Genovese and Reef have defined 7 exercise levels which their patients should progress through over the course of healing. A zero level would be stall rest. This is where therapy for most horses with tendon injuries begins. The first exercise level (EL-l) is hand walking, walking on a mechanical walker or treadmill walking. The type of exercise in the second level (EL-2) includes swimming, ponying, light lunging at the trot or trotting under saddle for no more than 5 to 10 minutes.Exercise at this level for the Standardbred would be walking (only) in a jog cart. Surprisingly, turning a horse out in the paddock provides a relatively heavy amount of exercise, and is considered level three (EL-3) in this rehabilitation program. The temperament of the horse should be carefully considered before allowing free paddock exercise, according to Dr. Genovese. The next step up (EL-4) involves hacking (walk, trot, canter) for 15-20 minutes, 3 days per week. The return to race training (galloping) is considered to be the next level (EL-5). Breezing is the next level (EL6), and the final level (EL-7) represents maximum athletic activity for all breeds.
Dr. Genovese explained the most critical aspect of their rehabilitation program, "It is important in the management of tendon healing to relate sonographic changes with the exercise level of the horse. The injured tendon may be healing as expected, but if the exercise level recommended, or in place, is too excessive, there will be a greater risk of relapse. Therefore, any sonographic evaluation must be correlated to the exercise level the horse is performing at the time of examination." The healing rate of each tendon injury is a little different from all others. It is impossible to set a time frame for healing and progressively increasing exercise level that is appropriate in all cases, according to Dr. Genovese. This is why he has developed a system of measuring the healing progress quantitatively. In addition to measuring the cross-sectional area of the lesion and the total lesion volume, Dr. Genovese uses a fiber alignment grading system, giving every lesion a score of 0-3, with 3 having the lowest percent of aligned fibers, or the greatest amount of damage. He also finds it useful to calculate the sum of the cross-sectional areas of th'e tendon in all zones, along with calculation of the cross-sectional area of the injured portion of the tendon. This allows ca!Culation of the total percent of hypoechoic fiber tracts (injured tissue). He dubs this "%T-HYP." The initial ultrasound examination becomes the baseline by which subsequent healing is measured. "The %THYP must show significant improvement from the baseline, and for maximum chance of success should be equal to or less than 10%," Dr. Genovese said. "Horses with tendon injuries that are slight might only reduce from a 5% or 6% to a 2% or 3% for example. In this instance, this level of reduction is an acceptable evaluation. More extensive tendon injuries will have a relatively greater reduction, but for optimal chance of success, should be reduced to the 10% range."
JOURNAL OF EQUINE VETERINARY SCIENCE
Others who evaluate a lot of tendons, especially surgeons, often place less emphasis on the percent of h)~poechoic area, believing that the size of the h y p o e c h o i c lesion in the sonogram may not accurately reflect the amount of damaged fiber tracts. For example, an initial blood clot in the tendon may take up more than 10% of the cross-sectional area in the principal zone of injury, but after tendon splitting surgery-- where the blood and debris is removed-- the hypoechoic area becomes significantly smaller, and the percent of hypoechoic area is much less. In this case, the sonographic difference may be significant, but the actual number of injured fiber tracts has not really changed. The rehabilitation involves at least three critical ultrasound evaluations. The first, of course, is to measure and define the baseline injury. The second is to evaluate the extent of healing prior to advancing to level 3 exercise, where paddock freedom often results in a rebow. Generally this second examination takes place 16 weeks after injury. The third ultrasound examination usually takes place just prior to putting the horse back into training. Dr. Genovese' s studies have shown that there must be at least a 50% improvement from the baseline evaluation before exercise level 5 (light training) begins. "The fourth critical sonographic evaluation time of tendon injury management is actually a group of examinations and are referred to as 'in training sonographic monitoring,'" Dr. Genovese explained. "These evaluations are made preceding EL changes at the training level, such as advancement from EL-5 to EL-6, and preceding advancement to EL-7. Once racing starts, frequent sonographic monitoring between races, especially between the first 4 or 5 races, can provide data to determine tendon sonographic stability or instability." Most racetrack practitioners attending the symposium were impressed with
Volume 16, Number 4, 1996
the Genovese/Reef system of evaluation of tendon injuries and the use of it in rehabilitation. It will take a long time to educate the majority of trainers to the benefits of such a system, but I believe that eventually the standard for tendon rehabilitation will center around a system of tendon injury quantitation similar to that discussed at this Symposiu~n. Dr. Larry Bramlage discussed the surgical remedies available for bowed tendons, specifically tendon splitting and superior check ligament desmotomy. He feels that both surgeries are indicated in many cases, and they help to improve the prognosis for eventual return to racing. While Drs. Milos Chvapil and William M. Davis explained the histologic details of tendon healing, and provided considerable hope that the new drug Bapten will augment the healing process, Dr. Roy Pool presented a rather pessimistic picture of what occurs after severe tendon rupture. In his opinion, while scar tissue can fill the experimentally-created gap or the core lesion o f spontaneously occurring tendinitis and while scar tissue can remodel and mimic the architecture, it probably never reclaims the original mechanical properties. He was also pessimistic about the helpfulness of tendon splitting surgery. Other types of soft tissue injury were discussed. Dr. Leo Jeffcott brought some new information about the diagnosis and management of back problems.He emphasized that diagnosis of back problems is notoriously difficult and always requires a thorough and systematic examination. Dr. Bill Moyer discussed soft tissue injuries of the foot, emphasizing that precise diagnosis and assessment of damage can be difficult because the affected tissues are often obscured from view via their position in a horny capsule. The correction of problems usually requires attempts at altering the causative factors, reducing inflammation and pain, and providing support
with correct or corrective shoeing. Dr. Dan Hawkins captivated the audience with his discussion of the physical examination of the musculoskeletal system. He said that the diagnostic aids and technical procedures that greatly assist diagnosis are diagnostic regional nerve and intra-articular blocks, radiography, ultrasonography, scintigraphy, and locomotion analysis. These ancillary diagnostic aids confirm and expand information obtained by physical examination and clinical history. The combined information contributes to an accurate diagnosis and an effective therapeutic plan. Diagnosis was the major emphasis of the Symposium, with treatment taking a decided back seat. This was probably because most of the new developments have recently come in the area of diagnosis. Dr. Norman Rantanen captivated the audience with his explanations of the principles of magnetic resonance, computed tomographic, ultrasonographic and scintigraphic imaging of the soft tissues of the horse. The newest technique on the horizon for veterinary diagnostics is magnetic resonance imaging(MRI). "Because MRI provides diagnostic information regarding soft tissue and bone, it has potential value in examining the tendons and ligament s of the horse," he said. There is technology being developed to allow using a small remote magnet for MRI imaging by MAGNEVU, a California-based company. This technology differs from the standard MRI scanning in that a small magnet is used to oppose the tissues in standing, tranquilized horses. The system is very portable and makes for ideal equine imaging. Dr. Tracy Turner seemed to convince the entire group that thermography definitely has a place in diagnosis of soft tissue problems of the horse. He also e f f e c t i v e l y illustrated how scintigraphy can be used to diagnose specific types of soft tissue problems.
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