Treadmills for Diagnosing Lameness
Quiet progress in using sophisticated techniques for diagnosing lameness has been taking place in research laboratories around the world. Researchers from Missouri to Australia and from Virginia to Switzerland are perfecting techniques for utilizing high-speed cameras and treadmills to diagnose obscure lamenesses and help determine correct trimming and shoeing procedures for individual horses.
Another approach that is still in the developmental stage at the equine clinic of the University of Missouri-Columbia Teaching Hospital involves evaluating lameness by using body sensors to send wireless signals to a computer without the use of a treadmill (see "Transducer Diagnostics" on page 46).
The research, both with the treadmill and with the wireless body sensor approach, promises multiple benefits to farriers and veterinarians in their ongoing struggle to diagnose obscure lameness in horses.
Leading a research effort at the University of Missouri-Columbia is Kevin Keegan, DVM, MS, Dipl. ACVS, associate professor of equine surgery, who has presented papers and lectured at various forums around the world. Research work and practical adaptations of the treadmill and high-speed photography techniques are also occurring at the Equine Centre, University of Melbourne, Australia; the University of Austria in Vienna; Michigan State University, where much research has been conducted involving gait analysis; and the University of Zurich in Switzerland, which houses the world's only force-measuring equine treadmill. A treadmill for use in lameness diagnosis has been installed at the Marion du Pont Scott Equine Medical Center, Virginia-Maryland Regional College of Veterinary Medicine, but, says Nathaniel A White II, DVM, MS, Dipl. ACVS, "We are not at a stage where we have anything to report." The treadmill at the medical center is housed in the James P. Mills Diagnostic Treadmill building that was constructed in 2003.
Studies on Treadmills
The research work utilizing the treadmill and high-speed photography has been occurring at something of an accelerated pace for the past two to three years, Keegan says, with the bulk of the research taking place at the institutions listed.
Treadmills, of course, are not new, but in the past they frequently have been used to measure horses' fitness by examining and recording respiration and heart rate data, as well as for gait analysis.
A pioneer in treadmill use and development was Professor Sune Persson, a faculty member of the Department of Medicine and Surgery at Swedish University of Agricultural Science in Uppsala, Sweden. He began evaluating the Swedish Trotter on the treadmill back in the 1960s and is believed to be the first person to use a treadmill to study equine exercise physiology.
The early treadmills only moved fast enough for a horse to walk and trot, but now are capable of moving at speeds of up to 60 miles per hour. The work of Persson and his colleagues in Sweden provided valuable scientific data and, as a direct result, a number of research facilities around the world began using treadmills.
Soon researchers were discovering specific parameters involving equine exercise physiology. Among other things, they have learned:
- The cantering and galloping horse takes one breath with each stride. When traveling at a full gallop, a horse normally will take approximately 150 breaths per minute, with each of those breaths containing 12 liters of air. (Compare this to about 12 breaths per minute of five liters each at rest.)
- A galloping horse takes breaths that are more rapid and shallow than does the trotter; however, both must move large volumes of air very quickly in order to remain at maximum performance.
- Even mild degrees of upper airway obstruction and small increases in mucus, as well as airway spasm, quickly compromise a horse's ability to perform at its maximum level.
There also have been instances where treadmills have been used to help condition racehorses for competition.
Treadmills for Diagnostics
Through the years, the treadmill has been a valuable asset in diagnosing various respiratory problems and complications in athletic horses, especially those involving the larynx and upper airways. Now another dimension has been added--the evaluation of obscure lameness.
Keegan does not see the treadmill/high-speed camera approach as something that will strongly impact the practitioner in the field in the near future, other than perhaps as a referral situation for obscure lameness. Of course, he considers it a valuable tool in providing research information about various lameness problems.
A drawback to broad scale usage of treadmills is the fact that they are expensive, and at present, analyzing the voluminous data involves sophisticated computer technology.
At Missouri, Keegan says, the treadmill/high-speed photography approach is used infrequently because more conventional diagnostic approaches are successful in greater than 90% of the horses evaluated. However, he says, the approach is highly successful in helping to determine obscure, mild lameness; multiple-leg lameness; shifting-leg lameness; changing lameness, such as a horse that is no longer visibly lame after being warmed up; and difficult-to-diagnose lameness in gaited horses like Missouri Fox Trotters.
Following is the approach taken at Missouri when the treadmill and high-speed cameras are used, as described by Keegan and his colleagues.
First, the horse is acclimated to the treadmill. To date, Keegan says, all horses evaluated have accepted being worked on the treadmill. The acclimation occurs more quickly with some than with others. Generally speaking, it takes from one to three days for a horse to become comfortable on the treadmill. Horses are never forced on the treadmill, Keegan says, nor are they tranquilized. The latter approach is avoided because the horse will not travel in a consistent manner on the treadmill if tranquilized.
Once the horse accepts treadmill work, a determination is made as to the optimum speed at which it can trot comfortably without being goaded or coerced. Once this point is reached, it is time for an evaluation.
Four soft, sponge-like retro-reflective spheres, only 25 millimeters in diameter, are attached with Velcro to discs glued on the horse to serve as markers for the cameras. One is attached at the poll, one at the point of the croup, one on the hoof wall of the right front limb, and one on the hoof wall of the right rear limb. Three to four high-speed cameras, capable of recording the horse's movements at the rate of 120 frames per second, are situated to the right and above the horse. The cameras are connected to a computer in an adjacent control room. When the horse reaches its pre-determined trotting speed, the cameras begin recording for 30 seconds to two minutes. (At the same time, the horse is filmed with two regular-speed digital cameras--30 frames per second--from the right side and the rear to provide backup information to the researchers.)
Simply put, the information recorded by the cameras is fed into a computer that analyzes the images and provides answers as to where the lameness is occurring.
The vertical movement of the horse's head correlated with the vertical movement of his right forefoot is used to measure forelimb lameness, and the vertical movement of his pelvis correlated with the vertical movement of his right rear foot is used to measure hind limb lameness.
Lameness, as evaluated on the treadmill at the University of Missouri, is classified as either Type 1 or Type 2. Type 1 lameness, according to Keegan, is the most common and results when the horse feels acute pain at either the impact or stance phase of a stride. Type 2 lameness occurs when the pain is most acute during the break-over phase of the stride.
Keegan feels the treadmill/high-speed camera approach is effective in diagnosing subtle lameness. In a number of cases, he says, the lameness is undetectable to the human eye and can result in guesswork on the part of the diagnostician.
The same is true when the horse is lame on more than one limb. The horse might, for example, be suffering from navicular disease in the left front foot and from degenerative joint disease in the right front. Simply watching the horse move in such a situation often presents a confusing picture. The treadmill and high-speed photography are able to establish that a problem exists in each limb.
It also is useful, Keegan says, in evaluating lameness that is apparent when a horse begins exercising, then disappears once the animal has warmed up.
Gaited horses, such as Missouri Fox Trotters, often pose a challenge in evaluating lameness because their ambling style of movement can mask lameness in one limb or another. Again, the treadmill and high-speed photography eliminate the guesswork.
Other Treadmill Research
As mentioned earlier, other research facilities also are using the treadmill and high-speed cameras to study lameness. The treadmill installed at the University of Melbourne Equine Centre was put into place in late 2003, thanks to $136,629 in funding from the A.E. Rowden White Foundation. The Foundation also funded a new gamma camera to the tune of $600,000 in conjunction with Racing Victoria a year earlier. The gamma camera, according to information on the Equine Centre's Web site, can detect minor bone changes that can cause lameness and gait abnormalities.
Another leader is the University of Zurich's Veterinary School, where Jorg A. Auer, DVM, Dipl. ACVS, ECVS, heads up the Veterinary-Surgical Clinic, which is involved in both research and teaching. A key component in the research program is the treadmill, which contains a force plate for measuring the impact of each stride.
Force plates are not new, according to Keegan, but normally they can measure the impact of only a single stride when in a fixed location. However, by incorporating the force plate into the treadmill as Auer has done, multiple strides can be measured, thus enhancing the accuracy of impact readings.
There has been a great deal of progress with both treadmills and high-speed photography since Professor Persson first reported on his work with Swedish Trotters back in the '60s. Based on what is happening at the University of Missouri and other research institutions around the world, it appears that there is much more to come, all of which will ultimately benefit lame horses.
BEYOND TREADMILLS: Transducer Diagnostics
While Kevin Keegan, DVM, MS, Dipl. ACVS, associate professor of equine surgery at the University of Missouri (UM), thinks treadmills and high-speed cameras are valuable in evaluating lameness, he is even more excited about an approach being developed at UM that is capable of providing the same, and even more specific, information without that equipment.
The approach is relatively easy from a physical point of view, he says, involving only about five minutes to prepare a horse for the lameness evaluation.
Battery-powered transducers, slightly smaller than matchbooks and weighing only a few grams, are attached in the same locations as the retro-reflective spheres with the treadmill/high-speed camera approach--one at the poll, one at the point of the croup or pelvis, one on the right foreleg, and one on the right rear leg. The transducers at the poll and croup (or pelvis) are attached with Velcro, but those on the legs are also secured with a leg wrap to cut down on vibration and to make certain they stay in place.
The horse is then moved out at a trot. This can be done, Keegan says, on a longe line, while being ridden, or when the horse is trotted in a straight line on a lead shank.
The transducers are actually accelerometers and gyroscopes that measure acceleration and angular velocity during each stride. This information is then transmitted to a receiver on a laptop computer containing software that is programmed to record and analyze precisely what is happening at each phase of the stride. A key advantage, Keegan says, is that wireless technology is involved, meaning that no wires or cables to record or transmit the information are needed.
Signals at the rate of 200 per second are recorded and transmitted by the tiny battery-powered transducers. When analyzed by the computer, the information pinpoints the affected leg and when during the stride that peak pain occurs. This information, Keegan says, would be helpful to the veterinarian in focusing on the specific location of the problem within the limb.
Keegan sees promise with this approach for the veterinarian in the field, once all of the "quirks" have been worked out, because of the ease of application. "We are still in the process of improving the software," he says.
Interest has been shown by private industry in helping develop the equipment commercially, Keegan says. The software at UM is the product of collaboration between Keegan and an engineer who also is a member of the faculty.--Les Sellnow
About the Author
Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.
POLL: Enriching Your Horse's Environment