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S P O R T

H O R S E S

"If you don't understand locomotion, you shouldn't be shoeing horses".

-- H AY D N P R I C E

Hock Displacement

Lateral Extension Shoes to Support the Hind Limb in Sport Horses By Fran Jurga with Haydn Price and Mark Johnson

W

orking on behalf of the British Equestrian Federation to monitor horses that may represent Great Britain at the 2004 Olympic Games, farrier

Haydn Price Dip WCF and British Equestrian Federation team veterinarian John McEwen BVMS have collaborated with biomechanics expert Mark Johnson to develop a system to evaluate and periodically re-evaluate potential team horses. (See related story.) Johnson accompanied Price to America for a demonstration at Rood and Riddle Equine Hospital in Lexington, Kentucky in June 2004.

The information collected by the British system can overcome some of the subjectivity and shortfalls in information when practicing veterinarians and farriers assess the gait of individual horses. Kinematic information such as stride length, breakover distance, and carpal/tarsal/fetlock flexion can now be measured and reported for evaluation of individual horses, wherever they are located. "If you don't understand locomotion, you shouldn't be shoeing horses," Price always reminds his audience. Price uses pre- and post-shoeing video gait analysis--often viewing a horse's footfalls frame by frame by frame--to monitor minor adjustments made in the shoeing of the British team horses. The British system uses three cameras and sophisticated software. While there is strict protocol to follow, it is a more "on-the-job" system than Dr Hilary Clayton's carefully controlled system (see related article on hock research), since it is portable and is used for determining therapeutic options. It can however, monitor knee action, hock displacement, and stride length, as well as other parameters desired by the testers. Price also likes to informally videotape the horses on the surface where they will be working, to see how his oftenminute shoeing adjustments function for performance. A real concern in the shoeing of dressage horses is that the horse should "float" over the surface, and not sink too deeply into soft footing. Expert shoeing modifications and shoe designs can keep the horse from expending excess energy, stressing joints, tendons, and ligaments, or looking like he is laboring to a judge. Of prime importance to Price is "hock displacement", since the hock seems to be displaced laterally toward the end of a stride; in America, this might be called a "wobbly" or "floppy" hocks. Remedying this condition is critical in the maintenance of sound jumping and dressage horses. Farriers working on sport horses

At recent seminars sponsored by the International League for the Protection of Horses in England and Rood and Riddle Equine Hospital in Kentucky, horses are walked on a runway and taped from different angles by multiple digital video cameras. Data is graphed by motion analysis software and a readout traces stride length, straightness of movement, or other characteristics of the horse relevant to performance. Taping before and after shoeing graphically shows the effects of shoe modifications on sport horses.

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are continually battling the deterioration of gaits and performance attributed to weakness or degeneration of the hocks or conformational weaknesses such as sickle hocks. When horses are identified as being at high risk for hock lameness, Price employs what looks like a radical device, a winged hind shoe. An arching extension of steel bursts from the heel quarter to the heel, often an inch of so in width at its widest point. The radius of the extension is modified to help stability and there is no ground contact under the outer edge of the extension. "We're not trying to stop the hock from moving, just provide support," he said. "Once shod, the horse is filmed and the displacement analyzed using the computer system to see if there has been improvement." In America, farriers routinely use "trailers" or

"heel extensions", usually with a lateral "kick", to achieve this goal; since trailers aren't common in the UK, their effects have not been measured. Price responsibly grinds down his lateral extension so that the horse is not bearing weight on it when standing on a hard surface or stall mats. However, when the horse begins working in soft footing, the extension prevents the horse from sinking too deeply, and creating a need for more energy from the hock joints. He stresses that the extension is not permanent equipment on performing horses, but rather an aid. He feels that he has proven that the shoeing modification alters the position of the foot's "planting" pattern and changes the limb's trajectory, sparing the weakened hock. It will, however, change the horse's musculature over time and must be used cautiously and only temporarily.

WHAT IS HOCK "DISPLACEMENT"? "Wobbly", "floppy", "weak" or "collapsing" are common USA terms to describe a horse's action when one hock or the other (or sometimes both) seems to "bow" excessively to the outside (or sometimes the inside) when watching the horse move from behind. While it is not a lameness condition, many believe it is the precursor to hind end problems in gait or actual deterioration of the hocks. In a high-performance horse such as a jumper, dressage, reining or cutting horse, weak hocks can make a trainer very nervous, or effect the sale price of a horse. Farriers have always been pressured by trainers to "fix his hocks, willya?", often at the cost of perpetuating imbalance in the hind feet. In recent years, top farriers have studied the balancing of hind feet in great detail, while trying to understand the changes that foot balancing may make to the hock and stifle joints. A system like the British "Equinalysis" could shed light on how a horse's hock displacement develops over time, as well as how changes in shoeing and balance can help or worsen the movement. Of particular value would be whether changes that seem to help immediately will be effective over the shoeing interval if they lose effect, for instance, as the horse adapts to new angles or shoe width.

Price also replaces wedges on show jumpers with the lateral extensions when hock displacement is a problem. When he removed the wedges from a jumper's shoes, the video analysis system showed a difference in hock flexion of less than one degree. "So the effects of wedges are probably minimal, in dynamic terms," Price commented, "even though they are so effective in statically aligning the hoofpastern axis." The British horses are also evaluated for front end problems. One case presented by Price showed a long-toed warmblood, shod with toe clips and what appeared to be good coverage and length. The stride length and knee action were analyzed before and after the shoeing was changed. With a shortened toe, the horse required less knee action as breakover effort decreased. The effect would probably be multiplied when the horse had to overcome the resistance of soft arena footing. "You mustn't just apply a bigger (longer) shoe to a foot to compensate for a longer toe," Price determinedly stated, "Because that long toe will impede performance." By American standards, his shortening of the toe was very conservative, yet there was a measurable difference in the horse and at least a perceived improvement with just a few millimeters of change. "Farriery is a reactive profession," he stated. "We wait until there is a problem, and then we change the shoes. This new system helps me change the shoes and prevent the problem."

To Learn More....

Haydn Price is a well-traveled educator in the world of international farriery with a specialty in advanced education for working farriers. He will be a lecturer at the Rochester Equine Clinic farrier/vet conference in Rochester, New Hampshire on November 45, 2004. For those unable to attend, his web site about the monitoring system and its potential uses for pre-purchase exams, young horse evaluations, training progress, and other uses can be viewed at www.equinalysis.com. Haydn is farrier consultant to the British Equestrian Federation, traveling to FEI competitions to consult on farriery. He is a former member of the international champion Welsh Farriers Team and author of the book, Shoeing for Performance. Some photos in this article are courtesy of the International League for the Protection of Horses.

Haydn Price worked with biomechanics researchers at the University of Bristol (UK) to develop protocols for analyzing movement before and after shoeing. He later recruited software expert and biomechanics analyst Mark Johnson to assist in the program. After the 2004 Olympic Games in Athens, the "Equinalysis" system will be licensed to veterinary and farrier practices around the world.

Evaluating horses' hind end conformation and muscle development are often neglected until a problem is identified. Horses can be base narrow or base wide in their hind legs, as well as the front, with similar consequences to gait. Asymmetry of the hind end and hind end stance are often overlooked clues to soundness problems.

Typical shoeing application by Haydn Price (left); above, (different horse) testing out heel wedges applied to hind feet using video joint motion analysis showed that a wedge had as little as a one-degree effect on hock flexion in spite of its obvious benefit for hoof-pastern axis manipulation.

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SUCCESSFUL SPORT HORSE FARRIERY THROUGH MEDIA-BASED MECHANICS

lateral

medial

ou may not think that cricket has much to do with dressage. But a technique that has long been used to assess the performance of cricketers and other sportsmen is now being used to help Britain's international-level horses--and their chances for medals in the 2004 Olympic Games.The gait analysis team of John McEwen MRCVS, British Equestrian Federation director of sports science and medicine, farrier Haydn Price DipWCF of The Farrier Centre (UK) and biomechanist Mark Johnson, has been collecting data on British "international team" horses since early 2003. The process starts with the team horse being filmed in walk and trot, on a flat, hard surface. Every joint center on the horse -- 34 in all -- is identified with a sticky label marker, and three cameras are used to obtain a fore, hind and lateral view. By running this video through a software program that provides motion analysis and noting the position of the markers, quantifiable information such as joint flexion angles and stride lengths can be determined. "Footage of each horse is captured in a way that enables us to re-screen the horse in the future and so highlight any changes in gait," says Mark Johnson, who mans the cameras and crunches the numbers. All data and images are stored on cd-rom and accompanied by a portfolio that is kept with the horse. A returning vet or farrier can then quickly review how the horse was previously moving. "This way of filming the horses means that we have a record of movement and if, at a later stage, a problem develops such as an irregular stride length, it can be more easily identified and assessed thanks to the video record," says John McEwen. British Olympic dressage rider Richard Davison was initially highly skeptical about the gait analysis

Y

program. Now though, he is keeping video records of all his horses, including his European Championship (and Athens Olympics) horse Ballaseyr Royale, small tour ride Hiscox Karachi and five-year-old Hiscox Kamanchi. "With Hiscox Kamanchi I don't see any point in allowing unnecessary wear and tear to build up over the years," says Richard. "I'm keeping the horses regularly monitored as the flight paths of their limbs change as they get stronger. As a result, we're making subtle changes all the time in the way they're being shod."

Pro-active shoeing

The program has been an opportunity for farrier Haydn Price to pursue his goal of shoeing to assist the horse's capabilities. "Farriery as an industry shoes horses statically [standing], not dynamically [moving]. I want to be proactive -- assessing a horse's locomotion and soundness rather than just reacting to a problem," he says. After Haydn's initial analysis of a horse's movement, the video provides more information about its locomotion. The video records have

enabled the gait analysis team to develop a process of baseline measurement of the following while the horse is moving, measuring · angles of limb movement; · angles of limb extension; · joint flexion; · hock movement (displacement). This means that Haydn can take into account the needs of the limb, if required, instead of just shoeing the foot. This is important, because as well as fitting a shoe to accommodate the horse's movement there is a growing awareness that shoeing should take into account the amount of "loading" on a limb. The team subscribes to the theory that loading is directly related to the effectiveness of the joints and that it can affect tendon and ligament function.

lateral wing for a left hind leg as recommended by Haydn Price

normal support for the medial heel and quarter

vet, is to extend the shoe laterally, to stabilize the displacement, especially in soft footing. "We're not trying to stop the hock from moving, just provide support," he says. Once shod, the horse is re-filmed and the displacement analyzed using the computer system to see if there has been improvement. This type of shoeing only adds around 15 minutes to the time taken to shoe the horse, according to Haydn, who is a veteran farrier and former member of the Welsh national team for international competition.

Show jumpers

ABOVE: The forged (non-welded) lateral extension shoe, for hock support is recommended by Haydn Price as a means of decreasing stress on weakened hocks. BELOW: Asymmetric extension shoes are recommended for horses in training that have been diagnosed with weak or damaged hocks. According to Price, they are a proactive measure to help support a horse that needs to perform. Haydn also experiments with the amount of steel in contact with the ground on a hard surface and will grind off the contact area so the support is only "active" in soft footing.

Limb rotation during locomotion

Even at a lower level of performance, hind limb rotation, (eg cow hocks or sickle hocks) can be detected by vets and farriers at the walk and trot on a straight line. Such problems become much more obvious in advanced movements like piaffe and passage. If, on watching the video evidence, there seems to be a deviation from what would be desirable for that horse, Haydn can consult with the rider/trainer/vet, and offer a description of what he has noticed to find out if it fits with what the rider feels. If there is common ground, then the farrier can suggest a way to compensate for the rotation and offer the limb greater stability. This can have the secondary pro-active effect of providing additional support for the tendons and ligaments before they are weakened or injured by the inefficiency of the abnormal gait. "Each case must be taken on its own merits," says Haydn. "Some conditions can be helped with one shoeing, but others can only change gradually. The main thing is to work

within the parameters of acceptability to the horse." Again, the constantly updated video record helps here. "We can measure the change as a result of the shoeing," says Haydn. "And we can monitor whether one limb needs more or less support than another."

In the case of show jumpers, many in Britain are routinely shod with wedged hind shoes, in an attempt to ease degenerative conditions in the hock. Using the same analysis system, Haydn has shod them with lateral extensions in place of the wedges. The idea is to improve the hock's angle in locomotion. On viewing the videos pre- and post-shoeing, it is evident that the horses moved in a similar way following traditional shoeing in place of the wedges. "Here, we found that the wedges were creating problems and that the horses didn't need them," says Haydn. "The answer was just better traditional shoeing." For the future, the gait analysis team hopes that success in shoeing Britain's top horses will filter down to other sport horses. They point out that the system is practical and can be used by any vet or farrier to improve the care of equine athletes.

Hock displacement

Hock displacement, sometimes called "floppy" or "wobbly" hocks, is a

common concern in the grand prix dressage horse, which, through training, learns to shift more weight onto its hind limbs. It can be particularly evident in piaffe, passage and pirouette, for example. Haydn's most common solution, on viewing both the legs and hooves of the horse and the video record, and consulting with the rider, trainer and

This article by Seamour Rathore originally was published in a slightly different form in the British horse magazine, Horse and Hound; it appears here with their kind permission.

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T E C H N O L O G Y

COMPUTERIZED FARRIERY ANALYSIS: SOFTWARE TO MEASURE THE ART AND THE SCIENCE

In 2003, Equinalysis teamed up with a software company and began developing a motion analysis software tailored to the equine industry. This software allows reliable biomechanical data to be collected by practicing vets and farriers and so could contribute towards a more evidence-based approach to equine performance evaluation. It also allows slow motion and frame-byframe viewing of video clips. The software, called Equinalysis, has been designed to be user-friendly and can be used by mobile vets, and farriers or be set up at equine practices for screening programs.

All things high-tech were the order of the day at the International Conference on Equine Locomotion, held at Michigan State University College of Veterinary Medicine in June. A demonstration of soft- and hardware showed the potential for being able to quantify all aspects of a horse's gait, posture, stride length and landing pattern. A transducer-equipped saddle pad (photo, right) attaches to a transmitter on the rider's back and sends a signal to a data collection device. Below, force plates for measuring hoof pressure have been updated so that a horse need not walk over a sensor block, as in the past. The new Tekscan sensor is a thin plastic mat that measures landing patterns, or changes in weightbearing in the standing horse. Footscan, a similar system in use at the University of Utrecht in The Netherlands, is used in human athletic shoe stores in Europe to help with shoe selection and fit. At Utrecht, researcher Meike van Heel used the system to measure changes in foot balance from newly shod to the end of the shoeing period. A sample readout (below) from the Footscan recorded landing, loading, and weightbearing patterns.

Test horse has been set up with joint markers applied; horse is walked in a straight line while cameras "pick up" motion of markers. Horses can be evaluated on hard surface or arena footing to see how shoes will "perform" in competition, especially for dressage horses. Equinalysis is a measurement tool and does not diagnose or interpret results.

Of particular interest at ICEL was the use of a film-like Mylar sensor strip. In this case, the strip is cut to hoof perimeter shape and inserted in an Old Macs boot. As the horse works, even a racehorse under saddle, the sensor's readings can be collected. Dr. Clayton's new gait analysis system is the state-of-the-art; it collects data from all

angles and creates a three-dimensional horse on a video screen, rather than a twodimensional stick figure as in the past. This is similar to animation systems used to create high-tech movies like "Toy Story" or "Shrek". In the McPhail laboratory, it will assist in the study of joints, such as the hock, that move in three dimensions. The horse wears sensor dots, as in Equinalysis. As the new equipment moves out of the laboratory and into the field, pre-purchase and insurance applications will quickly develop. Appaloosas won't be the only horses with spots any more.

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