There are some points on the question of shoeing notoriously at issue between writers and shoers, theorists and practitioners, so that hardly any agreement can be found to exist even on essential principles, and this diversity of opinion will probably continue until the known human artifices shall have been superseded by unknown or natural agencies.
–Prof. William Russell, 1903
I hold Prof. Russell in the highest regard for the work he has done. I was unaware his work ever existed until Ruel Darling told me about it just before my lecture at the AFA convention in Kentucky in 1990. You could have knocked me over with a feather! Especially since I started my quest of understanding the balance of the equine foot some twenty years earlier. It is obvious to the reader that I was not influenced by Russell’s work because there is a tremendous difference, when making a comparison.
–David Duckett, FWCF 1998
Russell’s words are as prophetic today as they were 104 years ago. Disagreement exists on many planes in the science of farriery. Some of the most heated debate has centered around principles of hoof balance. Recently two names have come to the forefront of this debate: Prof. William Russell and Dave Duckett, FWCF. Both have been quoted, and misquoted, as having said the same thing. Many people consider each a variation of the other. Most people do not fully understand the work of either.
In reality, they are quite different. Each, in his day, put forth cutting edge theories and methods, using the scientific tools available at the time. These ideas furthered the understanding of farriery significantly.
Duckett is British. Russell, an American, came and went before Duckett was born. When Duckett developed his theory, he knew nothing of Russell’s work. Russell’s work is based on anatomy as it relates to the concept of hoof capsule symmetry. Duckett’s work is based on the sciences of anatomy, physiology, physics, and biomechanics.
Russell invented the hoof gauge (Russell’s Scientific Hoof Adjuster) and the T square method of medial/lateral balancing (Russell’s Scientific Hoof and Leg Tester). Duckett gave us Duckett’s Dot, the center of weight bearing of the foot, and Duckett’s Bridge, an external reference to the mechanical center of the hoof.
BASIC PRINCIPLES
Russell’s basic principle of hoof balance is symmetry. He maintains that the hoof capsule should have medial/lateral symmetry, that each half should be a mirror of the other. He tells us digital alignment must be maintained. He insists the natural angle of the hoof is about 50 degrees. He tells us to leave the sole and frog alone when trimming and to only remove that which is about to exfoliate anyway. He tells us the shoe should fit the perimeter of the bearing surface with nothing protruding. He tells us the bearing surface of the shoe should be perpendicular to the leg column.
Duckett’s basic principle of hoof balance is biomechanical neutrality. He maintains that the shoe should support Piii and the coffin joint, that the breakover should be at the point where a line through the centers of rotation of the phalanges exits the bottom of the foot, and that the heel support should be at least as far behind the coffin joint as the breakover is in front of it. He maintains the natural angle of the hoof should be approximately 54 degrees. He tells us the hoof capsule is not symmetrical but remodels to accommodate the stresses put upon it by shoeing, conformation, and the environment. He tells us medial/lateral balance should address joint congruency rather than a “one size fits all” formula.
CENTER OF GRAVITY / CENTER OF WEIGHT BEARING
Russell: “… the effort of the weight of the horse fixes the real point of support neither upon the heel nor the toe, but on the middle or ball of the foot between both, where is located the center of gravity, which is easy to demonstrate anatomically: thus, the cannonbone presses on the head of the upper pastern, this on the lower pastern, this again on the navicular and coffin-bones, the center from where it is projected upon the ground bearing of the hoof without. …[T]hus making … the coffin joint the center of gravity of the foot.
Duckett: “The center of gravity of the foot, by itself, is irrelevant because we have to consider the weight forces of the horse bearing upon the entire solar surface. After all we are shoeing the whole horse, not just his feet. Therefore, we have to consider two centers.
A. The center of the third phalanx which is the center of weight bearing when the limb is fully loaded, (Duckett’s Dot) and
B. The center of articulation of the coffin joint. (Corresponds to Duckett’s Bridge). The mechanical center of the foot.”
The anatomical significance of the Dot is that “… it is the only external reference-able anatomical landmark representing the center of the coffin bone by measurements and by mass,” says Duckett. In his lectures, Duckett exhibits a cadaver foot with a drill bit inserted at Duckett’s Dot, perpendicular to the bearing surface. “The drill passes through the apex of the sensitive frog, the center of the attachment of the DDF tendon at the semi-lunar crest and the anterior articular surface of the extensor process, through the extensor tendon attachment to exit just behind the coronary band,” Duckett says.
The Dot, as the center of weight bearing when the limb is fully loaded, was later proven by Doug Leach, DVM using load sensors attached to the hoof.
SYMMETRY AND WEIGHT BEARING
Russell: “… from a line drawn through the longer axis of the frog the measurements to opposite points should be the same on both sides of the foot; this means simply that a longitudinal line through the center of the frog must at all points be the center of the foot or divide it in exact halves, as in this way only will the force of the foot-fall be carried through the center of the column of bones and be equally and naturally distributed upon the supporting apparatus of bones and tendons and the weight-bearing portion of the hoof. The active principle of this indispensable arrangement is best illustrated in Figs. 02 and 03.”
Duckett: “Equine feet are not at all symmetrical. In a well formed foot, we find the lateral aspect of Piii bolder than the medial aspect. In poorly formed feet we find that Piii remodels to accommodate the stresses placed upon it by the imperfect structures above. The hoof capsule, in turn, remodels to accommodate these internal forces. Moreover the hoof capsule remodels still further based upon the external forces applied to it. Environment, conformation, and shoeing all have an effect on the shape of the hoof capsule. Attempting to make a foot symmetrical will likely cause more problems than it will solve. There is no ‘one size fits all’ answer to hoof capsule shape.”
HOOF / PASTERN ANGLE
Russell: “It would be misleading to lay down any arbitrary degree of obliquity, as it naturally varies more or less in almost every individual horse, short pastern horses standing at a greater angle than those with long pasterns and hind feet more than fore: Hence, the natural bias of the superimposed structures is the only safe guide to follow.” He then states, “the degree of obliquity varies in almost every horse, ranging from 45 to 56 (degrees) on front toe of fore feet, and perhaps a little more for the hind feet.” Later, he says, “The correct rule for the angles of the front feet to be observed is, when the former stand at an angle of 48 degrees, the latter should be at 50 degrees, for the reason that the hind legs constitute the propelling powers of the horse. This has been my never-failing rule.” He states, “The angle of the wall varies in different animals; what that angle should be in each instance must be determined by a lateral survey of the foot and leg.”
Duckett: “It is important to establish that the dorsal surface of Piii is parallel with the exterior surface of the hoof wall at the toe, that angle being approximately 54 degrees for a front foot and slightly higher for the hind foot on the domestic horse. Why 54 degrees? The dorsal angle of Piii is 45 degrees in relation to the ventral surface of the bone. Its orientation in the hoof capsule is elevated at the heel approximately 8 to 10 degrees for the purpose of providing a biomechanical advantage to the tendons. Every horse must be evaluated as an individual and each horse balanced according to its own structure, and it is imperative to maintain alignment of the phalanges whenever possible.”
SAGITTAL VIEW OF THE LOWER LIMB
Russell’s illustration (Figure 01) shows a sagittal view of the internal anatomy of the equine front leg. He has indicated a line through the phalanges that exits the foot at the apex of the horny frog, stating this point as “the normal center of equipoise.”
The sagittal photograph (Figure 04) shows the same line exiting the foot significantly farther forward. Duckett maintains this line will exit the foot at the proper point of breakover.
Careful comparison of Russell’s illustration and the accompanying photograph shows a discrepancy. Russell has allowed for a very thick laminar bed, thus moving the bone structure posterior in the hoof capsule. It should be noted that the shape of Russell’s bones are different from those in the photograph, further changing the geometry of Russell’s illustration. (Those with sharp eyes will see the tip of Piii in the photograph is missing. This could be the reason for the demise of the horse that provided the cadaver limb for this article.)
SCIENTIFIC HOOF ADJUSTER / HOOF GAUGE
Russell: “… [N]ow, to be up with the spirit of the times, the shoeing smith needs more scientific tools for expert workmanship in leveling and adjusting the angles of the foot, to secure that precision and perfection imperatively demanded, and to supply this long-felt want I am performing a duty which needs no other words of explanation in referring my readers to the ‘Russell Foot Adjuster’ (Figure 05), a description of which is inserted here with the directions and illustrations for the practical use, as a preliminary guide to the subject proper….” Russell also recommends “the use of the adjuster on both inner and other quarters, carefully observing the angle of each and the line of the wall that one side may be made uniform with the other side in height and degree of obliquity.”
Duckett: “For the student, the use of a hoof gauge can be an aid to gain one’s eye. For decades, we have relied upon the hoof gauge to establish some form of unity in gaining a pair of feet, or for the purpose of establishing a foundation for communication from trainer to farrier, or established in veterinary reports and biomechanical studies. However we must look at the way we use the hoof gauge and fully understand its inconstancies. The basic concept of this gauge is to measure the angle between the dorsal hoof wall and the ventral surface of the foot. From a math class of trigonometry we are taught that we need three basic elements to project an angle. One: a perpendicular (this signifies the limb of the horse). Two: a base line (this is the ground the horse stands on). Three: a point to measure from (this is the toe of the foot). In using the hoof gauge it is obvious that we destroy two of the major elements of projecting an angle by simply lifting the leg off the floor. The third element, a point to measure from, can vary greatly with the length of toe. Also, we have hoof gauges from different manufacturers, many of which measure differently. Of course some of them when used often become loose and in disrepair. Therefore, it places in question the use of a hoof gauge in a scientific arena, and possibly could be the reason for the large variations in clinical responses in biomechanical studies.”
Duckett maintains that the medial quarter is nearly always steeper than the lateral quarter. He offers a collection of Piii bones as proof. In observation, all of them show a steeper medial quarter than lateral quarter.
FITTING THE SHOE
Russell: “Fig 06 illustrates the correct way of fitting a shoe, with proper length at toe and heel, with foot leveled and balanced, and front of wall in line with the natural inclination of the ankle from toe to fetlock…. Hence, we learn that the shoe must be made uniform with the spread of the hoof and perfectly plain or flat in its actual bearings, in order to adapt it to a close, even seat all around; not too thick or wide … nor projecting beyond the natural circuit of the ground tread.”
Duckett: “Because of the natural physiology of the hoof capsule, we have to take into consideration the tolerance margins of expansion, contraction, compression, and distortion. It is well documented that as the hoof capsule comes under weight loading it changes its configuration by contraction of the heels, expansion of the quarters and compression at the toe. We further have to consider the element of shearing forces as the horse turns and maneuvers its body mass over the foundation of the foot (Figure 07).
“Therefore, the shoe should support the foot in all phases of loading and unloading and provide proper biomechanical support to the limb – all this within the considerations of the breed and discipline of the animal. (e.g., the plating of the thoroughbred racehorse compared to the working draft horse.)
“Those who wish to have a graphic example of how the hoof wall accommodates forces can use a foam coffee cup. Cutting the cup at the angle of a horse’s foot with a ‘V’ at its rear portion to simulate the frog will provide an ideal model. With your finger placed upon the uppermost edge, press down. The coffee cup will adjust to the forces. I have used this example in my classes since 1985. It has proven to be a valuable asset for a student’s common understanding.”
THE NATURAL MODEL
Russell: “If we examine the natural healthy feet of many horses, we will find that their essential shape is the same…. It will be found that the bottom of the foot is nearly circular, the sole concave, the frog broad, the bars distinct, the commissures deep, and the heels expanded.”
Duckett: “Much discussion has taken place in recent years regarding the wild or ‘natural’ horse. Questions arise: What is a wild horse? How does the geographic environment effect the overall configuration of the hoof?
“It is evident that in arid mountainous conditions one witnesses an upright hoof wall with rounded borders on its solar surface. In contrast, the horses of the low lands, such as the barrier islands of the east coast of the United States, produce a hoof form which is flatter, longer, with flares and cracks. Therefore, the wild or natural foot is a product of its environment. How can we use this as our ideal model?
“The domestic horse’s foot is also a product of its environment. Many horses are confined to their stalls, often standing in their own excrement and urine, or in small paddocks up to their hocks in mud. From the wild horse studies, very little useful information can be extrapolated and used in shoeing the domesticated animal.
“Wild horses are not ridden, driven, shod, or trimmed. If they are, they have to succumb to the elements of confinement, which has a dramatic effect on how we perceive the horse’s foot.”
PREPARING THE FOOT
Russell: “It may be accepted as a guiding principle that in a natural healthy foot, the outside rim of the horny wall and that small portion of the sole immediately attached to it on which the shoe is to rest are the only portions of the foot to be interfered with in preparing the foot for the shoe, and, whenever possible, the necessary trimming ought to be effected by means of a rasp…. My practice is to remove only … those portions which are exfoliating … and then reduce the wall to a level with the untouched, healthy, or sound sole. I aim to have every part of the wall … receive a good, broad, equal bearing on the shoe, unless there is some special reason for doing otherwise.
“Sometimes the hoof will grow all to toe, and again the growth at the heels will be more marked, or the foot may be run over by having one side too high or the toe worn off excessively. To rectify this, and to better its adjustment, a good plan is to look at the old shoe to see where it has worn most and be partly guided by that…. This after all must depend upon the judgment, expertness and ingenuity of the farrier….
“… there is one practice not open to argument, and which all alike severely condemn, and that is the utterly senseless and atrocious custom so characteristic of the common every-day horseshoer of thinning out the sole and trimming or mutilating the frog. No man has ever been able to assign a reason for acting contrary to the first principle of his own work by destroying that which he is aiming to preserve….
“From the connection, thickness and flexibility of the horny sole, as well as its arch-like external contour, it is wholly designed … to serve as a cushion to the sensitive sole….By hollowing away the sole … the horse loses his natural defense against violent shocks….
“The horny frog is also designed for contact with the ground for the prevention of jar and injury to the limb….The frog is nature’s cushion and hoof expander (in connection with the bars), and to alter this state is fatal to its usefulness….the frog is also the main support of the plantar cushion, which in turn supports the back tendons….
“… In normal conditions the sole and frog should, on no pretext whatever, be disturbed by the shoer.”
Duckett: “I am in total agreement with Prof. Russell on this issue, especially his inference of not trimming the sole. The solar plate is a protective covering for the sensitive tissue beneath. Es, the removal of exfoliating tissue is permissible. Reservations are held with this principle that in cases where the sole has reproduced but is not in a state of exfoliating, the trimming of the sole is necessary but should only be done by the skilled practitioner.
“For those that are adamant in removing the sole with a paring knife so that it is smooth and can yield under thumb pressure, I have a very simple and graphic demonstration for the student in the class. That is, take your shoes and socks off. I’ll jump on your back with a bloody big stick, and smack you on your backside as you go trottin’ up the driveway!”
OPENING THE HEELS
Russell: “The junction of the wall with the bars affords a firm natural bearing for the heel of the shoe, and is to be rasped level with the wall and so low as to be exactly even with the frog, but the so-called process of ‘opening up the heels’ by removing the bars, is a most disastrous practice, to be strictly avoided. The bars are lateral braces and binders of the foot, and the arch which they form on either side admirably fits then to admit and limit … the expansion of the foot, as well as to powerfully oppose any disposition there may be in the hoof to contract by assisting the heels in retaining their natural form.”
Duckett: “Prof. Russell has discussed two elements relating to the trimming of the heels, with one of which I agree, the other I adamantly oppose. As Mr. Russell has stated, opening up the heel by hoof removal is a practice that should be forbidden. If the heels are contracted, I suggest one looks further to the cause and not to the aesthetics.
“Where we totally disagree is the concept of lowering of the heels to ‘be exactly even with the frog.’ A blanket statement as this could create many problems. For example, if the tissue of the horny frog is atrophied, do we lower the heels? Primary consideration should be given to preserve the heel height and maintain the correct alignment of the phalangial axis. Indiscriminately lowering the heels is a policy that will have a negative effect on the biomechanics of the limb. Therefore, it is imperative that we think in a three dimensional perspective and not act on lineal dimensions. Lowering the heels of the foot to gain posterior support has been a fashionable theory recently. The question I asked the authors of this theory is, how does the wild horse lower his heels, and/or how does the mule or donkey fair in the light of this misguided information? To date I have not received a satisfactory response.”
COFFIN BONE AXIS
Russell: “Fig. 08 represents a perfect front foot. The vertical line A, A passes down through the axis of the cannon bone and reaches the ground at the posterior angle of the wall and bar. The line B, B intersects the line A, A at the center of the ankle joint and passes through the axis of the coffin bone to the ground, which indicates the perfect poise of the coffin bone when the foot is at rest….Fig 09 shows the proper position [of the coffin bone].” This indicates Russell’s contention that the distal surface of the coffin bone is parallel to the ground in a properly balanced foot.
Duckett: “As I have stated before, the coffin bone has a heel high axis of approximately 8 to 10 degrees to offer a biomechanical advantage to the flexor tendons. Further to that, there is no such thing as perfection. If you should find a perfect horse, buy it. You’ll have the only one!”
T SQUARE METHOD OF MEDIAL-LATERAL BALANCE
Russell: “By using my leg and foot tester … the foot and leg can be correctly balanced under the body….
“Figure 10 shows how to use the leg and foot tester. First, hold the leg up in the left hand, as shown in the drawing; then lay the tester straight down the tendons, as shown, with the lower end across the heels, as indicated in the drawing. Looking over the bottom of the foot, it will readily be seen if the bottom of the foot is level…. In some cases the foot and pasterns will twist in or out. If the foot twists in, the outside will be too high; if the foot twists out, the inside will be high.
“The great science in horseshoeing is to know how to balance the foot under the leg and body, so that when the foot lands on the ground it will land perfectly level from heel to toe.
“Figure 11 shows the foot resting on a level floor, with the leg tester placed back of the leg. Whenever the dial letter, A, hangs straight, the foot and leg are perfectly under the body. This shows how every sound horse stands with perfect feet and legs.
“Figure 12, Russell’s Scientific Foot and Leg tester, shows by a side view how to apply the tester when the foot rests upon a perfect level floor.”
Duckett: “Dr. Hood, when he was at Washington State University, used slow motion cinematography to show that the front foot lands slightly medial heel first. Obviously this is another illustration how modern technology has helped to advance our understanding of the science of farriery.
“However, medial lateral balance is not so simple as Prof. Russell’s approach implies. There are a multitude of factors at work that determine a toe in or toe out posture. Hoof balance is but one of these factors. What we strive for is joint congruency under load.”
THE CENTER OF GRAVITY
Russell: “The illustrations prove that the fourteenth dorsal vertebrae is the center of gravity of the body, and the coffin joint is the center of gravity of the foot (Figure 13). Around these two pivotal points cluster all the science necessary to balance the carcass, the limbs, and the feet.”
Duckett: “The two points that Prof. Russell has made here are incorrect. The center of gravity of the body is an elusive point because of the continuing shifting of body mass. However, it has been documented that the center of gravity is just behind the 7th rib and approximately one third superior of the sternum (Figure 13).
“To reiterate, the center of weight bearing (not center of gravity) of the foot is Duckett’s Dot, which was proven in later years by Doug Leach, DVM by using pressure sensors on the hoof capsule and correlating the data.”
COMPARISON OF ILUSTRATIONS
Russell’s Figure 14 has brought about much confusion and is probably the principal source by which Duckett’s and Russell’s works are considered the same. As the text has shown, they are not. Early on, Duckett connected his four weight bearing points with an X, but quickly abandoned the practice because of the confusion it caused.
Figure 15 shows Russell’s Figure 14 with Duckett’s work superimposed upon it. Both lines D-D intersect with lines C-C and B-B. Russell considers this the center of the hoof. He obtains this center by suggesting we measure “1½ or 2 inches” on either side of the center of the toe to mark the forward points D,D and to use the heels as the location of the posterior points D,D. How the heels are trimmed and the choice between 1½ or 2 inches up front can dramatically alter the location of the X, which makes this an unreliable method for accurate location of the center of articulation of the coffin joint.
As we can see, Russell’s X is between Duckett’s Dot and Duckett’s Bridge but is not the same point as either.
In Russell’s illustration Figure 16, he maintains that point “C” is an “internal point … corresponding with the external summit of the horny frog.” Duckett has proven that, on an average size foot, the tip of the sensitive frog is 3/8 of an inch posterior to the apex of the horny frog.
By shoeing a cadaver foot, one half in Russell’s method and the other in Duckett’s method, we can see the differences rather dramatically (Figure 17).
CONCLUSION
It was obvious to me as I researched this article that Russell and Duckett are on the same track, and it is a good bet Russell would be very enthusiastic about Duckett’s work were he alive to see it. I think he said it best himself, “‘Experience keeps a dear school,’ but a wise man will learn to profit from the mistakes of others….”
Russell wrote, “Balance the feet and body, and every joint will work properly in its journals, and every muscle will move with its greatest yet most economical expenditure of force. The science of horseshoeing must be studied, the same as any other science, if you wish to become a successful farrier.” Certainly, Duckett is in total agreement with this statement.
Many of Russell’s theories prove incorrect. His statements are sometimes vague and leave a great deal of room for interpretation. His figures are not anatomically consistent or correct, and some of his anatomy is suspect. Further, it is obvious from the photographs and x-rays presented here that Russell’s method of determining the center of rotation of the coffin joint is inaccurate. His method of determining the “center of equipoise” is equally inaccurate. Russell makes no correlation between his centers and the placement of the shoe. Further, he does not defend his methods with valid science.
Russell was not as fortunate as Duckett. Duckett had access to radiographs and video equipment and the luxury of having modern science independently examine his work. Russell was confined to dissections, sagittal sections, and still photography. Also, the science of biomechanics was not available when Russell was working. Duckett took advantage of the developments in biomechanics to further enhance the science of farriery for the benefit of us all.
In their time Russell’s methods were a significant improvement above the status quo, as inaccurate as they have proven to be. In contrast, Duckett’s work has been proven accurate and reproducible by both the scientific community and the farrier in the field (Figures 18-20). Duckett’s work is considered by many to be the industry standard criteria for farriery science today.
Russell and Duckett should each be hailed as pioneers in our profession and given credit for great advancements. Both men show an exceptionally deep understanding of farriery and have given greatly of themselves for the benefit of the rest of us and all horses we shoe.
Figure 01: Sagittal view showing tip of frog not lined up with apex of sensitive frog. Note vertical lines showing Duckett’s Dot and Bridge, semilunar crest, attachment of extensor tendon.
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Figures 02-03: The longitudinal line through the center of the frog signifies the correct way to understand how weight bears upon each hoof, according to Russell.
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Figure 04: Sagittal view Duckett’s method. Note line through centers of rotation of joints passes through point of breakover. Also note line does not pass through tip of frog as Russell claims it should.
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Figure 05: Yale Union professor William Russell’s perfect fit foot adjuster.
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Figures 06-07: (Left) Specimen foot shod to Russell’s standard. Notice how much of the shoe is in front of the center of bridge. (Right) Specimen foot shod to Duckett’s standard. Note the proportions. The shoe is exactly centered under the Bridge from breakover to posterior support.
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Figures 08-09: (Left) Perfect front foot: A,A axial line of leg. B,B axial line through coffin bone. (Right) Coffin bone lateral view with correct positioning.
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Figures 10-12: Proper technique for application and reading of the foot tester.
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Figure 13: The skeleton and outline of a horse drawn from nature.
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Figures 14-15: (left) Russell’s diagram showing under the surface of a perfect front hoof properly prepared for the shoe, with guidelines for leveling and balancing the foot. (right) Duckett’s explanation overlaying Russell’s ideal foot mapping.
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Figure 16: Russell’s “point C” is the contended external summit of the horny frog.
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Figure 17: A comparison and contrast image of Russell’s and Duckett’s definitions of the underside geography of the hoof.
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Figures 18-20: New technology has aided Duckett in understanding and evidencing his work.
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“… whatever tends to defeat the purpose of nature in organizing the locomotory apparatus by interfering with or misdirecting its normal movement will ultimately result in that loss of harmony and lack of balance by disabled functions and testified by lameness.”
– Prof. William Russell