“...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 cannon-bone 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.”

Figure 1.

Sagittal view showing tip of frog not lined up with apex of sensitive frog. Note vertical lines showing Duckett’s Dot and Bridge, semi-lunar crest, attachment of extensor tendon.

“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 measurement and by mass” says Duckett. In his lectures, Duckett, through live demonstration, 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(see photo at left).

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.

“...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. 25 and 26.”

The sagittal photograph 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.)

Figure 3.

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.

“...[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,” a description of which is inserted here with directions and illustrations for its practical use, as a preliminary guide to the subject proper ...” Russell also recommends “the use of the adjuster on both inner and outer 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.”

“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.

“Fig. 28 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.”

	Specimen foot shod to Russell’s standard. Notice how much of the shoe is in front of the center of bridge.
Specimen foot shod to Duckett’s standard. Note the proportions. The shoe is exactly centered under the Bridge from breakover to posterior support.

Figure 4.

“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.

“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. (For example: 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 (see Figure 5). 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.”

“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.”

“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 proportions which are exfoliating ... and then to 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.”

“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 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!”

“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.”

“By using my leg and foot tester ... the foot and leg can be correctly balanced under the body...”

“Fig 1 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.”

“Fig 2 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.

“Fig 3, 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.”

“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.”

Figure 7.	Figure 8.

“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.

“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.”

Russell’s Figure 23 (right) 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.

The illustration below shows Russell’s Fig.23 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. Russell obtains this center by suggesting we measure “1 ½ 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 1 ½ or 2 inches up front can dramatically alter the location of the X, making accurate location of the center of articulation of the coffin joint using this method unreliable.

Figure 11.

As we can see, Russell’s X is between Duckett’s Dot and Duckett’s Bridge, but is not the same point as either.

Figure 10.

In Russell’s illustration Fig. 24, 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.

Figure 12.

By shoeing a cadaver foot, one half in Russell’s method, the other in Duckett’s method, we can see the differences rather dramatically – see photo below. Thanks to Fran Jurga for this concept.

Figure 13.