Farrriery

The Basics of Farriery as a Prelude to Therapeutic Farriery

Introduction

Fig.1: Bare foot trim; note the rounded off distal wall border.
Fig. 1
Fig.2: Schematic presentation of the barely shod hoof and 8 weeks later; although both the toe and the heels grow (dotted line, parallel to the coronary band) only the heels continue to wear, the result is that the digital axis is broken back.
Fig 2
Fig.3: Wear marks on the upper heel surface of the shoe: if the heels, on the upper surface of the steel shoe are worn, how much heel of the foot has been worn down?
Fig 3
Fig.4: Sole trimming begins around the apex of the frog.
Fig 4
Fig.5: Only the exfoliated sole should be trimmed away.
Fig 5
Fig.6: Section of the foot parallel to the coronary band; note how the frog and digital cushion form an expansion organ in the caudal part.
Fig 6
Fig.7: When the quarter-wall is trimmed to the sole level, a light dorso palmar cup will form, which doesn’t easily accommodate a flat shoe. Courtesy M. Savoldi.
Fig 7
Fig.8: The bars should be bearing weight on the upper surface of the heels of the shoe, as can be seen here from the burn marks of the hot shoe.
Fig 8
Fig.9: The heels, when trimmed to the largest part of the frog, increase the caudal surface area of the hoof.
Fig 9a
Fig.10: a “club” foot is best described as a hypo extension of the DIP joint, the degree of hypo extension can be measured radiologicaly.
Fig 10
Fig.11: Dorso palmar horizontal rx of the left fore limb with a varus deviation, if the outside of the hoof would be larger, lateral “pinching” of the phalangeal joints would be more pronounced, note that the distal phalanx is not parallel to the ground.
Fig 11
Fig.12: Right fore with an inwardly rotated digit; The mid line of the frog and the hoof capsule (dotted line) are rotated relative to the direction of movement (straight line). Note the atrophy of the medial heel and lateral toe, which is where landing, respectively break over, take place.
Fig 12
Fig.15: Left fore with a combination of inward rotation of the digit and slight varus of the fetlock, note that the largest asymmetry is in the toe area.
Fig 15
Fig.16: a),b). Hoof wall deformation, note the bent hoof wall/horn tubules.
Fig 16a
Fig 16b
Fig.17: Horizontal L.M. X ray with the coronary band marked with radio opaque material¸ note the quarter crack originating from the upwardly shunted heel (continuous line).
Fig 17
Fig.18: The ungular cartilage should have a palpable free margin, above the coronary band, of at least 15 mm; otherwise a Quarter crack may occur.
Fig 18
Fig.19: Right hind. a) To lower the sheared medial heel, a “wedge” is cut away after the basic trim, the important detail is to start the second trim at the toe.
b) When the shoe is then nailed on and the foot set down, the gap disappears, as the medial wall settles down; notice the good alignment of the bulbs.
 
Fig 19a
Fig 19b
Fig.20: a) To take horizontal DP X rays for latero medial joint space evaluation, the central horn tubule should be marked and the foot placed on a rotating podoblock.
b) Only those X rays where the marker aligns with the central cleft of the frog are to be used for joint alignment.
Fig 20a
Fig 20b
Fig.21: a) b) Use of the Finnegan hoof gauge: the bottom of the hoof should ideally be at 90° to the central horn tubule.
Fig 21a
Fig 21b
Fig.22: In deep ground the toe can sink in.
Fig 22
Fig.23: When fitting a new shoe, rockering it where the horse has worn the old one at the toe, will allow it to break over in its favorite spot, without first having to wear down the shoe .
Fig 23
Fig.24: a) Horizontal DP X ray of the left fore of a live horse on a 14° inclined plane, which mimics a sharp turn (without the speed).
b) Effect of different shoe profiles, and hoof lengths, on the side to side leaver arms, acting on the digital joints.
Fig 24a
Fig 24b
Fig.25: A combination of rockered, rolled and set back toe, facilitates dorsal break over, the nail heads have to be filed down.
Fig 25
Fig.26: Full rolling motion shoes facilitate lateral and medial break over the most.
Fig 26
Fig.27: a) b) French rockered toe.
Fig 27a
Fig 27b
Fig.28: Flaps are shock absorbing in the heel area.
Fig 28
Fig.29: Plastic shoes maintain vertical mobility at the heels
Fig 29
Fig.30: a) Dorsal extension of the front limb with the DED.
b) Lateral elevation, maximum elevation is reached when the opposite side of the hoof lifts of the board.
c) Medial elevation.
d) De degree of tolerated dorsal extension, lateral or medial elevation, is measured by putting the arrow at water level and reading the angle on the protractor scale.
Fig 30a
Fig 30b
Fig 30c
Fig 30d
Fig.31: Right fore; (Medial collateral desmitis of the DIP joint) The shoe facilitates dorsal and lateral break over, the pad keeps the medial side from sinking in to the deep surface.
Fig 31
Fig.32: A wide webbed toe, narrow heeled shoe, prevents the toe from sinking into the ground, which would exaggerate fetlock extension in the mid stance phase. Courtesy Loic Entwistle
 
Fig 32
Fig.33: At speed, horses land heel first.
Fig 33
Fig.34 In the mid stance phase and at speed, the fetlock is at maximum extension. Courtesy Dr. Gaspar Castelijns
Fig 34
Fig.35: Open toe, heart bar shoe, with dental impression material in the palmar part of the hoof.
Fig 35
Fig.36: Onion shoe, the enlarged foot surface of the shoe’s heels recruits the bars of the hoof in to weight bearing.
Fig 36
Fig.37: The shock absorbing effect of pads and packing, and the benefits of predrilling the nail holes in the pad, can be measured with the help of accelerometers and specialized software, in this case the podéquinométrique system © 3 .
Fig 37
Fig.38: Shock absorbing shoeing systems are more stable if they have metal inserts, they can be bulky however and/or wear fast in the heavily worked horse.
Fig 38
Fig.39: Asymmetrical shoes, in this case with a wide lateral branch, have less asymmetrical weight distribution if made out of Aluminum alloys.
Fig 39
Fig.40: a) This large warm blood, with an extremely toed out conformation, interfered hitting the (opposite) fetlocks of both front limbs.
b) It stopped interfering when shod in lightweight Aluminum shoes
Fig 40a
Fig 40b
 

Farriery and farrier derive from “ferrer” (French, to shoe) and includes the root “fer” (iron). The French term for farrier however is Maréchal ferrant, whereby “Maréchal” means officer (general even!), and “ferrant” he/she who shoes. Equine veterinary text books from the middle ages often have marechaucie, marescallie, mariescalla in their titles, both denoting the importance of farriery and the fact that the equine vet and farrier often were one and the same and even of noble birth! [1]

The technique of nailing an iron (steel) shoe onto a hoof is currently the most economic form of hoof protection as far as material costs go, as the metal is cheap. In the Galo-Roman period or in the Middle Ages, however, mining ore and forging iron into horseshoes was a luxury, only justifiable with the need to efficiently protect the feet of valuable horses, especially the heavy war horse. [2]

The point of this historical etymological recall being that: a) Farriery had enormous importance at the time when horses were immensely valuable (a war horse could cost as much as a farm!).

b) Shoeing was and is sometimes the only way to permit the horse to function in the service of humans.


2. The Trim

Domesticated horses need hoof care, as it is rare for the wear and growth of the hooves to be in perfect equilibrium.

When the quality of the hooves (size in relationship to body mass, sole depth, wall thickness, quality of inter tubular horn, etc.) is good, the footing favorable, and the workload not excessive, horses can, and should, generally be left bare foot. Exceptions being poor conformation; e.g. an important angular deviation of a limb may cause excessive, asymmetrical wear and growth across the otherwise strong hoof, and certain pathologies; e.g. a horse affected with bone spavin may wear the outside of its hind hooves excessively.


2.1 The barefoot trim.

Trimming the feet of a horse which does not need shoes is not very different from trimming for shoeing, except that the hooves and specifically the walls should be left slightly longer (3-5 mm) and the outside edges rounded off at a radius of at least half the wall thickness. [Fig. 1] Rounding the outside edge of the toe slightly more may be indicated for those horses which live on dry, hard (that is impenetrable) ground. If the horse lives on wet, deep ground it might be useful to leave slightly more toe wall, to keep it from sinking in too much.

 

2.2 Trimming the foot for shoeing.

When preparing the foot for the application of a shoe, the wall should be trimmed as short as possible, especially in the dorsal half of the foot, as the shoe will protect this part (and not the heels) from wear. During the shoeing interval the hoof will grow downwards and forwards in the direction of the horn tubules losing some degree of angle, relative to the ground as seen from the side, as the heels, with their latero-medial movement on the rigid shoe surface, will continue to wear. [Fig. 2-3] [3]

It is therefore important to keep shoeing intervals short (5-6 weeks, depending on growth rate) and regular. [4] The basic trim should commence with the apex of the frog and the surrounding defoliating sole flakes, until the compact non exfoliating sole horn is reached. [Fig.4] This is followed by removing the rest of the exfoliated sole, including the sole between the bars and the heels (seat of corn), all the way to the white line. [Fig. 5]

The rest of the frog is then trimmed only enough to guard the triangular shape with its small central cleft, which forms the ideal breaking, shock absorbing and expansion organ, as seen in a transverse section. [Fig. 6] A light trim of the lateral and medial body of the frog is also important to make (self) cleaning of the corresponding sulcae possible, especially of the shod hoof.

After the sole trim, the excess hoof wall length is easy to judge and easy to trim. It should be noted, however, that the sole follows the slight cup of the distal phalanx, not only in the latero-medial sense, but also in the dorso palmar (plantar) sense, so if the trimmed bottom of the hoof is to be flat, to accommodate the application of a flat shoe, the wall might slightly protrude from the trimmed sole plane at the level of the quarters. [Fig. 7] The bars should be even with the wall at the heels, at least in their portion which contact the shoe, so as to be weight bearing, as otherwise the weight, on the upper surface of the heels of the shoe, is only borne by the heel wall. [Fig. 8]

Ideally the wall should be trimmed back to the largest part of the frog, compatible with the sole depth at the seat of corn, as this increases the foot’s surface, and therefore dispersion of pressure in the delicate palmar/plantar area. [Fig. 9] [5]


3. Hoof capsule distortion versus adaptation in form.

3.1 Hoof capsule adaptation to limb conformation .

Few horses have perfect limb conformation. The shape of a hoof of a limb with conformation defects will adapt in a predictable way to these defects (as will the shape of the distal phalanx [6]). This adaptation in hoof shape serves the horse well, as it limits the deleterious effects of faulty conformation on the muscles, tendons, ligaments and joints.

In the sagittal plane, conformation defects can best be described as hyper extensions (more than normal) or hypo extensions (less than normal) of the joints, as seen from the side. [Fig. 10]

The shape of the hoof, as seen from the side for example, will depend mainly on the tension of the deep digital flexor tendon (and the integrity of the dorsal laminar apparatus), which will determine the palmar, plantar angle of the distal phalanx. Too much tension and you will have a club foot (hypo extended distal inter phalangeal joint) with an upright dorsal wall angle, a narrow short toe and long strong heels. In the adult horse with this condition, the limited capacity for extension in its DIP joint (dorso flexion) is best served by this hoof shape which facilitates quick break over.

In the frontal plane, abnormal conformation is described as valgus (the limb’s segment distal to the affected joint deviating outwards) or varus (the distal segment deviating inwards).

Thus again as an example, the shape of a hoof of a limb with a varus fetlock will be narrower on the outside and wider on the inside, which again serves the horse well as it diminishes excessive lateral torque on the proximal and distal inter phalangeal joints, which in this conformation are not parallel to the ground. [Fig.11]

In the horizontal plane, conformation abnormalities are characterized by axial rotations of the limb or its segments, either outwards or inwards. Thus choosing again a frequently encountered defect, this time in the horizontal plane, a limb with an inward rotation of the digit relative to the cannon bone will develop a hoof which a diagonal asymmetry, with a narrow lateral toe and medial heel and a wide medial toe and lateral heel. [Fig. 12]

This wry, perhaps unpleasing hoof shape, again offers some biomechanical advantages, aligning the two heels on landing and diminishing the leaver arm on break over, as with this conformation the inter phalangeal joints are not “hinged” at 90° to the direction of movement of the horse or it’s body midline. [Fig. 13] [7]

The descriptions, of different hoof shape adaptations to specific conformational deviations of the limb, are schematically summarized in figure 14. [Fig.14]

Fig 13
Fig.13: Hoof shape modification, DIP joint orientation (PPS), leaver arm reduction to break over point (pb) and heel alignment (t 1, t 2), in the case of axial rotation of the digit (p).
Fig 14
Fig. 14: Hoof shape adaptation to conformation with: a) Normal conformation. b) Varus fetlock. c) Rotation of the digit. d) Steep (broken forward) digital axis. e) Sloping digital axis.

A single limb may, and often does, present several conformational defects, which will each add its influence on the shape and outline of the hoof. Although this may render the interpretation of the hoof shape harder, it still follows the same logic. That is: the overburdened parts of the hoof are less developed, while the less burdened parts over develop.

The fairly frequent combination, for example, of an inwardly rotated digit combined with a varus fetlock in the same limb, will result in a hoof with an asymmetrical toe (as both conditions will “shrink” the outside toe), but more symmetrical heels (as in the heel area the two different conformation defects tend to even out their influence on the hoof). [Fig. 15]

The conclusion that a crooked limb is best served by an asymmetrical hoof shape is not only supported by theoretical biomechanical considerations, but also by a thorough doctorate research project which resulted in more than 10 peer reviewed articles. [8] Especially interesting is the finding that in a dorso palmar x-ray of the digit, joint spacing should be even, although the distal phalanx may not be parallel to the ground, that is, with an asymmetrical hoof shape. Also noteworthy is the discovering that a correct protocol is needed to take meaningful dorso palmar x-rays to evaluate latero medial joint spacing and phalangeal alignment and rotation.

It is furthermore an old and respectable principle of farriery to shape the shoe to the (asymmetrical) foot and not to trim the foot to fit the (symmetrical) shoe.

 

3.2. Hoof capsule distortion and correction.

Abnormal limb conformation leads to hoof shape adaption, but the asymmetrical ground reaction force on the hoof, due to uneven landing, weight bearing and propulsion, can also easily lead to hoof capsule distortion. Distinguishing between the two is at the heart of preventive shoeing as distortion should be corrected, adaptation of hoof shape not.

True hoof capsule distortion is characterized by bent horn tubules. Under excessive, repetitive strain, the distal part of the horn tubules in the dorsal part of the hoof will bend outward, causing a flare. In the palmar/plantar part of the hoof however, the distal part of the tubules will bend inward or even forward at the heels (underrun heels). [Fig.16 a,b]

The explanation of the apparently different responses, depending on location, is that on landing, with the limb protracted, the hoof wall in the heel area is compressed towards the inside of the foot, while during break over the dorsal wall is pulled away from the center.

Thus, in the example of the inward axial rotation of the digit, the two atrophied areas of the hoof (lateral toe, medial heel) will distort differently. The outside toe wall will flatten and flare out; the medial heel wall will become steeper and its distal part might even bend inwards (roll under). Another, related form of distortion may occur in the palmar/plantar area of the hoof and is characterized by upward displacement of the coronary band, as the affected quarter heel may shunt upward under excessive load, especially so when the wall here is vertical or rolled under. [9]

An upwardly sheared heel may not leave enough free margin, above the coronary band, to the ungular cartilage for its normal abaxial movement under load, thus causing a quarter crack. [Fig.17] Hoof distortion correction, appropriate and necessary, is done by removing flares of the dorsal hoof wall with the rasp until there is a straight line from the coronary band to the distal border of the hoof.

In the heel area a distortion is addressed by a double trim method. First the foot is trimmed to keep the joint spacing even in the latero medial aspect. As seen from the side, the aim is to keep a straight pastern dorsal hoof wall alignment. A second trim is then performed on the side of the under rolled, upwardly shunted heel, starting at the toe and running in a straight line all the way to heel, ideally going from 0 mm at the toe, to as many mm one needs to take away at the heel to give it the same length as the contro lateral heel of the same foot. On nailing on the shoe the upwardly shunted heel will then settle down onto the shoe, eliminating the space created by the second trim. The lowered coronary band will then free up space for the ipsi lateral ungular cartilage to expand upon weight bearing. The free margin, above the proximal border of the hoof wall, of the ungular cartilage, should be a minimum of 15mm on an average sized foot. [10] [Fig.18]

The second trim usually removes most of the under rolled distal heel wall, which on settling down also moves slightly outwards (abaxially), lessening the verticality of this area of the wall. [Fig.19 a,b]

 

4. Instrumental aids for trimming.

As outward marks of the foot (uniform sole depth, widest part of the frog, apex of the frog, hoof pastern alignment, horn tubule direction, etc.) are not always easy to interpret in horses with limb conformation abnormalities, and as very few horses have perfect limbs, the use of some instruments may aid the trimming process.

X-ray imagining is discussed in chapter 3, it should be noted however, that to get a dorso palmar horizontal x-ray which is usable for trimming measurements, a special protocol should be used. [8]

The foot should be placed on a rotating podoblock, the opposite foot lifted up and the X-ray beam has to be aligned with the sagittal plane of the foot. To obtain this, a linear metal marker is placed onto, and aligned with, the central horn tubule. Only those horizontal DP foot X-rays on which the marker is aligned with the central cleft of the frog can be used for accurate joint space analysis. Even joint spacing should be the aim of the trim in the latero medial sense. The central horn tubule can be found by aligning the central frog cleft with a point at the toe, the horn tubule at the dorsal wall which hits this point is the central one. In many feet, especially front feet, this point coincides with a black grayish interruption of the white line, which denotes the presence of the crena marginalis (notch of the dorso distal border) of the distal phalanx. [Fig.20 a,b]

Fortunately the same exhaustive study concluded that in the overwhelming majority of cases the same trimming results could be obtained with the use of a Finnegan hoof gauge [©1], whereby the bottom of the foot is trimmed at 90° to the direction of the central horn tubule [ Fig.21 a,b]. When using this instrument, it is essential to keep the bottom slit of the gauge aligned with the central cleft and apex of the frog. If the dorsal slit corresponds and is aligned with the central horn tubule, the latero medial trim allows for even joint spacing of the inter-phalangeal joints.

 

5. Shoeing

It is the author’s conviction that, except for particular severe foot conditions like founder, “the foot tells us how it should be trimmed”, as discussed above. In other words, if for therapeutic or performance reasons we want to modify the hoof-shoe combination, there is a not a lot of leeway in the trim of a particular foot, while the applied shoe type, placement and adjustments give us endless possibilities.

A practical example of this principle is therapeutic shoeing for podotrocleosis (Navicular syndrome, palmar hoof pain). In the typical patient, dorsal extension of the affected limb will be limited due to the pathology. Theoretically it makes sense to limit the hyper extension of the distal inter-phalangeal joint by leaving the heels longer. [11] In practice however, we get upward displacement of the walls at the heels [10], a shorter, often underrun, solar surface of the palmar part of the hoof, more heel wear on the branches of the shoe and a different stance of the horse as seen from the side, with the horse placing his front limbs further back, under itself. The same case can be treated without these “collateral” effects by trimming the heels to the widest part of the frog, as previously discussed, and then shoeing at short, regular intervals with a shoe which facilitates dorsal break over (blunt, set back toe, reverse shoe, rockered toe etc.).


5.1 General Principles

No matter what the final performance or therapeutic aim, some general principles apply to all or most shoe applications:

- Only shoe when necessary, that is when wear and tear are more than the hoof can bear, or when shoes are part of necessary treatment, or when horses need shoes for traction.

- The trim is the most important part of a shoeing job; flares and sheared heels should be corrected. The hoof should be short and proportioned, as it will only grow longer and forwards before the next shoeing.

- The shoe should be shaped to the foot, or in any case the nail holes should correspond to the white line; nail too coarse and the result may be compression or infection of the solar, white line, or laminar corium; nail too fine and the wall will break apart over time.

- Choose the appropriate materials: The choice of shoe depends on the horse, hoof shape and quality (like hoof wall thickness), type of work and footing. There is no single shoe type which is appropriate for all horses and all disciplines. The type of nail depends on the type of shoe, hoof quality and type of work but in any case the type, number and placement of nails should

assure that it is the weakest link; in the case of shoe loss no part of the wall should come away with the shoe.

- The best shoeing job looks and works awful if the shoes are left on too long. Respect shoeing intervals first and foremost and allow for appropriate shoe width and length at the heels, as the foot grows forward and widens between shoeing appointments. After a reasonable shoeing interval the shoe should still cover the wall at the heels.


5.2 Performance, prevention, therapy.

A detailed discussion on the relationship between performance and shoeing is outside the scope of this publication. Shoeing influence on performance is closely related to the disciple the horse is used in. Examples are gaited horses (e.g. Icelandic, Tennessee Walking), trotters and pacers. If a racing trotter has a tendency to pace during acceleration, the three shoeing modifications which might prevent this are: heavier shoes, longer toes or more grip. None of these are necessarily very healthy. Sometimes the equine practitioner is called upon to rein in the excessive enthusiasm of trainer and farrier for extreme solutions, perceived as being performance enhancing. The definite argument being that a lame horse will not perform at all.

Prevention is related to both discipline and therapy as some sports are associated with specific injuries and prevention of (re)injury is better than (re)treating a lameness.


6. Therapeutic shoeing ways and means.

The basic therapeutic shoeing means at the disposal of the equine podiatrist are:

1) Break over modifications, e.g. rockered toe.

2) Ground surface modification of the shoe, e.g. egg bar shoe

3) Modifications of hoof support and weight bearing, e.g. the use of hoof packing or of a heart bar.

4) Shock absorbing shoeing (pads, plastic shoes).

5) Weight reduction, e.g. aluminum shoes.

6) Hoof wall defect stabilization e.g. quarter crack repair with patches, glue on shoes.

Of course most of these means can be, and often are, combined in the treatment of a specific pathology.


6. 1 Break over modifications.

Dorsal break over is defined as the moment the heels lift off the ground in the last part of the stand phase. In the horse moving straight, with normal conformation and on flat hard surface the fulcrum (break over point) is not the center of the toe, but slightly lateral of this point [12], at least on the front feet.

In a limb which presents conformation abnormalities, like axial rotations or angular deviations, the point of break over will vary, even when moving on a straight line on flat hard ground. Thus, a toed out conformation will cause the point of break over to change towards the center, or even the medial part of the toe. Even more markedly, a toed in horse will clearly break over the outside toe.

On deep ground, the same force pulling the distal phalanx out of its most extended position into flexion, that is the deep digital flexor tendon, will find less resistance as the toe of the shoe can “roll” into the ground. [Fig22]

When a horse is turning or when it travels on uneven ground, the fulcrum is again modified; on a right hand turn, the left fore will break over at the medial toe, the right fore over the lateral one.

On an individual horse, the average point of break over is worn of the ground surface of the shoe, at a specific area of the toe. It is good, preventive farriery practice to roll or rocker the toe at this same point on the new shoe. [Fig.23]

The anatomical structures which are solicited most in the last part of the stance phase, just prior to break over are:

The deep digital flexor tendon, its accessory ligament (inferior check ligament), the collateral ligaments of the distal sesamoid, the navicular bursa, the impar ligament, the dorsal laminae, the dorsal aspects of the carpal joints, but also the dorsal margins of the distal inter phalangeal joint.

When the last phase of the stance phase occurs on a sharp turn, like a show jumper changing direction towards the next obstacle, the collateral ligaments of the navicular bone, DIP, PIP joint, metacarpo phalangeal joint and even the suspensory branch opposite to the side of the turn, are stressed, as is the subcondral bone of the joints on the side of the direction change. [Fig24 a,b]

Facilitating dorsal break over can be done by setting back the shoe, relative to the toe of the trimmed hoof, blunting the toe of the shoe, rolling the ground surface of the shoe in the toe area, rockering it or a combination of all three. [Fig 25]

Facilitating sideways break over can be done by choosing shoes with a narrowed ground surface all around their perimeter, like some concave shoes, half round section shoes, or full rolling motion shoes. [13] [Fig 26]

A simple and very effective way to facilitate dorsal, lateral and medial break over, is the “French Rockered Shoe”. In the French (and Swiss) tradition, sport horses are routinely shod with a rocker, which starts at the second or even third nail hole and goes around the toe, all the way to the opposite toe or even quarter. In this type of rockered shoe, the inside ground edge of the shoe should still be on the anvil (or ground of the shod foot). The dorsal part of the shoe does therefore look like a dish or bowl. Apart from offering multi directional ease of break over, this shoeing method also gives sole relief (as the inside foot edge of the shoe is forged down) and improves nail pitch. [Fig.27 a,b]

Flexible shoes like plastic shoes or flaps [Fig28.]. Also maintain vertical flexibility in the hoof, absorbing a few degrees of the inclination in the hoof capsule, instead of in the joints, upon a sharp direction change of the horse. [Fig.29]

The use of a digital extension device (DED) permits the exact measurement of the tolerance to dorsal extension, lateral and medial elevation (and even flexion) on the standing horse of each (front) limb on both the sound and the lame horse. [Fig.30 a,b,c,d]

The value of this test is not so much diagnostic, as for example a reduced tolerance to dorsal extension may depend on many different lesions, but indicative of the specific type of therapeutic shoeing that will be most effective.


In other words it predicts which therapeutic shoe will help. (See table 1)

Condition: DIP, PIP Arthrosis, and/or Podotrocleosis

Intolerance to (DED test)

Works on surface

Shoeing, Trimming Techniques

Single collateral ligament lesion, single lobe of distal DDFT single collateral ligament of DS

Lateral or medial elevation

Deep

Narrow web shoe, beveled ground surface on the side of intolerance, wider ground surface on the opposite side, short hooves, short shoeing intervals

Compact

1) Flexible shoes (e.g., flaps, easy walker)

2) Strongly beveled ground surface (outside rim) on the side of intolerance

3) Rockered ipsilateral toe shoe (“French rockered toe”), full rolling motion shoes, slightly displaced toward the opposite side of the intolerance

4) Note: Short intervals; do not leave heels too long/high, especially in the case of dorsal entheseophytes

DIP arthrosis

Lateral and medial

Deep

1) Short, barefoot trim, well-rounded borders not too much heel

2) Flexible shoes, short shoeing intervals

3) Half round section shoes, tightly fit (e.g., classic roller or eventer)

Compact

 

1) “French rockered toe” (rocker goes from quarter over the toe to opposite quarter; heels stay flat)

2) Half round section shoes

3) Full rolling motion shoes (e.g., “rock n roll”, PG shoes)Note: consider shock absorption (aluminum, pads), keep shoeing intervals short, do not set the shoes too wide

Navicular bursitis, distal DDF, tendonitis, impar lig.. desmitis

Dorsal extension

Deep

Rolled-rockered-set back toe shoes

2) The same plus egg bar

3) Reverse shoeing

Compact

1) Rolled-rockered toe

2) Blunt—set back toe (e.g., NBS or sagittal, aluminum, square toed (wear is faster in the toe between shoeing intervals)

3) Shock absorbing pads, mild frog support pads (test for sensibility of the frog area)

4) Full rolling motion shoe’s with the ground area at the toe strongly beveled; the higher total thickness of the shoe permits an extreme rolled toe

DIP arthrosis and podotrocleosis

Dorsal extension and lateral and medial elevation.

Deep

1) Set back shoe (blunt toe) with beveled ground edges and egg bar

2) Palmar frog and sole support (less heel penetration)

3) Full rolling motion shoe with heel bar

Compact

1) Full rolling motion shoe, with small central base, well set back

2) Shock absorbing pad if sensitive to hammer blows to the shoe, short shoeing intervals

Table 1:
Summary of therapeutic shoeing techniques in relationship to: diagnosis, DED test results, and surface the horse works on.

A study of 250 sound horses, freshly shod or trimmed, gave the following values:

Dorsal extension (mean [CI95%] = 43.18° ± 0.93°, lateral elevation (mean 18.83° ± 0.26°) and medial elevation (mean= 19.79° ± 0.32°).

The SDs were 7.46°, 2.12° and 2.53° respectively. [14]

To illustrate the correlation between the hypothetical result of a digital extension test and the therapeutically shoeing needs of the hypothetical patient, the following example may be useful: if the right fore lame limb shows 28° degrees of tolerance to dorsal extension, 15° of lateral elevation and 19° of medial elevation (before the opposite side of the hoof lifts off the board (Fig), the hoof of the right fore needs a therapeutic shoe which facilitates dorsal and lateral break over, for example a shoe with a setback, blunted and rolled toe and with the lateral ground surface ground away. [Fig, 31]


6.2. Ground surface modifications

As opposed to break over modifications, which have an effect both on compact and on penetrable ground (although they may be more necessary on compact ground), ground surface modifications, such as wide webbed heels, toes or branches of the shoe have most of their effect on penetrable ground. A wide webbed toe, narrow heeled shoe [Fig. 32], prevents the toe from sinking into the ground at the mid stance phase in deep footing, but on hard ground a normal shoe (placed in the same position) will do the same. Or to give an example in the opposite sense, an egg bar shoe will prevent heel sinking, relative to a normal shoe, only on penetrable ground.

On penetrable footing, the modifications of the ground surface of the shoe (and its placement relative to the trimmed foot) will change the center of ground reaction force in all three moments of the stance phase, sometimes with unintended consequences.

At speed, horses land heel first, soliciting the back part of the foot and its shock absorbing function, but also the digital extension tendon and its distal insertions. [Fig.33]

In the mid stance phase, with the fetlock at maximum extension, the suspensory ligament and the superficial digital flexor tendon are at peak tension. [Fig.34]

At the end of the stance phase, just before break over, the deep digital flexor tendon (and other previously discussed structures) will be at peak stress. [15]

Thus, an egg bar shoe with a setback blunted toe, will favor the sinking in of the toe on penetrable footing, facilitating break over, relieving the deep digital flexor tendon. On the other hand, in the mid stance phase, it might solicit the suspensory ligament and superficial digital flexor tendon more. On landing, the palmar part of the egg bar will cause more of a

pull on the distal insertion of the digital extension tendon. Briefly put, “there is no free lunch”; when relieving one anatomical structure, during a particular phase of the stance, other structures will be charged more in the other stance phases.


6.3 Modifications of hoof support and weight bearing.

One of the drawbacks of a classical, nailed on, open shoe, is that it distances the sole, frog and part of the bars from the ground, thereby reducing the weight bearing parts of the hoof to the walls, and ultimately to the laminar suspensory apparatus.

Many hoof conditions, such as weak and under run heels, hoof wall defects, laminitis, etc. can benefit from recruiting the bars, frog, or parts of these, into weight bearing. Special shoes which have this function are the heart bar and the onion heel shoe, which respectively recruit the frog and the bars into weight bearing. [Fig. 35, 36]

Specialty pads, with or without fast setting hoof packing materials, can also have this function, besides having shock absorbing properties. Sole packing materials are distinguished by different hardness (expressed in shore on the A scale), chemical composition, weight, wear resistance, setting times, adhesiveness to the sole, ability to perspire and application method. Some of the currently available products and their properties are listed in table 2: Properties of some commercially available sole packing materials: [16]

Pads and sole packing can also be used to protect thin soles against bruises, especially the softer, light weight ones.

When applying a sole packing, it is useful to do a check on the tolerance to pressure of the frog, remembering that the overlaying structures include the digital cushion, deep digital flexor tendon, navicular bursa and distal sesamoid, all of which can be inflamed and painful, as also a thrushy frog.

This check can be done with hoof testers, or by placing the frog on a wooden handle and lifting up the opposite foot. A positive (pain) reaction should counsel the use of soft packing material.

NAME

HARDNESS

WEIGHT
INGR X 1000CC

HAND MIXED

MIXING GUN

% (VOLUME) OF HARDER

CURING TIME AT 20°C

HUMIDITY OF THE SOLE

MANUFACTURER

CHEMICAL FAMILY

FLUID DURING APPLICATION

STICKS OF THE SOLE

MV2 10S

SSS (10SHORE)

100

X

1:1

5'

++

VAILLANT

SILICONE

±

NO

HORSE PAD

SSS (16SHORE)

100

X

1 LINE X MEASURE

4'

++

TECHNOLOGY HORSE PAD

SILICONE

(KNEED ABLE)

NO

MV2 18S

MMM (18SHORE)

100

X

1:1

5'

++

VAILLANT

SILICONE

±

NO

120S

SS

50

X

8%

6'

DRY "BREATHES"

LUWEX

POLYURETHANE

-

YES

WOLKE7

SS

80

X

X

1:1

6'

++

LUWEX

SILICONE

±

NO

HOME MADE EASY BLUE

S

60

X

100CC 120S 30CC M20 +10CCH

3'

0

LUWEX/ HOME MADE MIX

POLYURETHANE

-

YES

MB12

S

110

X

120CC + 16ML

3'

+

LUWEX

POLYURETHANE

++

YES

MV2-50S

SH

120

X

1:1

5'

++

VAILLANT

SILICONE

±

NO

M9

SH

110

X

120ML + 18-20ML

2'

+

LUWEX

POLYURETHANE

++

YES

M15XXL

SH

110

X

150ML + 20-28ML

3'

+

LUWEX

POLYURETHANE

++

YES

EQUI PAK

H

110

X

1:1

1'

0

VETTEC

POLYURETHANE

++

YES VERY STRONGLY

M20

H

110

X

60ML + 18ML (30°)

2'

+

LUWEX

POLYURETHANE

++

YES

PREMIUM REHE

HH

75

X

1 LINE X MEASURE

3'

++

LUWEX

SILICONE

(KNEED ABLE)

- -

NOT ALL ALL

ERGOSIL

HH

170

X

1 LINE X MEASURE

5'

++

ERGOSIL

SILICONE

(KNEED ABLE)

- -

NOT AT ALL

EQUIBUILD
HHH 110   X 1:1 10' + VETTEC POLYURETHANE ++ YES VERY STRONGLY
TABLE 2

6.4 Shock absorbing shoeing.

Shock and high frequency vibrations are implicated in pain, ischemia and osteo articular degeneration, similar to “white finger syndrome” in humans. A useful clinical sign is when the horse is uncomfortable with the hammer blows, while driving the nails when setting a shoe. Horses which often benefit from shock absorbing shoeing are those that are called upon to work on hard surfaces, like harness or carriage horses.

Shock absorption can be achieved by interposing pads and sole packing between the shoe and the hoof, or with specialty shoes which absorb shock on the ground surface. In the first case it is important to drill holes in the pad, in correspondence to the nail holes of the shoe, before nailing the shoe/pad combination to the foot, so as to preserve the micro movement of the pad independently from the nails. [Fig 37]

The farriery industry is constantly coming out with specialty shoes with shock absorbing claims, but objective, comparable data (at least to the bare foot and normally steel shod foot) are often lacking.

For many fast disciplines (racing, eventing etc.) many of these products are too bulky and/or too heavy. For working day horses, excessive wear and/or cost is also often a problem. [Fig.38]

An interesting solution is offered by products that have a rigid half shoe or metal insert at the toe, for stable nailing, and shock absorbing flexibility in the heel area, like “flaps”, Epona© shoes etc., as they preserve vertical mobility at the heels. [Fig.28]


6.5 Weight reduction

Light weight shoes, mainly aluminum alloy, are used for performance (flat racing etc.), but also have other, preventive and therapeutic properties. Aluminum alloys absorb high frequency vibrations better than steel on hard, compact ground [17], offer better grip on this type of surface and cause less fatigue. They also make it possible to have asymmetrical, wide web, or bar shoes, without excessive (asymmetrical) weight increase and they diminish the limb’s deviations from the normal flight arch. [Fig. 39] Medial or lateral deviations, out of the sagittal plane, of the flight arch of the shod hoof, are common in horses which respectively toe out or in, which in the first case often causes interference injuries to the contro lateral limb. [Fig.40 a,b]

Weight reduction also reduces hyper flexion (and extension) of the limb in the air between stance phases, which might benefit patients with articular (fetlock and carpus e.g.) and tendon or suspensory ligament lesions.


6.6 Hoof wall defects stabilization, repair and glue on shoes.

Many severe hoof conditions can be successfully treated with these materials and methods, which will be amply addressed in Chapters 11 and 13. Glue on shoes for foals will be discussed in Chapter 14.


7. Conclusion

In most cases therapeutic farriery depends on a correct trim (which is not necessarily the easiest part of farriery), as leaving extra length at one side of the hoof, at the heels, or at the toe, will lead to hoof capsule distortion. It is then, that the type, placement and modifications of the shoe will make the (therapeutic) difference.

In lame horses, using a digital extension test may give valuable information as to the most appropriate type of shoe for the specific lameness, as it will let the horse “speak for itself”.

This is especially important, as our diagnostic capabilities have become more precise, often resulting in multiple diagnostic findings in the same limb, many of which might not be the cause of pain or diminished function.

When choosing the therapeutic features of the shoe/shoeing, it is useful to keep the type of horse, hooves, conformation, work and surface on which the horse works in mind. The latter is very important, as the therapeutic shoe/ground interaction is often at the heart of the success or failure of the intended podiatry treatment.


References:

[1] Causati Vanni, M.A.. In: Giordano Brusso nelle scuderie di Federico II imperatore ovvero ,l’arte di curare il cavallo. Velettri: Editrice Vela; 2000. pp. LVI-LIX.

 

[2] D’Autherville, P.; Historique In : Précis de Maréchalerie. Paris : Maloine S.A. Editeur ; 1982. pp. 15-20.

 

[3] Craig, M; “The Value of Measuring the Hoof”. The Farriers Journal, n°148, 02/2011, pp. 6-14.

 

[4] Van Heel, M.C.V.; “Changes in Location of center of pressure and hoof-unrollment pattern in relation to an 8 – week shoeing interval in the horse”, chapter 5, “Distal Limb development and effects of shoeing techniques on limb dynamics of today’s equine athlete”. Doctoral thesis, Febodruk BV, Enschede, 2005, pp. 75-90.

 

[5] Savoldi, M.T.; “Identifying the true foot of the horse”, proceedings, 10 th Geneva Congress of Equine Medicine and Surgery, 11-13 December 2007, pp. 63-67.

 

[6] Craig, J.J., Craig, M.F, Burd, M., Turner, T.; “The Palmar – Metric: Quantifying the Quality of the Equine Distal Phalange”, The Farriers Journal, n°149, 04/2011, pp. 8-22.

 

[7] Castelijns, H.H.; “L’aplomb dans le plan diagonal”, proceedings, 11 ième Congrès Marèchaux et Vétérinaires, La Roche Sur Foron, 28-30 January 1999, pp. 69-70.

 

[8] Caudron, J. ; « Approche orthopédique des affections osteo-articulaires dégénératives de l’extrémité digitale du cheval, prévention et traitement ». Doctoral thesis, Université de Liège, Faculté de Médecine Vétérinaire, 1997-1998.

 

[9] O’Grady, S.E., Castelijns, H.H.; " Sheared heels and the correlation to spontaneous quarter cracks " . Equine Vet. Educ. (2011) 23 (5) 262-269.

 

[10] Castelijns, H.H.; “Pathogenesis and treatment of spontaneous quarter cracks – quantifying vertical mobility of the hoof capsule at the heels”, Pferdeheilkunde, 22 Jahrgang, 2006, Ausgabe 5, September – Oktober, pp. 569-576.

 

[11] Lawson, S.E.M.; Château, H.; Pourcelot, P.; Denoix, J.M. ; Crevier – Denoix, N. ; “Effect of toe and heel elevation on calculated tendon strains in the horse and the influence of the proximal interphalangeal joint”, J. Anat. (2007) 210, pp. 583-591.

 

[12] Van Heel, M.C.V., Barneveld, P.R., Van Weeren, P.R., Back, W.; “Dynamic pressure measurement for the detailed study of hoof balance; the effect of trimming”., Equine Vet. J. (2004) 36 (8), pp. 778-782.

 

[13] Serteyn, D., Vanschepdael, P., Caudron,I., Miesen, M., Lalot, P., Grülke, S., Staquez, S.; “Evaluation Clinique de la ferrure orthopédique Equi+® Lors de pathologies de l’articulation interphalangienne distale”, Pratique Vétérinaire Equine, 1995, 27 (2), pp. 105-110.

 

[14] Castelijns, H.H. ; "How to Use Digital Extension Device in Lameness Examinations », 2008, Vol. 54/AAEP Proceedings, pp.228-231.

 

[15] Van Heel, M.C.V., Van Weeren, P.R., Back, W.;”Shoeing sound Warmblood horses with a rolled-toe optimizes hoof unrollment and lowers peak loading during break over”. Equine Vet J. 2005.

 

[16] Castelijns, H.H.; “Sole and frog support systems”, proceeding 11 th SIVE Congress, 28-30 January 2005, pp. 52-55.

 

[17] Benoit, P., Barrey, E., Regnault, J.C., Brochet, J.L.; “Comparison of the Damping Effect of Different Shoeing by the Measurement of Hoof Acceleration”, Acta ANAT. 1993, 146, pp. 109-113.

 

Hans Castelijns
D.V.M - Certified Farrier