How to Construct and Apply the Wooden Shoe for Treating Three Manifestations of Chronic Laminitis

Reprinted with permission from the American Association of Equine Practitioners.
Originally printed in the 2007 AAEP Convention proceedings

1. Introduction

The treatment of chronic laminitis presents a challenge to veterinarians, farriers, and horse owners. Our ability to rehabilitate horses with laminitis, regardless of the method of treatment, is related to the severity of damage to the lamellae. Chronic laminitis is defined by the presence of mechanical collapse of the lamellae and displacement of the distal phalanx within the hoof capsule.¹ Two forms of displacement of the distal phalanx are widely recognized: dorsal capsular rotation (the most common form of displacement) and distal displacement. Recently, two of the authors (AHP and SEO) have become more aware of the rotation that occurs in a medial or lateral direction where the distal phalanx displaces distally on one side. If dorsal capsular rotation is severe, the instability of the distal phalanx combined with the weight of the horse often leads to prolapse of the sole or prolapse of the distal phalanx through the sole. Recently, the wooden shoe has emerged as the most consistently successful method to address these three entities of chronic laminitis and are used extensively by two of the authors (SEO and MLS).² The wooden shoe allows the distal phalanx to be realigned. It has all the mechanical advantages of the other shoes previously advocated for the treatment of laminitis, because it addresses the forces exerted on the compromised lamellae. Additionally, it is able to concentrate weight bearing evenly over a specified section of the foot because of its flat, solid construction. The major advantages of the wooden shoe are that it is easy to construct, it is applied in a non-traumatic manner, and it can easily be altered according to the radiographic appearance and structural requirements of each individual foot/horse.

2. Radiology

The lateral radiograph has always been considered the "gold" standard for evaluating chronic laminitis, but it does not allow for identification of asymmetrical medial or lateral distal displacement. Therefore, the authors consider it crucial that a dorsopalmar (dorso 0° palmar) radiographic projection is included as part of the radiographic study for either acute or chronic laminitis. High-quality radiographs are required to visualize the osseous structures within the hoof capsule as well as the hoof capsule itself. Radio-opaque markers can be used to determine the position of the distal phalanx in relation to surface landmarks.

The radiographic features of chronic laminitis are well documented.³ The following observations from the lateral radiograph are important in determining the prognosis and guiding treatment: the thickness of the dorsal hoof wall, the degree of dorsal capsular rotation, the angle of the solar surface of the distal phalanx relative to the ground, the distance between the dorsal margin of the distal phalanx and the ground, and the thickness of the sole.

Fig. 1. Radiograph of asymmetrical downward displacement of the distal phalanx on the medial side. Note that the line drawn through the solar foramens is not parallel with the ground. Also note the disparity in the joint space from the lateral to the medial side.

Fig. 2. The basic wooden shoe where the proximal piece is cut vertical, and the thicker piece is cut on a 45° angle. Note the wedge pad attached to the wooden shoe for heel elevation, if necessary.

The dorsopalmar radiograph is examined to determine the position of the distal phalanx in the frontal plane. Asymmetrical distal displacement of the distal phalanx on either the lateral or medial side is present if an imaginary line drawn across the articular surface of the distal interphalangeal joint or between the solar foramens of the distal phalanx is not parallel to the ground, if the joint space is widened on the affected side and narrowed on the opposite side, or if the width of the hoof wall appears thicker than normal on the affected side. If the position of the coronary band is visible on the radiograph, then the distance between the coronary band and the palmar processes of the distal phalanx will be greater on the affected than the unaffected side (Fig. 1).

3. Materials and Methods

Construction of the Shoe

The authors chose wood because its light weight, the ease with which it can be shaped (both before and after application), and its ability to dissipate energy at impact while remaining rigid.⁴ The basic shoe is made from two pieces of plywood. An aluminum shoe with a broad toe that is available in sizes 00-5 is used as a template.^a One piece of plywood is 0.250-0.375 in thick, and the second piece is 0.75 in thick. Using the aluminum shoe as a template, the thinner piece of plywood is cut out with a vertical border, and the thicker piece is cut out with a border beveled at a 45° angle using an angle saw.^b As a modification to the basic pattern, the palmar or heel section of the wooden shoe can be cut at a 15°, 30°, or 45° angle or left straight, if desired. The pieces of plywood are glued together; the thinner portion is proximal, and two 1-in drywall screws are used to secure the two pieces together. A wood rasp is used to blend the cut angles into a uniform slope (Fig. 2).

Fig. 3. Wooden shoe fabricated from a single piece of plywood. Note the recess in the foot surface of the shoe created with a router.

Fig. 4. Proximal section of plywood cut in the shape of a "W." Note the 3° wedge to elevate the heels.

The shoe can also be fabricated from a single piece of 1.125-in plywood (purchased as subflooring plywood). If the sole or distal phalanx is prolapsed, a recess can be created in the proximal surface of the shoe by cutting a half-moon shape dorsal to a line that is one-third the length of the shoe in the thinner piece of plywood with a router. A hand grinder can be also used to create a trough in the shoe below the area of the sole or bone that has prolapsed (Fig. 3).

The same end can be achieved by cutting the thinner piece in the shape of a "W" and then attaching it to the thicker section of plywood as described above (Fig. 4).

Goals of Treatment for Chronic Laminitis

Trimming and shoeing has always been the "mainstay" of treating chronic laminitis, and it is directed at reducing/removing the adverse forces on the compromised lamellae. In considering hoof care in horses with chronic laminitis, there are three goals for therapy: to stabilize the distal phalanx within the hoof capsule, to control pain, and to encourage new hoof growth to assume the most normal relationship to the distal phalanx possible. Realignment of the third phalanx to create a better relationship of the solar surface of the distal phalanx with the ground is used as the basis for treating chronic laminitis.^5-7 Applying the wooden shoe after this procedure compliments the realignment of the distal phalanx and further decreases the forces on the lamellae. The same shoeing principles for other methods are applied to the wooden shoes that are used to treat chronic laminitis. They are to recruit ground surface, to reposition the breakover palmarly, and to provide heel elevation as needed.⁵

Fig. 5. Lateral radiograph showing dorsal capsular rotation. Note the lack of hoof-wall growth at the coronet at the toe. The red arrow denotes the center of articulation. The black line shows the amount of heel to be removed.

Dorsal Capsular Rotation

Dorsal capsular rotation describes the divergence of the dorsal hoof wall from the dorsal parietal surface of the distal phalanx independent of the relationship of the distal phalanx with the phalangeal axis.⁸ A generalized outline will be used to describe the preparation of the foot and application of the wooden shoe for this type of displacement; it must be noted that each case of chronic laminitis must be treated on an individual basis. The foot must be trimmed, and the shoe must be sized and positioned in relation to the underlying distal phalanx, regardless of the conformation of the hoof. Therefore, measurements must be made from radiographs taken before shoeing. Using the radiograph for guidance, a vertical line is drawn from the center of the distal end of the second phalanx to the ground. This line should correspond to the widest part of the foot. A line is then drawn parallel to the solar border of the distal phalanx starting 15 mm below the palmar process of the distal phalanx and continuing dorsally. The hoof wall to be removed in the heel area can be determined from the mass below this line (Fig. 5).^5-7

A line is drawn across the widest part of the foot and the hoof wall; the area palmar to this line is trimmed according to the lines drawn on the radiograph. If, as is frequently the case, the wall and sole dorsal to the line drawn across the sole is <15mm, trimming in this manner will create two different planes on the ground surface of the foot. A line is also drawn across the center of the wooden shoe (Fig. 6).

Fig. 6. Using the widest part of the foot as a guideline (red line), the heels are trimmed in a palmar direction. The red line drawn in the middle of the wooden shoe is used to determine the proper size wooden shoe to use.

The correct size of the shoe is determined by placing the lines on the foot and the shoe on top of each other; the appropriate size shoe will extend from the line drawn across the foot to the end of the heel or 6-8 mm palmar to the heel. To compensate for the increase in tension in the deep digital flexor tendon that is caused by lowering the heels of the hoof capsule, the heels can be raised by applying a wedge pad to the hoof surface of the wooden shoe. The angle of the wedge is usually 2-4°, depending on the amount of heel horn removed. The wedge pad is attached to the shoe with 1-in drywall screws. Using a 0.078-in drill, a guide hole is drilled through the lateral and medial side of the hoof wall at the widest part of the foot, and a 1.5-in drywall screw is placed in each hole and screwed in until just visible on the ground surface of the foot. To better increase weight bearing by the sole, bars, frog, and sulci, a deformable impression material^c is applied to the solar surface of the foot. The shoe is now placed on the ground surface of the foot and attached using 2-in drywall screws. The foot is placed on the ground and allowed to bear weight; this allows the impression material to set between the foot and the shoe in the optimal form. Two to three more holes are drilled through both sides of the hoof wall, and the shoe is secured in place using additional screws. If the mass of the hoof wall is insufficient or if the quality of the hoof wall is insufficient to hold the screws, screws can be placed in the wooden shoe against the available hoof wall to act as struts, and an acrylic composite^d is used to form a bond between the hoof wall, screws, and wooden shoe. With the foot on the ground, a vertical line is drawn from the dorsal coronet to the ground. The point where the line meets the ground is where the breakover point of the shoe should be positioned (Fig. 7).

Fig. 7. (A) A wooden shoe with impression material and a wedge pad to provide heel elevation. The black arrow is the widest part of the foot. The red line denotes the point of breakover on the ground surface of the shoe. (B) A wooden shoe fabricated from a single piece of plywood with the same guidelines as A.

This point will usually be just dorsal to the margin of the distal phalanx. Setting the breakover to this point in the shoe is easily accomplished using a hoof rasp with the foot being held in the farrier position. Deep digital tenotomy has been the recommended treatment when prolapse of the distal phalanx has occurred secondary to dorsal capsular rotation. One author (SEO) has observed that the wooden shoe has provided an alternative and often better means to treat this condition without surgery.

Fig. 8. Left forelimb with distal phalanx offset toward the medial side.

Fig. 9. Diagrammatic illustration of the method used to move the forces toward the unaffected side.

Medial or Lateral Asymmetrical Displacement of the Distal Phalanx

In displacing asymmetrically, the distal phalanx rotates in the frontal plane within the hoof capsule and moves away from the hoof wall on the affected side. The reason that some horses displace asymmetrically is not completely understood. Clinical observations by two of the authors (SEO and AHP) suggest that asymmetrical displacement is usually toward the medial side, and the distal phalanx within the hoof capsule is usually offset toward the affected side (Fig. 8).

Occasionally, these two authors have observed distal displacement laterally in instances where the horse developed laminitis in one foot after prolonged weight bearing subsequent to severe lameness in the contralateral limb. Aside from general trimming of the foot, removal of hoof wall at the heels may not be necessary. The sizing of the shoe and the application of impression material will be the same as described for dorsal capsular rotation. The crucial difference between treating medial or lateral asymmetrical displacement compared with dorsal capsular displacement is the mediolateral positioning of the shoe. Based on the apparent asymmetry of the distal phalanx within the hoof capsule visible on radiographs, a clinician's first response might intuitively be to try and restore the asymmetry of the distal interphalangeal joint and the position of the distal phalanx in relation to the ground. This would most readily be accomplished by raising the side of the hoof on which the distal phalanx is displaced. However, this will increase the weight bearing on the affected side and cause the distal phalanx to displace further in relation to the hoof capsule, which will increase the pain. Therefore, the appropriate technique is to decrease weight bearing by the affected wall, which is accomplished by sharing weight bearing with the sole and frog and increasing weight bearing with the unaffected wall. This can be achieved by placing an extension on the unaffected side (Fig. 9).

Because of its flat solid surface, the wooden shoe combined with impression material seems to load those structures away from the affected side. The width of the hoof wall on the affected side is reduced using a rasp on the outer surface. The wooden shoe is then fitted so that the edge of the shoe is even with or just under the hoof wall on the affected side, and the shoe forms an extension of ~0.25-in beyond the hoof wall on the unaffected side (Fig. 10).

If insufficient hoof wall is present on the affected side to accommodate screws, screws can be placed into the wooden shoe on an angle so that they lie against the hoof wall. They should be bonded with an acrylic composite.

Fig. 10. (A) Wooden shoe fitted with an extension on the lateral side. Note the screws that are inserted as struts to attach the shoe to the hoof wall with acrylic. (B) Wooden shoe with extension being attached to foot with screws.

Prolapse of the Sole or Distal Phalanx

For prolapse of the distal phalanx, the foot is trimmed to establish realignment, and heel elevation is applied to the shoe to decrease the forces on the deep digital flexor tendon. Before applying the shoe, the wooden shoe is placed against the ground surface of the foot and pressed against the exposed corium of the distal phalanx. The moisture of the tissue or a suitable dye applied to the corium will create an impression on the foot surface of the wooden shoe. A router can be used to cut out the impression, or a trough can be created with a grinder. The shoe is now applied, making sure that the impression material is concentrated palmar to the apex of the frog. The affected area can be packed with an appropriate antiseptic from the front of the shoe.

4. Results

Success of any given treatment for chronic laminitis is hard to evaluate because of the individual diversity between each case. In reviewing the records on horses with the three types of displacement described in this paper, the authors established basic guidelines to evaluate the response after application of the wooden shoe. All evaluations were for a period of 8 wk post-application of the wooden shoe. All three types of displacement were evaluated for a decrease in the level of pain. To better evaluate the wooden shoe for dorsal capsular rotation, the authors chose cases that had been treated previously with other methods of farriery with minimal response. Increased hoof-wall growth at the coronet at the toe and an increase in sole depth were used on horses where the wooden shoe was applied for dorsal capsular rotation. Increased hoof-wall growth at the coronet on the affected side of the foot was used for horses with unilateral displacement. Finally, cornification of the exposed corium of the distal phalanx as well as hoof-wall growth was used on those cases where the distal phalanx had penetrated through the sole.

There were 21 cases of dorsal capsular rotation, and 17 (81%) had a favorable response to wooden shoes. There were 11 cases of asymmetrical displacement, and 8 (65%) had a favorable response to wooden shoes. There were 9 cases of penetration of distal phalanx through the sole, and 7 (77%) had a favorable response to wooden shoes.

5. Discussion

The wooden shoe provides another very consistent farriery option when treating a horse with chronic laminitis. Removing the stresses on the lamellae has always been difficult when using traditional shoes to treat chronic laminitis. Traditional shoes are placed under the hoof wall, which concentrates the load on the compromised lamellae. The plane of the wooden shoe combined with the impression material allows the foot to become load sharing, because the load is shared by the hoof wall and the soft-tissue structures of the foot. Furthermore, cutting the perimeter of the wooden shoe at a 45° angle around the circumference of the foot is thought to decrease the torque on the lamellae.⁶ Creating a recess in the shoe under the distal phalanx in the toe area relieves the load on the bone, and then, the weight-bearing function is concentrated in the palmar section of the shoe. When displacement of the distal phalanx within the hoof capsule is severe, the wooden shoe can be used as a transient treatment to build sufficient hoof mass for the application of a more conventional shoe.

References and Footnotes

1. Hood DM. The mechanisms and consequences of structural failure of the foot. In: Hood DW, ed. The veterinary clinics of North America, vol. 15:2. Philadelphia: W.B. Saunders Co., 1999;437-461.
2. Steward ML. How to construct and apply atraumatic therapeutic shoes to treat acute or chronic laminitis in the horse, in Proceedings. 49th Annual American Association of Equine Practitioners Convention 2003;337-346.
3. Redden RF. Clinical and radiographic examination of the equine foot, in Proceedings. 49th Annual American Association of Equine Practitioners Convention 2003;174-185.
4. Reid SR. Impact energy absorbing mechanisms in crushing and indentation of wood, in Proceedings. IUTAM Symp On Imact Dynamics 1994.
5. O'Grady SE. Realignment of P3—the basis for treating chronic laminitis. Equine Vet Edu 2006;8:272-276.
6. Parks AH. Chronic laminitis. In: Robinson NE, ed. Current therapy in equine medicine, vol. 5. St. Louis: W.B. Saunders Co., 2003;520-528.
7. Parks AH, O'Grady SE. Chronic laminitis: current treatment strategies.In: O'Grady SE, ed. The veterinary clinics of North America, vol. 19:2. Philadelphia: W.B. Saunders Co., 2003;393-416.
8. O'Grady SE, Parks AH, Redden RF, et al. Glossary of podiatry terms. Equine Vet Edu 2007;(in press).

1. Natural Balance Shoe, EDSS, Penrose, CO 81240.
2. Craftsman Angle Saw, Sears, Roebuck and Co., Hoffman Estates, IL 60179.
3. Equilox Pink Impression Material, Equilox International, Pine Island, MN 55963.
4. Equilox Adhesive System, Equilox International, Pine Island, MN 55963.