Fracture of the distal phalanx is not an uncommon injury in equine practice. Although this fracture is most common in racehorses, it can occur in any breed. Causes could be racing on hard track, kicking an unyielding object, landing on blunt objects while exercising and penetration of the hoof by a foreign body. Other hoof problems such as pedal osteitis, bone infections, flat feet and improper trimming and/or shoeing may predispose the horse to this type of injury. As with any fracture the emphasis of treatment will be based on stability and support. This report describes a relatively simple method of therapeutic shoeing that incorporates all the principles necessary for stabilization of distal phalanx fractures.

Classification:

Fractures of the distal phalanx have been classified according to their configuration.

Type Configuration:

I Non-Articular Wing Fracture
II Articular Wing Fracture
III Midsagittal Articular Fracture
IV Extensor Process Fracture
V Solar Margin and Misc. Fractures

The involvement of the coffin joint influences the outcome of the case and the future soundness of the animal. Fractures that involve the articular surface usually account for increased lameness, a longer length of convalescence and a poor prognosis for a return to full athletic ability. On the other hand, non-articular wing fractures carry a much better prognosis.

Diagnosis:

Affected horses will show a moderate to severe supporting limb lameness that is acute in onset. Trotting on a hard surface will generally accentuate the lameness. Increased digital pulse, sensitivity to hoof testers over the sole and swelling around the coronary band are noted. With time, the sensitivity of the hoof testers will become localized to the area of the fracture. Clinical signs are similar to those displayed by horses with a sub solar abscess or a severe subsolar bruise. Once the clinical examination has isolated a foot-related problem and no abscess is found, high quality radiographs are necessary to confirm the presence of a fracture. It is the author's opinion that digital nerve anesthesia should not be used prior to radiographs in acute lameness situations, even if clinical signs are minimal, as full weight bearing on the foot may cause the fracture line to increase in length, become comminuted, or cause non-articular fractures to become articular. Radiographic examination should consist of several views of the coffin bone. Several oblique views are often required to position the primary x-ray beam directly over the fracture site. When an articular fracture is suspected, this can often be confirmed with a straight-on anterior-posterior view, which will reveal a "step" in the distal inter phalangeal joint as a result of the fracture. If the clinical signs indicate a possible fracture of the distal phalanx but the initial radiographs are negative, the horse should be stall confined for 7 to 10 days and subsequent radiographs may demonstrate the fracture line due to bone demineralization at the site of the initial injury. A Plll fracture can be diagnosed in the acute stage using nuclear scintigraphy if the initial radiographs are negative.

Treatment:

In older horses with all types of fractures, basic therapy would consist of strict stall confinement, the judicial use of nonsteroidal anti-inflammatory drugs (NSAIDs) and therapeutic shoeing.

Nonsteroidal anti-inflammatory drugs should be given in such a dosage as to decrease inflammation but not entirely eliminate pain, as this may cause further damage at the fracture site and it may be difficult to evaluate the effectiveness of the therapeutic shoe. If the fracture invades the joint, the administration of intramuscular Adequan® on a weekly basis would appear to be rational therapy.

Therapeutic Shoeing:

The most successful method of therapeutic shoeing consists of a straight bar shoe with a continuous rim attached to the perimeter of the shoe, encasing the distal border of the hoof wall to limit expansion of the hoof wall, decrease the independent vertical movement of the heels and provide stabilization to the third phalanx. This author is packing the solar surface of the foot with silastic material (Equilox® - Pink) along with the continuous rim shoe for the following reasons. Firstly, when any form of restrictive shoe is applied to the distal outer hoof wall, the foot tends to contract, especially at the heels, over a short period of time. Solar/frog support in any form appears to lessen this process quite markedly. Secondly, the coffin bone descends in a distal palmar/plantar direction when weight is born on the limb with no form of support from the ground surface. Also, if the fracture is
articular with the larger fragment being displaced ventrally, this added support may increase the stabilization in this direction.

Method:

The continous rim shoe is fabricated from steel and is relatively hard to construct. The author has modified the method of constructing a continuous rim shoe to where it is much more user friendly. This technique has been used on 4 cases with very encouraging results based on radiographic follow-up. The heels of the foot are trimmed to the widest part of the frog if possible to increase the ground surface of the foot. The toe is shortened by backing up the dorsal hoof wall to decrease any lever that might be present. A magic marker is used to mark the ground surface of the foot 1 to 1.5 inches beyond the widest part of the foot on both the medial and lateral side. A steel or aluminum straight bar shoe preferably with side clips is fitted slightly fuller than usual to the circumference of the hoof in the toe, quarter and heel area. Or an open aluminum or steel shoe can be fitted to the foot and a straight bar can be welded in between the heels of the shoe. The shoe should extend beyond the heels to provide palmar/plantar support. A Plll articular wing fracture will be used as an example to illustrate the method (Figure 1).

A piece of gutter guard is cut to fit the solar surface of the shoe and glued in place (Figure 2). The gutter guard is essential to hold the impression material in place. Small pieces of fiberglass are cut and mixed with a 2 oz jar of an acrylic composite (Equilox®). A ¼ inch layer of the composite, the width of the shoe (approx 1 inch) is applied to the perimeter of the solar surface from the mark beyond the widest part of the foot on the medial side to the corresponding mark on the medial side. Another ¼ inch layer of composite 1-1.5 inches in width is placed on the outer hoof wall adjacent to the composite on the solar surface. The fitted shoe using the side clips as a guide is gently placed into the composite making sure the composite comes through the nail holes. The continuous rim of composite on the outer hoof wall is shaped with a finger, the whole foot is covered with plastic and the composite is allowed to cure while holding the foot off the ground. Upon completion of the cure, the composite rim on the outer hoof wall is further shaped using a drum sander or a rasp. One or two nails are now placed in both branches of the shoe using the second and third nail holes (Figure 3). One or two nails on either side are all that are necessary if clips are present and fitted properly. The two part impression material is now mixed in equal parts and inserted into the solar surface of the foot making sure it is pressed into the gutter guard. The foot is again held up while the silastic material cures. Holding the foot off the ground ensures the impression material will form a mould of the solar surface of the foot in an unloaded position (Figure 4).

The above procedure can also be used with glue-on shoes. An aluminum straight bar shoe is fitted to the foot as described above. A section of gutter guard is attached to the solar surface of the shoe. The shoe is attached to the solar surface of the foot and the excess composite is used to create a rim around the perimeter of the foot. Impression material is used in the same manner as described above. One major advantage is that it provides a non-traumatic method to attach a shoe.

The shoe should be changed at 4-6 week intervals. To remove the shoe, rasp the composite continuous rim of the outer hoof wall and remove the shoe in a routine manner. At each reset the foot can be radiographed to monitor healing. It is this authors opinion that a lack of lysis along the fracture site and increasing bone density is a good indication that the distal phalanx is stable.