584


EQUINE VETERINARY EDUCATION / AE / NOVEMBER 2020


a)


Fig 5: Radiograph shows a marked flexural deformity involving the distal interphalangeal joint (red circle). [Colour figure can be viewed at wileyonlinelibrary.com]


b)


Fig 4: Photograph of toe extension shows the leverage on the hoof capsule and the point on the dorsal wall where the force is exerted (red arrow). Note the heel off the ground. Illustration of foot shows ground reaction force (GRF) is moving dorsally in the toe as the muscle tendon unit shortens and tension increases in the DDFT (Image courtesy of Andrew Parks). [Colour figure can be viewed at wileyonlinelibrary.com]


author has not been able to subsequently lower the heel or remove the wedge and establish an acceptable hoof angle with the heel on the ground. Once a marked flexural deformity of the DIPJ with the heels of the hoof capsule lifted off the ground or a distorted hoof capsule characterised by a foot with a steep hoof angle, a prominent fullness at the coronet, a broken forward hoof-pastern axis, a disparity in the length of the heel relative to the toe of the hoof and some degree of concavity in the toe is apparent; the author recommends transection of the accessory ligament of the DDFT combined with the appropriate farriery. The farriery is generally performed prior to the surgery


either before or while the foal is anaesthetised to prevent manipulating the limb and handling the surgical site following the procedure. A toe extension is not used; rather an acrylic


© 2019 EVJ Ltd


composite is applied to the solar region of the toe to create a reverse wedge (Stone and Merritt 2009; Hunt 2012; O’Grady 2012, 2017). The wedge affords protection for the toe region and appears to redistribute the load to the palmar aspect of the foot, thus mildly increasing the stresses on the DDFT, and appears to restore the concavity to the sole. The heels are lowered with a rasp from the point of the frog palmarly, until the sole adjoining the hoof wall (sole plane) at the heels becomes solid. This will generally place the hoof wall and the frog on the same horizontal plane. Any concavity or bending in the dorsal aspect of the hoof wall is removed with a rasp in order to redirect the forces directly under the coronet at breakover. The ground surface of the foot dorsal to the frog and the perimeter of the dorsal hoof wall are sanded and prepared for the composite wedge using a rasp or motorised burr (Dremel tool). Deep separations in the sole-wall junction at the toe are explored and filled with clay, if necessary, to prevent tracts for infection beneath the composite. Foals undergoing this procedure are usually between 3 and 5 months old; therefore, due to their size and weight, reinforcing the composite with fibreglass is necessary to prevent excessive wear. A small section of fibreglass is separated into strands and mixed with the composite. The acrylic composite is applied to the solar surface of the foot beginning at the apex of the frog and extending to the perimeter of the hoof wall where a thin lip is formed around the perimeter of the dorsal hoof wall at the toe. The composite is moulded into a wedge starting at 0° at the apex of the frog and extending to 2° to 3° at the toe (Stone and Merritt 2009; O’Grady 2012, 2017) (Fig 6). If desired, a piece of 1/8-inch aluminium plate can be cut out in the shape of the dorsal aspect of the sole. Multiple holes are drilled in the plate, and it is gently placed into the composite. The aluminium is pushed down so that the composite material extrudes through the holes, and the aluminium plate is then covered with additional composite. This additional reinforcement allows the older foals to be walked daily or turned out in a small paddock without the foal wearing through the composite. The foal is placed under general anaesthesia, and the surgery is performed in a routine manner that is well described in the veterinary literature.


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