EQUINE VETERINARY EDUCATION / AE / AUGUST 2020


419


a)


b)


Line 2 Line 1


Breakover


A. Parks


Fig 7: a) A schematic illustration of a radiograph with dorsal capsular rotation showing the lines drawn parallel to the solar surface of the distal phalanx and the line drawn parallel to the parietal surface of the distal phalanx (Image courtesy of Andrew Parks). b) The illustration applied to a radiograph with dorsal capsular rotation. Black line represents COR.


Application of the shoe


The trim Before beginning the trim, the horse should be observed in motion, noting the degree of lameness, if present, on the straight and on turns. The strike pattern of the horse is determined whether the horse lands flat, markedly heel first, toe first or lands asymmetrically on one side of the hoof capsule. The initial step to trim the foot in all cases is to draw a line across the widest part of the foot. The widest part of the foot is 5–10 mm dorsal to the COR which makes it a good guideline to begin the trim. The frog is trimmed by removing any loose exfoliating horn and the hoof wall is rasped from the middle of the foot palmarly to where the hoof wall at the heels and the frog are on the same plane. This creates additional ground surface from the middle of the foot to the heels which moves the load in a palmar direction. In most cases where the wooden shoe is used, the dorsal section of the foot will be compromised with limited sole thickness, so the toe length can be reduced using the nippers in a vertical direction according to the radiograph or by rasping the dorsal hoof wall (O’Grady 2010; Parks and O’Grady 2015). A template superimposed on a radiograph can be used


as a guide when trimming the case with chronic laminitis (O’Grady 2010; Parks and O’Grady 2015) (Fig 7). The quarters and heels of the hoof wall are trimmed from the widest part of the foot palmarly to coincide with line 1 drawn distal and parallel to the solar margin of the distal phalanx on the radiograph. The solar surface of the foot dorsal to the widest


a)


part of the foot is not trimmed. The toe length is reduced from the dorsal hoof wall according to line 2 drawn dorsal to the parietal surface of the distal phalanx. If possible, the ideal end product when trimmed according to the template, will have two different planes on the ground surface of the foot with the heels of the hoof capsule and the frog on the same plane (Fig 8a). This method of trimming redistributes the load to the palmar section of the foot and functionally unloads the toe. Following the trim, the foot is placed on the ground and


the horse is observed to see whether the heel of the foot is touching the ground at rest. In motion, the horse is observed for signs of lameness or increased lameness following the trim and whether it lands toe first in a straight line. If any of these signs are present, heel elevation will be necessary to


compensate for the increase in tension in the deep digital flexor tendon caused by trimming the heels of the hoof capsule. Heel elevation is easily added to the wooden shoe using a wedge pad (O’Grady 2010; Parks and O’Grady 2015) (Fig 8b).


Fitting and applying the shoe The foot surface of a wooden shoe is measured from dorsal to palmar drawing a line across the middle of the shoe. The correct size of the shoe is determined by superimposing the line drawn across the widest part of the foot and the line drawn across the shoe over each other; allowing the wooden shoe to extend marginally beyond the perimeter of the hoof capsule and 1–3 cm palmar to the trimmed heel.


b)


Fig 8: a) The two planes on the solar surface of the foot when trimming for realignment of the distal phalanx. Note the position of the block on the foot using the widest part of the foot as a guide. b) A wedge pad added to the wooden shoe for heel elevation (Image courtesy of Andrew Parks).


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