Dr. Judith L. Mulholland

X-rays are a valuable diagnostic tool. They tell us whether or not the distal phalanx is sinking lower into the hoof capsule, they show the positions of the wall and pedal bone, the thickness of sole, and indicate whether there is fluid, infection or gas forming in the soft tissue space.

Many people describe the pedal bone as ‘rotated’. X-rays during the acute phase often show the pedal bone against the angles created by a flared and distorted hoof capsule. This can be misleading when assessing for rotation or sinking. The term ‘rotation’ creates panic and scares many owners unnecessarily. They expect the pedal bone to drop through the sole at any moment.

Rotation is defined as a state of being pivoted around an axis. The axis in this case is the distal interphalangeal (coffin joint). The phalanx bones are normally all at the same angle. When the heel is raised or the toe is shortened this angle is broken forward at the coffin joint and the pedal bone appears to have rotated around its pivot point at the center of the joint. I have described true cases of rotation in the section on club feet, as this is what a rotated pedal bone is. Therefore rotation is incorrectly described if the pastern bones are in normal alignment, or the hoof is distorted with a laminitic wedge or if the heel is long or toe is short and these imbalances have not been corrected for with farriery before the radiograph is taken.

When x-rays are taken, the hoof/pastern angle should be normal, and the hoof in a normal weight-bearing position; i.e., trim the foot if necessary, as laminitis does not always strike a neatly balanced foot. If the wall at the toe  is chronically flared, the top 1/4 is still usually in a normal alignment and forms a guide to trim the rest off from the front. The excess heel is judged with experience. Then an accurate x-ray of the pedal bone and the hoof capsule is achieved.

If an x-ray is taken of a chronic laminitic foot while it is non weight bearing and the hoof is untrimmed, and then another x-ray is taken after addressing these problems, the difference is dramatic. In these cases, I doubt that any rotation truly exists other than that created by a lack of good farrier.

Long term changes to the distal phalanx associated with long term neglected laminitis include a curling upward of the pedal bone around its edges (pixie toe), pedal osteitis, remodelling of the distal phalanx e.g., the solar surface flattens. Even these feet, with a correctly trimmed hoof capsule, will appear dramatically better when re-radiographed.

Occasionally very flat feet with a long toe/low heel laminitic feet are allowed to develop a severely broken-back hoof/pastern angle. This increases the tearing forces on the damaged laminae at the toe. This is prevented by good, regular farriery. Normal hoof angles at all stages of the treatment of laminitis essential.

After the acute stage, the rapidly forming laminitic wedge exaggerates the forces affecting the wall at the toe, forcing it away from the pedal bone, which is now repositioned within the capsule that has moved around it. The deep digital flexor tendon plays only a small part in this effect, and most rotated x-rays are produced from chronic feet with excess heel or short toe, or a flared toe and wide laminitic wedge. In other words, the hoof capsule is distorted more than the bone structure. This could be described as counter rotation of the pliable hoof capsule, while the phalanx bones are in normal alignment. True rotation does occur, but cannot be accurately assessed by using the distorted hoof capsule as a guide. The first step is always to normalise the hoof as much as possible.

The hoof is still held in place all the way around the back, in most cases, by the laminitic attachment of the lateral cartilages and bars, and the pedal bone within the hoof is attached to the deep digital flexor tendon at the back and extensor tendons at the front.

Consider the relative heights of the coronary band and extensor process on x-ray and the alignment of the phalanx bones, rather than using a distorted hoof capsule as a guide. This has more diagnostic relevance than "rotation" when the hoof capsule is distorted.