HOOF EVALUATION: RADIOGRAPHS FOR THE FARRIER
By: Tracy A. Turner DVM, MS, DiplACVS, DiplACVSMR
Radiology of the equine hoof is used to confirm various disease processes such as laminitis, third phalanx fractures, osteoarthritis (ringbone), navicular disease and extensive hoof wall separations. It has evolved to where it quite beneficial for the farrier to use radiographs for guidance when trimming the equine foot. We can immediately see the additional information that can be gained from a radiograph taken of a distorted hoof capsule. One can see the orientation of P3 within the hoof capsule, the hoof/pastern axis, how much and where the foot should be trimmed for better alignment and where the shoe should be placed under the limb for the best mechanical advantage. The extent of a hoof wall separation associated with White Line Disease can also be observed. The two radiographic views useful to the farrier are the lateral view (from the side) and the dorsal/palmar view (from the front).
When using radiographs for guidance in trimming the foot it is important that the image generated by the x-ray machine is the same as the foot i.e. no magnification. In this way, measurements taken from the x-ray can be transferred to the foot. This is controlled by what is known as the focal-film distance (FFD) and it is easy to calibrate. We use a special block with markers of a known distance between them; when we take a radiograph software can automatically calibrate the radiograph and we immediately know distances measured are accurate.
The feet should be thoroughly cleaned, for farrier radiographs the shoes can and should be left in place. The horse should be stood on a flat, level surface. To appreciate bone position, the radiographs should be taken with the horse bearing weight and both feet placed on wooden blocks of equal height. The cannon bone should be perpendicular to the ground. This can be accomplished by placing a level on the dorsal surface of the cannon bone. A small carpenter’s line level can be placed on top of the x-ray machine to ensure that it is level with the ground. Radiopaque markers such as a thumbtack can be placed near the apex of the frog and the end of the heel. After taking the radiographs, the spot in the apex of the frog where the thumbtack was placed should be marked by creating a small channel in the frog with the hook of the hoof knife. Likewise, a small channel can be placed in the outer hoof wall next to where the tack was placed at the end of the heel. These marks will act as landmarks for transferring measurements obtained from the radiographs to the foot.
The lateral radiograph will show the position of P3 within the hoof capsule. The ideal situation is to have the center of rotation in the middle of the foot. A perpendicular line dropped from the center of rotation should correspond to the widest part of the foot. The distance from this line to the heels and the distance from this line to the toe should be approximately equal or a ratio of 60% toe / 40% heel. The lateral view will show the length of toe present and the alignment of the dorsal surface of P3 with the dorsal hoof wall. In the laminitic horse, rotation or distal displacement of the third phalanx can be accessed along with whether a flexure deformity is present involving the distal interphalangeal joint. One of the most important aspects of using radiographs is to accurately determine the sole depth and what steps can be taken to improve it if necessary. Inadequate sole depth will usually be accompanied by excessive toe length.
The x-ray will show whether the hoof pastern axis is parallel. If the axis is broken forward (club foot) or if the axis is broken back (long toe underrun heel), the radiograph will reveal the degree of deformity and the best way to trim the foot to improve it.
Using landmarks, measurements can be drawn on the radiographs and transferred to the foot. These measurements can be used to realign the third phalanx within the hoof capsule in the case of the laminitic horse. Using the groove placed in the frog when the x-rays were taken, the distance to the center of rotation or to the point of optimum breakover can be determined. Using the channel placed at the heel, one can determine how much additional heel support should be provided, how far to extend the shoe or how long to make a bar shoe.
In summary, using radiographic guidance when trimming feet can be an asset to the farrier. It will also enhance communication between veterinarians and farriers. This added communication can only benefit both professions and most of all, the horse.The dorsal/palmar view can be used to evaluate medial/lateral orientation. Caution should be used here as a change in the medial/ lateral orientation is often coupled with the conformation of the limb. What is important when viewing the dorsal/palmar radiograph is if there is narrowing on one side of any of the joint spaces within the foot or above. This can often be corrected through trimming.
” Working with Dr. Turner has always been a no-brainer. He’s one of the best, and he always treats us like we’re the most important clients he sees that day. It’s great to get to talk through what’s going on so we leave with a full understanding of the problem AND the reasoning behind the course of treatment. Everything is very logical, and Turner is always conscious of what I can afford.
As far as the feet go…
Dr. Turner listened to what I’d seen change in my horse’s feet and overall temperament. He was patient and took my input very seriously. Every point in his inspection and work over (you can replace that with something else) was very thorough, and he explained WHY he was doing the things he did. The guide the team at Turner Equine did for me was excellent. It was extremely detailed, and in a language everyone could understand. There was no need for a frantic call to Justine (or Katie, or Turner) to try to figure out what something meant, or because I forgot details of the appointment. I simply emailed the recommendations to my farrier, and had a printed copy ready for him at our appointment. It was so convenient. We had massive improvements within the week, and they have worked for us in the long-term.”