Laminitis in horses is a commonly encountered condition. Veterinarians are often asked to make prognostic assesments regarding the severity of the condition and the future use of the horse. Radiology of the distal phalanx of the horse is a method, that can provide diagnostic, prognostic and therapuetic information.

Radiology is a procedure commonly performed in equine practice. However, we must consider some special factors when we are preparing to obtain radiographs of the laminitic horse. As with any radiographic procedure, good quality radiographs are a must. A "diagnostic" quality radiograph is what we all strive for, but without proper preparation we may end up with radiographs that are of little value to anyone.

The location where the radiographs are performed is very important. Transportation of the painful horse may be contraindicated, however excellent field films may be obtained with a little preparation. I select a flat spot to position my equipment. Ideally, this site would have a smooth surface, such as brushed concrete, rubber mats, or wood. However, a flat patch of dirt, grass or gravel can also be used.

Clean the hoof so it is free of debris on the outer portion as well as on the sole. Unlike other common distal limb procedures, the shoe does not necessarily need to be pulled. In fact, leaving the shoe on can be useful. The horse may be more comfortable and willing to stand. The shoe can serve as a radiographic landmark for evaluating the hoof capsule and distal phalanx.

As with any views of the distal phalanx, the foot must be elevated above the ground level. I have a selection of wood pieces that can be used to adjust the height of the foot. The foot should be weight bearing. Oftentimes the horses pain will make standing on a block difficult. I employ the use of sedatives, analgesics or regional anesthesia as needed.

Once the horse is positioned on the block the cassettes can be positioned for the exposure. At least two views of the affected foot should be taken, commonly a lateromedial and a dorsopalmar view. Sixty degree dorsopalmar oblique views may also be taken to evaluate the distal solar margin. If only one foot appears clinically effected, I will still radiograph the contralateral foot to serve as a comparison.

I prefer to use a "soft" exposure technique. By using a technique with less energy, it allows better visualization of the hoof capsule. The lighter technique facilitates better evaluation of the third phalanx position relative to the dorsal hoof wall and coronary band.

The lateromedial view is the most important view for evaluating displacement of the third phalanx. The positioning I use for the lateromedial view is as follows: The vertical axis of the cassette should be parallel to the vertical axis of the foot. The dorsopalmar axis of the cassette should be parallel to the dorsopalmar axis of the the foot. The radiograph machine should be positioned so that the central beam is directed perpendicular to the cassette in both the horizontal and vertical planes. The use of a radiographic machine with a lighted collimator will greatly facilitate the positioning. The height of the central beam should be positioned so that is directed at an imaginary point that approximates the center of the distal phalanx. This point will be slightly more distal than that used to evaluate the coffin joint. It is imperative that the beam is directed parallel to the ground surface (hence the importance of the flat ground). Otherwise, the distal phalanx will be imaged obliquely on the radiograph.

Following exposure and development, we now have a film to evaluate. If the film is poorly positioned, inadequately exposed, or has excessive motion, we must repeat the faulty exposures. Repeat exposures can be costly and time consuming, but the improved image is worth the effort. The properly taken radiograph will allow us to evaluate the foot for a number of possible changes which may include distal phalanx rotation, distal displacement of the distal phalanx, lammellar changes, abscessation, and gas pockets.

We must remember that the absence of radiographic changes does not necessarily mean the absence of laminar or third phalanx pathology. Additionally, laminitis is not a static process. The foot that appears radiographically normal, may end up with future rotation if therapuetic measures are not instituted. Use of serial radiographs can aid in assessing the clinical progression and serve as a guide for therapuetic shoing.

© 1996 Robert D.Harrington, D.V.M.