Subtle changes within a horse’s foot can be indicative of pathology that affects the horse’s performance and quality of life, so it’s important to know how to take and interpret radiographs of the equine foot.
While extensive study and experience are needed to accurately evaluate foot radiographs, this article will cover some of the main principles behind taking and interpreting x-rays of the equine foot.
When Are Radiographs of a Horse’s Foot Indicated?
Common indications include lameness localized to the foot, suspected laminitis, navicular disease, trauma, infection, conformation or balance problems, or any other issues of the foot.
Additionally, radiographs can serve a preventive and management function, to help prevent some issues before they arise. This can be done during a pre-purchase examination, as part of a consultation with a farrier, etc.
Setting Up for and Obtaining Diagnostic Quality Radiographs
Since some of the abnormalities that indicate/lead to pathology can be subtle, it’s important to set up an x-ray study very precisely. Otherwise, interpretation can be inaccurate.
For example, a horse that is not distributing its weight equally between its right and left sides may slightly hold up one of its feet. This can result in a false diagnosis of an abnormal angle of part of the hoof when measurements are made.
Here are some tips that can help a veterinarian obtain the best possible radiographs of a horse’s feet…
Be very familiar with the anatomical structures, and have a good reference image for comparison.
Radiograph all of the feet (or at least take bilateral views), even if not all are showing symptoms of a problem. This may help uncover pathology that is radiographically evident but not yet clinically evident. At the very least, if no abnormalities are detected in the other feet, the views of the unaffected feet can serve as a great reference for comparison to normal within that individual horse.
Ensure that equipment is good quality and well-maintained/undamaged.
Have a systematic approach each time, to ensure nothing is forgotten. Know which views need to be obtained and which technique should be used for each.
Do the study on level ground, so that the horse can stand in a normal position. Make sure the horse bears weight equally between the right and left foot and keeps its neck and head straight so that the foot being radiographed is at a standard, weight-bearing angle that can be effectively compared to reference images and measurements. Wooden blocks are typically used to align the beam to about the level of the bottom of the coffin bone.
Common Radiographic Views of the Equine Foot
Orthogonal lateromedial and dorsopalmar/plantar horizontal views are the most commonly obtained radiographic views of the foot, and a good starting point.
Depending on which pathology is suspected, additional views may include various oblique or angled shots.
Tips for success include cleaning the foot to remove any foreign material that could obstruct visualization of normal anatomy or create an artifact.
After cleaning, it is recommended to pack the sulci with a pliable material such as Play-Doh, to eliminate gas artifacts.
Many experts also recommend placing radiopaque markers (such as Barium paste) at certain positions on the hoof, to serve as a point of reference for measurements.
Describing the technique and positioning for all of these views is beyond the scope of this article, but more detailed instructions on setting up and taking views are described in reference texts.
Measurements of Radiographs of the Equine Foot
In addition to what can be seen with the eye qualitatively, there are standard measurements of various parts of the equine foot that can greatly aid in radiographic interpretation. Some of those measurements are covered here.
For example, asymmetry or deviation of the distal interphalangeal joint space on the DP view is considered abnormal in terms of the medial-lateral balance of the foot.
Also, dorsal hoof wall thickness measurements can help identify laminitis. Rotation of the distal phalanx (P3 or coffin bone) may be noted if the lines are drawn along the hoof wall and dorsal cortex of P3 are no longer parallel to one another.
Or, laminitis may be noted as “sinking” of P3, when the lines along the hoof wall and the dorsal cortex of P3 are still parallel to one another but are displaced lower than they should be (noted as an increased distance between the coronary band and the proximal edge of the extensor process of P3).
These measurements can be made by hand, but some digital systems and software allow for measurements made right on the images on-screen, with automatic calculations.
Either way, a good reference text should be used to be sure measurements are made comprehensively and accurately, and to compare the measurements to standard reference ranges.
Having a good understanding of the anatomy of a horse’s foot, a systematic process for obtaining diagnostic quality radiographs, and practice with measurements and interpretation of the radiographs will help a vet make the most of their x-ray studies of the equine foot.
Written by: Dr. Tammy Powell, DVM
