Learning to Read Radiographs (X Rays)

When you're talking about evaluating a horse's foot, a radiograph or X ray can tell you a whole lot more than just whether there's a fracture or not. When the radiograph is taken to show soft tissue detail as well as bone, it can provide tons of information on the health of the various soft tissues within that foot.

Reading such radiographs takes a trained eye, and it's an important part of evaluating the horse's foot, especially when lameness exists. During the recent Bluegrass Laminitis Symposium, host Ric Redden, DVM, founder of the International Equine Podiatry Center, discussed radiograph interpretation for the audience of veterinarians and farriers.

Number one on his list of important points was that radiographs aren't the be-all, end-all of diagnosing foot problems. They are but one part of the entire examination of that horse, which also includes physical examination, gait analysis, and possibly other diagnostic procedures. And as much as we might like a nice checklist of things to do for lameness examination, he says it isn't that easy.

"Everybody wants a standard, but that's the easy way out," he began. "We don't need a standard, we need a standard way of thinking. When you make this evaluation a careful, systematic thinking and observation process, you'll see a lot of things you might otherwise miss."

The Physical Examination
"The physical examination remains the most important aspect of evaluating the health of the foot," he stated. "The exam is tailored to the situation at hand, focuses on the demands of the client, and involves your horsemanship skills, farrier skills, a working knowledge of normal feet in many breeds, and the ability to listen to the horse's history."

He offered the following key points of the physical examination:

  • Physical examination is the most important part of evaluating the foot.
  • Develop a methodical approach and use it every time.
  • Look for all the normal areas first (bearing in mind the range of normal for that horse's breed, age, environment, and use). What's left over points to the problem you seek. 
  • Localize the seat of pain to one or more quadrants of the foot.
  • Visualize the underlying bone and associated soft tissues when looking at the hoof. 
  • Think in terms of identifying the failing structure(s).

"The key is to use a disciplined, methodical approach that is designed to disclose and define the various normal soft tissue parameters, normal bone anatomy, normal hoof capsule anatomy, and how each component is interrelated," he said.

Radiographic Examination
"Over the many years I have worked as an equine podiatrist, I have come to appreciate the fact that soft tissue pathology is present to some degree in every footsore horse," Redden stated. "Thus, evaluation of the soft tissue zones within the hoof capsule is an extremely important part of radiographic examination of the foot. I only investigate bone detail after I've thoroughly evaluated the soft tissues; horses will usually have soft tissue lesions long before bone lesions.

He measures the following characteristics of each foot on a radiograph

  • Sole depth (SD, distance between the bottom of the tip of the third phalanx and the sole surface); 
  • Palmar angle (PA, green lines showing the angle the bottom of the third phalanx bone makes with the ground surface of the hoof). This horse has a negative 7� palmar angle. 
  • Digital breakover (DB, purple line showing the distance along the ground from the tip of the third phalanx bone to the forwardmost point of contact between the shoe and the ground). 
  • Horn-lamellar zone (HL zone, red arrows showing the space between the face of the coffin bone and the outside of the hoof wall). 
  • Coronary band-extensor process distance (CE, blue vertical line showing the distance between the top of the extensor process of the coffin bone and the top of the wall at the coronary band).

Take-Home Message
"It is not enough for us to reach a medical diagnosis; our examinations must have the dual goal of directing us toward a solution to the horse's problem, both for immediate relief and a long-range plan for restoring and preserving structural and functional integrity," Redden said. "That goal can be met only when our examinations are aimed at collecting as much specific information as possible about every component of the digital unit. Errors of omission and misinterpretation are minimized when the examiner collects as much information as can be gained from both procedures and considers the significance of the findings in total.

"There are no shortcuts to examining the foot," he concluded. "You have to methodically learn everything you can about that foot and that horse in order to understand what's going on, what you should do to help it heal, and why your solution will work."

Take the Next Step
For more information, see Redden's in-depth paper on procedures for examining the foot: www.TheHorse.com/viewarticle.aspx?id=1457.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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