The Board Test for Lameness

Extension tests (such as trotting a horse off after he stands on a toe wedge for a short time) are sometimes used to detect certain lamenesses, but their use and interpretation are generally not very standardized between practices and practitioners. Until now. At the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif., one practitioner discussed a custom-made digital extension device for measuring a horse's tolerance to digital extension in dorsal (forward), lateral (to the outside), and medial (to the inside) directions. Hans Castelijns, DVM, CF, of Cortona, Italy, described the device, his observations with its use, and its implications for trimming/shoeing changes.

The "board test" commonly used in Europe involves standing one hoof (usually a front one) on the end of a long board while the other hoof is held up by an assistant. The clinician slowly elevates the other end of the board in front of the horse, then to the sides, and observes whether the horse becomes visibly uncomfortable or the opposite side of his foot lifts off the board at a lower than normal angle. Castelijns developed a robust metal "board" system that incorporates a protractor and level into the handle to allow accurate measurement of the angle at which a horse becomes intolerant to elevation.

After Castelijns developed the device, he tested it on 250 clinically sound, recently trimmed/shod horses to identify normal ranges of elevation. They are as follows:

  • Dorsal elevation averaged 43.2°
  • Lateral elevation averaged 18.8°
  • Medial elevation averaged 19.8°

 

Protractor for board test
Dorsal extension

Protractor with spirit level, demonstration of dorsal extension.

He found that while dorsal elevation angle before pain is quite variable between horses (likely due to wide variations in conformation), medial and lateral elevation angles are "amazingly consistent across breeds and conformation types.

"If you get less than 17° of lateral elevation or 18° of medial elevation, that's clinical proof of a problem in my opinion," he said. The exception to this rule is if a small lateral elevation angle goes with a large medial elevation angle (or vice versa); in this case, lateromedial (side-to-side) hoof imbalance might be the culprit. For dorsal extension, observing different values between feet (especially if one is steeper) is not unusual, but he noted that any dorsal elevation of less than 30° is "suspect."

He explained that extension tests stress many different internal structures (tendons, ligaments, bursae, etc.), so they won't provide an exact diagnosis. However, testing will identify intolerance to elevation in one direction or another, which helps guide therapeutic farriery to reduce extension in that direction and promote flexion. For example, a horse that shows pain on dorsal elevation might benefit from improved dorsal breakover, such as with a shortened, beveled, and/or rolled toe. Or a horse with reduced lateral elevation might like a shortened lateral hoof wall or a shoe with a narrow lateral web (which sinks deeper into soft ground than the opposite wider one). This "stretches" the lateral joint spaces and avoids the pain on lateral joint compression found during the elevation test.

"Digital extension test values do not pinpoint a specific lesion; nevertheless, they have great clinical value," Castelijns concluded. "They are extremely useful in shoeing prescriptions when there is more than one lesion found with diagnostic imaging, and they also give a rational approach to lateromedial balancing of the foot. You already know what the horse will like in terms of shoeing mechanics."

 

Editor's note: Castelijns has no personal financial stake in this digital extension device, which is manufactured by Colleoni.

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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