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

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