Measurement of the Curve of Spee in horses.

The Curve of Spee is well known, yet hardly understood in the horse, as there is a striking lack of biometrically related data which could help to explain its biomechanical significance. Older horses display drastic alterations of the Curve of Spee in routine clinical examinations. Since the Curve of Spee is known to be biomechanically related to the masticatory forces in humans, the same may apply to the equine, and masticatory deficits can be expected in the geriatric horse. Quantitative data of the Curve of Spee cannot be obtained directly by means of measurements in the horse's long and narrow oral cavity. Instead, the radiographs of 24 heads and 6 skulls of horses of different age were used to develop a geometrical procedure facilitating a quantitative analysis of the height of the Curve of Spee. The geometrical values gave clear evidence that the height of the Curve of Spee was smaller in groups of older horses compared with those of younger horses. This finding was in accordance with biomechanical studies which reported decreased masticatory forces in older horses.