Evaluation of displacement of the digital cushion in response to vertical loading in equine forelimbs

To evaluate patterns of digital cushion (DC) displacement that occur in response to vertical loading of the distal portion of the forelimb in horses. Sample Population-Forelimbs from 10 horses with normal feet. Patterns of DC displacement induced by in vitro vertical limb loading were determined. Load-induced displacement of the DC was defined as the magnitude and direction of displacement of 6 radio-dense, percutaneously implanted markers in specific regions of the DC. The effects of solar support and nonsupport on displacement of the DC were compared. Regional displacement of the DC occurred principally along distal and palmar vectors in response to vertical loading. Medial or lateral abaxial displacements were variable and appeared to be dependent on response of the limb to the applied load. Displacement of the DC was not affected by the degree of solar support. Data indicated that the biomechanical function of the DC is to act as a restraint to the displacement of the second phalanx or as a passive structure that allows flexibility of the caudal two thirds of the foot. Results did not indicate that the DC provides a force that induces displacement of or an active restraint against outward displacement of the hoof wall capsule.