Researchers Explore the Digital Cushion

Researchers at Colorado State University used 16 saddle horses to investigate the biomechanics and cellular structure of the digital cushion (DC).

The horses were involved in an earlier experiment that included creating a forelimb carpal joint lameness, resting the horses for 2 weeks, then exercising them on a treadmill 6 minutes a day, 5 days a week for 8 weeks. The horses were examined for lameness, then sacrificed 70 days after the beginning of the study, so tissues for both studies could be obtained for testing and examination.

Core samples of the DC were taken from a palmar location inside the heel bulbs and a second, more dorsal position just behind the navicular bone. The samples were tested in a hydraulic press to measure elasticity and examined microscopically.

There were no measured differences in the elasticity of the DC samples or their microscopic, cellular structure and tissue composition between the lame and non-lame limbs. The DC tissue from the dorsal location closer to the navicular bone had a higher elastic modulus than the tissue from the palmar location. This area also had more ground substance, a gel-like material that fills the spaces between cells and fibers in connective tissue, compared with the palmar location.

These results should not be surprising, given that the relatively short duration of the lameness may not have allowed time for the DC to remodel in response to the lameness. Also, as one might expect given different remodeling forces likely act…