Effects of ground surface deformability, trimming, and shoeing on quasistatic hoof loading patterns in horses

Objective-To determine whether solar load distribution pattern on a solid nondeformable ground surface is the product of contact erosion and is the mirror image of load distribution on a deformable surface in horses. Animals-50 clinically normal horses. Procedures-Solar load distribution was compared among 25 clinically normal horses during quasistatic loading on a solid nondeformable surface and on a highly deformable surface. Changes in solar load distribution patterns were evaluated in 5 previously pasture-maintained horses housed on a flat nondeformable surface. Changes in solar load distribution created by traditional trimming and shoeing were recorded. Results-Unshod untrimmed horses had a 4-point (12/25, 48%) or a 3-point (13/25, 52%) wail load distribution pattern on a flat solid surface. Load distribution on a deformable ground surface was principally solar and located transversely across the central region of the foot. Ground surface contact areas on solid (24.2 +/- 8.62 cm(2)) and deformable (69.4 +/- 22.55 cm(2)) surfaces were significantly different. Maintaining unshod horses on a flat nondeformable surface resulted in a loss of the 3-and 4-point loading pattern and an increase in ground surface contact area (17.9 +/- 2.77 to 39.9 +/- 12.77 cm(2)). Trimming increased ground surface contact area (24.2 +/- 8.60 to 45.7 +/- 14.89 cm(2)). Conclusion and Clinical Relevance-In horses, the solar surface is the primary weight-loading surface, and deformability of ground surface may have a role in foot expansion during loading. Increased surface area induced by loading on deformable surfaces, trimming, and shoeing protects the foot.