Wedge and eggbar shoes change the pressure distribution under the hoof of the forelimb in the square standing horse

The shoe types most commonly applied to horses with navicular disease or other forms of palmar heel pain are shoes with heel wedges and eggbar shoes, although their efficacy has been a matter of debate among veterinarians and farriers for centuries. To quantify the effect of these different types of "navicular" shoeing on static hoof pressure distribution, 6 warmblood horses were shod with 6degrees wedge, eggbar, and plain shoes. While standing square with weight evenly distributed across both forelimbs, the center of pressure and pressures at selected areas of interest (AOI: toe, medial and lateral toe, medial and lateral heel) were measured using a Footscan (RsScan International, Belgium) pressure plate in a Latin square design using the plain shoe as a reference. Wedge shoes did not provide a significant shift in the center of pressure. The application of eggbar shoes did not alter the relative position of the center of pressure under the hoof. However, the absolute distance from the toe to the center of pressure was significantly larger with eggbar shoes (77+12 mm) compared with plain and wedged shoes (70+/-8 mm, P<.05) resulting in an absolute, caudal shift of the center of pressure. When pressure (N/cm(2)) values at the five AOIs were averaged for each shoe type, the wedge and eggbar shoe recordings showed a significantly lower mean pressure than plain shoes (P<.05). In conclusion, mean AOI pressures decreased with wedge and eggbar shoes, and eggbar shoes provided a caudal shift in the center of pressure. These effects are believed to decrease the moment of the coffin joint and reduce the pressure on the navicular bone. Thus, the findings of this study might contribute to the scientific evidence of efficacy of the use of wedge and eggbar shoes in "navicular" lame horses.