Effects of shoeing on forelimb biomechanics in walking horses

BACKGROUND: Hoof trimming and shoeing techniques are used to manage and prevent equine limb injuries. However, quantitative studies comparing the effects of different shoeing techniques on equine joint biomechanics over the full gait cycle are lacking. OBJECTIVES: To measure and compare joint motion and net torques at the distal forelimb joints when horses walk overground unshod, with a standard flat shoe, and with a rocker shoe. STUDY DESIGN: In vivo study. METHODS: Gait data were recorded from 12 sound horses during walking. Three shoeing conditions were tested: unshod, flat shoe, and rocker shoe. Data were recorded for each shoeing condition immediately after trimming (short hoof condition) and again after 6 weeks of hoof growth (long hoof condition). Three-dimensional motion capture and retro-reflective skin markers recorded left forelimb motion, while synchronised force plates measured the corresponding ground reaction force. Inverse dynamics was used to calculate the net torques developed about the distal forelimb joints. Statistical comparisons were performed with multilevel mixed effects generalised linear models. RESULTS: While there were limited effects of trimming and shoeing, the rocker shoe was associated with higher walking speed (by 9.3 ± 9.7%) and reduced stride duration (by 4.9 ± 6.9%) compared with the flat shoe for the short hoof condition (p < 0.001). Throughout the stride cycle, the fetlock joint was less extended (by 9.0 ± 13.7°) while the distal interphalangeal joint (DIPJ) was more extended (by 10.7 ± 16.6°) for both shoeing types compared to unshod regardless of hoof growth (p < 0.005). Higher peak torques were generated at the DIPJ for flat shoe compared to unshod (by 0.05 ± 0.27 Nm/kg) in the short hoof condition, and for flat shoe compared to rocker shoe (by 0.03 ± 0.14 Nm/kg) in the long hoof condition (p < 0.05 for both). MAIN LIMITATIONS: The horses were tested at a low-speed walking gait. CONCLUSIONS: Forelimb joint biomechanics did not differ substantially across the three shoeing and two hoof-growth conditions. Future studies should test the robustness of these findings at the trot and canter.