Photoelastic stress analysis of strain patterns in equine hooves after four-point trimming

Objective-To evaluate changes in strain patterns in normal equine hooves fo llowing 4-point trimming, using photoelastic stress analysis. Sample Population-15 equine front limbs with normal hoof configuration, Procedure-Limbs were disarticulated at the carpometacarpal joint. Weight-be aring surfaces of each hoof were trimmed level to ensure 100% ground contac t. Hoof walls were coated with a custom-made strain-sensitive plastic, and limbs were loaded to a third of body weight. Using a polariscope, strain di stribution, magnitudes, and directions were evaluated in level hooves as we ll as before and after standardized 4-point trimming. Repeated-measures ANO VA was used to compare strain magnitudes and directions before and after tr imming. Results-In leveled specimens, strain fields were symmetrically distributed above the heels and at quarter-toe junctions along a line between the middl e and distal thirds of the hoof wall. After 4-point trimming, strain epicen ters localized above the contact points, whereas strain magnitudes signific antly increased by approximately 50%. Decreasing contact area by 50% result ed in an additional significant increase (32%) in strain magnitude. Trimmin g did not have a significant effect on strain orientations. Conclusion and Clinical Relevance-This study documents that 4-point trimmin g results in strain concentration above the hoof contact points and that st rain magnitude is dependent on contact area.