Hoof size, shape, and balance as possible risk factors for catastrophic musculoskeletal injury of Thoroughbred racehorses

95 Thoroughbred racehorses that died between 1994 and 1996 examined through the California Horse Racing Board Postmortem Program were used in this investigation. 38 quantitative measures of hoof size, shape and balance were obtained from orthogonal digital images of the hoof and were compared between case horses with forelimb catastrophic musculoskeletal injuries (CMI, 70 animals), suspensory apparatus failure (SAF, 43), and cannon bone condylar fracture (CDY, 10) injuries and control horses whose death was unrelated to the musculoskeletal system (non-CMI, 25). Comparison of group means between cases and controls was done using ANOVA and multivariable logistic regression was used to estimate odds ratios. Odds of CMI were 0.62 times lower for a 5-mm increase in ground surface width difference and 0.49 times lower for a 100-mm² increase in sole area difference. Odds of SAF were 6.75 times greater with a 10° increase in toe-heel angle difference and 0.58 times lower with a 100-mm² increase in sole area difference. Odds of CDY were 0.26 times lower with a 3° increase in toe angle, 0.15 times lower with a 5-mm increase in lateral ground surface width, and 0.35 times lower with a 100-mm² increase in sole area difference. It is suggested that decreasing the difference between toe and heel angles should decrease risk of SAF for Thoroughbred racehorses and should be considered in addition to increasing toe angle alone to help prevent catastrophic injury. It is added that trimming the hoof to perfect mediolateral symmetry may not be a sound approach to avoiding injury.