Avaliação radiográfica e morfológica do dígito e boleto dos membros torácicos de equinos puro sangue inglês de corrida

Abstract

The Thoroughbred breed has been selected for centuries for phenotypes that allow superior performance on the race. However, a high incidence of forelimb injuries has been described in young Thoroughbred racehorses, which culminates in an important source of injury and raises important concerns regarding animal welfare. With the hypothesis that the population of Thoroughbred racehorses in sports activities at the Jockey Club of São Paulo has a high prevalence of hoof distortions and pathological alterations in the fetlock, forelimbs of 59 animals aged between 3 and 4 years were evaluated with the objective of morphologically description of the thoracic digit of these animals through evaluations of photographic and radiographic images and to identify the radiographic lesions in the metacarpophalangeal joint, as well as the prevalence of alterations in the proximal sesamoids in these animals. Although, by visual evaluation, 44.8% of the animals presented a linear axis between the dorsal wall of the hoof and the pastern, and only the others visually presented the dorsal angle of the hoof smaller than the dorsal angle of the pastern, radiographic analysis using different methods demonstrated consistently that 100% of the animals had the podophalangeal axis broken backwards. The evaluated animals also presented mean of toe and heel angles diverging by 19.75° from each other, values that raises more concerns than those previously described in other countries with traditionalism in Thoroughbred racehorses, which leads to the classification of the evaluated animals as showing underheel. A mean palmar angle of 0.38° (±2.01) was also found. This value is much lower than desired, with only 4% of the evaluated animals presenting values within the normal range and 56% of the animals presenting a negative palmar angle. These findings demonstrate that within this population of Thoroughbred racehorses in Brazil, the hooves present important distortions. Although all animals were in sports activity and without signs of injuries involving the locomotor system, osteophytes or entheseophytes were found in 76% of the assessed metacarpophalangeal joints. Another relevant finding was the high prevalence of subchondral irregularities, mainly involving the dorsal metacarpal (39%). The results involving the proximal sesamoids are even more striking, with up to 92% of the sesamoids evaluated presenting sesamoiditis, indicating overload of the fetlock suspensory apparatus. These findings corroborate the fact that distortions in the morphological aspect of the hoof and positioning of the third phalanx are related to lower biomechanical efficiency and the development of injuries.