The aim of the present study was to evaluate the mechanical behaviour of the femur and humerus of Cerdocyon thous through three-point bending and axial compression tests. For this, 13 femurs and 15 humerus were used in the bending test, and 14 femurs and 15 humerus in the compression test; after the assays were completed, bone fragments were collected for evaluation by means of conventional optical and polarized light microscopy, and scanning electron microscopy. It was observed that the humerus is more resistant in relation to the femur in both tests, and that bone length and weight, in addition to the width of the diaphysis, are influential on the mechanical behaviour. Microscopic evaluation showed that, on the cranial surface of the fractured bones under flexion, the fracture was caused by the deflection mechanism, while the caudal surface was ruptured by delamination. In bones submitted to axial compression, diaphyseal fractures occurred by deflection, while physeal fractures were caused by several mechanisms. There was no significant correlation between the arrangement of collagen fibres or mineral content on the mechanical properties obtained in both assays. It can be concluded that there are significant differences in the mechanical behaviour of the femur and humerus of C. thous, where the humerus is more resistant than the femur in both flexion and compression loads. Such data allow us to predict the bone mechanical behaviour of C. thous in the face of trauma caused by flexion and compression impacts, such as those resulting from running over.

The aim of the present study was to perform the macroscopic and microstructural morphological classification of long bone fractures of Cerdocyon thous. Eighteen cadavers of the species were necropsied, and subjected to radiographic and microscopical evaluation when long bone fractures were detected. Among the 18 cadavers, eight (44%) had fractures equally distributed (33.33%) in the femur, humerus, or tibia. More frequently (61.54%), the fractures were simple and affected the diaphysis, and in smaller proportions (23.08%) reached the physeal line. In diaphyseal and metaphyseal fractures, microscopical evaluation revealed cortical bone tissue, with longitudinal osteons that contained longitudinal and intermediate collagen fibres and lamellae with a delamination aspect. On the other hand, in epiphyseal fractures, trabecular bone tissue was more frequently observed, consisting of trabeculae with disorganised collagen fibres and absence of osteons. In both cases low activity, osteocytes, and low coverage of osteoblasts on the bone surface were noted. It was concluded that the frequency of fractures in the long bones of C. thous was 44%, with females being more predisposed. The findings support the hypothesis that fractures in such animals are caused by being run over by automobiles. The present study contributes significantly in alerting clinicians and surgeons to the types of fractures that C. thous is more predisposed to, its places of greatest occurrence, and its microstructure. Thus, there is a need for joint actions aimed at reducing the number of cases of wild animals being run over by automobiles.