Retrospective study of primary intention healing and sequestrum formation in horses compared to ponies under clinical circumstances.

In accidental wounds, trauma and infection can result in dehiscence of primarily closed wounds and in sequestrum formation when cortical bone is exposed. In experimental studies, it has been shown that second intention healing is faster and occurs with less complications in ponies than in horses. Also, a greater initial inflammatory response was seen in ponies. Based on these experimental data, it was hypothesised that accidental wounds in ponies would heal with a lower incidence of wound dehiscence and/or sequestrum formation compared to horses. A retrospective study of 89 ponies and 422 horses with traumatic wounds was performed. The animals, wounds and treatments were categorised and related to the success rate of primary closure and to the incidence of sequestrum formation. The ponies and horses were of similar age and sex. The wounds that were treated were comparable for localisation, duration, degree of contamination and depth in both groups of animals, but there were significantly more cases with ruptured extensor tendons in ponies. Antibiotics and NSAIDs were administered significantly less often to ponies. The success rate of primary closure was significantly higher in ponies than in horses, and sequestra were formed significantly less often in ponies. It was concluded that the results of healing were better in ponies although the external conditions were less favourable. This may be associated with the differences in the initial inflammatory response after injury as found in earlier experimental work, which may result in a better local defence against wound infection.