The arterial shift features in the equine proximal sesamoid bone

Sesamoidosis in horses is characterised by lameness and radiographic changes in the proximal sesamoid bones and the aetiology is attributed to either mechanical factors or circulatory disturbances. In this study arteriograms of proximal sesamoid bones were investigated in 17 lame patients suffering from sesamoidosis, 6 sound horses and 4 yearlings. The arterial patterns of the proximal sesamoid bones from the patients, showed a shift from an abaxial to a basal arterial blood supply. This shift was only found in radiographically changed bones. Histological evaluation showed a significantly higher percentage of arteries with a large diameter in sections from the base of proximal sesamoid bones that showed an arterial shift. The presence of the shift appeared to be related to a change in shape of the bone, in particular to new bone formation along the abaxial border. The results of this study suggest that in horses suffering from sesamoidosis changes in the arterial pattern arise which might be a compensatory mechanism in respons to a vascular iischaemic challenge. Further investigations are needed to characterise the initial stimulus that induces this compensation and to determine if the compensation is sufficient to maintain a continuous and adequate blood supply.