Fusion of the distal sesamoid and distal phalanx in a yearling colt

This paper describes a rare malformation of the distal portion of the left foredigit of a 15-month-old half-bred colt which was severely lame. Radiological, pathological and tomographic studies revealed hypoplasia of the metacarpophalangeal skeleton, absence of the distal sesamoid and deformation of the distal phalanx. Morphological analysis of the lesion and computerised measurement of the width of the articular surface of the distal phalanx suggested an early fusion between the distal sesamoid and distal phalanx.