Overview
As in the thoracic limb, the bovine metatarsus is formed mainly by the large metatarsal bone or cannon bone (ossa metatarsalia III et IV), the result of fusion of metatarsals III and IV. Compared with the metacarpus it is longer and more square in section, and its dorsal groove is deeper. It runs from the tarsus to the fetlock, covered only by skin, tendons and vessels.
Key features
- Proximal end: articular surface for the fused second and third tarsal bone and the centroquartal bone.
- Metatarsal II (os metatarsale II): may be present as a small, sesamoid-like bone on the plantaromedial side of the proximal end.
- Dorsal longitudinal groove (sulcus longitudinalis dorsalis): well marked and deep, it shows the line of fusion and carries vessels. The plantar surface has a similar groove.
- Proximal and distal metatarsal canals: connect the dorsal and plantar surfaces at the ends of the dorsal groove and carry vessels.
- Distal end: two condyles with a sagittal ridge, one for each main digit, separated by the intercapital notch (incisura intercapitalis); they articulate at the fetlock with the proximal phalanx and the proximal sesamoid bones.
Clinical relevance
- Fractures in calves: like metacarpal fractures, they are common and often caused by excessive traction during assisted calving. They may be diaphyseal or physeal, through the distal physis.
- Treatment: closed fractures usually heal well in a cast; open fractures are common because of the scant soft tissue cover, and they worsen the prognosis.
- Examination: the cannon bone and its condyles can be palpated under the skin along their whole length.