A common site for metacarpal base fractures is the fifth metacarpal. Most of these fractures are comminuted and impacted, and are often associated with carpo-metacarpal fracture dislocations. Additional dorsal shearing fractures of the hamate may be present. These fractures are usually fixed with plates, or K-wires in the case of small fragments, and may need bone grafting.
CT scans are very helpful to determine the number, size and position of the fragments.
Depending on the fracture geometry, simpler fractures can be treated with lag screws (e.g. extensor carpi ulnaris tendon avulsion fractures), or with T-, Y- or L-shaped plates.
Dislocation of the 4th metacarpal
Fractures of the fifth metacarpal base may be associated with a carpo-metacarpal dislocation of the fourth ray. In that case, the fourth metacarpal displacement is reduced first and usually stabilized with transfixion K-wires. Occasionally, there is a subluxation of the 3rd metacarpal, or even the 2nd metacarpal, and any combination of additional fractures can be seen.