Imaging description

A Bennett fracture is an intra-articular, simple, oblique fracture at the base of the first metacarpal (Figure 39.1). A Rolando fracture is an intra-articular, comminuted fracture at the base of the first metacarpal (Figure 39.2).

Importance

It is important to identify a Bennett fracture due to its instability coupled with the need for early treatment with near anatomic reduction and fixation. If a Bennett fracture heals with greater than 1 mm of step-off at the metacarpal base articular surface, the patient is at increased risk for symptomatic first carpometacarpal joint osteoarthritis in 5–7 years. Unfortunately, the Bennett fracture tends not to hold its reduced, anatomic position with just closed reduction and Spica casting. In a Bennett fracture, the main substance of the metacarpal head and shaft are left intact, but they are avulsed off of a large portion of the volar-ulnar aspect of the metacarpal base. The base is held in place by a strong intermetacarpal ligament while the main portion of the metacarpal (small part of the radial base, the shaft, and the head) is displaced radially and dorsally primarily by the abductor pollicis longus tendon. This displacement leads to an incongruous first carpometacarpal joint followed by early, symptomatic osteoarthritis. A Rolando fracture that is only minimally comminuted and has large fragments is usually treated similar to a Bennett fracture (if near anatomic reduction can be achieved). Unfortunately, a severely comminuted Rolando fracture cannot be anatomically reduced and the usual outcome is post-traumatic osteoarthritis.