Review Question - QID 213993

This patient has sustained a partial articular base of the first metacarpal fracture (Bennett fracture). In these fractures, the small fracture fragment maintains its connection to the trapezium by the anterior oblique ligament (AOL; also known as volar beak ligament), which is labeled B.

In Bennett fractures, the volar-ulnar fracture fragment of the first metacarpal base is held reduced by the AOL. The AOL originates at the base of the first metacarpal base and inserts on the volar tubercle of the trapezium. While the AOL maintains the first metacarpal base reduced to the trapezium, other strong deforming forces pull the metacarpal shaft dorsally, proximally, ulnarly and in supination. The most critical in these deforming forces are the abductor pollicis longus (APL) inserting on the base of the metacarpal which pulls the metacarpal shaft proximally and dorsally and the adductor pollicis (AP) which inserts on the ulnar aspect of the proximal phalangeal base and angulates the metacarpal shaft ulnarly.

Breen et al. reviewed the biomechanical and treatment complexities of fractures involving the thumb carpometacarpal (CMC) joint. They reported that the most essential factor for obtaining a good functional result is an anatomic restoration of the articular surface. They recommended maintenance of articular congruity, fracture stability, and early motion for maximum return of function.

Carlsen and Moran reviewed thumb trauma including Bennett and Rolando fractures. They reported that in Bennett fractures, the volar-ulnar fragment is held in place by the AOL, and that the fracture is unstable due to the displacing forces acting on the distal fragment. They recommended that Bennett fractures be treated with surgical fixation, whether using open or percutaneous techniques to maintain reduction of the metacarpal at CMC joint.

Figure A is a radiograph demonstrating a Bennett fracture. Figures B (volar view) and C (dorsal view) are schematics depicting the ligaments about the CMC joint. Illustration A is a labeled version of Figures B and C.

Incorrect Answers:
Answer 1: This is the anterior intermetacarpal ligament, which has no connection to the trapezium.
Answer 3: This is the posterior intermetacarpal ligament, which has no connection to the trapezium.
Answer 4: While the dorsoradial ligament is important for CMC stability, it is not the primary stabilizer and does not keep the fracture fragment connected to the trapezium.
Answer 5: This is the posterior oblique ligament, which is not as important in first CMC stability as the AOL.