Review Question - QID 217861

The dorsoradial ligament (DRL) is believed to contribute to the highest degree of thumb carpometacarpal joint (CMCJ) stability.

Thumb CMC dislocations are rare injuries that occur due to axial force on a flexed thumb. Diagnosis is clinical and can be confirmed by orthogonal radiographs. Treatment often consists of closed reduction and immobilization, with unstable injuries requiring surgical stabilization. There are several ligaments that help stabilize the thumb CMC joint. The deep anterior oblique (beak) ligament allows for pivoting of the CMCJ for pronation of the thumb. The dorsoradial ligament is a stabilizer (“check rein”) to radial subluxation and becomes taut with radial/dorsoradial subluxation before other ligaments; if all other ligaments but the DRL are cut, the CMCJ remains reduced.

Bosmans et al. reviewed isolated traumatic dislocation of the thumb CMCJ, also called the trapeziometacarpal joint (TMCJ). They reported on which ligaments are the true key stabilizers for the joint and therefore need to be damaged to result in dislocation. They concluded with optimal treatment strategies for thumb CMCJ dislocations and proposed a treatment algorithm.

Strauch et al. performed an anatomic study to provide an understanding of the ligamentous disruption that occurs during acute dislocation of the thumb carpometacarpal joint. They reported that the primary restraint to dorsal dislocation was found to be the dorsoradial ligament, with the anterior oblique ligament allowing dislocation by subperiosteal stripping from the base of the first metacarpal. They concluded that the dorsoradial ligament is the primary restraining force with respect to acute dorsal dislocation of the thumb carpometacarpal joint.

Shah et al. reported on four cases of complete CMC dislocation of the thumb. They found that in each case, the dorsal ligaments were ruptured while the anterior oblique ligament remained intact, resulting in dorsal subluxations. They concluded that the dorsal capsule and ligament should be explored during surgery and reconstructed by free tendon grafts.

Figure A is the unlabeled ligaments of the thumb CMC joint. Illustration A is the corresponding labeled ligaments of the thumb CMC joint.

Incorrect Answer:
Answers 1&3: This is the anterior & posterior intermetacarpal ligament. It is an extracapsular ligament that runs obliquely from the dorsoradial aspect of the second metacarpal to the volar-ulnar tubercle of the first metacarpal base, just radial and volar to the ECRL tendon insertion on the second metacarpal base. It restricts radial translation of the first metacarpal
Answer 2: This is the anterior oblique (beak) ligament (AOL). It has its origin at the volar tubercle of the trapezium and attaches to the volar beak of the first metacarpal base, at the ulnar-volar aspect of the joint. It contributes to volar stability of the joint. Previously, the AOL was considered the most important stabilizing ligament of the thumb CMC joint, resisting dorsoradial and volar subluxation, but more recent studies have increasingly stressed the importance of the dorsal ligaments and de-emphasized the AOL in ensuring joint stability.
Answer 5: This is the posterior oblique ligament (POL). The POL is purely a dorsal structure, ulnar to the dorsoradial ligament