Traumatic dislocations and instability of the trapeziometacarpal joint of the thumb.

The surgeon treating traumatic injuries to the TMC joint should be aware of the fundamental misconceptions and pervasive axiomatic myths perpetuated in the medical literature: namely that the volar beak ligament is the prime stabilizer, that the dorsal ligament complex plays no significant role in TMC joint function, and that the APL is a deforming force in Bennett fractures. On the contrary, stability of the TMC joint in power pinch and power grasp depends on the TMC joint's two prime stabilizers, the volar beak of the thumb metacarpal and the dorsal radial ligament complex; and the APL is not a deforming force in a Bennett fracture. Screw-home-torque occurs in the final phase of opposition; the acute Bennett fracture can be treated closed and percutaneously fixed if the screw-home-torque technique is used to anatomically reduce the fracture. After soft tissue interposition, if a semi-acute Bennett fracture is diagnosed late, it should be treated open with a volar approach, the screw-home-torque reduction technique, and screw or pin fixation. Rolando multipart fractures of the thumb metacarpal into the TMC joint are best treated closed, with traction in opposition with pin fixation; pure dislocations of the TMC joint that tear the dorsal ligament complex and Bennett fractures with an associated dorsal ligament complex tear (as diagnosed by the screw-home-torque technique) require open reduction and dorsal ligament complex repair. The current literature is so replete with myths and folklore regarding the anatomy that a conscientious surgeon treating a traumatic dislocation or in-stability of the TMC joint should return to the cadaver room and carefully review and understand TMC joint anatomy.