Fractures of the base of the thumb metacarpal.

The thumb trapeziometacarpal joint is a saddle joint that is subject to high compressive forces during prehensile hand function. Fractures to the base of the thumb metacarpal occur commonly following axial load to a partially flexed thumb. Although reduction is easily performed, severe deforming forces act to displace the fractures into a varus and shortened position. Most extra-articular fractures can be treated with closed reduction and cast immobilization. Angulation up to 30 degrees can be tolerated because of the substantial compensatory motion at the thumb carpometacarpal joint. In Bennett fractures, good functional results are observed even with residual deformity and articular incongruity. However, the goal of treatment for intra-articular fractures should be the anatomic reduction of the joint surface with less than 1 mm of articular step-off to minimize the long-term risk of posttraumatic arthritis. Most Bennett fractures can be treated with closed reduction with percutaneous Kirschner wire fixation. Fractures with large Bennett fragments and Rolando fractures should be treated with open reduction and internal fixation to allow anatomic reduction with rigid fixation and early range of motion. Comminuted intra-articular fractures are challenging injuries that are best treated with application of an external fixator with limited open reduction and internal fixation, followed by bone grafting of metaphyseal bone defects if necessary.