Functional ligamentous anatomy of the trapezium and trapeziometacarpal joint (gross and arthroscopic).

A detailed description of the ligamentous anatomy of the thumb basal joint is presented from a gross, arthroscopic, and functional point of view. All 16 ligaments that stabilize the trapezium and trapeziometacarpal (TM) joint are discussed in association with their presumed functional relevance regarding trapezial and trapeziometacarpal joint stability. Geometric and mathematical models are introduced to help describe and support anatomic observations with regard to ligament function. The dorsoradial ligament appears to be an important stabilizer of the TM joint against dorsally directed forces. The trapeziotrapezoid, trapezio-II metacarpal, and trapezio-III metacarpal ligaments appear to function as tension bands to help support the trapezium against cantilever bending forces imparted onto the trapezium by the thumb metacarpal.