Functional Anatomy of the Wrist

Abstract

The microarchitecture of the distal radius has evolved to resist physiological loads from the carpus. The layered subchondral bone plate acts as a ‘leaf-spring’ to absorb and distribute loads. The arrangement of the trabeculae as an ‘arch bridge’ allows load distribution to the strong cortical bone of the diaphysis. Eight carpal bones are tightly arranged with corresponding facets at the distal radius and held by ligaments. The extrinsic dorsal and volar radiocarpal ligaments are distributed along the cortical rim, and each has a specific function. The ulnocarpal ligaments prevent ulnocarpal sag and are stabilizers of the distal radioulnar joint. The interosseous ligaments provide stability and proprioception and compromise results in intercalated instability. The extrinsic extensor tendons are arranged into six separate compartments. The second and sixth compartments insert opposite corresponding flexor tendons and form a ‘double-pulley’ system to control radial and ulnar deviation with flexion and extension. The digital flexors pass through the fibro-osseous carpal tunnel. The complex osseo-ligamentous relationships within the wrist allow a high degree of stability within multiple axes of motion.