[Functional anatomy and biomechanics of the carpus]

The wrist is an exceedingly complex structure composed of several joints and a dedicated ligamentous system. Its functional principles allow a wide range of carpal motion and make the wrist remarkably resistant to external stress forces:The proximal carpal row serves as an intercalated link interposed between the static elements of both the forearm and the distal carpal row. Like a flexible place-holder, the proximal row synchronously adapts to the spatial and temporal requirements of the wrist. There are synergistic movement patterns including simultaneous flexion of the proximal row as the wrist is deviated radially and simultaneous extension during ulnar deviation. Together with pronosupination of the radioulnar joints, the combined radial/ulnar inclination and flexion/extension enable spherical, out-of-plane movements of the hand. Carpal function is best explained by the "model of a ring under tension."This review addresses the anatomy and the biomechanics of the wrist and illustrates systematic image analysis by using carpal lines and angles as well as indices of carpal height.