ABSTRACT
The biomechanics of the hand and wrist represent a subject of immense complexity, and a thorough understanding is difficult. The interphalangeal (IP) joints are simple single-axis hinge joints. They allow flexion and extension and are powered by two motors. Movement at the carpometacarpal (CMC) joints of the fingers is limited, especially in the index and middle fingers. Brachioradialis (BR) crosses the elbow and acts as an elbow flexor as well as a midpronator or midsupinator, depending on forearm rotation. Extensor carpi radialis longus (ECRL) acts as a wrist extensor and radial deviator as well as a weak elbow flexor. A system of thickenings within the fibro-osseous sheaths of the flexor tendons are known as the flexor pulleys. Carpal instability complex (CIC) results when instability within and between rows is combined. CIC results from significant disruption of intrinsic and extrinsic soft tissues, or fractures, and the movement of the carpal bones reflects the disruptions.
