Normal sonographic anatomy of the wrist and hand.

The advent of ultra-high-frequency sonographic transducers has significantly enhanced our ability to image superficial structures. As a result, sonography now can be used to assess injuries of the tendons in the wrist and hand. A clear understanding of normal sonographic anatomy is required to prevent misdiagnosis and ensure optimal patient care. The anatomy of the wrist and hand is best described by considering the extensor and flexor surfaces separately. The carpal extensor retinaculum divides the dorsal extensor tendons into six separate synovial compartments, which are demarcated by the points of its attachment to the radius and ulna. The course of these tendons from the wrist to the sites of their insertion can be traced by using sonography. The intrinsic wrist ligaments, triangular fibrocartilage, and dorsal finger extensor hood also can be assessed sonographically. The anatomy of the flexor surface of the wrist is defined principally by the flexor retinaculum. The median nerve, which is located deep to the retinaculum in the carpal tunnel, and the ulnar nerve, which is superficial to the retinaculum in the Guyon canal, can be easily detected. The long flexor tendons in the wrist and hand are also clearly depicted at sonography. The flexor annular pulley system is formed by five foci of thickening along the long flexor finger tendon synovial sheath, and the second and fourth annular pulleys can be identified sonographically in most patients. Sonography provides a rapid, cheap, noninvasive, and dynamic method for examination of the soft-tissue structures of the wrist and hand. Familiarity with the appearance of normal anatomic structures is a prerequisite for reliable interpretation of the resultant sonograms.