CHAPTER 4: Imaging the Hand and Wrist

1. INTRODUCTION: FAST HAND AND WRIST FACTS

❑ Traumatic Injuries

• Falls—the most common mechanism of injury to the wrist is a fall on an outstretched hand.

  • ◗ In children, the distal radius is the most frequently fractured bone anywhere in the skeleton.

  • ◗ In adults, the distal radius is the most frequently fractured bone in the wrist, followed by the scaphoid and the lunate.

• Work Related—the exposed location of the distal phalanges of the hand account for more than half of all hand fractures in adults that are work related.

❑ Athletic Injuries

• ◗ Tears of the triangular fibrocartilage complex (TFCC) are seen in sports in which there is repetitive force on a wrist positioned in extension and/or ulnar deviation, such as gymnastics, pole vaulting, boxing, hockey, and racquet/batting sports. Tears may also result from falls, distal radial fractures, or power-drill injuries (the bit binds and the wrist is forcibly rotated).

❑ Compression Neuropathies

• Carpal tunnel syndrome is a common compression of the median nerve owing to increased pressure in the carpal tunnel.

  • ◗ Ulnar tunnel syndrome is compression of the ulnar nerve in Guyon's canal, usually caused by a growth (e.g., ganglion, scar tissue).

  • ◗ Wartenberg's syndrome, a somewhat rare condition, is a compression of the sensory radial nerve in the distal forearm, a result of post-surgical injury or external compression (wrist watch, handcuffs). It also occurs in association with the inflammation of de Quervain's tenosynovitis.

❑ Soft Tissue Disorders

• De Quervain's tenosynovitis is inflammation of the synovial sheath of the abductor pollicis longus and extensor pollicis brevis tendons, causing pain at the base of the thumb.

❑ The Imaging Choices

• Radiographs are the initial study for all hand or wrist problems. Radiographs adequately demonstrate most fractures and dislocations, as well as nontraumatic disorders such as the various arthritides.

• Computed tomography (CT) provides optimal visualization of complex fractures, especially in characterizing fracture–dislocations of the thumb, distal radial fractures, hook of the hamate fractures, and carpal collapse owing to osteonecrosis.

• Magnetic resonance imaging (MRI) has been the study of choice for evaluating radiographically occult fractures, especially of the scaphoid and lunate, staging osteonecrosis of the lunate, and identifying tears of the TFCC and tears of the intercarpal ligaments.

• Musculoskeletal ultrasound (MSUS) is used for the evaluation of many soft tissue problems at the wrist, including wrist ganglia, tenosynovitis, and tendon rupture; detection of TFCC tears; diagnosis of carpal tunnel syndrome; and guidance of interventional procedures at the wrist.

❑ The Available Guidelines

• ACR Appropriateness Criteria: Currently, 12 presentations of acute hand and wrist trauma and 10 presentations of chronic wrist pain have been researched.

• Diagnostic ...