A 38-year-old patient presented with pain in the distal portion of the dorsal forearm, where the musculotendinous junction of the abductor pollicis longus and extensor pollicis brevis crosses over the extensor tendons of the second compartment. Ultrasound revealed an effusion within the sheaths of the second and third compartments (Fig. 20.2). The fluid in the latter compartment may have been the result of communication between the second and third compartment sheaths.

The sheaths of the dorsal extensor tendons begin above the upper edge of the extensor retinaculum. Each compartment usually contains a single synovial sheath, but areas of communication may exist between the sheaths of the second, third, and fourth extensor tendon compartments [2].

A 32-year-old patient was operated on for a ganglion of the radiocarpal joint and developed an allergic reaction to the sutures. Clinically, he presented with pain and swelling on the volar side of the wrist. Ultrasound showed tenosynovitis of the extensor digitorum communis, extensor indicis proprius, and extensor carpi radialistendons (Fig. 20.3).

Tenosynovitis is characterized by inflammation of the synovial sheath. Sonography is a valuable tool for diagnosing and evaluating damage to the extensor tendons and their sheaths [3].

A 9-year-old ballet dancer presented with pain over the right radial styloid that was exacerbated by movement of the thumb. Sonography showed hypoechoic thickening of the retinaculum, fluid within the sheath of the extensor pollicis brevis tendon, and fibrous septation of the first compartment. The abductor pollicis longus tendon had multiple terminal laminae (Fig. 20.4).

Anatomic studies have documented the existence of variations in the number of tendons and the division of the first extensor compartment. Sonography can be used to identify several types of anatomic variations in patients with de Quervain’s disease [4].

In this patient with left distal forearm pain, ultrasound disclosed an effusion within the sheath of the extensor carpi radialis brevis tendon (Fig. 20.5).

Intersection syndrome is an overuse disorder of the dorsal distal forearm.It presents with pain and tenderness in the area where the musculotendinous junctions of the abductor pollicis longus and extensor pollicis brevis cross over the extensor tendons of the second compartment, or where the extensor pollicis longus tendon passes over the extensor tendons of the second compartment [2]. The sheath of the radial carpal extensors originates above the upper edge of the extensor retinaculum, 0.5–1 cm from the insertion; it then divides into two separate sheaths, one for each tendon [5].

A 72-year-old patient developed pain and paresthesias over the lateral aspect of the wrist after cephalic vein cannulation. Sonography showed enlargement and hypoechogenicity of a branch of the radial nerve (Fig. 20.6).

The superficial branch of the radial nerve divides into three separate branches at the level of the proximal intersection. Nerve injury at this level can be caused by Colles’ fractures, penetrating trauma, or cephalic vein cannulation [6].

This 21-year-old patient with volar wrist swelling from birth presented with sudden-onset radial pain. Clinical diagnosis: carpal tunnel syndrome. Sonography revealed reversal of the palmaris longus (Fig. 20.7a) and flexor carpi radialis tenosynovitis (Fig. 20.7b).

A reversed palmaris longus may cause a compartment syndrome in the wrist area, carpal tunnel syndrome, and Guyon’s canal syndrome [7].

A 34-year-old patient with symptoms of median nerve compression in the carpal tunnel. Ultrasonography showed tenosynovitis of the flexor tendons and an anatomic variation of the median nerve (bifid median nerve) (Fig. 20.8).

High division of the median nerve proximal to the carpal tunnel (bifid median nerve) has an incidence rate of 2.8 %. Bifid median nerves can cause carpal tunnel syndrome because of their larger cross-sectional area, but other causes should be considered in patients with unilateral symptoms [8].

A 36-year-old patient presented with volar wrist pain several days after experiencing penetrating trauma. Sonography revealed scar tissue encasement of the palmar cutaneous branch of the median nerve (Fig. 20.9).