Extensor digitorum brevis manus muscle
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origin: distal radius and posterior radiocarpal ligament
insertion: extensor hood of 2nd or 3rd digits (variable)
innervation: posterior interosseous nerve
action: extension of the digits
It is thought to be present in ~3% of the population 1. It can be bilateral in up to half of cases.
The EDBM muscle lies along the ulnar side of the extensor tendon of the 2nd digit (usually fourth wrist compartment 5). It commonly arises at the distal end of the radius and posterior radiocarpal ligament to insert most commonly on the 2nd digit. However, insertion can also be seen on the 3rd, 4th, or 5th digits, as well as multiple insertions on more than one digit.
The muscle is usually painless although rarely it can present as a painful mass over the dorsal aspect of the hand. Occasionally it may be associated with exercise-induced pain or tenosynovitis of the extensor tendons.
Can be normal.
Sonography may reveal a soft-tissue mass with muscle echotexture; in real time, it usually undergoes morphologic changes during active finger extension.
Signal characteristics include:
T1/T2/PD: isointense to muscle on all sequences
C+ (Gd): no enhancement in uncomplicated cases (e.g. unless there is inflammation)
History and etymology
The muscle was first described by Bernhard Albinus (1697-1770), German-born Dutch anatomist, who discovered the muscle in 1734 and initially named it the extensor brevis digiti indicis vel medii 8,9.