Flexor carpi radialis brevis: a rare accessory muscle presenting as an intersection syndrome of the wrist

Abstract

The flexor carpi radialis brevis (FCRB) is a rare accessory muscle of the forearm and wrist. It is typically asymptomatic, but has been discovered either incidentally during cadaveric studies or at the time of surgery in patients with distal forearm injury. Rarely, the FCRB muscle is associated with pain. We report a patient with wrist pain related to intersection between the tendon of the FCRB muscle and the tendon of the flexor carpi radialis (FCR) muscle, with an associated longitudinal split tear of the FCR tendon, documented by magnetic resonance imaging (MRI). To our knowledge, this is only the second report in the English literature of this intersection syndrome.

The prevalence and distribution of the flexor carpi radialis brevis muscle in the Turkish population

“…Symptoms caused by FCRB are related to its location and function 17 – 19 . Radial-sided pain of the wrist, interosseous anterior compression, inflammation due to overuse of the muscle where it attaches to the radius, and FCRB tenosynovitis are some of the disorders that may occur 19 , 20 .…”

The Flexor Carpi Radialis Brevis: A Description of an Anomalous Wrist Flexor and Surgical Exposure Technique

“…In addition, it has been implicated as a cause of radial sided wrist pain because of symptomatic tears, intersection with the FCR, and carpal tunnel syndrome. [4][5][6] Volar wrist pain postoperatively (thought to be a result of tenosynovitis) has also been reported. 7 Knowledge of pertinent anatomy has implications for surgical exposure and for the protection of its innervation and vascular supply.…”

Back to the roots of rheumatology – Imaging of regional pain syndromes

“…Overuse edema of the FCRB has been described as the cause of pain around the radial volar aspect of the distal forearm and wrist in a piano player [9]. Compression of the anterior interosseous nerve by the FCRB and a syndrome of intersection between its tendon and the FCR muscle has also been described [10].…”