Flexor carpi radialis brevis muscle, a rare anomalous muscle of the forearm; a case report and literature review

Abstract

The flexor carpi radialis brevis (FCRB) is a rare abnormal muscle of the distal forearm or wrist. Its incidence varies in different reports, which oscillating between 2-8%. This paper reports a case of FCRB found in the anatomy of the forearm. The abnormal muscle, which started from the facies volaris distal radii, occupies the terminus of pronator quadratus, and was observed with dysplasia in the pronator quadratus. We also reviewed the literature on FCRB anatomy, especially the surgical exposure of distal radius fractures and the clinical symptoms caused by FCRB. Knowledge of the anomalous muscles of the forearm and wrist can highly improve clinician's understanding of the disease during surgery and imaging examination, and reduce unnecessary trauma caused by misdiagnosis.

Keywords: Flexor carpi radialis brevis (FCRB); anomalous muscle; forearm.

Figure 1

Left forearm: The muscle started from the facies volaris distal radii and ending at the base of the palmar side of the second metacarpal bone. 1: Flexor carpi radialis brevis (FCRB); 2: The muscle-belly of the FCRB; 3: Base of the second metacarpal bone; 4: The tendon of FCRB; 5: The insertion of the pronator quadratus in the radius (dysplasia in pronator quadrates).

Figure 2

Right forearm: 6: Flexor carpi radialis brevis (FCRB); 7: The tendon of FCRB; 8: The insertion of FCRB is at the base of the first metacarpal base.