Flexor carpi ulnaris muscle Flexor carpi ulnaris muscle The flexor carpi ulnaris muscle (or FCU) is a muscle of the human forearm that acts to flex and adduct (medial deviation) the hand. Flexor carpi ulnaris muscle arises by two heads, humeral and ulnar, connected by a tendinous arch beneath which the ulnar nerve and artery pass. Its insertion is into the pisiform bone, into the hamate bone via the pisohamate ligament and into the fifth metacarpal bone via the pisometacarpal ligament. The muscle acts to flex and adduct the wrist joint. The flexor carpi ulnaris muscle is innervated by the ulnar nerve which has
Carpal bones with a total range of 170 degrees. During radial abduction the scaphoid is tilted towards the palmar side which allows the trapezium and trapezoid to approach the radius. Because the trapezoid is rigidly attached to the second metacarpal bone to which also the flexor carpi radialis and extensor carpi radialis are attached, radial abduction effectively pulls this combined structure towards the radius. During radial abduction the pisiform traverses the greatest path of all carpal bones. Radial abduction is produced by (in order of importance) extensor carpi radialis longus, abductor pollicis longus, extensor pollicis longus, flexor carpi radialis, and flexor pollicis