Case 13: Ruptured Flexor Carpi Radialis

Flexor Carpi Radialis originates on the medial epicondyle of the humerus and inserts on the anterior aspect of the base of the second metacarpal, and has small slips to both the third metacarpal and tuberosity of the trapezium.

On the anterior aspect of the forearm, proximal to the wrist, flexor carpi radialis is the most lateral tendon and is clearly visible when the wrist is brought into flexion. If palmaris longus is present it lays immediately to the medial side of flexor carpi radialis.

In the distal forearm flexor carpi radialis lays over the tendon of flexor pollicis longus.

At the level of the carpal tunnel the tendon of flexor carpi radialis does not enter the carpal tunnel itself but lays more laterally passing over the scaphoid while the tendon of flexor pollicis longus lays within the lateral aspect of the carpal tunnel just medial to the scaphoid.

In this case a 46 year old female patient was referred with pain and weakness in the right dominant forearm following trying to lift a heavy box. Examination demonstrated a painful swelling in the distal forearm. Resisted wrist flexion was weak and elicited pain. In addition the patients hand flexed into ulnar deviation when flexion was attempted.

A longitudinal scan demonstrated the flexor carpi radialis ‘bunching’ within the distal forearm (yellow arrow) over an intact flexor pollicis longus.

In transverse there appeared to be thickening and loss of normal echogenicity and fibrillar pattern of the tendon.

A diagnosis of a ruptured flexor carpi radialis was made and the patient was referred for a surgical opinion. A repair using palmaris longus is being planned.