Flexor Carpi Radialis Tendon Injection

Indications and Clinical Considerations

Flexor carpi radialis tendinitis is seen with increasing frequency in clinical practice as golf and racquet sports have increased in popularity. The flexor carpi radialis tendon is susceptible to developing tendinitis at the distal portion. It is subject to repetitive motion that may result in microtrauma, which heals poorly because of the tendon’s avascular nature. Exercise and repetitive trauma are often implicated as the inciting factors of acute flexor carpi radialis tendinitis, and improper grip of golf clubs and tennis racquets and the prolonged use of a heavy hammer are common inciting causes. Tendinitis of the flexor carpi radialis tendon frequently coexists with bursitis, creating additional pain and functional disability. Calcium deposition around the tendon may occur if the inflammation continues, making subsequent treatment more difficult. Continued trauma to the inflamed tendon may ultimately result in tendon rupture ( Fig. 78.1 ).

The onset of flexor carpi radialis tendinitis is usually acute, occurring after overuse or misuse of the wrist joint. Inciting factors may include activities such as playing tennis or golf and prolonged use of a heavy hammer. Injuries ranging from partial to complete tears of the tendon can occur when the distal tendon sustains direct trauma while the wrist is in full ulnar deviation under load or when the wrist is forced into full ulnar deviation while under load. The pain of flexor carpi radialis tendinitis is constant and severe and is localized in the dorsoradial aspect of the wrist. Significant sleep disturbance is often reported. Patients with flexor carpi radialis tendinitis will exhibit pain with resisted ulnar deviation of the wrist. A creaking or grating may be palpated when passively radially deviating the wrist. As mentioned, the chronically inflamed flexor carpi radialis tendon may suddenly rupture with stress or during vigorous injection procedures when inadvertent injection into the substance of the tendon occurs. Plain radiographs and magnetic resonance scanning are indicated for all patients with radial-sided wrist pain. Ultrasound imaging may also be useful in further delineating the cause of the patient’s wrist pain and functional disability ( Fig. 78.2 ).

On the basis of the patient’s clinical presentation, additional testing, including complete blood count, sedimentation rate, and antinuclear antibody testing, may be indicated. Magnetic resonance and/or ultrasound imaging of the wrist is indicated if tendon rupture is suspected and to further confirm the diagnosis ( Fig. 78.3 ). Radionuclide bone scanning is useful to identify stress fractures of the wrist not seen on plain radiographs.

Clinically Relevant Anatomy

The flexor carpi radialis muscle is located in the forearm. Its primary action is to flex and abduct the hand. Its origin is at the medial epicondyle of the humerus and traverses the forearm just lateral to the flexor digitorum superficialis to insert on the anterior aspect of the base of the second metacarpal. The tendon lies adjacent to the median nerve ( Fig. 78.4 ). The muscle also has secondary insertions on the third metacarpal and the tuberosity of the trapezium. The flexor carpi radialis muscle is innervated by the median nerve and receives its blood supply from the ulnar artery.