Flexor Digitorum Superficialis and Profundus Injection for Tendinitis and Trigger Finger

Indications and Clinical Considerations

Trigger finger is an inflammation and swelling of the tendons of the flexor digitorum superficialis caused by compression by the heads of the metacarpal bones. Sesamoid bones in this region also may cause compression and trauma to the tendons (see Chapter 90 ). The inflammation and swelling of the tendon are usually a result of trauma to the tendon from repetitive motion or pressure overlying the tendon as it passes over these bony prominences. If the inflammation and swelling become chronic, a thickening of the tendon sheath occurs, resulting in a constriction of the sheath ( Fig. 88.1 ). Frequently a nodule develops on the tendon because of chronic pressure and irritation. These nodules often can be palpated when the patient flexes and extends the fingers. Such nodules may catch in the tendon sheath as the nodule passes under a restraining tendon pulley, causing a triggering phenomenon and the finger to catch or lock as the nodule catches on the pulley ( Figs. 88.2 and 88.3 ).

Coexistent arthritis and gout of the metacarpal and interphalangeal joints may also exacerbate the pain and disability of trigger finger. Trigger finger occurs in patients engaged in repetitive activities that include hand clenching, such as gripping a steering wheel or holding a horse’s reins too tightly.

The pain of trigger finger is localized to the distal palm, with tender tendon nodules often palpated. The pain of trigger finger is constant and made worse with active gripping activities of the hand. Patients note significant stiffness when flexing the fingers. Sleep disturbance is common, and the patient often awakens to find that the finger has become locked in a flexed position during sleep. Physical examination reveals tenderness and swelling over the tendon with maximal point tenderness over the heads of the metacarpals. Many patients with trigger finger exhibit a “creaking” with flexion and extension of the fingers. Range of motion of the fingers may be decreased because of pain, and a trigger finger phenomenon may be noted. Patients with trigger finger often demonstrate nodules on the tendons of the flexor digitorum superficialis.

Plain radiographs are indicated for all patients with trigger finger to rule out occult bony disease. On the basis of the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, uric acid, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging and/or ultrasound imaging of the hand is indicated if joint instability or tendinopathy is suspected. Ultrasound imaging may also help identify soft-tissue abnormalities that may be responsible for the triggering phenomenon ( Fig. 88.4 ). The injection technique described later serves as both a diagnostic and a therapeutic maneuver.

Clinically Relevant Anatomy

The nidus of pain from trigger finger is the tendon flexor digitorum superficialis at the level of the head of the metacarpals (see Fig. 88.1 ). Sesamoid bones present in this region also may impinge on the tendon and tendon sheath and cause inflammation and swelling. As mentioned earlier, arthritis and gout of the metacarpal joints may accompany trigger finger and exacerbate the patient’s pain symptoms.