Stenosing tenosynovitis, or trigger thumb, is an irregularity of the hand caused by painful inflammation of the flexor tendon. A trigger thumb becomes stuck in the bent position, restricting normal extension of the finger. Although pediatric trigger thumb is commonly considered a congenital condition, it often develops long after birth. Infants with trigger thumb are most likely to experience a spontaneous recovery, but if the condition worsens as the child gets older, surgery may be necessary to correct the problem.
Condition
Movement of the hand is controlled by tendons that connect the arm muscles to the finger bones. The flexor tendon in the thumb slides back and forth through a tunnel-like sheath known as the A1 pulley, allowing the digit to bend or extend. Constriction of the A1 pulley prevents the flexor tend from moving freely, placing stress on the thumb when the infant tries to extend it. The ongoing tension between the A1 pulley and the tendon can cause swelling in both areas, eventually leading to permanent locking of the thumb, according to the American Society for Surgery of the Hand.
Symptoms
Continual irritation of the tendon results in swelling and inflammation beneath the skin, causing pain and soreness in the thumb and the palm of the hand. Over time, a lump forms at the base of the thumb, further restricting movement of the finger. You may hear a popping sound when the infant's thumb catches and releases. Stiffness is usually more pronounced in the morning or during periods when the child is inactive, the Vermont Orthopaedic Clinic states, but renewed movement can loosen the thumb.
Cause
The cause of stenosing tenosynovitis in babies is difficult to determine. In some cases, a nodule is present on the tendon at birth and worsens over time. Congenital trigger thumb can also be the result of an undersized A1 pulley. Factors such as frequent gripping or the presence of rheumatoid arthritis are believed to increase the risk of developing stenosing tenosynovitis, but these factors do not typically apply to infants.
Diagnosis
Consult a physician if you observe involuntary locking of the thumb in a baby. Pay attention to any symptoms that accompany the condition and the degree of pain the child experiences. The doctor will make similar observations, then perform a physical examination to determine the severity of the condition and the proper treatment. Spontaneous release of the A1 pulley occurs less frequently in children over the age of 1, according to the Children's Hospital of Boston, so the physician may recommend surgical treatment if your child is not an infant.
Treatment
Treatment of trigger thumb depends on the source of the condition and its severity. When stenosing tenosynovitis is the result of temporary irritation, rest, medication or a finger splint may be enough to reverse the symptoms. Serious cases of trigger thumb are treated with outpatient surgery. The physician makes a small cut in the A1 pulley to widen the sheath and allow the flexor tendon to move without restraint. Normal movement of the hand returns immediately after surgery, but the child may experience soreness for a few weeks.
