Trigger Thumb and Carpal Tunnel Syndrome Connection

by Aubrey Bailey

    Painful hand conditions make daily activities difficult. Trigger thumb and carpal tunnel syndrome are common disorders that affect the thumb on the palm side of the hand. These conditions frequently occur together and share some common risk factors. However, researchers have not been able to establish a direct link between trigger thumb and carpal tunnel syndrome.

    Symptoms of trigger thumb typically develop over time. The tendon that bends the thumb travels through a sheath -- a slippery tunnel that allows it to glide smoothly as the thumb bends. Several pulleys hold this tunnel in the correct position in the hand.
    Inflammation and swelling in the tendon sheath progressively limit the tendon's ability to glide smoothly. The tendon gets stuck as it travels under the pulleys, causing the thumb to temporarily "catch" or lock in the midst of trying to bend or straighten. A painful popping sensation occurs as the thumb moves past the catching point.

    As with trigger thumb, the symptoms of carpal tunnel syndrome evolve gradually. The carpal tunnel is located within the base of your palm, just above the wrist. Nine tendons -- including the tendon that bends the thumb -- and the median nerve travel through this tunnel. Swelling and inflammation cause increased pressure in the tunnel, compressing the median nerve. This produces pain, tingling and numbness in the thumb, index, middle and thumb side of the ring finger.

    Trigger thumb and carpal tunnel syndrome frequently occur together, although the symptoms of one condition or the other often predominates. A study published in 2009 in the "Journal of Brachial Plexus and Peripheral Nerve Injury" assessed 180 patients presenting to a hand clinic with complaints of carpal tunnel syndrome or trigger finger symptoms. Sixty-one percent of these patients were found to have both conditions. However, a common cause was not identified.

    The causes of carpal tunnel syndrome and trigger thumb are not known, although they have several risk factors in common. Repetitive hand movements -- particularly thumb and finger flexion -- are thought to irritate the median nerve in the carpal tunnel as well as the sheath through which the thumb flexor tendon travels. Occupations that require frequent use hand-held or vibrating tools may increase the risk for these conditions. However, research does not conclusively support this association. Trigger thumb and carpal tunnel syndrome can both be caused by direct trauma. Swelling in the palm increases pressure within the thumb flexor tendon sheath and the carpal tunnel. Both trigger thumb and carpal tunnel syndrome affect women more commonly than men.

    Trigger thumb and carpal tunnel syndrome may resolve with conservative treatment. Antiinflammatory medication and oral steroids are frequently prescribed to reduce inflammation in the hand. Physical therapy interventions such as heat and ultrasound are used to decrease localized inflammation, improve blood flow and promote healing. Daily activities are modified to avoid repetitive gripping and bending of the thumb to reduce stress on the painful structures. Splints are worn while sleeping and intermittently during the day to hold the wrist in a straight position to reduce strain on the median nerve. The thumb is splinted to prevent it from bending, thus preventing "triggering." Cortisone injections are also used to treat both of these conditions. These methods are often successful for short-term symptom relief.

    Trigger thumb and carpal tunnel release surgeries are sometimes required to address these conditions. Release of the affected pulley involved in trigger thumb can sometimes be accomplished through the skin. A needle is used to penetrate and cut the pulley. This procedure is performed in a doctor's office. According to a study published in 2005 in the "British Medical Journal," success rates have been shown to be more than 90 percent. An open surgical release of the pulley can also be performed under anesthesia. Success rates for an open release vary from 60 to 97 percent.
    Carpal tunnel release is performed under anesthesia to relieve pressure on the median nerve. The procedure involves cutting the transverse carpal ligament, the fibrous connective tissue that forms a roof over the carpal tunnel. According to an article published in 2012 in "The Open Orthopaedics Journal," approximately 70 to 90 percent of patients have long-term success with this procedure. People with both diagnoses may have both procedures performed during the same surgery.

    About the Author

    Aubrey Bailey contributes to various websites in the areas of health, wellness and other physical therapy-related topics. She holds a Bachelor of Science in physical therapy and a Bachelor of Arts in psychology from the University of Buffalo, as well as a post-professional Doctor of Physical Therapy from Utica College. Dr. Bailey is also a certified hand therapist.

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