Trigger thumb is an involuntary, sometimes painful condition. It is named after the clicking of the affected fingers, or popping of the joint, that can interfere with the function of the hand during routine activities as the fingers or thumb bend toward the palm (a movement referred to as flexion). Patients may complain of morning stiffness instead of triggering, but more severe cases involve a 'locking' of the joint.
Most commonly affected joints are those of the thumb, middle finger, and ring finger; and the condition is normally present in both hands. In children however, symptoms are often restricted to the thumb alone. Although the condition is bilateral, it does appear to be more severe in the dominant hand, indicating that usage may be a factor.
Initial symptoms include a painful clicking of the finger. This is caused by degenerative changes in the flexor pollicis longus tendon along the bones and across the inner joints of the finger or thumb, creating a swelling which interferes with the movement of the tendon within its sheath.
Who it affects
It occurs more often in adults than in children, and is four times more common among women than men - particularly those in their fifties and sixties. When it occurs in children it is referred to as congenital trigger thumb, though it does not normally develop until sometime after infancy. Children are not as likely to complain of pain, and it is probable they will be taken to a physician when they are one to four years of age.
The condition is more likely to occur in patients with diabetes, osteoarthritis, or conditions related to proliferation1 of the tenosynovium2 (eg, inflammatory arthritis, fungus infection, atypical mycobacterial infection, or gout). It is also statistically linked to carpal tunnel syndrome and de Quervain disease (radial styloid tendovaginitis). In patients with rheumatoid arthritis, the proliferation of the tenosynovium has been known to result in stiffness, without the intermittent 'triggering'.
Up to 30% of cases may find their symptoms disappear without treatment. If the symptoms do not include 'locking' of the joints, non-surgical treatments are offered before surgical correction is suggested. These include relief of the irritation through:
Immobilisation of the joints with splints
Splints are set to hold the joints at a 15-degree angle, and are worn either at night or for 10-14 days continuously. Splinting for too long a period may lead to permanent stiffness. Splinting is effective about 50% of the time, without further medical treatment.
Oral steroidal, or non-steroidal drugs and/or from one to three corticosteroid injections. Patients responding to such non-surgical treatments normally show improvement after the first injection. Up to 90% experience relief if they are given a third injection.
Patients who have experienced locking for more than four months are more likely to need surgical relief. This is often accomplished by the 'opening' of the A1 pulley3; but recent studies suggest that enlarging the A1 Pulley may be just as effective, if more demanding of the surgeon. A detailed sketch of the phalangeal anatomy, including the A1 pulley, can be found here.
The appropriate surgical procedure results in a 95% relief of symptoms or better. The reoccurrence rate is about 3%.
Further information on Trigger Thumb
1 Proliferation is the rapid reproduction of tissue that results in constriction of the tendon within the tenosynovium.
2 Tenosynovium is a slippery covering of the tendons that help them glide smoothly through the ligaments.
3 Pulley = a term used for the ligament (sheath) attached to the bone, that covers the tenosynovium covering the tendon.