When Thumb and Wrist Problems Go Hand in Hand
Sometimes, trouble runs in twos, especially for some patients with arthritis at the base of the thumb. This thumb condition, called basal joint arthritis is often joined by carpal tunnel syndrome. There is a definite link between these two problems, but the cause is unknown.

Both diseases occur most often in postmenopausal women, which may help explain the link. Another possible cause is the size and shape of the carpal tunnel in the wrist. The carpal tunnel is an oval-shaped space formed by bones and ligaments. Tendons and the median nerve pass through this tunnel.

Anything that narrows the carpal tunnel can put pressure on the median nerve causing painful symptoms. Arthritic changes of the trapezium bone at the base of the thumb can be part of the problem. This bone forms one wall or border of the carpal tunnel. Bone spurs, points of bone projecting from this bone, may press into the carpal tunnel.

Surgery to correct this problem is usually in two-steps. First, the surgeon cuts the ligament that crosses the carpal tunnel. It attaches to the trapezium. Then, the trapezium is removed completely. This changes the position of the nerve and the shape of the tunnel. The carpal tunnel changes from an oval shape to a more round or circular shape.

MRI (magnetic resonance imaging) can be used to measure the size or volume of the carpal tunnel. Doctors use the image to see if the operation opened up the narrow tunnel. Researchers are exploring whether or not changing the shape of the carpal tunnel is enough to get rid of pain and other symptoms.

Several small studies have been done. More studies with larger numbers of patients are needed to help answer questions about how much surgery is needed and exactly what steps are needed. The information will also help solve the puzzle of why it is common for patients with basal joint arthritis to also have carpal tunnel syndrome.
References
Charles A. Goldfarb, MD, et al. The Relationship Between Basal Joint Arthritis and Carpal Tunnel Syndrome: An MRI Pilot Study. In The Journal of Hand Surgery. January 2003. Vol. 28A. No. 1. Pp. 21-27.