The thumb is generally considered to be the most important single digit in the hand.
The basal joint of the thumb, or carpometacarpal joint (CMC-1), is made up of a carpal or wrist bone (trapezium) and the first or metacarpal bone of the thumb. This joint is very near the wrist and under the fleshy part of the thumb. It is subjected to an unusual amount of stress, as the thumb must be strong enough to counteract the force of four fingers put together. It has been calculated that one pound of pinch between the thumb and index finger will produce six-to-nine pounds of pressure at the basal joint of the thumb.
The joint is held in position by the contours of its surface and by the ligaments and muscles surrounding the joint. Disruptions of the joint surface or the supporting ligaments can lead to slipping of the joint (subluxation) as well as pain and swelling.
Arthritis is a common term meaning inflammation of a joint. Although arthritis can apply to more than 100 different diseases, the three most common types affecting the basal joint of the thumb are osteoarthritis (degenerative arthritis), rheumatoid arthritis, and traumatic arthritis (generally due to a fracture in the joint).
Symptoms of arthritis in the base of the thumb are pain and swelling about the thumb and wrist, particularly with grasp and pinch. These symptoms may appear the first thing in the morning and be present for a half hour or so before the thumb “loosens up.” They might then subside throughout the middle of the day, only to return with a “dull aching” type of pain towards the end of the day or after vigorous use. A “bump” may appear at the joint, due to the shifting of the base of the metacarpal bone as the ligaments loosen through swelling.
When the doctor examines the joint, an attempt is made to determine accurately whether the patient’s pain symptoms are due to arthritis in the thumb basal joint. Tests to determine loosening of the joint as well as the smoothness of the cartilage surfaces are performed. X-rays taken of the joint in various positions help the physician determine the severity of the disease.
Treatment of the condition depends upon the symptoms and stage of the disease. For mild-to-moderate symptoms of pain and swelling, treatment consists primarily of anti-inflammatory medication, rest, splinting, and education. Aspirin has been a standard anti-inflammatory medication for many years, but a wide selection of non-steroidal anti-inflammatory medications may be used as well. Various splints fabricated to support the joint can prove to be quite helpful. Education is also of great importance, as the patient learns about the arthritic process and how to minimize symptoms and protect the damaged joint surfaces.
For more severe symptoms, the patient and doctor may decide on surgery. Because basal joint arthritis is such a common problem, many types of surgical procedures have been developed to deal with it. Surgery generally falls into two main categories; one involves a fusion of the two bones making up the joint, thereby eliminating the joint and the painful symptoms. A potential drawback here is some loss of motion and some stiffening of the thumb joint.
The other major category of surgical correction involves removal of the arthritic surfaces and insertion of material between the two ends of the bones. Many types of materials have been developed; the most frequently used are natural tendon from the patient or a synthetic plastic rubber shaped to fit the space. Each type of surgery has its potential benefit and drawbacks, and each person’s requirements are different.
After surgery, the doctor may prescribe a course of therapy designed to increase the mobility and strength in the thumb following the surgery. A hand therapist provides vital supporting instruction and assists the patient in regaining thumb function.
Pain and stiffness at the base of the thumb are extremely common symptoms of an arthritic condition and should prompt consideration of an evaluation by your physician.