 |
 click to enlarge |
The basal joint is formed by a small wrist bone (trapezium) and the first bone of the thumb (metacarpal). Because of its design, it has a wide mobility and is prone to earlier degeneration than the other joints in the hand. Because of its critical role in thumb and hand function, pain at the basal joint is also more disabling than arthritis elsewhere in the hand.
The basal joint is the second most common joint in the hand to develop osteoarthritis. Also call degenerative arthritis, osteoarthritis occurs when the gliding surface cartilage of the joint wears out, allowing the bones on either side of the joint to rub together and eventually destroying the joint.
While this joint is prone to wear and tear from normal use of the hand, many people may be predisposed to arthritis in this joint. For example, this type of arthritis is more common in women who enjoy greater join laxity (range of motion), and typically begins after the age of 40. One out of five females over the age of 50 have this type of arthritis. It is also a common problem for musicians who typically pinch their thumb and index finger toward each other, such as playing the piano or holding the bow of a bass or cello. Also, previous injuries to the basal joint, including fractures and sprains, can increase a person's chances of developing this arthritis. Patients who have basal joint arthritis may or may not have arthritis in other parts of the body.
Generally, the first symptom a patient with basal joint arthritis notices is pain in the joint when opening jars and turning keys and door knobs--any activity that involves grasping or pinching an object between the thumb and fingers. Gradually, pain is produced even more easily (e.g. when writing) and swelling may develop. There may also be a bony bump over the joint, and weather changes may cause pain as well. Eventually, in the more severe cases, the joint begins to appear enlarged, the pinch strength is decreased, and the thumb's movement is restricted.
First, your physician will take a history of the problem by asking you about the pattern of pain, what activities cause the pain, and the history of any previous thumb injuries. Then he or she will attempt to reproduce the symptoms by stressing the joint. The motion of the thumb may also be tested, as it becomes more difficult with the progression of the arthritis. In addition, pressing the thumb firmly against the wrist bone while moving the basal joint may also be done to see if there is pain and/or a gritty feeling, which means the bones are rubbing together. X-rays should be taken to assess the severity of the arthritis--these help to plan treatment and predict outcomes. In the most severe cases, the metacarpal bone collapses into the palm and causes the second joint in the thumb to overextend when grasping larger objects.
In its early stages, the pain of basal joint arthritis can typically be relieved with splints to limit movement and inflammatory medications--including low-dose oral steroids--to decrease swelling and pain. Exercise programs are not recommended since they often exacerbate the problem.
Depending on the severity of the symptoms and disability, surgery may become necessary. In the early stages of the arthritis when most of the joint cartilage remains, ligament reconstruction alone can restore painless stability and minimize further degeneration. In the most severe cases, arthroplasty--replacing the arthritic joint surfaces or the entire trapezium with soft tissue from the wrist to stabilize the remaining bone--may be required. Following this surgery, four to five weeks of immobilization in a cast followed by three to five months of range of motion and pinch strengthening exercise is necessary for the best results.
