Thumb Arthritis (CMC)

Background

Osteoarthritis (OA) of the carpometacarpal (CMC) joint of the thumb is a condition known as thumb CMC arthritis, or thumb basilar joint arthritis. This condition involves wear and tear of the joint at the base of the thumb, which is particularly prone to these changes due to its significant range of motion.

Causes

Wear and tear during aging leads to progressive degeneration of the cartilage layer at the CMC joint. Trauma of the joint can predispose to arthritis, e.g. a history of fracture. Some patients have significant joint laxity that predisposes them to arthritis. Genetic predisposition can play a varying role.

Symptoms

Symptoms include pain and swelling at the base of the thumb, worsened after prolonged use. Loss of range of motion and reduced grip and pinch strength can result. The deformity at the base of the thumb can lead to changes in the biomechanics of the other thumb joints (called zig zag deformity). A “bump” is often seen near the CMC joint and represents growth of additional bone called “bone spurs” or “osteophytes” (see ultrasound image below).

Diagnosis

The physical examination is the first step, and is supplemented with xrays of the thumb to show the extent of the degenerative changes. Specific maneuvers performed during the physical exam include the CMC grind test, looking tenderness over the CMC joint, crepitus with motion, and examining for joint laxity. Overall range of motion of the thumb is assessed, as well as pinch and grip strength. The position of the other joints of the thumb is also examined, since these may affect the choice of treatment.

Furthermore, other conditions can mimic CMC arthritis. Other joints nearby such as the triscaphe / STT joint can lead to similar symptoms. DeQuervain tendinitis also can be confused with thumb arthritis. Occasionally, laxity of the CMC joint can present with similar symptoms as arthritis. Lastly, some patients with carpal tunnel syndrome can experience cramping in the thumb (thenar muscle). These conditions need to be differentiated.

Treatment

Almost always begins with conservative measures, including splinting, hand therapy, activity modification, and use of antiinflammatories (topical or oral). The next step is a steroid injection. This is often done under ultrasound guidance which is more precise and less painful.

Although the injections provide relief and can be repeated, some patients may be candidates for surgery which involves cleaning out and reconstructing the arthritic joint. Several operations have been described.

Dr. Dowlatshahi offers the following procedures:

• CMC joint denervation.
• arthroscopic (keyhole) hemi-trapeziectomy, and soft tissue interposition.
• trapeziectomy with or without interposition.
• trapeziectomy with ligament reconstruction.
• stabilization of the CMC joint.
• LRTI (Ligament Reconstruction with Tendon Interposition).

Dr. Dowlatshahi will discuss his specific recommendations with you during your visit.