The physicians of Muir Orthopaedic Specialists believe good medical care is a result of mutual understanding, respect and trust.  In today's fast paced world, we recognize the importance of communication and spend as much time as possible to provide information explaining condition and treatment options so that our patients can make informed decisions about their care.

CARPOMETACARPAL JOINT ARTHROSIS

What is it?
Carpometacarpal joint arthrosis (CMCJ arthrosis), refers to osteoarthritis which develops at the base of the thumb. Osteoarthritis is the most common form of arthritis and the thumb is one of the most common locations. Arthrosis at the base of the thumb goes by several names including basilar thumb joint arthrosis, trapezoid-metacarpal arthrosis, degenerative joint disease and various other terms.

What Causes CMCJ Arthrosis?
CMCJ arthrosis is very common and there are many causes. Approximately 50 percent of woman over the age of 50 and approximately 75 percent of all individuals over the age of 65 can develop CMCJ arthrosis. The base of the thumb is subjected to high mechanical sheer and compression forces. These forces are greatly magnified by the length of the thumb and are concentrated at the base of the thumb. Pinching and grasping activities can literally wear out the joint over the course of a lifetime. The joint surface becomes damaged and can wear down completely, causing the bones to rub together. Prior injuries such as sprains and fractures can accelerate this wear and tear.

CMCJ arthrosis also occurs in association with other diseases. For example, inflammatory conditions such as rheumatoid arthritis can also affect the joint. CMCJ arthrosis frequently develops in postmenopausal women for reasons which are not entirely clear. The protective effect of the circulating hormones is lost during menopause, and the joints can be susceptible to mechanical wear and tear. Replacement hormone therapy does not appear to alter the degeneration.

Clinical Features
CMCJ arthrosis results in pain and swelling at the base of the thumb. Bone spurs can develop which gives the thumb a squared-off appearance. The swelling is associated with laxity and instability of the ligaments that support the thumb, resulting in further wear and tear of the joint. The joint can become unstable to the point of dislocating. Under these circumstances, the next two joints along the ray of the thumb assume a hyper extended position which can further aggravate the overall pain and deformity of the thumb. In severe cases of instability, the thumb can be contracted into the palm of the hand, making it difficult to grasp items. This combination of changes results in painful grasp and pinch which can severely compromise daily activities. 

Treatment
CMCJ arthrosis is a common disorder. Unfortunately, there are no significant preventative measures available, and treatment is dependent upon the extent and severity of the existing symptoms. Mild cases can be adequately treated with over-the-counter medication such as aspirin or Tylenol, appropriate restrictions in activities, as well as rest, ice and elevation. More severe cases may benefit from formal fabrication of custom splits which help stabilize the base of the thumb joint while allowing full motion at the wrist and the reminder of the digits.

More resistant cases of CMCJ arthrosis may benefit from a cortisone injection into the joint itself. Although cortisone does not affect the arthritic condition, it can significantly improve the pain and shrink the swollen, soft tissues. In severe cases, surgery to replace the thumb joint can restore function and significantly improve pain. In general, surgery is designed to either replace the arthritic joint with a tendon spacer, or remove the arthritic joint and fuse the bones on either side of the joint in order to relieve pain. Surgery is performed as an outpatient in a surgical suite and requires several weeks of postoperative splinting and therapy.

Outcome
Many patients can resume virtually all of their normal activities while undergoing treatment. Medication, splinting and cortisone injections can provide significant benefit without the need for surgery. Although the arthrosis can progress, this does not necessarily mean that pain will progress.

The outcome following surgery is highly dependent upon individual circumstances. In general, most patients have significant benefit with respect to their pain, but there can be approximately a 20-30 percent permanent loss of motion and grip strength. The outcome regarding individual circumstances can be further discussed with your physician.

Copyright 2003 Muir Orthopaedic Specialists