Joint Replacement - Thumb

Joint replacement of the thumb is most often associated with arthritis of the basilar joint of the thumb, or basilar joint arthritis. A form of osteoarthritis, basilar joint arthritis affects women more commonly than men and the basilar joint is the second most common joint to develop osteoarthritis. It generally occurs after the age of 40, as a result of many of the same joint conditions prompting osteoarthritis of other joints - joint instability, cartilage deterioration, wear and tear.

Severe forms of basilar joint deterioration can cause deformity and debilitating pain. When the deteriorating joint becomes nonresponsive to other treatment options and pain and limited function hinder a patient’s quality of life, joint replacement of the thumb may be indicated. A basilar joint replacement eliminates pain and restores strength and function to the finger and hand by replacing the damaged joint(s) with an artificial one.

About the Thumb
The basilar joint of the thumb consist of a small wrist bone and the first bone of the three located in the thumb. The unique shapes of these small bones permit its movement in and out of the plane of the palm to oppose the other fingers. The thumb is able to attain a greater range of movement in many directions compared to the fingers - easily rotating 90 degrees compared to the average 45 degrees of the other fingers, as a result of the surface shapes of the two bones of which it is comprised.

The phalanges are connected to the longer first metacarpal bone in the hand. Utilizing muscles arranged around the first metacarpal, the joint at the base of the thumb, the basal joint, is able to rotate and oppose the fingers - easily enabling grasping and pinching. And a band of fibrous tissue connecting the bones at the base of the thumb, called the ulnar collateral ligament, helps control thumb movement - preventing it from pointing excessively away from the hand.

The stability of the carpometacarpal joint of the thumb depends on these ligaments, which allow movement but remain close to the joint surfaces. If the ligaments loosen and permit too much sliding of the joint surfaces, increased wear on the joint cartilage may occur - leading to arthritis. A fracture or injury can also lead to joint dysfunction and deterioration, ultimately leading to arthritis as well.

Severe deterioration may prompt bony spurs around the joint. In complete joint destruction, there is an inward collapse of the metacarpal and deterioration around the trapezium. Other joints may also become affected as they react to the changes.

The Procedure
Once the decision is made to proceed with joint replacement, a series of tests and imaging scans are performed in order to ensure the best possible outcome. The procedure is performed as either an in-patient or out-patient procedure, depending on the condition of the patient, number of joints affected and anticipated length of the procedure.

Once the patient is prepared for surgery and anesthesia is administered (either general anesthesia or local anesthesia depending on patient conditions), the procedure begins with an incision in the back of the thumb just over the joint. Once the joint surfaces are exposed, the cartilage is removed from both surfaces. A canal is then formed in the bones of the thumb joint with a small cutter.

An implant designed specifically for the thumb joint and used as a "spacer" to fill the gap created when the arthritic surfaces are removed is placed in the newly formed canal at the base of the thumb. Surrounding tendons and ligaments are use to help hold the implant firmly in place. The wound is then closed with sutures and a dressing is applied.

The hand is kept elevated following the procedure in order to prevent swelling and subsequent stiffness that can result from swelling. Pain medication and possibly antibiotics are prescribed. Once the dressings are removed several days following surgery, a splint is applied to the thumb and rehabilitation is discussed.

Rehabilitation is a key component to a successful recovery and resumption of normal activity.