Thumb Arthritis: Overview

Thumb Arthritis: Overview

This video will provide an overview of arthritis at the base of the thumb. Arthritis at the base of the thumb joint, also known as thumb carpometacarpal or thumb C M C arthritis, is a progressive degenerative disease that is common in post-menopausal women. It is a very common disabling condition that leads to thumb joint pain and instability.

The thumb CMC joint is a saddle-shaped joint formed by the base end of the thumb metacarpal and the nearby wrist bone called the trapezium. The thumb CMC joint has a loose capsule, allowing multiple planes of motion to the thumb. This joint naturally sacrifices its stability for these multiple planes of movement.

The thumb has significant loads applied across this joint during daily activities. A force of 120 kg, or approximately 265 lbs, is absorbed by the thumb joint when power grasping. During pinching, the forces across the thumb CMC joint are 12× higher than the fingertips of the thumb and the index. These repetitive, compressive, shearing forces are responsible for the osteoarthritic changes over time.

For preventative measures, people may benefit from wearing protective gear, especially when moving objects. Exercise is important to maintain a healthy, moderate weight and posture. It is important to control blood sugar as other health conditions may affect the quality of joints and cartilage over time.

For diagnosis of a patient suspected to have thumb joint arthritis, the surgeon will perform a physical examination. Initially, the health care team will perform tests that cause and recreate pain caused by the arthritic changes to provide the diagnosis. Further diagnosis of the conditions will be confirmed with radiographic evaluation or an x-ray. Multiple views of the joint will be done to best see all angles of the joint.

There are 4 stages of the condition, from the most mild stage, stage 1, to the most severe stage, stage 4. In stage 1, the joint space shows mild widening due to inflammation that causes fluid to build in this space. There is mild movement of the thumb metacarpal over the trapezium. This movement is called subluxation. This is indicated by a step-off at the level of the thumb joint. In this stage, patients show mild weakness and mild, intermittent pain with heavy use of the hand.

In stage 2, there is more compromise of the joint space with increased subluxation and narrowing. There are also bony changes at the joint line, including the presence of small osteophytes, which are small bony growths. Clinically, the pain is now present during normal activities and the exam causes pain.

In stage 3, there is full bone-on-bone contact. The osteophytes are now even larger. There is significant subluxation, or movement of the normal position of the joint. Stage 4 is characterized by the presence of arthritic changes around the entire trapezium bone. Once the diagnosis is made, a treatment plan can be determined.