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A boutonnière deformity affects the fingers or thumb of the hand. It is the most common deformity associated with rheumatoid arthritis but it can be caused by other conditions.
This type of deformity occurs when disease or injury causes the middle joint of the finger or the base of the thumb to become flexed (bent). The end of the finger or thumb is pulled up into too much extension (hyperextension). In the thumb, the position looks like an exaggerated hitchhiker's thumb.
Prolonged inflammation in the joints from rheumatoid arthritis damages the lining aroudn the joint called the synovium. Over time the joint capsule starts to stretch and the extensor tendon slips out of place.
Weakness and an imbalance of forces results in the deformity. If it's not corrected, the patient may lose the ability to even passively correct the joint position. Function is affected, especially the pinch grip.
Early intervention may be able to prevent such serious deformities. But by the time a boutonnière deformity occurs, surgery is usually needed. The type of surgery depends on the condition of the ligaments, tendons, and joints.
The surgeon may be able to repair any soft tissues that are torn or ruptured. Sometimes joint fusion is required. In other cases, joint replacement is advised.
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