bone, joint, and muscle disorders
Boutonnière Deformity
Introduction
Boutonnière deformity is a deformity in which the middle finger joint is bent in a fixed position inward (toward the palm) and the outermost finger joint is bent excessively outward (away from the palm). (See also Overview of Hand Disorders .) Boutonnière deformity most often results from Rheumatoid Arthritis (RA) but can also result from injury (such as deep cuts, People with rheumatoid arthritis can develop the disorder because they have long-standing inflammation of the middle joint of a finger. If the deformity is caused by an injury, the injury usually occurs at the base of a tendon (called the middle phalanx extensor tendon). As a result, the middle joint (called the proximal interphalangeal joint) becomes “buttonholed” between the outer bands of the tendon that runs to the end of the finger. That is, the bones of the joint push out through the bands of the tendon like a button through a buttonhole. The deformity may interfere with hand function. The doctor makes the diagnosis of boutonnière deformity by examining the finger. Some disorders, such as rheumatoid arthritis, and injuries can cause the fingers to bend abnormally. In swan-neck deformity, the joint at the base of the finger bends in (flexes), the middle joint straightens out (extends), and the outermost joint bends in (flexes). In boutonnière deformity, the middle finger joint is bent inward (toward the palm), and the outermost finger joint is bent outward (away from the palm). 