A finger injury caused by a sudden flexion force tearing the central slip of the extensor digitorum communis muscle over the back of a proximal interphalangeal joint. Treatment includes splinting the interphalangeal joint in extension 24 h a day for 4–6 weeks, with the distal joint remaining free for flexion. During the early stages of the injury, lateral bands of the muscle enable the finger to be extended, but if the injury is untreated these bands slip forwards so that the finger can no longer be fully extended. A flexion curvature develops with the joint coming through the lateral bands like a button through its hole (the so-called boutonierre deformity).
Subjects: Sports and Exercise Medicine.