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flexion of the proximal interphalangeal joint with hyperextension of the distal interphalangeal joint of the finger, caused by separation of the extensor hood and protrusion of the head of the proximal phalanx through the resulting "buttonhole"; can result from degeneration (rheumatoid arthritis) or trauma.
Etymology: Fr, buttonhole
an abnormality of a finger marked by fixed flexion of the proximal interphalangeal joint and hyperextension of the distal interphalangeal joint. The condition occurs in rheumatoid arthritis and can occur following trauma to a finger.
bou·ton·nière de·form·i·ty(bū'tō-nyer' dĕ-fōrm'i-tē)
Rupture of the central slip of a digital extensor tendon at the middle phalanx, marked by extension of the metacarpopophalangeal and distal interphalangeal joints and flexion of the proximal interphalangeal joint.