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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.
Farlex Partner Medical Dictionary © Farlex 2012
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
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.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012