| A boutonniere deformity occurs when the extensor tendon attachment at the central slip on the middle phalanx is injured. The PIP joint is not able to straighten and remains bent (flexed). The DIP joint is pulled back into hyperextension by the extensor mechanism that has become out of balance. This results in a crooked and poorly functioning finger.
Arthritis, burns, Dupuytren’s contracture, and injuries, can disrupt the extensor tendon . The tendon may partially or completely tear. The extensor tendon can remain intact but pull a piece of bone away from where it attaches on the phalanx. This is called an avulsion fracture.
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