Boutonniere Deformity
aka buttonhole deformity

Misdiagnosed as a “jammed” or “sprained” finger

• Deformity occurs at the PIP joint
• Trauma to the PIP joint can cause the joint capsule to tear, the head of the phalanx can buttonhole thru the defect and the lateral bands of the extensor tendons fall laterally & contract
• The lateral bands then function as PIP flexors and not extensors
• DIP hyperextension due to excessive pull of the displaced lateral bands
• As a result, the pateint WILL be able to flex the DIP joint, but WILL NOT be able to extend   the PIP joint                                                                    
• OCCURS 1 - 3 weeks post injury
• May not present with classic textbook deformity
• The Elson test is the best way to detect the injury pattern before the deformity is evident
• https://www.youtube.com/watch?v=G9HY0qXWUvE