Boutonniere deformity


Boutonniere deformity is a deformed position of the fingers or toes, in which the joint nearest the knuckle is permanently bent toward the palm while the farthest joint is bent back away. Causes include injury, inflammatory conditions like rheumatoid arthritis, psoriatic arthritis, and genetic conditions like Ehlers-Danlos syndrome.

Pathophysiology

This flexion deformity of the proximal interphalangeal joint is due to interruption of the central slip of the extensor tendon such that the lateral slips separate and the head of the proximal phalanx pops through the gap like a finger through a button hole. The distal joint is subsequently drawn into hyperextension because the two peripheral slips of the extensor tendon are stretched by the head of the proximal phalanx. This deformity makes it difficult or impossible to extend the proximal interphalangeal joint.

Diagnosis

Stages

  1. Mild extension lag, passively correctable
  2. Moderate extension lag, passively correctable
  3. Mild flexion contracture
  4. Advanced flexion contracture
Higher numbers indicate a more severe problem and greater likelihood of a poor outcome.

Treatment

Usually treated with a splint placing the proximal interphalangeal joint in extension for 4–6 weeks. Occasionally surgery is needed when splinting is unsuccessful.