Irreducible or complex digital dislocations are those in which local structures pass in or around the joint space in a way which prevents closed reduction. This often is associated with a "buttonhole" anatomy for which attempts at closed reduction simply tighten a soft tissue noose around the head of the proximal bone (Fig. 14). Complex dislocations most often involve the border digit metacarpophalangeal joints, and are more common in joints which have associated sesamoid bones. They are much less common than simple dislocations, but carry the risk of digital nerve injury during the course of open reduction, as digital nerves may be stretched over the protruding surface of the proximal bone head (Fig. 14). Complex dislocation should be strongly suspected when there is dimpling of the skin or when radiographs show sesamoid bone interposition in the joint space.