What best describes a torsion wedge nonunion?

• A. An intermediate fragment without blood supply; the two ends of the vascularized bone heal, but the nonvascular portion does not
• B. A fracture with infection
• C. A nonunited fragment with robust blood supply
• D. A complete fracture healed with callus

Answer: (A)

A torsion wedge nonunion is a pattern where a small intermediate bone fragment becomes devascularized and sits between two vascularized fracture ends. The two ends have blood supply and can unite, but the nonvascular wedge does not heal, effectively blocking union. This concept fits the description of an interposed, avascular fragment preventing healing even though the surrounding bone remains viable.

This differs from an infected nonunion (which would involve infection signs and tissue changes), from a fragment with robust blood supply (which would be expected to heal), and from a completely healed fracture with callus (which is not a nonunion). In practice, treatment targets removing the devascularized wedge and providing stable fixation with possible bone graft to promote union.