An intramedullary rod for use in a mammalian body comprising an elongate nail having a stem and a head and a threaded element carried by the head and accessible at the proximal end for rotation relative to the head. A locking mechanism coupled to the threaded element and configured to preclude rotation of the threaded element relative to the head when the locking mechanism is in a first position and permit rotation of the threaded element relative to the head when the locking mechanism is in a second position.
