An adjustable implant (10, 60, 70, 80, 90) has a base (12) and a displaceable element (16) providing opposing tissue contact surfaces (14, 18). A linkage (20, 26) is pivotally connected to the displaceable element. A linkage mover (38, 40), engaged so as to be displaceable along the base, is associated with the linkage (20, 26) so as to define a displaceable pivot location (24, 30) for pivotal motion of the linkage relative to the base. In certain preferred embodiments, the base (12) has an internally threaded track (42, 44) in which a threaded segment of the linkage mover (38, 40) is engaged, so that rotation of the threaded segment about its central axis advances the linkage mover along the threaded track, thereby displacing the displaceable pivot locations and adjusting a separation between the first contact surface and at least part of the second contact surface.