An expandable implant (100, 150, 160, 200, 250, 300, 400) has a base (10) and a displaceable element (12) hingedly interconnected at one end. At the other end, the base and the displaceable element are formed with complementary jaws (24, 26) which provide continuous overlap of facing surfaces over a range of angular positions of the displaceable element relative to said base. In some cases, the first end portion (16) of the displaceable element (12) is formed with projecting teeth (28) forming a partial gear centered on an axis (18) of the hinged interconnection with the base (12) for engaging a worm gear. In certain embodiments, the base is formed with a socket (30) for removably receiving a worm gear tool (32) for engaging the teeth (28) and displacing said displaceable element. After expansion, the worm-gear tool (32) can be removed.
