An implant assembly includes a first implant member, a second implant member, and a contractible element that is connected between the first and second implant members. The first implant member is configured to be placed against a first bone portion, and the second implant member is configured to be placed against a second bone portion. The contractible element is fixed at a first end to one of the first and second implant members, and movable at a second end with respect to one of the first and second implant members so as to induce tension in the suture, thereby providing a compressive force against the first and second bone portions. The second end can then be fixed with respect to the first and second implant members. The contractible element can contract in length in response to bodily fluids, thereby ensuring adequate post-operative compression. An instrument is also disclosed that is configured to implant the first and second implant members adjacent the first and second bone portions, respectively.
