A coil fusion implant is formed as a length of wire helically wound up or torqued about a center axis. It has terminal sections at opposed ends that can be releasably gripped and axially twisted about the reference axis to reduce the outer diameter of the coil. The coil can be screwed into place between opposing bony surfaces of a joint while it is constrained in a reduced diameter state. Following its insertion between the prepared bony surfaces, the coil is permitted to gradually recoil as its diameter increases. The coil, in its expanded state then exerts compressive forces radially outward against the bone surfaces in opposition to forces exerted by the ligaments and other tissues connecting the contacted bones of the joint.