A system for fastening prosthetic implants such as ankle prostheses is provided. The ankle prosthesis includes: a talar implant having a body for mounting to a top of a talus and with at least one talar fastening hole a tibial implant having a plate for mounting to a bottom of a tibia, a flange extending from the plate for bearing against an anterior surface of the tibia, the flange comprising at least one tibial fastening hole a mobile bearing for positioning between the talar implant and the tibial implant and a plurality of fasteners for locking engagement with the at least one talar fastening hole and the at least one tibial fastening hole, each of the fasteners comprising locking means and an elongated unthreaded body.