The invention facilitates the fixation of bone fractures. In particular, the invention relates to a cap that has an inside surface comprising an interface component that is operable to engage a flexible wire. The flexible wire is connected to a head component that engages a first bone fragment. The outside surface of the cap may include cutting threads to facilitate attachment to a second bone fragment. A tensioner may be used to exert tension on the wire, the cap and the head component, thereby drawing the first bone fragment to the second bone fragment. In various embodiments, the cap is a planar disk that has a central hole that restricts backward translation and expands when the cap is translating down a wire.