Treating fractures using one or both of an implant, such as an intramedullary nail, and a fastening assembly, such as a lag screw and compression screw assembly. The implant in some implementations has a proximal section with a transverse aperture having a non-circular cross-section that may be shaped to selectively constrain the fastening assembly within the transverse aperture. Two or more components of the fastening assembly may be received to slide, in a controlled way, in the transverse aperture of the implant, and to cooperate to resist a force moment applied thereto.
