Abstract: A bone fixation system includes an intramedullary nail and a lag screw. A proximal portion of the intramedullary nail includes a first proximal bore configured to accept the lag screw and a second proximal bore configured to accept a portion of an antirotation screw insertion tool. A distal portion of the intramedullary nail defines at least one opening configured to accept a distal locking screw. The lag screw includes a sheath and a rod mounted for sliding movement within the sheath. The rod has a threaded distal end defining a diagonal bore configured to accept an antirotation screw.