An orthopedic device includes an implant member with a thru-bore having an entry diameter, an intermediate diameter, and an exit diameter. According to one embodiment the intermediate diameter of the thru-bore is larger than both the entry diameter and the exit diameter. Additionally, the orthopedic device includes a screw assembly configured to be coupled to the thru-bore, including a thread portion and a selectively expandable head portion. The selectively expandable head portion includes both an expandable ring and a pull-lock pin configured to selectively expand the expandable ring as the pull-lock pin is pulled from said screw assembly.