A bone fixation system includes a bone fastener and a tower including a detachable distal section with a thread formed on an inner surface thereof, the tower having at least one flexible section and at least one rigid section to accommodate and/or mitigate tower interference and/or collision. The distal section can be detached from the tower to function as a head locking unit of the bone fixation assembly, with the detached distal section capable of accommodating set screws, fixation rods and/or other spinal hardware.
