A locking mechanism including a non-threaded, self-adjusting locking device for locking a rod in place within a screw and rod assembly. A non-threaded, self-adjusting locking device for locking a rod in place within a screw and rod assembly. A spring for locking a rod in a screw and rod fixation assembly. A assembly including an implant body including a rod seat for seating a rod therein, a biasing device seat for seating a biasing device therein, and a biasing device seated in the biasing device seat for biasing a rod against a rod seat. A method of biasing a rod against a rod seat in a screw and rod fixation assembly.
