A pedicle screw assembly comprises a bone fastener (70) having a lower end for engaging bone and an upper end remote from the lower end a head having a rod-receiving channel attached to the upper end of said bone fastener, a spinal rod insertable into the rod-receiving channel of said head, said spinal rod having an outer surface extending between first (160) and second ends thereof, wherein at least one of the first (160) and second ends has a reduced diameter section. The spinal rod has an outer surface extending between a first end and a second end thereof, wherein the outer surface of said spinal rod has a reduced diameter section at at least one of the first (160) and second ends.
