The pedicle screw assembly includes a threaded screw extending from a tip to a head. A tulip head is coupled to the head of the screw. A hollow interior of the tulip head has a slot which receives a spine rod therein. A locking nut and preferably also a saddle and locking cap bear on the spine rod and secure the spine rod within the slot of the tulip head and against the head of the screw. The head of the screw is semi-spherical. Portions of the tulip head and structures residing within the tulip head which abut against the head are also preferably semi-spherical. The saddle and locking cap abut against the spine rod with semi-cylindrical surfaces, such that surface contact is provided against the spine rod for secure coupling of the spine rod to the pedicle screw.
