A modular pedicle screw and rod implant assembly includes a shant screw, a rod holding element, a locking member, a rod, and a nut. The shant screw has a lower threaded shaft portion for insertion into the pedicle and a top shaft portion which is unthreaded, a portion of which is tapered. The locking member has a threaded upper portion and a smoothly tapered lower portion. It further includes an axial bore which is similarly tapered at the bottom for seating on the upper portion of the shant screw. This tapered bottom portion is slotted so that it may be expanded or compressed in accordance with a radial force applied thereto. The rod holding element includes two through holes; one for receiving the rod, and the other, transverse to the rod receiving hole, which is tapered. The two holes are overlapping so that when the rod is seated in the first hole and the tapered portion of the locking member is in the second hole the surfaces of the rod and the locking member are in contact. The upper portion of the locking member is threaded, and receives the nut. Tightening of the nut causes the rod and locking member to compress against one another, and for the locking member to compress against the top of the shaft screw, thus locking the assembly together securely.