Driver for a bone screw

1. A bone screw driving system comprising:

a bone screw having a drive recess and a seating surface of the drive recess;

a driver including an elongate shaft assembly having a proximal end portion, a distal end portion configured to connect to the bone screw, and a longitudinal axis extending therebetween;

an inner drive member of the distal end portion of the driver elongate shaft assembly configured to extend into the drive recess of the bone screw;

a distal surface of the inner drive member configured to seat against the seating surface of the drive recess;

an outer expansion locking member of the distal end portion of the driver elongate shaft assembly shiftable along the longitudinal axis relative to the inner drive member;

the outer expansion locking member having an initial configuration wherein the outer expansion locking member is proximal of the inner drive member distal surface and the inner drive member protrudes distally of the outer expansion locking member which permits the inner drive member to be advanced into the drive recess of the bone screw;

the outer expansion locking member configured to be advanced into the drive recess with the outer expansion locking member in the initial configuration thereof and the inner drive member protruding distally of the outer expansion locking member; and

the outer expansion locking member having an expanded configuration wherein the outer expansion member is shifted distally from the initial configuration while remaining proximal of the inner drive distal surface and the inner drive member protrudes distally of the outer expansion locking member, the outer expansion locking member in the expanded configuration thereof extending laterally outward of the inner drive member to engage the bone screw and fix the bone screw to the distal end portion of the driver elongate shaft assembly.

2. The bone screw driving system of claim 1 wherein the bone screw drive recess includes an undercut and the outer expansion locking member extends into the undercut with the outer expansion locking member in the expanded configuration thereof.

3. The bone screw driving system of claim 2 wherein the outer expansion locking member includes locking portions of a plurality of resilient arms of the elongate shaft assembly distal end portion, the locking portions configured to fit into the undercut with the outer expansion locking member in the expanded configuration thereof.

4. The bone screw driving system of claim 1 wherein the drive recess of the bone screw includes a proximal, smaller diameter portion and a distal, larger diameter portion; and

wherein the outer expansion locking member includes at least a portion thereof received in the lower, larger diameter portion with the outer expansion locking member in the expanded configuration and outside of the lower, larger diameter portion with the outer expansion member in the initial configuration.

5. The bone screw driving system of claim 1 wherein the inner drive member includes a ramp surface and at least one side surface extending intermediate the ramp surface and the distal surface; and

wherein the outer expansion locking member shifts along the ramp surface of the inner drive member and is urged laterally outward by the ramp surface as the outer expansion locking member is reconfigured between the initial and expanded configurations.

6. The bone screw driving system of claim 5 wherein the ramp surface includes a lower end portion and the bone screw drive recess includes a redirecting surface extending transverse to the longitudinal axis; and

wherein the inner drive member includes an axial height sized to position the ramp surface lower end portion substantially level with the redirecting surface when the distal surface of the inner drive member is seated against the seating surface of the drive recess.

7. The bone screw driving system of claim 1 wherein the driver elongate shaft assembly includes an outer sleeve portion connected to the outer expansion locking member, the outer sleeve portion and outer expansion locking member connected thereto being shiftable relative to the inner drive member in a proximal distal direction to reconfigure the outer expansion locking member from the initial configuration to the expanded configuration and being shiftable in an opposite, distal proximal direction to reconfigure the outer expansion locking member from the expanded configuration to the initial configuration.

8. The bone screw driving system of claim 1 wherein the screw has a unitary, one-piece construction.

9. The bone screw driving system of claim 1 wherein the bone screw and inner drive member form a pocket extending about the inner drive member to receive the outer expansion locking member with the inner drive member distal surface seated against the drive recess seating surface.

10. The bone screw driving system of claim 1 wherein the drive recess of the bone screw has a first width thereacross; and

wherein the outer expansion locking member in the initial configuration thereof has a distal end portion with a maximum width that is less than the first width of the drive recess to permit the distal end portion of the outer expansion locking member to be advanced into the drive recess while the inner drive member protrudes distally of the outer expansion locking member.

11. The bone screw driving system of claim 1 wherein the inner drive member has a central longitudinal axis;

wherein the inner drive member includes a ramp surface inclined relative to the central longitudinal axis, the ramp surface of the inner drive member increasing in distance from the central longitudinal axis as the ramp surface extends distally; and

wherein the outer expansion locking member includes an inclined surface configured to engage the ramp surface of the inner drive member as the outer expansion locking member shifts distally from the initial configuration to the expanded configuration.