Percutaneous Access Devices And Bone Anchor Assemblies

In the combination of a bone attachment structure having a receiver and a tool having receiver attachment structure at a lower end thereof that is operably mateable with the receiver;

• the improvement comprising:
• a) the receiver having a top, a bottom, and an undercut first surface projecting downwardly toward the bottom;
• b) the tool lower end having a projection with a second surface for mechanical overlapping and interlocking mating with the first surface;
• and
• c) the first and second surfaces being sized, shaped and positioned to provide for anti-splay arrangement of the tool with respect to the receiver when the second surface is aligned with the undercut first surface of the receiver.

In the combination of a bone screw having a head and a manipulation tool having attachment structure at a lower end thereof that is operably mateable with the bone screw head;

• the improvement comprising:
• a) the bone screw head having a top, a bottom, and a circumferentially extending undercut first surface facing downwardly toward said bottom;
• b) the manipulation tool lower end having a projection with a circumferentially extending second surface;
• and
• c) the first and second surfaces being sized, shaped and positioned to provide for operable mating overlapping alignment of the manipulation tool relative to the bone screw head.