The present invention generally relates to connectors that connect bone screws with fusion rods for use in stabilizing surgery such as spinal fusion surgery, and to bone screw systems comprising such connectors. In particular, the present invention relates to poly axial screw systems configured to attach the poly axial tulip head after the bone screw has been implanted. Furthermore, embodiments of the present invention relate to tulip connectors which have a hinged joint and a collet that are configured to rotatably and pivotably lock onto the ball head of a poly axial screw shaft. The poly axial tulip head features a collet which can attach to the rod prior to insertion onto the bone screw. The tulip head and rod are then affixed to the bone screw with a nut.
