Patent ID: 8475501

Claim:
A polyaxial head bone screw assembly for surgical implantation and comprising: (a) a shank having a threaded body and a capture end, the capture end having a top surface; (b) a head having a channel outwardly open and adapted to receive a rod within said channel; said head having a shank mating side with a bottom shank receiving bore formed therein, and an inner seating surface; said head having a cavity therein communicating with said bore; (c) said capture end of said shank being received within said cavity through said bottom bore of said head; (d) a retainer ring with a split therein to enable resilient expansion and contraction of a diameter of said retainer ring; said retainer ring being positioned in said head cavity so as to be able to expand and capture said shank while within said cavity so as to retain said shank capture end within said head; said shank and said retaining ring forming a joined shank and retainer ring structure wherein the top surface of the capture end is located above the retainer ring when the shank the retainer ring are joined, the retainer ring pivotally rotates in combination with said shank on said head seat surface enabling selective angular positioning of said shank with respect to said head, when in an assembly configuration; and (e) a closure member operably mountable within said head in such a manner as to close said channel.