Patent ID: 8241333
Filing Date: 2012-08-14
Classification: A61B

Abstract:
1. A polyaxial head bone screw assembly for surgical implantation and comprising: (a) a shank having a threaded body adapted to be implanted in a bone and a capture end; (b) a head having a channel adapted to receive a rod within said channel, said head having a top, a bottom and an inner seat, the bottom having a lower bore formed therethrough, said lower bore being sized and shaped to allow loading of said shank therethrough and so as to receive said shank when assembled; (c) said capture end of said shank being operably received within said head through said lower bore; (d) a retainer ring non-integral with said shank and loaded into said head separate from said shank; said retainer ring being mated on said capture end within said head so as to pivotally rotate with said shank relative to said head, while in an adjustment configuration; said shank and retainer ring joining to provide a shank and retainer ring structure to retain said capture end within said head and that pivotally rotates in said head seat so as to enable selective angular positioning of said shank with respect to said head, while in said adjustment configuration; and (e) a closure member operably received in said head in such a manner as to capture a rod located within said channel; wherein (f) said capture end extends above said retainer ring such that when in use said shank directly receives a downward force to lock said bone screw assembly and such that said head does not directly receive said downward force.