Patent ID: 7322981

Claim:
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 bore formed therethrough sized and shaped to allow uploading 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 bore of said head; (d) said capture end of said shank has a frusto-conical surface diminishing in diameter toward said shank; (e) a retainer ring non integral with said shank and secured on said capture end of said shank so as to rotate with shank said relative to said head while in an adjustment configuration and being located within said head to provide a shank and retainer ring structure to retain said capture end within said head and enabling selective angular positioning of said shank with respect to said head, while in said adjustment configuration; said shank and retainer ring structure extending into said channel such that upon assembly the shank and retainer ring structure is sized and shaped to be adapted to directly engage the rod; and (f) a closure member operably received in said head in such a manner as to be adapted to engage a rod located within said channel and to urge the rod into engagement with said capture end of said shank in such a manner so as to fixedly position said head relative to such a rod and to secure said head from angular movement relative to said shank, when in a locking configuration.