| 摘要 |
A polyaxial bone screw assembly includes a threaded shank body member hav ing an upper portion with an internal drive and, alternatively, a laterally extending alignment rib or fin. The bone screw assembly also includes a lock able receiver coupling member, an open retainer ring member having a slit or gap and a compression insert member. An inset conical or cylindrical surfac e on the shank upper portion frictionally engages a similarly shaped inner s urface of the retainer ring. The receiver includes a restrictive lower openi ng that allows for uploading the shank upper portion and compressed retainer ring into the receiver cavity, but prevents passage of the retainer ring ou t of the receiver once the ring inner surface engages the conical surface of the shank upper portion. |
