Patent ID: 8137386
Filing Date: 2012-03-20
Classification: A61B

Abstract:
1. A polyaxial bone screw comprising: a) a head adapted to receive a rod member in an upper channel thereof; said head having a cavity lower opening to an external surface of said head through said opening; said cavity having an integral partial lower mating surface and an upper larger cavity portion sized and shaped to allow expansion of an expandable retaining ring to capture a shank therein; b) a shank having a threaded body and a capture end; said capture end being insertable into said head cavity through said lower opening when said retaining ring is positioned in said cavity; c) the retaining ring having capture structure to expandingly receive and capture said shank capture end within the cavity and thereafter contract and polyaxially rotate in conjunction with the shank relative to the cavity during positioning of the shank relative to the head; the shank extending above the retaining ring after the shank and retaining ring are joined in the cavity; said ring having a partial spherical surface that operably seats on said head cavity partial spherical lower mating surface; and d) wherein an upper surface of the shank capture end solely receives a downward force to lock the position of the shank relative to the head.