US Patent 9615858 Spring clip-bottom loading polyaxial ball and socket fastener

The bottom loading fastening system that consists of the polyaxial ball and socket joint used in conjunction with a bone screw having threads on one end for use in anchoring to the spine and a spherical connector on the other end operating as a pivot point about which a connecting assembly moves in a polyaxial fashion. A substantially U-shaped connecting assembly has a lower receptacle having at least two retainer rings within at least two retaining ring grooves for use in securing the spherical connector to the connecting assembly.