Locking polyaxial ball and socket fastener

A ball and socket fastener comprising:

• an anchoring member having a shank and a spherical connector, said spherical connector including at least one guide surface;
• a connecting assembly having a socket constructed and arranged for receipt of said spherical connector along a first end and a securing element securable to a second end, an upper retainer ring disposed within said socket and positionable along an upper surface of said spherical connector, said upper retaining ring including at least one rail positioned to cooperate with said at least one guide surface, a lower retainer ring disposed within said socket and positionable along a lower surface of said spherical connector, said at least one guide surface and said at least one rail cooperating so that said connecting assembly moves mono-axially with respect to said anchoring member, said securing element traversable between an unlocked position and a locked position for controlling said mono-axial movement;
• a lower surface of said connector assembly includes a plurality of ramp surfaces positioned to cooperate with an upper surface of said lower retainer ring during securement of said spherical connector to said socket to open said lower retaining ring so that the major diameter of said spherical connector can pass through the lower retaining ring;
• wherein said spherical connector head is received through said first end and positioned between said upper and said lower retainer rings.