US Patent 8425576 Bone screw retention mechanism

A bone stabilization system is provided having a plate with a top and bottom surface and a hole therethrough extending along a longitudinal axis. An annular groove in the top surface encircles the axis and defines outer facing sides of a plurality of spring members integral to the plate. A plurality of slots define sides of the spring members the inward facing side of the spring members form the upper portion of the hole, which includes a first spherical portion. A fastener with a spherical portion on the fastener head extends into the hole with the spring members urged apart to allow the head to pass but restraining removal until the resistance provide by the spring members is overcome.