Patent ID: 9055983
Filing Date: 2015-06-16
Classification: A61B

Abstract:
1. A self-locking screw assembly comprising: a screw receiver opening for receiving a polyaxial screw, a bottom of the opening having a seat to hold a screw head; a polyaxial screw with a screw head having a spherical contoured surface increasing from a shank to a maximum diameter D a self-locking feature formed in a wall surface of the screw receiver opening for automatically preventing the backing out of the screw, wherein the self-locking feature is one or more nubs or projections formed into the surface wall in an eccentric orientation on one half of the receiver opening extending 120 degrees or less and spaced above the seat to allow the screw head to pass at the maximum diameter, and upon threading the screw, the one or more projections push against the screw head in a common direction away from the one or more nubs or projections as the screw head initially contacts the one or more nubs or projections, causing the screw head to deflect in the common direction until threaded past all of the one or more nubs or projections clearing the maximum diameter, the screw being tightened against the seat, and when the screw is tightened against the seat, the one or more nubs or projections reside along the surface curvature of the screw head.