Pivotal bone anchor assembly with twist-in-place insert having radially offset receiver engaging structures

摘要

A pivotal bone anchor assembly includes a shank, a receiver with an open channel in communication with an axial bore, and a pressure insert with an upwardly-facing seating surface for receiving an elongate rod. The axial bore includes a downwardly-facing surface below a closure top mating feature and one or more integral structures protruding inwardly toward a central longitudinal axis. The insert includes one or more notches formed into an outer side surface and an upwardly-facing surface positioned radially outward from the seating surface. Upon installation into the axial bore, the insert is rotatable about the longitudinal axis until the insert upwardly-facing surface is rotated under the receiver downwardly-facing surface to inhibit upward movement of the insert within the axial bore along the longitudinal axis and the receiver inwardly-protruding structures become positioned within the insert outer notches to prevent further rotation of the insert within the axial bore.