Pivotal bone anchor assembly with receiver pre-formed axial rotation stops

Abstract

A pivotal bone anchor assembly includes a shank having a shank head, and a receiver having a first channel for receiving a rod and an axial bore for receiving the shank head, with the axial bore including downwardly-facing abutment surfaces and opposed rotation blocking structures beneath a helically wound thread. The assembly also includes a pressure insert having a second channel and opposite outer projections. The pressure insert is loaded into the axial bore with the second channel in a mal-aligned position relative to the first channel, with subsequent rotation moving the second channel into alignment with the first channel and the opposite outer projections into an overlapping engagement with the downwardly-facing abutment surfaces to inhibit upward movement of the pressure insert. During rotation, the opposite outer projections are initially inhibited from further rotation by engagement with the opposed rotation blocking structures until a force is applied to the pressure insert with the tooling to further rotate the opposite outer projections at least partially past the opposed rotation blocking structures.