A pivotal bone anchor assembly for a securing an elongate rod to a bone includes a shank having a capture portion and an anchor portion extending distally from the capture portion, and a receiver having an upper portion defining a receiver channel for receiving a rod and a base defining a cavity for receiving the shank capture portion. The assembly also includes a retainer configured to capture and hold the shank capture portion within the receiver cavity, as well as a pressure insert having a central drive tool opening and upright arms forming an insert channel. The pressure insert is loaded into a first position within the receiver channel with the insert channel in a non-alignment orientation with respect to the receiver channel, and then rotated about a longitudinal axis into a second position with the insert channel in alignment with the receiver channel.