Pivotal bone anchor with tool engagement grooves and break-off extensions

A pivotal bone anchor assembly for anchoring to patient bone and coupling with an elongated implant via a closure, the pivotal bone anchor assembly comprising:

• a shank including a head and a bone engagement portion below the head;
• a receiver including a central bore formed around a longitudinal axis, a front surface and a back surface opposite the front surface, the receiver coupled with, or configured to couple with, the shank head and including:
• a base defining a lower cavity portion of the central bore in communication with a bottom surface of the receiver through a bottom opening, the lower cavity portion including a cylindrical sidewall surface having a first inner diameter and an inwardly curved surface between the cylindrical sidewall surface and the bottom opening having a second inner diameter less than the first inner diameter, the shank head being positionable into the lower cavity portion with the bone engagement portion extending downward through the bottom opening, the first inner diameter of the cylindrical sidewall surface being greater than an outer diameter of the shank head to allow the shank head to articulate within the lower cavity portion in an unlocked configuration;
• first and second upright arms extending upward from the base, each upright arm including a cylindrical outward facing surface and an inner threaded surface;
• a channel between the arms and extending transverse to the longitudinal axis between the front surface and back surface, the channel configured to receive the elongated implant, the channel configured for threaded engagement with the closure in coupling the elongated implant with the pivotal bone anchor assembly;
• a break-off extension extending from each upright arm;
• and
• a non-threaded radiused tool engagement groove extending horizontally and circumferentially entirely around the cylindrical outward facing surface of each upright arm to the front surface and the back surface of the receiver, each tool engagement groove being isolated from the central bore and located below a top surface of the respective upright arm that exists at least subsequent to the break-off extension having been removed from the respective upright arm;
• and
• a compression insert that is inside the receiver and is compressed between the elongated implant and the shank head when the elongated implant is coupled with the pivotal bone anchor assembly via the closure.