Receiver for inhibiting spreading apart of tooling receiver attachment portions

A bone anchor system intended for securing an elongate rod to a head of a shank via a closure top, the shank including a threaded anchor portion opposite the head configured for implantation into a bone of a patient, the bone anchor system comprising:

• tooling having a pair of spaced apart receiver attachment portions adjacent a lower end thereof;
• and
• a receiver comprising a vertical centerline axis, a base portion defining an internal cavity configured to receive the head of the shank with the shank extending downward through a lower opening, and a pair of upright arms integrally formed with and extending upward from the base portion to define an open channel configured to receive the elongate rod and communicating with the internal cavity to define a central bore, the upright arms including upper portions having a plurality of upwardly-facing arcuate surfaces centered about the vertical centerline axis, opposing internal surfaces extending between a forward-facing surface and a backward-facing surface of each upright arm, upper outwardly-facing curvate surfaces extending downward from at least one of the upwardly-facing arcuate surfaces, and inwardly-facing arcuate surfaces spaced outwardly and apart from the opposing internal surfaces, the upright arms further including:
• a discontinuous helically wound guide and advancement structure formed into an upper portion of the opposing internal surfaces of the upright arms and centered about the vertical centerline axis to define at least a portion of the central bore of the receiver, the guide and advancement structure extending below the inwardly-facing arcuate surfaces;
• arcuate tool engagement grooves formed in the upright arms and spaced outwardly with respect to the opposing internal surfaces and configured to at least partially receive the receiver attachment portions, the arcuate tool engagement grooves including upwardly-facing groove surfaces spaced a fixed distance below the upwardly-facing arcuate surfaces of the upright arms and outwardly-facing groove surfaces opposite the opposing internal surfaces, the upwardly-facing groove surfaces and the outwardly-facing groove surfaces extending to the forward-facing surfaces and the backward-facing surfaces of the upright arms;
• and
• opposite vertical tool-engagement slots extending at least partially between the plurality of upwardly-facing arcuate surfaces of the upright arms and the arcuate tool engagement grooves,
• wherein when the receiver attachment portions of the tooling are positioned on the receiver, the upper portions of each upright arm are configured to at least partially engage arcuate extending engagement surfaces at the lower ends of the receiver attachment portions of the tooling so as to inhibit outward spreading of the pair of spaced apart receiver attachment portions.