Patent ID: 9717534
Date: 2017-08-01
CPC Classifications: A61B

Claim:
1. A pivotal bone anchor assembly for securing an elongate rod to a bone, the bone anchor assembly comprising: a bone anchor having a proximal portion with an at least partially spherical outer surface and an integral anchor portion extending distally from the proximal portion for attachment to the bone; a receiver comprising a base with an internal cavity having a bottom opening in communication with a bottom surface of the base, and a pair of integral arms extending upwardly from the base to define a U-shaped upper channel with inner sidewall surfaces having structure to mate with a closure to close the upper channel; the upper channel communicating with the internal cavity to define a central bore, the internal cavity having a wider upper portion and a lower locking portion below the wider upper portion defined by a narrower width of the internal cavity adjacent the bottom opening, the central bore including an inwardly-facing interference wedging surface below the closure mating structure; a pressure insert movably disposed within the upper channel and central bore and having an upper curved saddle seating surface sized and shaped for engaging the elongate rod, the pressure insert having an exterior surface for engaging the receiver at the inwardly-facing interference wedging surface when the curved saddle seating surface is aligned with the upper channel to restrict movement of the pressure insert upward through the central bore; and a separate retainer movably disposed within the internal cavity and having a lower portion and an upper portion, the retainer upper portion having top surfaces engageable with an underside surface of the pressure insert and the retainer lower portion having at least one slit formed through a thickness thereof, the retainer lower portion being able to widen within the wider upper portion of the internal cavity to receive the bone anchor proximal portion as it is uploaded through the bottom opening and then to close around and capture the bone anchor proximal portion within the internal cavity while allowing for pivotal motion of the bone anchor relative to the receiver, the retainer and pressure insert being disposed within the receiver before the bone anchor, with the retainer being non-pivoting with respect to the receiver after capturing the bone anchor proximal portion, wherein upward movement of the retainer during the uploading of the bone anchor proximal portion is restricted by the engagement between the retainer top surfaces and the insert underside surface, and wherein after the bone anchor proximal portion is captured within the retainer lower portion, the pressure insert is downwardly deployable with a first tool within the receiver from a first position until the exterior surface of the pressure insert comes into a forced interference wedging contact with the receiver interference wedging surface at a second position so as to inhibit the pressure insert from moving back up within the receiver cavity.