Patent ID: 11918256
Assignee: nan
Field: Medical technology (Instruments)
Classification: CPC A | IPC A

Claim 0:
1. A pivotal bone anchor assembly for securing an elongate rod to a bone of a patient via a closure, the pivotal bone anchor assembly comprising:
a shank comprising a longitudinal axis, a capture structure at a proximal end, and an anchor portion opposite the capture structure configured for attachment to the bone, the capture structure including a circumferential capture recess centered on the longitudinal axis with a first radiused surface above the capture recess and a second radiused surface below the capture recess, the capture recess being defined by at least an upper ledge and an outwardly-facing recessed surface extending downward from the upper ledge;
a receiver comprising a vertical centerline axis, a base portion defining an axial bore centered around the vertical centerline axis, and an upper portion defining a channel configured to receive a portion of the elongate rod, the axial bore communicating with a bottom of the receiver through a bottom opening and extending upward through the channel to a top of the receiver, the axial bore having a lower portion configured to receive the capture structure of the shank including a partially spherical seating surface adjacent the bottom opening and an expansion chamber located above the seating surface having a downward-facing at least partially annular stop surface integrally formed therein; and
a resilient retainer positionable within the lower portion of the axial bore prior to the capture structure of the shank, the retainer having an upper surface, a lower surface, an outwardly-facing third radiused surface extending between the upper and lower surfaces, and an inwardly-facing inner retainer surface complementary with the recessed surface of the capture recess,
wherein upon the capture structure being uploaded into the lower portion of the axial bore through the bottom opening, the upper surface of the retainer is configured engage the stop surface of the expansion chamber and the inner retainer surface is configured to downwardly slidably engage the first radiused surface of the capture structure to cause the retainer to expand within the expansion chamber, until the retainer slides over and off the first radiused surface and snaps into the capture recess so as to couple the retainer to the capture structure and to align third radiused surface with the second radiused surface to form a partially spherical bearing surface configured to pivotably engage the seating surface of the axial bore.