Patent ID: 8926670
Filing Date: 2015-01-06
Classification: A61B

Abstract:
1. A polyaxial bone screw assembly for fixation to a bone, the assembly including a shank with a threaded body and an upwardly extending head portion, a retainer structure sized and shaped to join and polyaxially rotate with the shank, and a receiver that operably receives the head portion and retainer, the assembly further wherein: a) the head portion comprising a retainer engagement portion including a partially circumferential curvate groove with contoured upper and lower mating surfaces and a pair of spaced recesses; b) the retainer structure being sized and shaped to matingly engage the retainer engagement portion so as to form a substantially spherical ball-shaped pivoting surface with the head portion, the retainer structure comprising c) the receiver defining an open channel and having a base with a lower seating surface partially defining a cavity, the seating surface being sized and shaped to engage at least a portion of upper head portion, the open channel communicating with the cavity, the cavity communicating with an exterior of the base through an opening sized and shaped to receive the shank upper head portion by uploading the upper head portion through the opening, where the upper head portion mates with the retainer within the cavity.