CPC A61B 17/7035 (2013.01) [A61B 17/7028 (2013.01); A61B 17/7032 (2013.01); A61B 17/7037 (2013.01); A61B 17/864 (2013.01); A61B 17/8625 (2013.01); A61B 17/8685 (2013.01); A61B 2090/037 (2016.02)] | 24 Claims |
1. A pivotal bone anchor assembly configured for implantation into a bone of a patient with a drive tool and for securing a fixation rod to the bone with a fastener configured to apply a downwardly-directed force to lock the assembly, the pivotal bone anchor assembly comprising:
a receiver comprising a base defining a central bore centered about a vertical centerline axis and an upper portion defining a through channel configured to receive the fixation rod, the central bore communicating with a bottom of the receiver through a lower opening and extending upward through the channel to a top of the receiver and including a partially spherical engagement surface adjacent the lower opening and a guide and advancement structure adjacent the top of the receiver configured to mate with the fastener;
a shank comprising a longitudinal axis, an anchor portion at a distal end configured for fixation to the bone, and a capture portion at a proximal end including an upwardly-opening internal drive socket configured to mate with the drive tool and an integral partially spherical lower surface curving upwardly and outwardly from a neck portion that extends between the capture portion and the anchor portion, the capture portion being uploadable into the central bore of the receiver through the lower opening;
a retainer comprising a compressible, open ring-shaped body having at least one slit or missing section, a center opening, and an outer partially spherical surface configured for pivotal engagement with the partially spherical engagement surface of the receiver, the retainer being configured for positioning into the central bore prior to the capture portion of the shank and for capturing the capture portion upon its uploading through the lower opening so as to pivotally hold the capture portion of the shank in the receiver; and
an insert positionable within the central bore of the receiver comprising a center aperture configured to provide access to the internal drive socket for the drive tool, an upper recessed surface configured to engage the fixation rod, and a lower surface configured to transfer the downwardly-directed force toward the capture portion of the shank to lock the assembly.
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