Patent ID: 8518082

Claim:
A bone anchor assembly, comprising: a bone anchor having a proximal head and a distal bone engaging portion; and a receiving member having a proximal end having a first bore, a distal end opposite the proximal end and having a second bore, and a recess for receiving a spinal fixation element in communication with the first bore, the second bore being sized to receive the head of the bone anchor, the receiving member having a substantially U-shaped cross-section defined by two legs separated by the recess, each leg being free at the proximal end of the receiving member, wherein a first arcuate groove is formed on an exterior surface of the proximal end of a first one of the legs and a second arcuate groove is formed on an exterior surface of the proximal end of a second one of the legs, wherein the first arcuate groove has a proximal surface and a distal surface opposite the proximal surface and the second arcuate groove has a proximal surface and a distal surface opposite the proximal surface, wherein the proximal surface of the first groove and the distal surface of the first groove each are angled distally toward the exterior surface of the first leg and each are oriented at an angle greater than 0 degrees relative to an orthogonal line that is oriented perpendicular to a longitudinal axis of the receiving member, wherein the proximal surface of the second groove and the distal surface of the second groove each are angled distally toward the exterior surface of the second leg and each are oriented at an angle greater than 0 degrees relative to an orthogonal line that is oriented perpendicular to a longitudinal axis of the receiving member.