Patent ID: 9743957
Date: 2017-08-29
CPC Classifications: A61B,F16B

Claim:
1. A bone anchor assembly comprising a shank for attaching to a bone, a receiver in pivotal relation with an upper portion of the shank and a first pair of upward extending arms forming a channel therebetween to receive a connecting member, the first pair of arms having a partial inner thread form, a closure, and a compression insert positioned above and in direct downward locking contact with an integral top spherical surface of the shank, the closure including: a) a closed outer fastener having a body with a continuous outer thread form extending along at least a portion thereof and engaging the receiver inner thread form and a central bore with an internal surface guide and advancement thread form extending to and opening onto a bottom surface thereof; and b) an inner set screw having a continuous outer surface thread form extending from near a bottom surface thereof to near a top surface thereof and an opening along a central axis opening onto the top surface of the inner set screw having a sole internal drive structure to receive a tool, the opening terminating at a lower interior tool abutment surface located nearer the bottom surface than the top surface thereof, the inner set screw is threadingly received in the central bore with the inner set screw insertable into the outer fastener from the bottom surface thereof, and wherein c) in a final position, the outer fastener and the inner set screw do not extend above top surfaces of the receiver first pair of arms.