Patent ID: 8361129

Claim:
A bone anchor assembly for engagement to a connection element comprising: a receiver member having a proximal opening at the proximal end for receiving the connection element and a bore at the distal end, the bore terminating at a distal opening having a diameter greater than the proximal opening; a bone-engaging shank having a head at a proximal end, the head sized to fit through the distal opening of the bore of the receiver member; a semi-spherical shaped first insert; a semi-spherical shaped second insert separate and unconnected to the first insert, the first insert and the second insert each sized to fit within the receiver member, the first insert and the second insert each having a proximal end shaped for engaging the connection element and an inner surface shaped to engage the head of the bone shank, the first insert and the second insert positioned about the head; and a closure mechanism for securing the connection element to the bone anchor assembly, wherein distal advancement of the closure mechanism seats the connection element against the proximal end of the first insert and the proximal end of the second insert and seats the head of the bone shank against the inner surface of the first insert and the inner surface of second insert, the first insert and the second insert cooperating to retain the head of the shank within the receiver member.