Patent ID: 8591558

Claim:
A bone anchoring device comprising: an anchoring element comprising a shank having a free end and bone engagement end opposite the free end, the bone engagement end having a bone engagement structure to be anchored to a bone or a vertebra, the anchoring element further comprising a head, the head having an exterior surface with a spherical segment-shaped portion, wherein said shank and said head are separate parts; a receiving portion comprising a first end, a second end opposite to the first end, a longitudinal axis passing through the two ends, a bore coaxial with the longitudinal axis, and a first region adjacent to the second end for receiving the spherical segment-shaped section of said head; and a pressure element which exerts pressure on said head to lock said head in the receiving portion, the pressure element being of cylindrical construction and having a spherical recess on a side facing the head, which cooperates with the head when pressure is exerted; wherein said head has a hollow inner portion to receive a free end portion of said shank, wherein said head and said free end portion are formed such that the free end portion is elastically clamped by said head while the head and free end portion are located in the receiving portion and the head and the receiving portion are unlocked to each other, and wherein said free end portion is conically shaped, the diameter increasing towards the free end of the shank opposite the bone engagement end of the shank; wherein the greatest diameter of the free end portion of the shank is greater than an opening to the hollow inner portion of the head; wherein the head and the free end portion of the shank are configured such that, upon engagement and movement of the head and shank toward each other, the opening widens to allow insertion of the greatest diameter of the free end portion of the shank through the opening into the hollow inner portion.