Patent ID: 8034089

Claim:
A bone anchoring device comprising: an anchoring element comprising a shank to be anchored in a bone or a vertebra and a head, the shank having a conically shaped first end portion having a free end and a second end opposite the free end, the diameter of the conically shaped first end portion increasing in a direction from the second end to the first end portion, the head having an outwardly facing surface with a spherical segment-shaped portion and a hollow inner portion to receive the first end portion of the shank, 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 contacts the outwardly facing surface of said head to exert pressure on said head and contacts the free end of the first end portion of the shank 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 outwardly facing surface of the head when pressure is exerted; wherein the first end portion of the shank is moveable from a first position wherein the first end portion of the shank is elastically clamped by the head in the hollow inner portion of the head and the head is moveable in the first region of the receiving portion to a second position wherein the first end portion of the shank is closer to the second end of the receiving portion and the shank is locked to the head and the head is locked in the receiving portion.