Importance

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Abstract

A polyaxial bone anchoring device includes: an anchoring element having a shaft for anchoring in a bone and a head, the head having a spherically-shaped outer surface portion; a receiving part configured to be pivotably connected to the head, the receiving part having a top end and a bottom end, a longitudinal axis extending through the top end and the bottom end, a channel transverse to the longitudinal axis for receiving a rod, and an accommodation space for accommodating the head, the accommodation space having a lower opening at the bottom end, a sleeve-like insert piece configured to be positioned around a portion of the head and to pivot in the receiving part, the insert piece having a spherically-shaped outer surface portion, wherein a lower edge of the insert piece extends past the lower opening in a direction away from the receiving part when the insert piece is seated in the receiving part in a position in which a central axis of the insert piece is coaxial with the longitudinal axis, and wherein the insert piece has an opening with a diameter greater than or equal to a maximum diameter of the head when the head is not in contact with the insert piece; a pressure member configured to be arranged at least partially in the accommodation space, the pressure member having a lower surface portion configured to contact the head to exert pressure onto the head when the head and the pressure member are arranged in the receiving part; wherein when the head, the insert piece, and the pressure member are arranged in the receiving part, the insert piece is tiltable with respect to the longitudinal axis of the receiving part and with respect to a longitudinal axis of the anchoring element, and wherein the anchoring element and the insert piece can be locked at respective angles relative to the longitudinal axis of the receiving part by exerting pressure with the pressure member onto the head.

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First Claim