Patent ID: 9078705
Filing Date: 2015-07-14
Classification: A61B,F04C

Abstract:
1. A polyaxial bone anchoring device comprising: a bone anchoring element having a head and a shaft for anchoring to a bone; a receiving part for coupling the bone anchoring element to a rod, the receiving part having a head receiving portion with an accommodation space for accommodating the head, and a rod receiving portion having an inner wall defining a bore in communication with the accommodation space, the bore having a bore axis; and a pressure member movable in the bore and comprising a first surface for engaging the head and a second surface for engaging a rod; wherein when the bone anchoring element and the pressure member are in the receiving part, the pressure member is movable to a first position where friction between the first surface and the head generates a preload on the head to maintain the shaft at a temporary angular position relative to the receiving part, and to a second position different from the first position where the head is locked relative to the receiving part; and wherein the pressure member is configured to engage a first portion of the inner wall of the receiving part that faces the bore axis without a positive lock, wherein a holding force is generated at the engagement between the pressure member and the first portion of the inner wall of the receiving part for holding the pressure member at the first position, and wherein the pressure member is movable out of the first position by applying an axial force on the pressure member that is greater than the holding force.