Patent ID: 9119674
Filing Date: 2015-09-01
Classification: A61B

Abstract:
1. A polyaxial bone anchoring device comprising: a shank to be anchored in a bone or vertebra, a head, a ring, and a receiving part receiving the head for connecting the shank to a rod, the shank, the head, and the ring being separate parts, the head having a bore with a cylindrical inner surface defining a smallest diameter of the bore, the cylindrical inner surface extending uniformly from a first end of the head to a second end of the head and interrupted by a ring-shaped groove provided on the inner surface, and at least one slit extending from the inner surface to an outer surface of the head providing elasticity to the head; the shank having a first portion for anchoring in the bone or vertebra and a second portion with a cylindrical outer surface, wherein a ring-shaped groove is provided on the cylindrical outer surface; wherein the ring is configured to be arranged in the groove of the head or the shank; wherein in a first inserted position, the ring is positioned in the grooves of the head and the shank such that a surface of the ring engages a corresponding surface on the head or the shank, the engaging surfaces configured to form a positive-locking engagement that prevents sliding between said engaging surfaces and removal of the shank from the bore of the head when a force is applied to the shank in a direction opposite a direction of insertion; wherein the receiving part has a longitudinal bore passing through it from a first end to a second end, the longitudinal bore having a reduced diameter adjacent to the first end of the receiving part forming a seat for accommodating the head, the receiving part further having a U-shaped recess adjacent to the second end of the receiving part, the U-shaped recess intersecting the longitudinal bore such that two free legs are formed constituting a channel for receiving the rod; wherein the shank is insertable into the head while the head is arranged in the receiving part; and wherein a pressure element is arranged in the longitudinal bore and configured to fix the angular orientation of the shank relative to the receiving part, the pressure element acting onto the head such that it compresses the head which firmly clamps the head to the shank.