High angulation polyaxial bone anchoring device

摘要

A polyaxial bone anchoring device includes a bone anchoring element having a shank and a head, a receiving part having a first end and a second end, a central axis, a first bore, a second bore, and a first support surface between the first bore and the second bore that is substantially perpendicular to the central axis, and an insert piece having a seat for pivotably holding the head, a bounding edge, and a second support surface configured to engage the first support surface to support the insert piece when mounted to the receiving part, the second support surface formed by a projection at an end of the insert piece opposite the bounding edge, wherein the insert piece projects out of the second bore and is rotatable, and is configured to permit the bone anchoring element to pivot at a larger angle at a first location of the bounding edge.

主权项

1. A polyaxial bone anchoring device comprising:
a bone anchoring element having a shank for anchoring in a bone or a vertebra and a head; a receiving part for receiving a rod to connect the rod to the bone anchoring element, the receiving part having a first end and an opposite second end, a central axis passing through the first and second ends, two legs forming a channel therebetween for receiving the rod, a coaxial first bore at the first end, a coaxial second bore at the second end in communication with the first bore, and a first support surface between the first bore and the second bore that is substantially perpendicular to the central axis; an insert piece configured to be assembled and mounted to the receiving part, the insert piece having a seat for pivotably holding the head of the bone anchoring element, a bounding edge with an opening having a width that is smaller than a diameter of the head to prevent passage of the head therethrough, and a second support surface configured to engage the first support surface to support the insert piece relative to the receiving part when the insert piece is mounted to the receiving part, the second support surface formed by a projection at an end of the insert piece opposite the bounding edge; and a pressure member configured to be inserted in the receiving part, the pressure member having a surface for contacting the head of the bone anchoring element; wherein the insert piece is axially movable from the first end of the receiving part to a position where the first and second support surfaces are engaged while maintaining a rotational orientation in which a portion of the insert piece having the greatest width is radially aligned with at least one of the legs, wherein when the insert piece is mounted to the receiving part and the head is in the seat and in contact with the insert piece and the pressure member, the insert piece projects out of the second bore and is rotatable relative to the receiving part and the pressure member, the bounding edge is at an end of the insert piece facing away from the first bore, and the bounding edge is configured to permit the bone anchoring element to pivot at a larger angle at a first location of the bounding edge than at a second location of the bounding edge relative to the central axis.