POLYAXIAL BONE ANCHORING DEVICE

摘要

A polyaxial bone anchoring device includes an anchoring element having a shank and a head having an outer surface portion shaped as a segment of a sphere, a receiving part having a seat portion for receiving the head, and a pressure element having a head contacting surface portion having at least two circumferentially distinct projections and defining a recess for holding the head, the recess having a first region configured to receive the head and a second region defined by at least part of one of the projections and having an undersize compared to the shape of the head, such that when the head is held in the recess, the projections extend over a portion of the head with the largest outer diameter, and the head contacting surface portion corresponding to the second region is expanded from a neutral position to clamp the head by friction.

主权项

1. A polyaxial bone anchoring device comprising:
an anchoring element having a shank for anchoring to a bone and a head having an outer surface portion shaped as a segment of a sphere including a largest outer diameter of the sphere; a receiving part having a first end and a second end, a channel for receiving a rod therein, a bore extending from the first end in a direction of the second end along a bore axis, and a seat portion at the second end for receiving the head; and a pressure element having a head contacting surface portion comprising at least two circumferentially distinct projections and defining a recess for holding the head, the recess having a first region configured to receive the head and a second region defined by at least part of one of the projections and having an undersize compared to the shape of the head, such that when the head is held in the recess, the projections extend over a portion of the head with the largest outer diameter, and the head contacting surface portion corresponding to the second region is expanded from a neutral position to clamp the head by friction; wherein when the head and the pressure element are in the receiving part and the pressure element is holding the head in the recess, at least one of the projections is configured to extend at least partially into an accommodation space of the receiving part, and the head is pivotable with respect to the receiving part and can be fixed at an angle by exerting further pressure via the pressure element onto the head.