Polyaxial bone anchoring device with enlarged pivot angle

Abstract

A polyaxial bone anchoring device includes an anchoring element having a shank and a head, a receiving part having a first end and a second end, a central axis, and an accommodation space for accommodating the head, the accommodation space having an opening at the second end, a sleeve-like insert piece configured to be arranged around a portion of the head and to be arranged in and to pivot in the accommodation space, and a pressure member including a portion configured to exert pressure onto the head, wherein the anchoring element and insert piece are pivotable with respect to the receiving part such that respective angles formed by a central axis of the insert piece with the central axis of the receiving part and a central axis of the anchoring element are adjustable, and can be locked by exerting pressure with the pressure member onto the head.

1 . A polyaxial bone anchoring device comprising:
 an anchoring element having a shank for anchoring in a bone and a head having a spherically-shaped outer surface portion;   a receiving part having a first end and a second end, a central axis extending through the first end and the second end, a transverse channel at the first end for receiving a rod, and an accommodation space for accommodating the head, the accommodation space having an opening at the second end; and   a sleeve-like insert piece configured to be arranged around a portion of the head and to be arranged in and to pivot in the accommodation space of the receiving part;   wherein when the insert piece is arranged around the head, the insert piece is insertable into the accommodation space through the opening of the receiving part; and   wherein when the head and the insert piece are arranged in the receiving part, the anchoring element and insert piece are pivotable with respect to the receiving part, and can be locked by exerting pressure onto the head.   
     
     
         2 . The polyaxial bone anchoring device of  claim 1 , wherein the receiving part comprises a first engagement portion near the second end, and the insert piece comprises a second engagement portion for engaging the first engagement portion. 
     
     
         3 . (canceled) 
     
     
         4 . The polyaxial bone anchoring device of  claim 2 , wherein the accommodation space has a portion with a largest diameter, and wherein the first engagement portion extends from the opening towards the portion of the accommodation space with the largest diameter. 
     
     
         5 . The polyaxial bone anchoring device of  claim 2 , wherein the second engagement portion extends over a full outer surface of the insert piece. 
     
     
         6 . The polyaxial bone anchoring device of  claim 2 , wherein the insert piece is insertable into the accommodation space by engaging the first engagement portion and the second engagement portion, and wherein when the insert piece is inserted in the accommodation space and the first engagement portion and the second engagement portion are disengaged, the insert piece is freely pivotable in the accommodation space. 
     
     
         7 . The polyaxial bone anchoring device of  claim 2 , wherein when the insert piece is in the receiving part, the first engagement portion and the second engagement portion form a stop to prevent the insert piece from being removed from the receiving part. 
     
     
         8 . The polyaxial bone anchoring device of  claim 1 , wherein the insert piece is configured to be held on the head by friction. 
     
     
         9 . The polyaxial bone anchoring device of  claim 1 , wherein the insert piece has a first edge and a second edge, and wherein an engagement portion is provided at the second edge for engaging a tool. 
     
     
         10 . The polyaxial bone anchoring device of  claim 1 , wherein the accommodation space defines a hollow spherically-shaped portion, and the insert piece has an outer spherically-shaped surface portion. 
     
     
         11 . The polyaxial bone anchoring device of  claim 1 , wherein when the insert piece is arranged around the head and inserted in the receiving part, the insert piece and the anchoring element are independently pivotable relative to the receiving part when the shank of the anchoring element and an edge of the insert piece are out of contact. 
     
     
         12 . The polyaxial bone anchoring device of  claim 11 , wherein when the shank of the anchoring element engages the edge of the insert piece, the anchoring element and the insert piece are pivotable together. 
     
     
         13 . The polyaxial bone anchoring device of  claim 1 , wherein the insert piece has an inner spherical surface portion that forms a seat for the head. 
     
     
         14 . The polyaxial bone anchoring device of  claim 1 , wherein the insert piece is rigid. 
     
     
         15 . The polyaxial bone anchoring device of  claim 1 , wherein when the head and the insert piece are in the receiving part, the bone anchoring device is configured to be held at a position where a preload is exerted onto the head to clamp the head by friction at a first adjustable position before final locking of an angular position of the anchoring element relative to the receiving part. 
     
     
         16 . The polyaxial bone anchoring device of  claim 1 , wherein the insert piece is rotationally symmetrical. 
     
     
         17 . A method of coupling a rod to a bone or vertebra via a polyaxial bone anchoring device, the bone anchoring device comprising an anchoring element having a shank for anchoring in a bone and a head having a spherically-shaped outer surface portion, a receiving part having a first end and a second end, a central axis extending through the first end and the second end, a transverse channel at the first end for receiving a rod, and an accommodation space for accommodating the head, the accommodation space having an opening at the second end, a sleeve-like insert piece configured to be arranged around a portion of the head and to be arranged in and to pivot in the accommodation space of the receiving part, and a fixation element, the method comprising:
 connecting the anchoring element to the receiving part by introducing the head with the insert piece arranged around the head through the opening and into the accommodation space of the receiving part, wherein the anchoring element and the insert piece are pivotable with respect to the receiving part;   inserting the anchoring element into a bone or vertebra;   pivoting the receiving part relative to the anchoring element;   inserting a rod into the channel of the receiving part; and   advancing the fixation element in the channel, such that the fixation element exerts pressure on the rod, to exert pressure onto the head of the anchoring element, to lock respective angular positions between the anchoring element, the insert piece, and the receiving part.   
     
     
         18 . The method of  claim 17 , further comprising attaching the insert piece to the head of the anchoring element prior to connecting the anchoring element to the receiving part. 
     
     
         19 . (canceled) 
     
     
         20 . The method of  claim 17 , further comprising holding the bone anchoring device at a first position when the anchoring element is connected to the receiving part and the rod is not inserted into the channel, such that a frictional force is exerted on the head of the anchoring element to hold the angular position of the receiving part relative to the anchoring element, wherein said position is adjustable by applying a force greater than the frictional force on the receiving part or the anchoring element.