COUPLING DEVICE FOR USE WITH A BONE ANCHORING ELEMENT AND BONE ANCHORING DEVICE WITH SUCH A COUPLING DEVICE
A coupling device for use with a bone anchoring element includes a receiving part having first and second ends, a longitudinal axis, and a coaxial passage, and a pressure member having a first portion and an expandable portion connected axially to the first portion forming a seat for the head. The pressure member is movable to a position where the receiving part acts on the expandable portion to clamp the head in the seat. The seat can be asymmetric relative to the longitudinal axis while a central axis of the first portion is coaxial with the longitudinal axis, such that the seat facilitates pivoting of the bone anchoring element in a first direction to a first maximum angle and in an opposite direction to a second maximum angle smaller than the first maximum angle.
This application is a continuation of U.S. patent application Ser. No. 17/195,120, filed Mar. 8, 2021, which claims priority to and the benefit of U.S. Provisional Patent Application No. 62/988,540, filed Mar. 12, 2020, the contents of which are hereby incorporated by reference in their entirety, and claims priority from European Patent Application EP 20 162 697.5, filed Mar. 12, 2020, the contents of which are hereby incorporated by reference in their entirety.
BACKGROUND FieldThe application relates to a coupling device for use with a bone anchoring element and to a bone anchoring device including the coupling device and the bone anchoring element. The coupling device permits the bone anchoring element to pivot at a greater angle in one direction compared to another direction. A particular application of such a coupling device and bone anchoring device is in spinal surgery.
Description of Related ArtA bone anchoring device is known from U.S. Pat. No. 6,736,820 B2. The bone screw described therein has a screw member and a receiving part, wherein the receiving part has a first bore with a seat for the head at the bottom of the first bore and a second bore. To allow the screw member to be pivoted to at least one side by an enlarged angle, the edge bounding the free end of the second bore viewed relative to the axis of the first bore is of an asymmetric construction.
Another polyaxial bone anchoring device is known from US 2014/0031880 A1. In one embodiment the polyaxial bone anchoring device includes a receiving part for coupling a rod to a bone anchoring element, with a first passage at the bottom end having a first longitudinal axis and a second passage at the top end having a second longitudinal axis that intersects the first longitudinal axis. In the receiving part, a compression element is arranged which has a seat for the head. The polyaxial bone anchoring device provides for an enlarged pivot angle to one side compared to an opposite side, i.e., the device has a favored angle design.
SUMMARYIt is an object of the invention to provide an alternative or improved coupling device and polyaxial bone anchoring device that has a greater field of application.
The coupling device can be used with a bone anchoring element, wherein the bone anchoring element includes a head and a shank for anchoring in bone. The coupling device includes a receiving part configured to receive the head of the bone anchoring element, where the receiving part has a first end and a second end, and a passage extending from the first end to the second end and defining a longitudinal axis, and a pressure member positionable at least partially in the passage and configured to exert pressure onto the head to clamp the head in the receiving part, wherein the pressure member has a central axis which is coincident with the central axis of the receiving part and further has a seat for the head. The seat is configured to pivotably receive the head of the bone anchoring element and is further configured to permit pivoting of the bone anchoring element in at least one direction at a first maximum angle relative to the longitudinal axis and in an opposite direction to the one direction at a second maximum angle relative to the longitudinal axis, wherein the first maximum angle is greater than the second maximum angle, and wherein the second maximum angle is limited by an abutment provided by the pressure member against the bone anchoring element.
A bone anchoring device includes the coupling device and the bone anchoring element, and can be classified as a favored angle type of bone anchoring device. This type may be particularly useful in certain applications, such as in correction techniques carried out on the cervical spine.
The second maximum pivot angle is preferably 0° or about 0° or is limited to a small range of angles between 0° and about 10°, or 0° and about 5° or less, relative to the longitudinal axis of the receiving part. Thus, when the bone anchoring element is pivoted to the second maximum pivot angle, i.e. when it is at or near a zero angle position, the bone anchoring device functions similar to a monoaxial bone anchoring device in which a shank axis is substantially coaxial with the longitudinal axis of the receiving part. The wall thickness in the region of the abutment is sufficiently high so that higher fixation forces may be applied, compared to a polyaxial bone anchoring device in which the zero angle position is not defined by an abutment.
Since the second maximum pivot angle is defined by an abutment provided at the pressure member, the second maximum angle is basically independent of the shape of the receiving part. Various pressure members can be used in combination with a single type of receiving part to achieve various second maximum angles depending on the specific application.
The bone anchoring device may in some embodiments be a top-loading bone anchoring device, in which the bone anchoring element is inserted into the receiving part from the top end thereof.
Further features and advantages of the invention will become apparent from the description of embodiments by means of the accompanying drawings. In the drawings:
As shown in
Referring in greater detail to
At the bottom end 5b, the receiving part 5 has an inclined lower surface 56 that may be formed, for example, by cutting away a lower portion of the substantially cylindrical receiving part 5 in an oblique manner in a direction of the top end 5a. The inclined lower surface 56 extends at an angle to the central longitudinal axis C and is preferably oriented towards the middle of one of the legs 54, when viewed in a circumferential direction. As can be best seen in
The size of the portion of the opening 52 defined by the edge 52a is such that a portion of the pressure member 6 may extend therein to provide a sufficient area for seating the head 3, as explained in greater detail below.
At a center of each leg 54, in a circumferential direction and at an axial position above a bottom 53a of the substantially U-shaped recess 53, a pair of through-holes 57 extend through each leg 54. The through-holes 57 are configured to receive pins 58 as shown in
Referring now in addition to
A lower portion 63 of the pressure member 6 has a tapered, preferably conical, outer surface which is configured to cooperate with the tapered inner surface of the tapered portion 51a of the passage 51 in the receiving part 5. The tapered outer surface may be continuously joined with the upper cylindrical portion 61. A head receiving recess 64 is formed in the lower portion 63 and extends from the bottom end 6b to a distance from a bottom 62a of the rod receiving recess 62. The head receiving recess 64 has a lower section 64a close to the bottom end 64b that has a substantially hollow spherical shape, with a radius of the sphere matching that of head 3. Furthermore, an uppermost section 64b of the head receiving recess 64 is also hollow spherically-shaped with the same radius as the lower section 64a. By means of this, the lower spherical section 64a and the upper spherical section 64b provide a spherical support for the head 3, and thus form a seat in which the head 3 can pivot. Between these two spherically-shaped sections 64a, 64b, an intermediate widened section 64c may be provided that has a greater inner diameter than the lower end of the upper spherical section 64b. The intermediate widened section 64c may facilitate pivoting of the head 3.
In addition, the lower portion 63 of the pressure member has flexible wall sections 65 that are separated by axial slots 66 open towards the bottom end 6b. To obtain a certain degree of flexibility, the slots 66 may widen towards their closed ends 66a. In the axial direction, the slots 66 may extend preferably up to the transition between the intermediate section 64c and the upper spherical segment-shaped section 64b. The head 3 can be inserted by slightly expanding the flexible wall sections 65. Moreover, the head 3 can be held by friction in the head receiving recess 64 prior to final locking.
The bottom end 6b has an inclined portion, so that an inclined edge 67 encompasses the opening of the head receiving recess 64. The inclined edge 67 may be formed, for example, by cutting away material from the lower portion 63 in an oblique manner. As a result, the inclined edge 67 extends at an angle to the central longitudinal axis C, for example, in the direction of one of the sidewalls of the rod receiving recess 62, and has a substantially ellipsoidal shape. By means of this, the inclined edge 67 provides an enlarged space for the bone anchoring element 1 to pivot to one side, as shown in particular in
As can be seen in particular in
The pressure member may further include elongate recesses 68 formed in the sidewalls of the rod receiving recess 62. The elongate recesses 68 are oriented with their long side substantially parallel to the central longitudinal axis C. As shown in particular in
The parts and portions of the bone anchoring device may be made of any material, preferably however of titanium or stainless steel, or of any bio-compatible metal or metal alloy or plastic material. For a bio-compatible alloy, a NiTi-alloy, for example Nitinol, may be used. Other materials that can be used are, for example, magnesium or magnesium alloys. Bio-compatible plastic materials that can be used may be, for example, polyether ether ketone (PEEK) or poly-L-lactide acid (PLLA). The various parts can be made of the same or of different materials from one another.
The assembly of the polyaxial bone anchoring device may be such that first, the head 3 is inserted into the head receiving recess 64 of the pressure member 6. Then, the pressure member 6 with bone anchoring element 1 is inserted from the top end 5a into the receiving part 5 in a manner such that the rod receiving recess 62 and the substantially U-shaped recess 53 are aligned. Moreover, the pressure member 6 is orientated in such a manner with respect to the receiving part 5 that the inclined surface 56 of the receiving part and the inclined edge 67 of the pressure member 6 are aligned in the same direction. This rotational position may be secured by the pins 58 extending through the through-holes 57.
Referring now in greater detail to
Pivoting of the coupling device relative to the bone anchoring element will now be described. When the coupling device is pivoted relative to the bone anchoring element 1, more specifically relative to the shank 2, the coupling device can assume a plurality of angular positions relative to the bone anchoring element. By the abutment of the shank 2, in particular the neck portion 21, at the edge portion 52b, a first maximum pivot angle is defined. In
The highest position of the edge portion 52b is, in this embodiment, at a circumferential position that is 90° from the transverse axis T of the recess 53, or in other words, 90° relative to the rod axis of an inserted rod. It shall be noted that the edge portion 52b of the receiving part and the edge 67 provide an abutment also in cases where the bone anchoring element 1 is pivoted at an angle different from 90° to the transverse axis T or rod axis. Hence, the maximum angle may vary along the edge portion 52b. In addition, the second maximum angle in the opposite direction may be slightly greater than 0°. Therefore, the second maximum angle can be in a range of 0° to a maximum of 10°, preferably a maximum of 5°, or more preferably a maximum of 2° or less, in the opposite direction.
It shall be noted, that the bone anchoring element can also be pivoted to any position between the first maximum angle and the second maximum angle and be fixed there.
After having adjusted the receiving part 5 relative to the bone anchoring element 1, the rod is inserted into the receiving part and the entire bone anchoring device is locked by inserting and tightening the locking member 7. Using an instrument, any provisional clamping or locking can be loosened again. To unlock a provisional or final locking of the head, the instrument can engage the tool engagement recesses 59, 69 of the receiving part 5 and the pressure member 6, and thereby exerts an upwardly directed force onto the pressure member which reduces the pressure onto the head 3.
A second embodiment of the coupling device and the bone anchoring device will be described with reference to
The receiving part 5′ differs from the receiving part 5 in the design of the lower portion that defines the first maximum pivot angle. Referring in greater detail to
By means of this, an enlarged first maximum pivot angle α to one side is defined. Due to the particular orientation of the cut-out portion 56′ shown in the embodiment, the first maximum pivot angle is arranged at a radial direction that is 90° with respect to the transverse axis T or rod axis.
Referring now in greater detail to
Moreover, the head receiving recess 64′ may have, adjacent to the bottom end 6b, a substantially cylindrical section 64d′ which limits the second maximum pivot angle in a direction opposite to the cut-out to substantially 0° or exactly 0°. The cylindrical section 64d′ may be coaxial with the central longitudinal axis C and has a size such that it substantially matches the radius of the neck portion 21. Thereby, the neck portion 21 of the shank 2 abuts against not only an edge of the pressure member but a two-dimensional abutment instead.
Referring to
Referring to
When the bone anchoring element 1 is pivoted so that the shank 2 extends into the cut-out 56 ‘ and abuts against the edge portion 52b’ of the cut-out 56′ of the receiving part 5′, the pivot angle may be slightly increased compared to the second embodiment.
It shall be noted that the pressure member 6″ may be different from the pressure member 6′ in that its lower portion is longer to project out of the bottom end 5b. Alternatively, the pressure member 6″ may be identical to the pressure member 6′ of the second embodiment, but may be insertable more deeply into the receiving part, so that the bottom end 6b can project or project farther out of the lower opening 52 of the receiving part 5′. Therefore, with the same pressure member, slightly different first maximum pivot angles can be achieved.
Further modifications of the above described embodiment are also conceivable. In particular, features of one embodiment can be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.
The inclined surface at the lower portion of the receiving part may be oriented at various other angles relative to the rod axis.
The second maximum pivot angle in the opposite direction may be greater than about 10°, as long as it is smaller than the first maximum pivot angle.
While the bone anchoring device is shown as a top-loading bone anchoring device in which the bone anchoring element is inserted from the top end into the receiving part, a bottom-loading bone anchoring device may also be conceivable, where the pressure member can be preassembled with the receiving part and the bone anchoring element can be inserted from the bottom end of the receiving part. The receiving part can also have many different shapes. Instead of two elongate recesses and/or two tool engagement recesses, only one of each may be sufficient, or they can be omitted altogether.
While the head is shown to have an overall spherical segment-shape, the head and the pressure member may also be designed so as to allow pivoting only in one or more single planes. In another embodiment, the pressure member may lack the rod receiving recess, and may, for example, be rotatable within the receiving part. Alternatively, the pressure member may have a channel for the rod that is deeper than the rod diameter, in which case the locking member may be a two-part device that includes an outer screw for locking the head and an inner screw for locking the rod independently.
While the embodiments are shown with a rod for connecting several receiving parts, the coupling device may also be a bone plate. In such a case, the receiving part and the pressure member may not include rod receiving recesses, and the passage may be a hole in the bone plate which receives the pressure member.
While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is instead intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.
Claims
1. A coupling device for use with a bone anchoring element comprising a head and a shank for anchoring in bone, the coupling device comprising:
- a receiving part connectable to the head of the bone anchoring element, the receiving part having a first end, a second end, and a longitudinal axis extending between the first and second ends, and defining a coaxial passage extending from the first end towards the second end;
- a pressure member comprising a first portion and an expandable portion that forms a seat for the head, wherein the pressure member is movable in the passage to a position where the receiving part acts on the expandable portion to exert pressure on and clamp the head when the head is held in the seat;
- wherein when the pressure member is in the receiving part, the seat is configured to be arranged asymmetrically relative to the longitudinal axis of the receiving part while a central axis of the first portion of the pressure member is substantially coaxial with the longitudinal axis, such that the seat facilitates pivoting of a connected bone anchoring element in at least a first direction at a first maximum angle relative to the longitudinal axis, and a second direction opposite the first direction at a second maximum angle relative to the longitudinal axis that is smaller than the first maximum angle.
2. The coupling device of claim 1, wherein a wall thickness of the expandable portion of the pressure member is greater in the second direction than in the first direction.
3. The coupling device of claim 1, wherein the second maximum angle is substantially 0° relative to the longitudinal axis.
4. (canceled)
5. The coupling device of claim 1, wherein at least one of the pressure member or the receiving part defines an opening at or near the second end of the receiving part with a non-circular profile.
6. The coupling device of claim 5, wherein the opening is substantially elliptical.
7. (canceled)
8. The coupling device of claim 1, wherein the expandable portion of the pressure member comprises a surface in the second direction that extends vertically to facilitate increased contact with the shank.
9. The coupling device of claim 1, wherein the pressure member is configured to extend out of the second end of the receiving part.
10. A bone anchoring device comprising:
- a bone anchoring element comprising a head and a shank for anchoring in bone; and
- a coupling device for use with the bone anchoring element, the coupling device comprising: a receiving part connectable to the head, the receiving part having a first end, a second end, and a longitudinal axis extending between the first and second ends, and defining a coaxial passage extending from the first end towards the second end; a pressure member comprising a first portion and an expandable portion that forms a seat for the head, wherein the pressure member is movable in the passage to a position where the receiving part acts on the expandable portion to exert pressure on and clamp the head when the head is held in the seat;
- wherein when the pressure member is in the receiving part with a central axis of the first portion of the pressure member extending substantially coaxially with the longitudinal axis and when the head is held in the seat, the bone anchoring element is pivotable in at least a first direction at a first maximum angle relative to the longitudinal axis, and a second direction opposite the first direction at a second maximum angle relative to the longitudinal axis that is smaller than the first maximum angle,
- wherein the pressure member prevents the bone anchoring element from directly contacting the receiving part in at least the second direction.
11. The bone anchoring device of claim 10, wherein the pressure member forms an abutment that limits the pivoting of the bone anchoring element in the second direction.
12. The bone anchoring device of claim 11, wherein when the head is in the seat and the bone anchoring element is pivoted in the second direction, a neck of the bone anchoring element located between the head and the shank is configured to abut against the abutment.
13. The bone anchoring device of claim 12, wherein the abutment extends vertically to facilitate increased contact with the neck of the bone anchoring element.
14. The bone anchoring device of claim 11, wherein the expandable portion of the pressure member defines an opening for inserting the head into the seat, and wherein an edge of the opening comprises the abutment.
15. The bone anchoring device of claim 11, wherein a wall thickness of the expandable portion of the pressure member is greater in the second direction corresponding to the abutment than in the first direction.
16. The bone anchoring device of claim 10, wherein the second maximum angle is substantially 0° relative to the longitudinal axis.
17. The bone anchoring device of claim 10, wherein the expandable portion of the pressure member is configured to extend over at least part of a region of the head that defines a greatest width of the head.
18. The bone anchoring device of claim 10, wherein the seat is configured to clamp the head by friction prior to final locking of the head relative to the receiving part.
19-20. (canceled)
21. The bone anchoring device of claim 10, wherein the receiving part and/or the pressure member limit pivoting of the bone anchoring element to the second maximum angle in substantially every direction other than the first direction relative to the longitudinal axis.
22. A method for implanting a bone anchoring device into bone, the bone anchoring device comprising a bone anchoring element comprising a head and a shank for anchoring in bone and a coupling device comprising a receiving part, the receiving part having a first end, a second end, and a longitudinal axis extending between the first and second ends, and defining a coaxial passage extending from the first end towards the second end, a pressure member comprising a first portion and an expandable portion that forms a seat for the head, wherein when the pressure member is in the receiving part, the seat is configured to be arranged asymmetrically relative to the longitudinal axis of the receiving part while a central axis of the first portion of the pressure member is substantially coaxial with the longitudinal axis, and a locking element, the method comprising:
- anchoring the shank of the bone anchor to bone;
- adjusting an angular position of the receiving part relative to the shank when the pressure member is in the receiving part and the head is held in the seat, wherein the seat facilitates pivoting of the receiving part relative to the bone anchoring element in at least a first direction at a first maximum angle relative to the longitudinal axis, and a second direction opposite the first direction at a second maximum angle relative to the longitudinal axis that is smaller than the first maximum angle;
- advancing the locking element in the passage to move the pressure member in the passage to a position where the receiving part acts on the expandable portion to exert pressure on and clamp the head in the seat, for locking the head relative to the receiving part.
Type: Application
Filed: Aug 8, 2023
Publication Date: Feb 1, 2024
Inventors: Lutz Biedermann (VS-Villingen), Berthold Dannecker (St. Georgen)
Application Number: 18/446,266