Bone anchoring device

Abstract

The present application provides a bone anchoring device, comprising: an anchoring element (1), which has a handle (2) and a head (3) for anchoring in a bone; a receiving part (5'), which receives the head of the anchoring element in a pivotable manner so that the handle can take a plurality of angular positions, including a predetermined angular position relative to the receiving part; a pressure part (6), which is configured to apply pressure on the head, wherein the head includes an outer surface portion, the outer surface portion defines a first position indication structure, which is engaged with a second position indication structure of the pressure part; the first or second position indication structure includes a transition portion (33) between a first curved portion (31) and a second curved portion (32), and when the first and second position indication structures are engaged with each other and the head is pivoted from one of the plurality of angular positions to a predetermined angular position, the transition portion passes through the other of the second or first position indication structures to provide an indication of the predetermined angular position of the handle relative to the receiving part.

Description

Technical Field

[0001] The invention relates to a bone anchoring device of the polyaxial type, which is capable of indicating a predetermined angular position of a bone anchor relative to a receiving part. Background Art

[0002] Such a bone anchoring device is known from US 9833263 B2. The bone anchor assembly described therein comprises one or more features for indicating the relative position of a receiver part and a handle, for example in the form of surface features contained in the head of the bone anchor, which interact with a friction ring when the handle is positioned in a specific orientation relative to the receiver part so as to provide tactile or auditory feedback. In another embodiment, the head of the bone anchor and a compression cap arranged in the receiver part can each comprise an engagement feature, which cooperates so as to be able to selectively lock the orientation of the handle relative to the receiver part. In the known bone anchor assembly, an interaction between the head and the receiver part is required for indicating a specific angular position of the handle. Alternatively, when only directional indication features are provided on the head and the compression cap, the position of the compression cap is connected to the position of the handle relative to the receiver part. Summary of the invention

[0003] It is therefore an object of the present invention to provide an improved or alternative bone anchoring device which is able to indicate the position of the stem relative to the receiver part.

[0004] This object is achieved by the bone anchoring device of the present application. The present application also includes further developments.

[0005] According to one aspect, a bone anchoring device is provided, comprising: an anchoring element having a stem for anchoring in a bone and a head; a receiving part arranged to receive the head of the anchoring element in a pivotable manner so that the stem can adopt a plurality of angular positions, including predetermined angular positions relative to the receiving part, the receiving part having a channel defining a central axis; and a pressure part arranged to exert pressure on the head so as to clamp the head in the receiving part, the pressure part being at least partially arranged in the channel. The head comprises a first position indicating structure arranged to engage with a second position indicating structure of the pressure part so as to provide an indication of the predetermined angular position of the stem relative to the receiving part. Preferably, the pressure part comprises: a head receiving recess so as to receive at least a portion of the head; and a portion arranged to surround the head so that the head is retained in the head receiving recess by friction.

[0006] In one embodiment, the first position indicating structure or the second position indicating structure includes a transition portion between a first curved portion and a second curved portion having different curvatures. When the first position indicating structure and the second position indicating structure engage with each other and the head is pivoted from one angular position to a predetermined angular position, the transition portion is passed by the respective other of the second or first position indicating structure. This generates feedback. The feedback can be received by a user and / or can be detected by a detector.

[0007] More specifically, the first curved portion and the second curved portion may be surface portions of the head that abut each other and have different radii. When the second position indication structure provided at the pressure component moves from a surface portion with a smaller radius to a surface portion with a larger radius, feedback will be generated.

[0008] In another embodiment, the first position indication structure further comprises a first flat portion, and the second position indication structure further comprises a second flat portion, which is arranged to engage with the first flat surface portion, wherein preferably, the first and second flat surface portions are conical portions. More specifically, the head may comprise a substantially spherical segment shaped portion, and the first conical portion may be sandwiched between two spherical segments of the substantially spherical segment shaped portion. The second conical portion may be arranged on the pressure component.

[0009] In yet another embodiment, the first position indicating structure comprises a groove and the second position indicating structure comprises an edge or a protrusion arranged at least partially into the groove.

[0010] With the bone anchoring device, the surgical step of aligning the receiving part relative to the inserted stem when the rod and the fixing element have not yet been inserted into the receiving part is facilitated because the predetermined angular position can be verified. Since the head is temporarily held by friction relative to the receiving part before it is locked relative to the receiving part, other angular positions can be easily adjusted.

[0011] The predetermined angular position may be a position where the handle and the receiving component are coaxial relative to each other. This position is also referred to as the "zero position". When the handle is in the zero position, the surgeon may advantageously obtain feedback during the alignment of the receiving component relative to the handle.

[0012] With the bone anchoring device, the interaction for indicating the predetermined angular position is limited to the interaction only between the handle and the pressure member. When the handle is pivoted and brought into the predetermined angular position, the receiving member is not involved. Therefore, the indication of the predetermined angular position is substantially independent of the clamping of the head in the receiving member.

[0013] This feedback can be tactile feedback, wherein the user uses his or her hand to feel when the receiving part has reached the predetermined angular position. Moreover, when the receiving part is in the predetermined angular position and will leave, tactile feedback can also be generated by the resistance to be overcome.

[0014] In some configurations, the feedback obtained by the user may be an audible feedback.Such audible feedback may be caused by the elastic engagement of the first position indication structure and the second position indication structure.

[0015] The first and second position indicating structures on the head and the pressure member can be provided in a polyaxial bone anchoring device of a bottom loading type (i.e., the bone anchoring element is inserted into the receiving member from the bottom end) and in a polyaxial bone anchoring device of a top loading type (i.e., the bone anchoring element is inserted into the receiving member from the top end), respectively.

[0016] According to another aspect, a bone anchoring device is provided, comprising: an anchoring element having a stem for anchoring in a bone and a head; a receiving part arranged to receive the head of the anchoring element in a pivotable manner such that the stem can adopt a plurality of angular positions, including predetermined angular positions relative to the receiving part, the receiving part having a channel defining a central axis; and a pressure part arranged to exert pressure on the head so as to clamp the head in the receiving part, the pressure part being at least partially arranged in the channel. The head comprises a first position indicating structure arranged to engage with a second position indicating structure of the pressure part so as to provide an indication of the predetermined angular position of the stem relative to the receiving part. The pressure part comprises a head receiving recess so as to receive at least a portion of the head, wherein the head receiving recess comprises a spherical surface portion arranged to engage with a spherical surface portion of the head, the edge of the spherical surface portion being followed by a cutout so that the edge forms the second position indicating structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features and advantages will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

[0018] Figure 1 An exploded perspective view of a bone anchoring device according to a first embodiment is shown.

[0019] Figure 2 It indicated Figure 1 A perspective view of the bone anchoring device in an assembled state.

[0020] Figure 3 It indicated Figure 1 and 2 A cross-sectional view of a bone anchoring device, wherein the cross-sectional plane includes a central longitudinal axis of the receiving part and extends through a center of a leg of the receiving part.

[0021] Figure 4 shows a perspective view from the top of a portion of a bone anchoring element, the bone anchoring element being Figures 1 to 3 part of a bone anchoring device.

[0022] Figure 5 It indicated Figure 4 A side view of a portion of a bone anchoring element is shown in FIG.

[0023] Figure 6 According to Figures 1 to 3 A perspective view of the pressure member of the bone anchoring device of the first embodiment, seen from the top.

[0024] Figure 7 It indicates that Figure 6 A perspective view of the pressure component as seen from the bottom.

[0025] Figure 8 It indicated Figure 6 and 7 Top view of the pressure component.

[0026] Figure 9a Indicates the pressure part along Figure 8 Sectional view along line AA.

[0027] Figure 9b It indicated Figure 9a A magnified view of the details.

[0028] Fig.10 A portion of a bone anchoring device is shown in FIG. Figure 3 An enlarged sectional view is shown in an assembled state, in which the bone anchoring element is at an angle to the central axis of the receiving part, which angle differs from the zero angle.

[0029] Fig.11 It indicated Figure 3 An enlarged sectional view of a portion of a bone anchoring device in an assembled state when the bone anchoring element is in a zero-angle position.

[0030] Fig.12 The angle of the bone anchoring element is different from the zero angle position. Figure 3 An enlarged cross-sectional view of a bone anchoring device.

[0031] Fig.13 A perspective view of a part of a bone anchoring element according to a second embodiment of a bone anchoring device is shown.

[0032] Fig.14 It indicated Fig.13 Side view of a bone anchoring element.

[0033] Fig.15 An enlarged cross-sectional view of a portion of a second embodiment of a bone anchoring device is shown, wherein the bone anchoring element is in a zero-angle position.

[0034] Fig.16 It indicated Fig.15 , wherein the bone anchoring element is in an angular position different from the zero angular position.

[0035] Fig.17 A perspective view of a part of a bone anchoring element according to a third embodiment of a bone anchoring device is shown.

[0036] Fig.18a express Fig.17 Side view of a bone anchoring element.

[0037] Fig.18b It indicated Fig.18a The enlarged part.

[0038] Fig.19a A cross-sectional view of a polyaxial bone anchoring device according to a third embodiment is shown, wherein the bone anchoring element is in a zero-angle position, the section plane including the central longitudinal axis of the receiving part and the centers of the legs extending through the receiving part.

[0039] Fig.19b It indicated Fig.19a The enlarged part.

[0040] Fig.20a Expressed similar to Fig.19a sectional view of a polyaxial bone anchoring device of a third embodiment, wherein the bone anchoring element is in an angular position different from the zero angular position.

[0041] Fig.20b It indicated Fig.20a The enlarged part. DETAILED DESCRIPTION

[0042] Overall Figures 1 to 3 The polyaxial bone anchoring device according to a first embodiment shown in , comprises a bone anchoring element 1 in the form of a screw component, which has a shank 2 with a thread and a head 3. The shank axis S is determined by the longitudinal axis of the shank 2 or the screw axis. On its free end 3a, the head 3 may have a recess 4 for engaging with a tool. The bone anchoring device further comprises a receiving part 5 for connecting the bone anchoring element and an elongated stabilizing member, such as a rod 100. A pressure member 6 is arranged in the receiving part and on top of the head 3. In order to fix the rod 100 in the receiving part 5 so as to exert pressure on the pressure member 6, a locking element 7, for example in the form of a fixing screw, may be additionally provided, which cooperates with the receiving part 5.

[0043] The receiving part 5 is substantially cylindrical and has a first end or top end 5a, a second end or bottom end 5b and a passage 51 extending from the top end 5a toward the bottom end 5b, the passage 51 defining a longitudinal center axis C. The passage 51 forms an opening 52 at the bottom end 5b, the width of the opening 52 being greater than the maximum width of the head, so that the head 3 of the bone anchoring element 1 can be inserted through the bottom end 52. The passage 51 can have a plurality of portions having different widths and / or shapes and is not limited to the exact shape shown in the figures. The passage 51 has a narrow portion 51a near the opening 52, which narrows, for example, conically toward the bottom end 5b. The narrow portion 51a cooperates with a portion of the pressure member 6 so that a compressive force is applied to the inserted head 3 by the pressure member 6. The widened portion 51b follows the narrow portion 51a in the direction toward the top end 5a. The widened portion 51b is sized so that a portion of the pressure member 6 can expand therein to allow the head 3 to enter. Furthermore, the channel 51 may have a middle portion 51c, the width of which is smaller than the width of the widened portion 51b, and allows a portion of the pressure member to slide therein in the axial direction. Finally, the channel 51 is formed as a threaded hole 51d near the top end 5a and the middle portion 51c, having an inner diameter larger than that of the middle portion 51c, so as to allow the locking element 7 to be inserted and cooperate with the locking element 7. The threads 53 and 71 of the receiving part 5 and the locking element 7, respectively, may be threads that reduce or eliminate radial forces when tightening the locking element 7, such as square threads. A thread disengagement portion 53a may be provided at the bottom end of the internal thread 53. Furthermore, it is preferred that Figure 1 and 2 As shown in the figure, a substantially U-shaped recess 54 is formed at the top end 5a and extends a certain distance from the top end. The substantially U-shaped recess 54 divides the upper part of the receiving part 5 into two free legs 55 and forms a channel for receiving the rod 100. When the rod is inserted, the longitudinal axis of the substantially U-shaped recess 54 coincides with the longitudinal axis of the straight rod 100.

[0044] At the center of each leg 55 in the circumferential direction and at an axial position higher than the bottom 54a of the substantially U-shaped recess 54, a through hole 56 extends through each leg 55. The through hole 56 is configured to receive a pin, such as Figure 3 As shown in , the pin 57 can be used to rotationally fix the pressure member 6 in the receiving member 5. Also, the pin 57 can be used to limit the upward movement of the pressure member 6 in the receiving member 5. Moreover, the cutouts 58 can be formed on either side of the legs 55, which can help to reduce the size of the receiving member 5. Tool engagement portions 59, such as circumferential grooves and / or central recesses, can be optionally provided at the legs 55 to enable the receiving member 5 to engage with a tool.

[0045] The following will refer to Figure 4 and 5The bone anchoring element 1 is described in more detail. The head 3 has the general shape of a spherical segment, or in other words, a truncated sphere, which is dimensioned such that it includes a spherical portion having a maximum diameter E. The spherical segment may be arranged between the free end 3 a of the head and the neck portion 21 of the shank 2 such that the end having a smaller outer diameter is closer to the neck portion 21, while the other end having a larger outer diameter is closer to the free end 3 a (compared to the neck portion 21). However, the spherical segment may also extend to the same distance on both sides from the portion having the maximum diameter E, or may end at or below the maximum diameter E. The neck portion 21 may be substantially threadless.

[0046] More specifically, the head 3 includes a first curved portion 31 and a second curved portion 32 at its outer surface. The first curved portion 31 is determined by a spherical segment that forms the overall shape of the head 3 and has a first radius of curvature R1 determined by the radius of the sphere. Moreover, the first curved portion 31 is located near or close to the neck portion 21 and includes a maximum outer diameter E in the illustrated embodiment. The second curved portion 32 may be, for example, in the shape of a substantially annular segment and has a second radius of curvature R2 that is smaller than the first radius of curvature R1. The second curved portion 32 is located between the first curved portion 31 and the free end 3a of the head 3. In a section that passes through the center of the head 3 and includes the shank axis S, the surfaces of the first curved portion 31 and the second curved portion 32 form a substantially circular arc. Moreover, the first curved portion 31 and the second curved portion 32 are connected to each other in such a way that the outer surface of the head 3 is substantially continuous at the transition portion 33. Therefore, there is substantially no step at the transition portion 33, or in other words, the transition portion is stepless. The first curved portion 31 and the second curved portion 32 and their transition portion 33 form a first position indication structure provided on the head 3. It should be noted that only the portion of the entire first curved portion 31 and the second curved portion 32 in the area around the transition portion may form the first position indicating structure.

[0047] The axial length of the second curved portion 32 in the direction of the shank axis S can be significantly less than the axial length of the first curved portion 31. For example, the second curved portion 32 can have only the typical axial length of the chamfered area. For example, the second curved portion can be manufactured using a turning tool that is configured to form a radius on the edge of the workpiece. It should be noted that such a first position indication structure including a transition portion between the first curvature and the second curvature is relatively easy to manufacture, which helps to reduce costs.

[0048] The free end portion 3a may be substantially flat.The recess 4 for the tool may have any shape (polygonal, torque-shaped or any other shape) in order to provide a form-locking connection with the tool.

[0049] The following will refer to Figures 6 to 9bThe pressure member 6 is described in more detail. The pressure member 6 of this embodiment is a unitary piece. It has a first end or top end 6a and a second end or bottom end 6b. There is an upper portion 61 near the top end 6a, which can be basically cylindrical and has an outer diameter that enables it to move in the axial direction in the channel 51 of the receiving member 5. A rod receiving recess 62 is formed at the top end 6a, which provides a rod supporting surface. The lower part of the recess 61 can have a basically V-shaped cross-section, and its longitudinal axis extends basically perpendicular to the cylindrical axis of the pressure member 6, when the pressure member is in the receiving member 5, the cylindrical axis coincides with the central axis C of the receiving member 5. The depth of the recess 62 can be less than the diameter of the rod 100. Therefore, when the rod 100 rests on the supporting surface, it protrudes above the top end 6a of the pressure member 6, for example as Figure 3 The V-shape of the rod bearing surface allows the use of rods with different diameters.

[0050] The lower part 63 of the pressure member 6 comprises a tapered (preferably conical) outer surface, which is arranged to cooperate with the narrow part 51a of the receiving member at its lower area 63a near the bottom end 6b. A head receiving recess 64 is formed in the lower part 63, which extends from the bottom end 6b to a certain distance from the bottom 62a of the rod receiving recess 62. The head receiving recess 64 comprises a lower part 64a near the bottom end 6b, which has a substantially hollow spherical shape, and the radius of the spherical shape matches the radius of the first curved portion 31 of the head 3. Moreover, the uppermost part 64b of the head receiving recess 64 is also hollow spherical, having the same radius as the lower part 64a. In this way, the lower spherical part 64a and the upper spherical part 64b provide a spherical support for the first curved portion 31 of the head 3, thereby forming a seat in which the head 3 can pivot. Between the two spherical parts 64a, 64b, an intermediate part 64c is provided, which forms a cutout and has a larger inner diameter than the lower end of the upper spherical part 64b. In more detail, the intermediate widened part 64c widens, for example, in a substantially flat step from the lower end of the upper spherical part 64b, and continues to increase the inner diameter, for example, in a conical shape, until it matches the inner diameter of the lower spherical part ( Figure 9a , 9b ). By forming the step and the edge 65, the edge 65 is preferably rounded. Since the edge 65 is determined at the boundary of the spherical portion, the inner surface of the head receiving recess 64 can be formed without substantially protruding a single protrusion from the head contact surface of the spherical portions 64a and 64b to the inside.

[0051] In addition, the lower part 63 of the pressure member comprises a flexible wall portion 66 which is separated by an axial slot 67 which is open towards the bottom end 6b. In order to obtain a certain degree of flexibility, the slots 67 may widen towards their closed ends 67a. The slots 67 may preferably extend in the axial direction up to the transition between the middle portion 64c and the uppermost spherical segment-shaped portion 64b.

[0052] The dimensions of the head receiving recess 64 and the portion formed therein are such that, when the head 3 is inserted, the free end 3a of the head 3 protrudes into the upper spherical portion 64b. Then, a gap 68 is formed between the outer surface of the head 3 and the inner surface of the middle portion 64c of the head receiving recess 64. Moreover, the dimensions of the head 3 and the lower portion 63 of the pressure member (which includes the head receiving recess 64) are such that the head can be inserted through the bottom end 6b by opening the flexible wall portion 66 until the upper portion of the head 3 abuts against the edge 65. This connection is similar to a snap-fit ​​connection. When the head 3 is received in the head receiving recess 64, it is held in the head receiving recess 64 by friction by the flexible wall portion 66 before locking is performed (for example by the locking element 7).

[0053] The pressure member also includes an elongated recess 69 formed in the side wall of the rod receiving recess 62. The elongated recesses 69 are oriented so that their long sides are substantially parallel to the central axis C. Figure 3 As shown in FIG. 6 , the elongated recess 69 extends through the entire side wall and is arranged to receive the pin 57. Thus, when the pressure member 6 is mounted on the receiving member 5, it can be fixed in its rotational position by the pin 57 extending into the elongated recess 69. Moreover, the upward movement of the pressure member 6 relative to the receiving member 5 towards the first end 5a is limited by the pin 57 abutting against the bottom end 69a of the recess 69.

[0054] Finally, the pressure member 6 has a coaxial hole 60 for allowing access to the head 3 , more particularly to the recess 4 of the bone anchoring element 1 , by a tool.

[0055] The components and parts of the bone anchoring device can be made of any material, but preferably titanium or stainless steel or any biocompatible metal or metal alloy or plastic material. As a biocompatible alloy, a NiTi alloy can be used, such as Nitinol. Other materials can be magnesium or a magnesium alloy. The biocompatible plastic material used can be, for example, polyetheretherketone (PEEK) or poly-L-lactide acid (PLLA). The components can be made of the same or different materials from each other.

[0056] In use, the bone anchoring element 1 can first be inserted into a prepared hole in a bone or in a vertebra, and the receiving part 5 with the preassembled pressure member 6 can be mounted on the head 3. Alternatively, the bone anchoring device is preassembled in such a way that the receiving part 5 with the pressure member 6 is already mounted on the head 3. For mounting, the head 3 is inserted from the lower end 5a of the receiving part when the pressure member 6 is in the uppermost insertion position in which the pin 57 abuts against the lower end 69a of the elongated recess 69. Once the head 3 is inserted, the pressure member 6 moves downwards until the lower outer tapered portion 63a enters the narrowed portion 51a of the receiving part 5 and exerts a compressive force on the head 3. Also, in this state, the head 3 cannot be removed through the lower opening 52.

[0057] As long as the bone anchoring device has not yet been finally locked by inserting a rod and fixing the rod with the locking element 7, the receiving part 5 and the bone anchoring element 1 can be pivoted relative to each other so that the bone anchoring element 1 can assume various angular positions of the shank axis S relative to the central axis C of the receiving part. Depending on the strength of the friction grip of the head 3, any position can be temporarily maintained before locking. This can be done without inserting a rod and a locking element 7.

[0058] In this embodiment, the predetermined position may be a position where the handle axis S and the central axis C of the receiving component coincide with each other, such as Figure 3 and 11 In other words, the bone anchoring element assumes a zero angle position relative to the receiving part 5. Positions different from the zero angle position are Fig.10 and 12 When the bone anchoring element 1 is in an angular position different from the zero angular position, the edge 65 contacts the second curved portion 32 of the head 3 on the side opposite to the side to which the handle is pivoted. Then, when the head 3 is pivoted relative to the receiving part 5 toward the zero angular position, which is at the zero angular position, the edge 65 contacts the second curved portion 32 of the head 3 on the side opposite to the side to which the handle is pivoted. Figure 3 and 11 ), the edge 65 moves along the outer surface of the head 3 from the second curved portion 32 with a smaller radius to the first curved portion 31 with a larger radius, thereby passing through the transition portion. During the movement, the pressure member can expand slightly until the first curved portion 31 contacts the upper spherical portion 64b. The transition portion from the smaller radius to the larger radius acts in a ramp-like manner and generates tactile feedback to the user. The user can experience the slope change until the zero angle position is reached, or leave it again by pivoting to another angle position. Since the position indication structure provided by the different curved portions is rotationally symmetrical, feedback is generated when pivoting in any direction.

[0059] Once the right angular position has been found, the entire structure is locked by inserting the rod and the fixing element 7 and tightening it.

[0060] The following will refer to Figures 13 to 16 A second embodiment of a polyaxial bone anchoring device will now be described. The polyaxial bone anchoring device according to the second embodiment differs from that of the first embodiment in the shape of the bone anchoring element and the pressure member. The receiving member is identical to that of the first embodiment. Identical or highly similar components are denoted by the same reference numerals and will not be described repeatedly. The bone anchoring element 1' has a head 3' having a spherical segment-shaped portion 31' which may include a portion having a maximum diameter E and connects to the neck portion 21. The spherical outer surface is interrupted by a conical portion 34. The conical portion 34 tapers toward the neck portion 21. The conical portion 34 is located closer to the neck portion 21 (compared to the free end surface 3a). More specifically, the conical portion 34 is located in the lower portion of the head 3', i.e. sandwiched between the portion having a maximum diameter E and the spherical portion adjacent to the neck portion 21. The axial extension of the conical portion 34 may be much smaller than the axial extension of the entire spherical segment-shaped portion 31'. The axial length can be so large that there is still enough spherical surface for allowing pivoting. In particular, it can be, for example, less than one third of the axial length of the spherical segment-shaped part 31 ', or even less than one quarter.

[0061] The pressure member 6' is identical to the pressure member of the previous embodiment, except that it comprises a mating conical portion for engaging with the conical portion 34 of the head 3'. Fig.15 and 16 As shown in the figure, the conical portion 64d is formed in the lower spherical portion 64a of the head receiving recess 64. The conical portion 64d can have the same cone angle as the conical portion 34 of the head 3' and can have the same axial extension. However, the axial extension can also be smaller than the axial extension of the conical portion 34 of the head 3'. The conical portion 64d extends completely circumferentially in the inner wall of the head receiving recess 64 and is at such a height that it matches the conical portion 34 of the head 3' in the zero angle position.

[0062] In use, when the head 3' is inserted into the pressure member 6' in the receiving member 5 and the pressure member moves downward so that the outer conical portion 63a of the pressure member and the narrow portion 51a of the receiving member engage to clamp the head, the head is captured in the head receiving recess 64 so that the spherical segment-shaped portion 31' contacts the spherical portions 64a and 64b of the head receiving recess 64 to allow the bone anchoring element to pivot. When the bone anchoring element 1' is in the zero angle position, as shown in FIG. Fig.15 As shown in FIG. 1 , the conical portion 34 of the head 3 'is engaged with the 64d of the pressure member 6 '. In this way, the zero angle position will be automatically centered. When the bone anchoring element is pivoted to an angle position different from the zero angle position, such as Fig.16 As shown in FIG, the conical portion 34 of the head 3' and the 64d of the pressure member are substantially not engaged. Entering or leaving the zero angle position will generate feedback, preferably tactile feedback to the user. Therefore, the zero angle position can be easily identified.

[0063] It should be noted that Figures 13 to 16 The bone anchoring element 1' shown in FIG. 1 does not have a second curved portion 32 near the free end surface 3a, which has a smaller radius in the previous embodiment. However, it is conceivable that the bone anchoring element 1' also has a second curved portion 32 with a smaller radius, as in the first embodiment.

[0064] The following will refer to Figures 17 to 20b A third embodiment of a polyaxial bone anchoring device is presented.

[0065] The polyaxial bone anchoring device according to the third embodiment differs from the polyaxial bone anchoring devices according to the first and second embodiments in the shape of the bone anchoring element, more specifically in the shape of the head of the bone anchoring element. Components and parts that are identical or highly similar to those of the previous embodiments are denoted by the same reference numerals and will not be described repeatedly. The bone anchoring element 1 '' comprises a head 3 '' having an overall spherical segment-shaped portion 31 '', as in the second embodiment. The spherical segment-shaped portion 31 '' may include a portion having a maximum diameter E. A groove 35 is formed at a distance from the free end 3a, the groove 35 extending circumferentially and concentrically around the central axis. The groove 35 may have a circular inner contour, such as a spherical contour. Moreover, the groove 35 is relatively small and shallow. In particular, the depth of the groove 35 may be such that it is sufficient to produce a transition portion between the spherical outer contour of the spherical segment-shaped portion 31 '' and the groove 35. The axial position of the groove is such that the groove 35 is closer to the free end 3a than the neck portion 21. As shown in the figures, it may be at a distance from the free end 3a which is approximately the same as the width of the groove in the axial direction or only slightly larger.

[0066] In use, when the head 3'' is inserted into the head receiving recess 64 of the pressure member 6, the head 3'' abuts against the upper spherical segment 64b of the pressure member when the pressure member 6 is in the receiving member and moves downwards so that the lower outer conical portion 63a of the pressure member 6 engages with the narrow portion 51a of the receiving member to clamp the head. Fig.19a and 19b As shown in FIG. 1 , when the bone anchoring element is in the zero angle position, the edge 65 protrudes slightly into the groove 35. Therefore, the bone anchoring element 1 ″ is slightly kept in the zero angle position. When the bone anchoring element 1 ″ is pivoted, as shown in FIG. Fig.20a and 20bAs shown in , the edge 65 moves away from the slot 35. This provides feedback to the user, such as tactile feedback. Similarly, when the edge 65 enters the slot 35, such feedback is generated. The feedback can be a tactile resistance. Therefore, when moving to the zero angle position, feedback is provided to the user, and the user can easily identify the zero angle position.

[0067] It should be noted that the head may additionally have a conical surface, as in the second embodiment, and the pressure member may additionally have a conical surface, as in the second embodiment.Alternatively or additionally, the head may have an additional portion with a smaller radius, as in the first embodiment.

[0068] Variations of the above-described embodiments can be envisioned. Features of one embodiment can be combined with features of other embodiments to provide various other embodiments. The receiving component is not limited to the receiving components of the various embodiments shown. Because the interaction is only between the head and the pressure component, all known receiving components can be used and suitable bone anchoring elements and pressure components with first and second position indicating structures can be assembled. The position indicating structures are not limited to indicating only the zero position. They can also be used to indicate a predetermined position in which the handle takes an angle that is not zero relative to the receiving component. In this case, the position indicating feature can be in other positions.

[0069] Although the head is shown as a spherical head and the pressure member is shown as having a spherical head receiving recess, the bone anchoring device is not limited thereto. It is contemplated that the head and the pressure member are shaped to allow angulation only in one or more different planes.

Claims

1. A bone anchoring device, comprising: An anchoring element (1, 1', 1") having a stem (2) for anchoring in a bone and a head (3, 3', 3"); a receiving part (5) arranged to receive the head (3) of the anchoring element in a pivotable manner so that the handle (2) can adopt a plurality of angular positions including predetermined angular positions relative to the receiving part, the receiving part having a channel (51) defining a central axis (C); a pressure member (6, 6') arranged to exert pressure on the head (3, 3', 3'') in order to clamp the head in the receiving member, the pressure member being arranged at least partially in the channel, wherein the head (3, 3', 3'') comprises an outer surface portion, the outer surface portion defining a first position indicating structure, the first position indicating structure being arranged to engage with a second position indicating structure of the pressure member (6); The first position indicating structure or the second position indicating structure comprises a transition portion (33) between a first curved portion (31) defining a first curvature and a second curved portion (32) defining a second curvature different from the first curvature; wherein the first curved portion (31) is associated with a first radius and the second curved portion (32) is associated with a second radius, wherein the first radius is different from the second radius; and When the first position indicating structure and the second position indicating structure engage with each other and the head is pivoted from one of the plurality of angular positions to the predetermined angular position, the second position indicating structure or the respective other of the first position indicating structure passes through the transition portion to provide an indication of the predetermined angular position of the handle (2) relative to the receiving part (5).

2. The bone anchoring device according to claim 1, wherein: The first position indication structure comprises a transition portion (33).

3. The bone anchoring device according to claim 1 or 2, wherein: The curvature of the first curved portion (31) is smaller than the curvature of the second curved portion (32).

4. The bone anchoring device according to claim 1 or 2, wherein: The transition portion (33) between the first curved portion (31) and the second curved portion (32) is continuous.

5. The bone anchoring device according to claim 1 or 2, wherein: The second curved portion (32) is located close to the free end (3a) of the head (3).

6. The bone anchoring device according to claim 1 or 2, wherein: The second position indicating structure comprises an edge (65) which is arranged to pass through a transition portion (33) between a first curved portion (31) and a second curved portion (32) of the first position indicating structure.

7. The bone anchoring device according to claim 2, wherein: The pressure member (6, 6') comprises a head receiving recess (64) comprising an inner surface facing the inserted head (3), the inner surface defining a second position indicating structure, the inner surface comprising a third curved portion matching the curvature of the first curved portion (31).

8. The bone anchoring device according to claim 7, wherein: The head receiving recess (64) is arranged to receive the head (3, 3', 3'') in a snap-fit ​​manner so that the head is retained in the head receiving recess by friction before locking.

9. The bone anchoring device according to claim 1 or 2, wherein: The first position indication structure or the second position indication structure further comprises a groove (35).

10. The bone anchoring device according to claim 1 or 2, wherein: The first position indication structure further includes a first flat portion, and the second position indication structure further includes a second flat portion configured to engage with the first flat portion.

11. The bone anchoring device according to claim 10, wherein: The first flat portion and the second flat portion are conical.

12. The bone anchoring device according to claim 1 or 2, wherein: The first position indicating structure and the second position indicating structure are rotationally symmetric about respective axes of symmetry (C, S).

13. A bone anchoring device, comprising: An anchoring element (1) having a stem (2) for anchoring in a bone and a head (3'); a receiving part (5) arranged to receive the head (3') of the anchoring element in a pivotable manner so that the handle (2) can adopt a plurality of angular positions including predetermined angular positions relative to the receiving part, the receiving part having a channel (51) defining a central axis, a pressure member (6') arranged to exert pressure on the head in order to clamp the head in the receiving member, the pressure member being arranged at least partially in the channel, wherein the head (3') comprises a spherical segment shaped portion (31'), the spherical segment shaped portion (31') comprising an outer surface portion, the outer surface portion defining a first position indicating structure, the first position indicating structure being arranged to engage with a second position indicating structure of the pressure member (6) so as to provide an indication of a predetermined angular position of the handle (2) relative to the receiving member; The first position indication structure comprises a first conical portion (34), and the second position indication structure comprises a second conical portion (64d), the second conical portion (64d) being arranged to engage with the first conical portion when the head (3') is in a predetermined angular position.

14. The bone anchoring device according to claim 13, wherein: The first conical portion (34) is sandwiched between the two spherical portions of the spherical segment shaped portion (31').

15. The bone anchoring device according to claim 13 or 14, wherein: The first conical portion (34) is located at the underside of the head (3') closer to the shank (2) than the free end (3a) of the head.

16. The bone anchoring device according to claim 1 or 13, wherein: The receiving part (5) comprises a first end (5a) and an opposite second end (5b) and a recess (54) for receiving the rod (100) at the first end, the passage (51) extending through the first end and the second end and forming an opening (52) at the second end, the opening being sized to allow the head (3, 3', 3") to be inserted through the second end (5b).

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