Coupling device and instrument for arranging the coupling device on the head of a bone anchor

Abstract

A coupling device for coupling a rod to a bone anchor comprises a receiving part (20), which includes: a head receiving portion (22) including an internal seat (35) for pivotally receiving a head (3) of the bone anchor, the head receiving portion being expandable to allow the head to be inserted and compressible to lock the inserted head in the seat; a rod receiving portion (21) including a recess (24) forming two open legs (25) and a bottom (24a) defining a channel for receiving the rod, the rod receiving portion including a first engagement structure (32) for engaging with an instrument (100); a locking ring (40) surrounding the head receiving portion and including a second engagement structure (44a) for the instrument; when the locking ring surrounds the head receiving portion, the locking ring can adopt an insertion position and a pre-locking position, in which the head can be inserted into the head receiving portion and in which the inserted head is prevented from being removed from the head receiving portion; when the locking ring is in the insertion position and the first engagement structure is engaged with the instrument, the coupling device (10) is placed on the head.

Description

Technical Field

[0001] The present invention relates to a coupling device for coupling a rod to a bone anchor and to an instrument for arranging the coupling device on the head of the bone anchor. More specifically, the present invention relates to a coupling device and to an instrument that can arrange a receiving part with an external locking ring on the head protruding beyond the bone surface in situ, i.e., when the bone anchor has been inserted into a bone or vertebra. Background Art

[0002] Such a coupling device comprising an external locking ring arranged around a head receiving part is known, for example, from US 2018 / 0055545 A1. The coupling device is part of a polyaxial bone anchoring device, which comprises a receiving part having a rod receiving part and a head receiving part and a locking ring arranged around the head receiving part, which forms a compression part in order to exert pressure on the inserted head. The head receiving part comprises a plurality of slits, which make the head receiving part flexible, so that when pressure is exerted on the head receiving part through the locking ring, the head can be clamped and finally locked. In this document, a device for moving the locking ring from an insertion position of the head to a locking position of the head (and vice versa) is also described. Usually, the bone anchoring device is preassembled with the bone anchor.

[0003] US10258390B2 describes a device for arranging a receiving part of a bone anchoring device on a head of a bone anchoring element, the device comprising: a holding part; a chuck, which is arranged to be held in the holding part, the chuck having a tubular body and a distal part, the distal part being used to flexibly expand and compress in a radial direction; and a plunger, which is arranged to be positioned in the chuck. With this device, the receiving part can be engaged at the inner wall and arranged on a bone anchor that has been inserted into a bone. The bone anchoring device described in this document is of the type that uses an inner cap arranged in the receiving part as a compression part for applying pressure to the head through a rod or a locking part so as to lock the head.

[0004] Although the bone anchoring devices described in the prior art using an inner cap to clamp and lock the head can be suitable for many clinical applications, there is still a need for an alternative and / or improved bone anchoring device that allows the coupling device including the receiving part and the compression part to be arranged in situ on the implanted bone anchor. Summary of the invention

[0005] It is therefore an object of the present invention to provide a coupling device and an apparatus for use with the coupling device which is improved with respect to known devices.

[0006] This object is achieved by the coupling device according to the invention, by the apparatus according to the invention and by the system of coupling device and apparatus according to the invention. Further developments are given in the dependent claims.

[0007] The coupling device is of the type that uses an external locking ring as a compression member in order to apply pressure to the head and can be arranged in situ on a bone anchor inserted in a bone or in a vertebra. This in situ arrangement needs to be done carefully to avoid injuries due to the application of too much force. The instrument provides a handheld device that can arrange the coupling device in situ. This can be done gently without applying excessive forces that could cause injury. In particular, in spinal surgery, this procedure is very advantageous.

[0008] Moreover, the coupling device can be temporarily locked once arranged on the head of the bone anchor without the need for a rod or a locking member. The rod can even be inserted and does not need to be placed on the rod support, but can be in an elevated position. Thus, by moving the locking ring from the locking position to the pre-locking position (and vice versa), the bone anchoring device can be locked and unlocked so that a variety of adjustment steps can be performed. Only for the final locking at the end of the surgical treatment process is the presence of the rod and / or the locking member necessary. Thus, the possibility of arranging the coupling device in situ with a temporary and / or variable locking of the head will increase the variety of correction steps that can be performed during the operation.

[0009] With this instrument, the locking ring can be moved to a pre-locking position after being arranged on the head of the bone anchor. In this way, once the coupling device is coupled to the head of the bone anchor, the coupling device is prevented from being removed from the head of the inserted bone anchor. Thus, the instrument can be safely disassembled.

[0010] According to an embodiment, the coupling device is arranged to engage with the instrument at the inner wall of the leg of the rod channel. Since the receiving part does not engage with the instrument on the peripheral outer surface, the space required for arranging the coupling device on the head of the bone anchor that has been inserted into the bone can be reduced. This allows access to the implantation site using a narrow channel through human tissue. Therefore, the instrument and the coupling device can be particularly applied in minimally invasive surgery (MIS).

[0011] Furthermore, according to an embodiment, the arms of the instrument are resiliently flexible, which gives a tactile response when attaching the instrument to the coupling device. This facilitates attaching the instrument to the coupling device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Other features and advantages of the present invention will become apparent from the following description of embodiments with reference to the attached drawings.

[0013] In the attached figure:

[0014] Figure 1A perspective view of a portion of a spinal column with implanted bone anchors and an instrument according to one embodiment attached to a coupling device according to one embodiment is shown.

[0015] Figure 2 It indicated Figure 1 The enlarged part.

[0016] Figure 3 A cross-sectional view of an embodiment of a coupling device and an instrument arranged on the head of a bone anchor is shown, wherein the section is taken along a plane including a central longitudinal axis of the instrument and perpendicular to the center of the legs of the receiving part.

[0017] Figure 4 It indicated Figures 1 to 3 A perspective view of the receiving part of the coupling device from the top.

[0018] Figure 5 It indicated Figure 4 A perspective view of the receiving component from the bottom.

[0019] Figure 6 It indicated Figure 4 and 5 A top view of the receiving component.

[0020] Figure 7 It indicated Figures 4 to 6 The receiving component along Figure 6 Sectional view along line AA.

[0021] Figure 8 It indicated Figures 1 to 3 A perspective view of the locking ring of the coupling device as seen from the top.

[0022] Fig. 9 It indicated Figure 8 A perspective view of the locking ring from the bottom.

[0023] Fig.10 It indicated Figure 8 and 9 Top view of the locking ring.

[0024] Fig.11 It indicated Figures 8 to 10 Locking ring edge Fig.10 Cross-sectional view of line BB in .

[0025] Fig.12 It indicated Figures 1 to 3 A perspective view of the front portion of the apparatus.

[0026] Fig.13 Expressed as Fig.120026] A cross-sectional view of a front portion of the instrument shown in FIG. 1 , the section being taken along a plane including a central longitudinal axis of the instrument and extending through the center of the arm of the instrument.

[0027] Fig.14 Expressed as Figures 12 to 13 0014] A perspective view from the top of an end portion of a holding component of the instrument shown in FIG.

[0028] Fig.15 It indicated Figures 12 to 14 A perspective view of the holding component of the instrument as seen from the bottom.

[0029] Fig.16 It indicated Figures 12 to 15 Side view of the retaining component of the instrument.

[0030] Fig.17 Expressed as Fig.16 , the section including the central longitudinal axis of the instrument and extending through the center of the arm.

[0031] Fig.18 It indicated Figures 12 to 13 A perspective view of the front portion of the pusher component of the instrument as seen from the top.

[0032] Fig.19 It indicated Fig.18 A perspective view of the push component from the bottom.

[0033] Fig. 20 It indicated Fig.18 and 19 A side view of the front portion of the push member shown in FIG.

[0034] Figures 21a to 21d A side view showing the steps of attaching the instrument to the coupling device.

[0035] Fig. 22 A perspective view showing the step of fastening the front part of the instrument to the coupling device.

[0036] Fig.23 A perspective view showing the step of adjusting the pre-locking position of the locking ring relative to the receiving part using an instrument.

[0037] Figures 24a to 24c The steps of arranging the coupling device on the head of the bone anchor inserted into the bone using an instrument are shown.

[0038] Fig.25 A perspective view of a portion of a spinal column with an inserted bone anchor and coupling device and an attached further instrument for locking the coupling device relative to the bone anchor is shown. DETAILED DESCRIPTION

[0039] Figures 1 to 3 A first embodiment of a coupling device 10 is shown for engagement with an instrument 100 for arranging the coupling device on the head of a bone anchor. According to an embodiment, the bone anchor 1 may have been inserted into a bone, such as a pedicle of a vertebra 500, before the coupling device is mounted on the bone anchor 1. The bone anchor 1 comprises a handle 2 and a head 3, the handle 2 being configured to be anchored into the bone. The handle 2 may have a bone anchoring structure on at least a portion thereof, such as a bone wire or a barb or any other suitable structure for anchoring. The head 3 may have a spherical outer surface portion. For example, the head 3 may have a size such that it includes the maximum outer diameter of a sphere. An engagement recess 4 may be provided at the free end of the head 3 for engagement with a screwdriver. The coupling device 10 is configured to couple the bone anchor 1 to a rod (not shown) which is configured to be inserted and fixed in the coupling device. As shown in Figure 3 As can be seen in particular in the figure, the coupling device 10 comprises a receiving part 20 and a locking ring 40. The receiving part is used to accommodate the head 3 and to receive a rod (not shown). The locking ring 40 is configured to clamp and / or lock the head 3 in the receiving part 20. The bone anchor 1 and the coupling device 10 form a polyaxial bone anchoring device that is configured to allow a rod to be coupled to the bone anchor in a plurality of angular positions of the bone anchor.

[0040] Additional references Figures 4 to 7 , the receiving part has a first or upper end 2a and a second or lower end 2b. A longitudinal center axis C extends from the upper end 2a to the lower end 2b. The receiving part includes a rod receiving portion 21 near the upper end 2a and a head receiving portion 22 near the lower end 2b. The rod receiving portion 21 is substantially cylindrical, thereby defining a center axis C, and has a channel 23 extending from the upper end 2a into the head receiving portion 22. The channel 23 may have regions of different diameters and / or shapes. In this embodiment, the first region 23a may be a coaxial hole with a first diameter extending from the top end 2a to a distance from the head receiving portion 22. The first region 23a may be followed by a narrower second region 23b, which may be followed by a third region 23c with an even smaller diameter, which opens into the head receiving portion 22. A step 23d may be provided between the first region 23a and the second region 23b. Similarly, a step 23e may be provided between the second region 23b and the third region 23c. In addition, two opposite axially extending cylindrical segment-shaped recesses 39 may be formed in the second portion 23b, such as Figure 4 This notch 39 serves as a guide structure for a portion of the instrument 100. It should be noted that the detailed shape of the channel may vary from the embodiment shown.

[0041] A substantially U-shaped recess 24 with a bottom 24a extends from the top end 2a to a distance from the head receiving portion 22. Two free legs 25 are formed by the substantially U-shaped recess 24. The recess 24 provides a channel for receiving a rod. An internal thread 26 is provided on the leg 25 and extends substantially from the upper end 2a to a distance from the bottom 24a of the recess 24. In other words, the internal thread 26 is provided substantially along the first region 23a of the channel. The internal thread 26 may be, for example, a square thread, which may help prevent the leg 25 from spreading. An undercut portion 26a may be formed at the lower end of the internal thread 26, facing the head receiving portion 22. A groove or otherwise weakened portion 27 is provided at a distance from the upper end 2a, which groove or otherwise weakened portion 27 has a reduced wall thickness and allows breaking off the upper portion of the leg 25. A circumferentially extending notch or cutout 27a may be formed at the edge of the weakened portion 27 in the circumferential direction, which further weakens the weakened portion 27 and can facilitate the breaking off of the upper portion of the leg 25. Also, the internal thread 26 may be interrupted inside the channel 23 at an axial position corresponding to the lower edge of the weakened portion 27. Thus, the leg above the weakened portion 27 may act as an extended tab. With this extended tab, the polyaxial bone anchoring device with an inserted rod may be manipulated, which may be in a higher position relative to the bottom 24a of the notch 24. For example, a vertebra may thereby be pulled against the rod.

[0042] A rod receiving portion 21 may be provided on its outer surface for contact with an instrument (eg Fig.25 The invention relates to an engagement structure for engaging with a rod receiving part 20 (the device 300 shown in FIG. 1 ). The engagement structure may include circumferentially extending ribs 28, which may be arranged asymmetrically relative to a plane containing the central axis C of the receiving part 20 and the channel axis L of the substantially U-shaped recess 24. This means that the first rib starts at a distance from the edge of the U-shaped recess 24 on one side and extends a distance around the receiving part 20. The second rib starts at the opposite side relative to the U-shaped recess and extends a distance around the rod receiving part from there. Therefore, a ribless surface 29 is formed on each side of the U-shaped recess 24. Under each rib 28, a substantially flat outer surface portion 30 may be formed, which may have a rectangular or square profile and may be used to engage with a portion of the locking ring 40. Between the rib 28 and the substantially flat surface portion 30, two latching grooves or steps 31a, 31b may be arranged one after another in the axial direction. The latching grooves 31a, 31b are arranged to cooperate with a portion of the locking ring 40 so as to temporarily hold the locking ring in a specific position. The upper latching groove 31a can be used to prevent the locking ring in the inserted position from moving further upward. The lower latching groove 31b can be used to lock the locking ring 31b in the pre-locking position.

[0043] An engagement structure 32 for engaging with the instrument 100 may be provided at a position between the weakened portion 27 and the bottom 24a of the substantially U-shaped recess 24. The engagement structure 32 may be formed as a shallow circular groove, preferably in a substantially cylindrical shape, and may be located at the edge of the leg 25. Four such grooves may be provided, two on each leg 25, one on each side of each leg 25. The axial position of the engagement structure 32 may be slightly lower than the weakened portion 27. Preferably, the engagement structure 32 is shaped such that a corresponding engagement portion of the instrument 100 that fits it can slide into the engagement structure 32 and can slide out of the engagement structure 32. More specifically, the engagement portion of the instrument can be elastically snapped into the engagement structure 32.

[0044] Furthermore, a cutout 33 may be provided on either side of the substantially U-shaped recess 24, which cutout 33 may be used to receive therein a projection of a locking ring 40. Thus, the locking ring 40 may be fixed against rotation relative to the receiving member 20. From a position above the cutout 33 to the lower end 2b, the outer diameter or width of the rod receiving portion 21 decreases to form a step 34, which serves as a further abutment for the locking ring.

[0045] The head receiving portion 22 has a substantially hat-like shape with a hollow substantially spherical inner portion 35 forming a seat for pivotably receiving the head 3 therein. A plurality of slits 36a, 36b make the head receiving portion 22 flexible so that when the head 3 is inserted into the hollow inner portion 35, the head receiving portion 22 expands. When pressure is applied to the inserted head 3 through the locking ring 40, the head receiving portion 22 compresses. The slits open toward the lower end 2b and extend along the spherical portion. The slits 36a terminate at the end of the spherical portion, while the other slits 36b may extend into the region of the rod receiving portion including the third region 23c of the passage 23. The outer surface of the head receiving portion 22 may be concave in a radial direction relative to the lower end of the rod receiving portion 21. The outer surface may include a bottom portion 37a which may be cylindrical or slightly tapered outwards. The bottom portion 37a forms an annular protrusion which is arranged to cooperate with a corresponding portion of the locking ring 40. The bottom portion 37a is followed by a circumferential groove and a radially outwardly projecting portion 37b which is arranged to cooperate with another portion of the locking ring 40. The projecting portion 37b narrows in the direction towards the rod receiving portion, which provides the head receiving portion 22 with a concave shape.

[0046] The following will refer to Figures 8 to 11Introducing the locking ring 40, the locking ring 40 is designed to surround the head receiving portion 22 and has an inner surface structure that allows the locking ring to cooperate with the head receiving portion 22 to achieve complete locking of the inserted head 3 in the head receiving portion 22 when the locking ring is in its lowermost position. It also allows pre-locking to be achieved when the locking ring is in a position slightly higher than the lowermost position, which still allows the head 3 to pivot in the head receiving portion 22, but prevents the head 3 from moving out of the head receiving portion 22. Finally, the locking ring is used to allow the head 3 to be inserted into the hollow interior 35 when the locking ring is in the uppermost position relative to the receiving part.

[0047] In more detail, the locking ring 40 has a lower surface 4b and an opposite substantially annular upper surface 4a. A first radial projection 41 facing inwards is adjacent to the lower surface 4a, and the first radial projection 41 is arranged to cooperate with the outer portion 37a at the head receiving portion. The annular projection 41 is followed by a widened portion 42, which is followed by a second annular projection 43 that projects inwards (in the direction toward the upper surface 4a). Figure 3 As shown in FIG. 1 , when the locking ring 40 is mounted around the head receiving portion 22 , the first annular protrusion 41 is arranged to press on the first portion 37 a of the head receiving portion, and the second annular protrusion 43 is arranged to press on the protruding portion 37 b.

[0048] Two projections 44 project from the upper surface 4a of the annular portion of the locking ring 40, the two projections 44 having free end surfaces which form rod support surfaces 44a for the stabilizing rod. The projections 44 are diametrically opposed, i.e. offset by 180 degrees. o . The rod supporting surface may have a substantially V-shaped cross-section so that rods of different diameters may be safely supported. When the locking ring 40 is mounted on the receiving part 20 with the upper surface 4a facing the upper end 2a of the receiving part, the protrusion 44 may extend through the cutout 33, thereby ensuring the rotational direction of the locking ring 40 relative to the receiving part 20. The locking ring 40 further comprises two vertical arms 45. The two vertical arms 45 are positioned asymmetrically relative to a plane extending through the central axis C and through the middle of the rod supporting surface 44a in the same manner as the ribs 28 of the rod receiving part 21 of the receiving part 20. At the upper end of the arm 45, an engagement portion in the form of a circumferential rib 46 defining a groove 46a is provided for engagement with an instrument. Such an instrument may be, for example, a Fig.25. The inwardly facing upper edge 45a of the arm 45 can be arranged so that it is used to engage with the latch grooves 31a, 31b at the receiving part 20. In the assembled state, the engagement structure in the form of a rib 46 with a groove 46a is aligned with the engagement structure 28 at the receiving part 20, so that the ribless surface 29 of the receiving part 20 is exposed. Moreover, the arm 45 has a substantially flat inner wall, which is arranged to engage with the flat portion 30 at the rod receiving part 21. Thus, another form-fitting connection is established between the locking ring 40 and the receiving part 20. Between the protrusion 44 and the arm 45, there is a vertical flexible portion 47, the height of which is slightly greater than the height of the protrusion 44 and includes a ledge 47a at its inner wall. The ledge 47a is arranged to abut against the step 34 on the receiving part 20.

[0049] The bone anchoring device according to an embodiment may further include a rod configured to be inserted into the substantially U-shaped recess 24 and a locking member, such as a fixing screw, for being threadedly coupled between the legs 25 .

[0050] The following will refer to Figures 12 to 20 An embodiment of an instrument 100 for arranging the coupling device 10 on the head 3 of the bone anchor 1 is described in more detail. Figure 1 As shown in , the instrument 100 comprises a substantially tubular holding member 101 and an axial pushing member 120 arranged inside the holding member 101. The holding member 101 comprises a rear portion and a front portion, the rear portion being connected to or provided with a handle 102. The front portion is bifurcated by a narrow slot 104, so that it comprises two arms 105, which are arranged to be flexibly compressed and expanded in a transverse direction relative to the longitudinal tube axis T of the holding portion. The narrow slot 104 extends from the free end portion 101a of the holding member 101 in a substantially U-shaped manner, and its bottom faces the rear end of the holding member. The substantially straight portion 104b is continuous from the bottom of the narrow slot and opens to the elongated portion 104c. It should be noted that the narrow slot can have different shapes for obtaining different degrees of flexibility.

[0051] The arm 105 has a front portion 105a adjacent to the free end portion 101a. The front portion 105a is recessed from the overall cylindrical shape of the retaining member so as to fit into the rod receiving portion of the receiving member 20. By the recessed structure of the front portion 105a of the arm 105, an abutment surface 106 is provided at the end of the front portion 105a, which can abut against the upper end 2a of the receiving member when the front portion 105a of the arm is inserted into the rod receiving portion. The front portions 105a of the arm each have a notch 107 adjacent to the free end 101a, which can be substantially rectangular. Two shorter legs 107a are formed on each front portion 105a of the arm 105 by the notch 107. This design allows the front portion 105a of the arm to extend downwardly into the lowest region of the substantially U-shaped notch 24. The outer surface of the front portion 105 a includes an axially extending, substantially cylindrical segment-shaped rib or projection 108 that is configured to engage with a cylindrical recess 39 in the second portion 23 b of the rod receiving portion 21 .

[0052] Furthermore, at a distance from the abutment surface 106, each arm 105 comprises an engagement portion 109 which is arranged to engage with the engagement structure 32 at the rod receiving portion 21. In more detail, the engagement portion 109 can be formed as a cylindrical protrusion having a cylindrical axis transverse to the longitudinal axis T of the retaining portion and arranged and configured to engage with the groove 32. In particular, Fig.12 and 14 As shown in FIGS. 1 to 15 , each front portion 105 includes two engagement portions 109 located on the left and right sides of the axial cylindrical protrusion 108. The arm 105 may be substantially flat at its outer surface (except in the area of ​​the axial protrusion 108 and the engagement portion 109). At the inner wall of the front portion 105a, a coaxially extending cylindrical recess 110 is formed in an area adjacent to the recess 107, which provides a guide for the push member 120. Near the recess 110, the front portion 105a of the arm may include a widened diameter portion 111 on their inner side so as to provide sufficient space for allowing the push member 120 to slide through. A step portion 111a is formed between the recess 110 and the widened diameter portion 111, which step portion 111a may form an abutment for a step portion at the outer surface of the push member, as described later.

[0053] The following will specifically refer to Figures 18 to 20 Now, let's introduce the pushing member 120. Figure 1As shown in the figure, the pushing member 120 can be connected to a knob 121 at its rear side, and the knob 121 is used to move the pushing member 120 in the holding member 101. A mechanism (not shown) can be additionally accommodated in the handle 102, which converts the rotational movement of the knob 121 into an axial displacement of the pushing member 120 relative to the holding member 101. Various mechanisms can be considered to move the pushing member 120 relative to the holding member. For example, the mechanism can be designed so that by rotating the knob 121, the pushing member 120 can be pushed axially to the maximum position relative to the holding member, and when the knob 121 is further rotated, it will retract from the maximum axial position.

[0054] The front portion of the push member 120 is Figures 18 to 20 The push member 120 comprises a first substantially cylindrical portion 122 near the free end 120a, the outer diameter of which is adapted to fit in the axial cylindrical recess 110 at the inner wall of the front portion 105a of the retaining member (see also Fig.13 ). An elongated engagement portion 123 is adjacent or close to the free end 120a, the engagement portion 123 extending transversely to the longitudinal axis T, in particular perpendicularly to the longitudinal axis. In the embodiment shown, the elongated engagement portion 123 has a rod shape and can be realized by a pin extending through a transverse hole in the front portion 122. The length of the elongated engagement portion 123 is at least greater than the distance between the protrusions 44 on the locking ring 40, so that the rod bearing surface 44a of the protrusion 44 can engage with the elongated engagement portion 123. In other words, the elongated engagement portion 123 forms a kind of virtual rod, which is used to push on the rod bearing surface 44a. A second portion 124 of slightly larger outer diameter can be arranged near the first cylindrical portion 122, so that a shoulder 122a is formed between the second portion 124 and the first portion 122. The shoulder is used to abut against the stepped portion 111a on the inner side of the retaining member 101. The length of the second portion can be such that it extends further into the retaining member (compared to the length of the front portion 105a of the arm). Furthermore, for greater stability, a third portion 125 having a larger diameter may be provided.

[0055] The front portion 105a of the arm is arranged to be inserted into the rod receiving portion 21 and is dimensioned such that when the abutment surface 106 abuts against the upper end 2a of the receiving part 20, the leg 107a extends to a short distance from the bottom 24a of the substantially U-shaped recess 24 of the receiving part 20. In this position, the engagement portion 109 is at an axial height that can engage with the engagement structure 32 at the receiving part.

[0056] The components and parts of the bone anchors, coupling devices and instruments can be made of any material, but preferably a biocompatible material, such as titanium or stainless steel or any other biocompatible metal or metal alloy, or a plastic material. As a biocompatible alloy, a NiTi alloy can be used, such as Nitinol. Other materials can be magnesium or magnesium alloys. The biocompatible plastic material used can be, for example, polyetheretherketone (PEEK) or poly-L-lactide acid (PLLA). A component can be made of the same or different material as another component.

[0057] The following will refer to Figures 21a to 24c The use of the coupling device 10 and the instrument 100 will be described. First, the steps of assembling the coupling device 10 and the instrument 100 will be described. The coupling device includes a receiving part 20 and a locking ring 40 in a preassembled manner. Fig.21a , the push member 120 is in a retracted position further away from the free end portion 101a of the retaining member than the engagement portion 109. The locking ring 40 is mounted on the receiving member so that the protrusion 44 engages with the notch 33 of the receiving member. To engage with the instrument 100, the locking ring 40 is in an insertion position in which the edge 45a of the arm 45 abuts against the latch step 31a at an axially higher position. In the insertion position, the head 3 can enter the hollow interior 35 of the head receiving portion 22. The distance of the front portions 105a of the arms 105 is such that when the front portions of the arms are introduced between the legs 25, the front portions 105 are compressed towards each other.

[0058] like Figure 21b As shown in FIG. 1 , when the front portions 105 a of the arms are compressed toward each other by the inner walls of the legs 25, the front portions 105 can be advanced deeper into the channel 23. When the engagement portion 109 at the outer wall of the front portion 105 a of the arm reaches the engagement structure 32 at the receiving part 20, the engagement portion 109 snaps into the engagement structure 32, as shown in FIG. Fig.21c The holding part 101 is fixedly connected to the receiving part 20 because the front part 105a of the arm 105 is prevented from being compressed inwardly. As a result, the coupling device 10 is fixedly connected to the instrument. Fig.21d The fixed connection between the retaining member 101, the receiving member 20 and the pushing member 120 is shown in the forward pushed position in which the elongated engagement portion 123 contacts the rod bearing surface 44a.

[0059] Fig. 22 and 23 A more detailed perspective view of the position of the push member 120 relative to the holding member 101 is shown. Fig. 22 In the embodiment of the present invention, the push member is in a position above the engagement portion 109 and the engagement structure 32 and begins to unfold the front portion 105a of the arm. Fig.23In the embodiment of the present invention, the push member is pushed downward until the elongated engagement portion 123 is slightly above the rod bearing surface 44a of the protrusion 44. The elongated engagement portion 123 has not yet contacted the rod bearing surface 44. From this position, only a small axial movement of the push member downward is required so that the elongated engagement portion 123 can be pushed onto the rod bearing surface 44a. This in turn causes the locking ring 40 to move downward, so that the annular protrusion 41 of the locking ring 10 can engage with the bottom portion 37a at the outer surface of the head receiving portion 22. As a result, the lower opening of the hollow interior 35 can be narrowed so that the inserted head 3 cannot be removed.

[0060] refer to Figures 24a to 24c , the figure shows the arrangement and use of the coupling device 10 and the instrument 15 as well as the bone anchor 1. Fig.24a In the embodiment, the handle 2 has been inserted into a bone, for example a vertebra 500, before the coupling device is mounted on the head. The instrument is fixedly connected to the coupling device and the locking ring is in the insertion position, wherein the head receiving portion can be expanded to allow the head 3 to enter. The engagement portion 123 has not yet pressed on the rod bearing surface 44a. Figure 24b As shown in FIG, the coupling device is arranged on the head 3 by means of the instrument 100. Thus, the head 3 snaps into the hollow interior 35 of the head receiving part 22 and can be held there by friction. Fig.24c In the next step shown, the push member 120 moves toward the locking ring 40. Further downward movement of the push member will push the locking ring 40 downward until the engagement portion 123 contacts the rod bearing surface of the protrusion 44, as shown in FIG. Fig.24c As shown in . As a result, the arms 45 snap into the lower latch recesses 31b at the receiving part by their edges 45a. The locking ring 40 is now in the pre-locking position and latched therein. In addition, the ledge 47b of the protrusion 47 can snap under the step 34 at the outer surface of the rod receiving part, which further fixes the pre-locking position. After reaching the pre-locking position, the push member 120 is retracted. When the push member 120 is in a position where it no longer blocks the engagement portion 109 and the engagement structure 32, the flexible front portions 105a of the arms can be compressed toward each other and the instrument can be removed from the head.

[0061] After the coupling device is arranged, the polyaxial bone anchoring device is in a pre-locking position. The head can be held in the seat by friction, so that the coupling device can adopt an angular position relative to the stem, which can be temporarily maintained before final locking.

[0062] In clinical use, multiple polyaxial bone anchoring devices are inserted into bone parts or vertebrae, e.g. Fig.25, for example, inserted into the pedicle of a vertebra 500. The coupling device 10 is then aligned so that a rod (not shown) can be received in the rod receiving portion of at least two or more bone anchoring devices. Another instrument 300 different from the above-described instrument 100 is used, such as Fig.25 As schematically shown in FIG. 3 , the locking ring can be moved from the pre-locking position to the locking position and released. In the locking position, the locking ring 40 moves further downward until the head receiving portion 22 is firmly compressed, so that the head is locked therein. The instrument 300 may include, for example, an outer tube engaged with the locking ring (for example at the engagement portion 28) and an inner tube engaged with the rod receiving portion. The inner tube is movable relative to the outer tube, so that by moving the outer tube relative to the inner tube, the locking ring can be moved from the pre-locking position to the locking position, and vice versa. The adjustment of the coupling device relative to the bone anchor can be performed when the rod and / or the locking member are not arranged in the rod receiving portion, or the rod can be in an elevated position relative to the bottom 24a of the recess 24. It should be noted that locking and unlocking can be performed multiple times. When the correct position of the coupling device has been adjusted, the locking member threadedly connected between the legs 25 is used to lock the coupling device to the bone anchor. Finally, the upper part of the leg can be broken off.

[0063] Variations of the embodiments described are contemplated. The components are not limited to the detailed shapes described in the embodiments. In particular, the specific shapes of the receiving component and the locking ring may vary. The shape and structure of the engagement of the receiving component and the instrument may differ from the illustrated embodiments. The design of the instrument (particularly the front portion) for arranging the coupling device on the head is not limited to the specific design shown in the embodiments. Other shapes may also be suitable. For example, the instrument may also engage with the receiving component at its outer surface.

[0064] The rod shall include any elongated means for connecting two bone anchoring means.For the bone anchor, all types of bone anchors, such as bone screws, bone nails etc. can be used.

[0065] Furthermore, a method of assembling a coupling device 10 with an instrument 100 is provided, wherein the coupling device comprises a receiving part, the receiving part comprising: a head receiving portion for pivotably receiving a head of a bone anchor; a rod receiving portion, the rod receiving portion comprising a recess forming two open legs and a bottom, the recess defining a channel for receiving a rod; and a locking ring, the locking ring being arranged to be arranged around the head receiving portion, wherein the locking ring can assume an insertion position, in which the head can be inserted into the head receiving portion to a pre-locking position, in which the head is prevented from being removed from the head receiving portion; the instrument comprises: a retaining part, the retaining part being arranged to engage with the receiving part; and a pushing part, the pushing part being movable relative to the retaining part and being arranged to engage with the locking ring; the method comprising the step of engaging the receiving part with the retaining part when the locking ring is in the insertion position. The assembling step is performed before arranging the coupling device on the head of the bone anchor.

Claims

1. A coupling device for coupling a rod to a bone anchor, comprising: A receiving component (20), the receiving component comprising: a head receiving portion (22) comprising an internal seat for pivotably receiving a head (3) of the bone anchor, the head receiving portion being expandable to allow insertion of the head and compressible to lock the inserted head in the seat; a rod receiving portion (21) comprising a recess (24) forming two open legs (25) and a bottom (24a), the recess defining a channel for receiving the rod, the rod receiving portion comprising a first engagement structure for engaging with the instrument (100); and a locking ring (40) arranged to surround the head receiving portion (22), the locking ring comprising a second engagement structure for the instrument (100); wherein the second engagement structure comprises a protrusion (44) at the locking ring (40) for forming a rod support for the inserted rod; wherein, when the locking ring (40) surrounds the head receiving portion (22), the locking ring can adopt an insertion position in which the head (3) of the bone anchor can be inserted into the head receiving portion and a pre-locking position in which the inserted head (3) is prevented from being removed from the head receiving portion; and Therein, the coupling device (10) is arranged to be placed on the head (3) of the bone anchor (1) when the locking ring (40) is in the insertion position and the first engagement structure is engaged with the instrument.

2. The coupling device according to claim 1, wherein: The bone anchor (1) is a bone anchor that has been inserted into a bone.

3. The coupling device according to claim 1 or 2, wherein: The locking ring (40) is arranged to be moved to a pre-locking position by the instrument (100) by engaging the second engagement structure with the instrument (100).

4. The coupling device according to claim 3, wherein: The locking ring (40) is arranged to be moved to the pre-locking position by means of an instrument (100) by pressing on the second engagement structure.

5. The coupling device according to claim 1 or 2, wherein: The first engagement structure comprises a recess or a projection configured to engage with a corresponding projection or recess at the instrument (100).

6. The coupling device according to claim 5, wherein: At least one notch or protrusion is formed on each leg (25) at positions opposite to each other.

7. The coupling device according to claim 1 or 2, wherein: The first engagement structure is located at a portion of the inner wall of at least one leg (25).

8. The coupling device according to claim 7, wherein: The first engagement structure is located at or near an edge of a recess (24) for receiving the rod.

9. The coupling device according to claim 1 or 2, wherein: The second engagement structure comprises two projections (44) for forming a rod support for an inserted rod, the two projections (44) being offset by 180 degrees. o .

10. The coupling device according to claim 1 or 2, wherein: The receiving part (20) includes a third engagement structure arranged to engage with the locking ring (40) so as to prevent the locking ring from moving beyond the insertion position in a direction away from the pre-locking position.

11. The coupling device according to claim 10, wherein: The third engagement structure is located at the outer surface of the rod receiving portion (21).

12. The coupling device according to claim 1 or 2, wherein: The receiving part (20) comprises a fourth engagement structure arranged to engage with the locking ring (40) so that the locking ring is latched in the pre-locking position relative to the instrument (100).

13. The coupling device according to claim 12, wherein: The fourth engagement structure is located at the outer surface of the rod receiving portion (21).

14. The coupling device according to claim 1 or 2, wherein: The locking ring (40) can adopt a locking position relative to the head receiving part (22), in which the inserted head (3) is locked.

15. An instrument for arranging a coupling device on the head of a bone anchor, wherein: The coupling device (10) is a coupling device according to any one of claims 1 to 14; The device (100) comprises: a retaining member (101) configured to engage with the receiving member (20); and A pushing component (120), wherein the pushing component (120) is movable relative to the retaining component (101); Therein, the instrument (100) is configured to arrange the coupling device (10) on the head (3) of the bone anchor (1) when the retaining part (101) is engaged with the receiving part (20) and the locking ring (40) is in the inserted position.

16. The apparatus of claim 15, wherein: When the coupling device (10) is arranged on the head (3) of the bone anchor (1), the pushing member (120) is arranged to engage with the locking ring (40) so as to move the locking ring to the pre-locking position.

17. The apparatus of claim 15 or 16, wherein: The retaining member (101) has a longitudinal axis and includes a front portion having two arms arranged to be inserted between the legs (25) and arranged to engage the rod receiving portion (21).

18. The apparatus of claim 17, wherein: The arm is arranged to flexibly expand or compress in a direction transverse to the longitudinal axis and includes an engagement portion (109) arranged to engage with an engagement structure (32) at an inner wall of a leg (25) of the rod receiving portion (21).

19. The apparatus of claim 17, wherein: The pushing member (120) is configured to push between the arms, thereby causing the arms to expand, so as to fix the holding member (101) on the receiving member (20).

20. The apparatus of claim 15 or 16, wherein: An elongated engagement portion (123) at the end of the push member (120) has a longitudinal axis extending transversely to the longitudinal axis of the retaining member (101).

21. The apparatus of claim 20, wherein: The elongated engagement portion (123) is configured to engage a rod bearing surface (44a) at the locking ring (40).

22. A system of coupling devices and instruments for coupling a rod to a bone anchor, wherein: The coupling device comprises a coupling device (10) according to any one of claims 1 to 14, and the apparatus comprises an apparatus (100) according to any one of claims 15 to 21.

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