Receiving member for coupling a rod to a bone anchor

Abstract

A receiving component for coupling a rod to a bone anchor is provided, the receiving component comprising: a head receiving portion, which includes a seat (54, 54') for pivotally receiving the interior of a head (3) of a bone anchor (1), 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, which includes a recess (58) forming a channel, the recess having a bottom (58a) for receiving a rod (100, 101), the recess forming two open legs (59); an expansion limiting member (6) which at least partially surrounds the head receiving portion on the outside of the head receiving portion; wherein when the legs (59) are opened, the head receiving portion is compressed to apply a locking force to the inserted head (3).

Description

Technical Field

[0001] The present invention relates to a receiving member for coupling a rod to a bone anchor, and more particularly to a multi-axis bone anchoring device in which the bone anchor can be locked in an angled position of a shank without using a separate compression member. Background Art

[0002] This type of multi-axis bone anchoring device is known, for example, from US 7,530,992 B2. The known multi-axis bone anchoring device includes a receiver member for hingedly connecting a bone anchoring element to a rod. The bone anchoring element includes a shank and a head, and the receiver member has an opening for receiving the shank and the head and a recess for forming a channel for receiving the rod. Two slit-shaped recesses are formed at a lower portion of the receiving member to provide elasticity for clamping the head. The head is locked in place by the action of a force that tends to spread the legs and thereby cause compression of the receiver member.

[0003] Another bone anchor assembly is known from US 9,498,254 B2. The known receiver member is bottom-loading and may include a seat having an opening whose size can be selectively increased and decreased to allow the bone anchor to be bottom-loaded. A closure element can be coupled to the receiver member and can apply a force to reduce the size of the seat and the size of the opening, thereby fixing the receiver member at an angle relative to the bone anchor.

[0004] Although the above-known multi-axis bone anchoring devices can securely lock the head of the bone anchor in the receiving member, there is still a need for a multi-axis bone anchoring device that can securely lock the head in the receiving member with a minimum number of components while allowing for a variety of options for surgical correction steps. Summary of the Invention

[0005] This object is solved by a receiving member, a multi-axis bone anchoring device, and a system of a receiving member or a multi-axis bone anchoring device and an instrument according to the present disclosure. Further improvements of the invention are given in the dependent claims.

[0006] According to an embodiment, a receiving member for coupling a rod to a bone anchor, the receiving member comprising: a head receiving portion having an internal seat for pivotally receiving a head of the bone anchor; and a rod receiving portion including a recess forming a channel having a bottom for receiving the rod, the recess forming two open legs. The head receiving portion is expandable to allow insertion of the head and compressible to lock the inserted head in the seat. Additionally, an expansion limiting member configured to at least partially surround the head receiving portion is disposed outside the head receiving portion. When the legs are opened, the head receiving portion is compressed to apply a locking force to the inserted head.

[0007] The receiving member is configured to clamp and lock the head without using an additional member such as a compression member that is typically placed on top of the head. Thus, the receiving member is easier to manufacture compared to receiving members having a compression member.

[0008] Locking of the head can be achieved by a locking device inserted into the receiving member from the top end, the locking device cooperating with the receiving member to cause the legs to open. The locking device remains in the receiving member for final locking of the multi-axis bone anchoring device. Alternatively, locking can be achieved by using an instrument that causes the legs of the receiving member to open. When using the instrument, the locking is temporary. A separate locking device can be used to finally lock the multi-axis bone anchoring device. Thus, with one receiving member, various different surgical steps can be performed, which greatly increases the applicability of the multi-axis bone anchoring device.

[0009] In one embodiment, the expansion limiting member is a ring. Such a part is easy to manufacture.

[0010] The receiving member can be used as a modular screw together with the bone anchor, which allows selection of a suitable one of several bone anchors that may differ in terms of the length, size, and shape of the shank. In particular, a bottom-loading bone anchoring device can be assembled in which the head of the bone anchor is inserted from the bottom end of the receiving member.

[0011] In another embodiment, the ring is configured to pre-lock the inserted head in the receiving member. As a result, the head cannot be removed even if it has not been locked.

[0012] In another embodiment, the expansion limiting member applies a frictional force to the head inserted into the receiving member. As a result, the bone anchor can be held in a desired angular orientation before locking the bone anchor relative to the receiving member.

[0013] In another embodiment, the receiving member includes a rod support surface configured to support rods of different diameters in a secure manner. In particular, the rod support surface may include two inclined surfaces that hold the rod therebetween. In this case, a force component can be generated that further increases the locking force acting on the head.

[0014] In another embodiment, the seat portion may extend slightly above the region of the head having the largest outer diameter such that the head can be temporarily held in the seat portion.

[0015] In another embodiment, a system of a receiving member and an instrument is provided, wherein the instrument is configured to spread the legs of the receiving member to compress the head receiving portion. Thereby, the head can be temporarily locked in the head receiving portion by the instrument without inserting a locking device and / or a rod into the channel for the rod.

[0016] Another system of a receiving member and an instrument is provided, wherein the instrument is configured to act directly on an inserted head in the head receiving portion to temporarily lock the angular position of the head. This also allows the head to be temporarily locked during a surgical procedure.

[0017] Finally, in yet another embodiment, a receiving member for coupling a rod to a bone anchor includes: a head receiving portion having an internal seat for pivotally receiving the head of the bone anchor; and a rod receiving portion including a recess forming a channel having a bottom for receiving the rod, the recess forming two open legs. The head receiving portion is expandable to allow insertion of the head and compressible to lock the inserted head in the seat. A mating surface is provided in the rod receiving portion and is configured to mate with a mating surface on a spreading member to spread the legs. When the legs are spread, the head receiving portion is compressed to apply a locking force to the inserted head. The spreading member can be the lower edge of a locking device or a part of an instrument. The mating surfaces may include surfaces with different inclinations on the receiving member and the spreading member, respectively, that generate a force component tending to spread the legs when they contact each other and move relative to each other. Description of the Drawings

[0018] Other features and advantages of the present invention will become apparent from the description of embodiments with the aid of the drawings. In the drawings:

[0019] Figure 1 : shows an exploded perspective view of a first embodiment of a receiving member and a bone anchor forming a first embodiment of a multi-axis bone anchoring device.

[0020] Figure 2 : shows a Figure 1 multi-axis bone anchoring device in an assembled state with an inserted rod in a perspective view.

[0021] Figure 3 : shows Figure 1 and Figure 2 a cross-sectional view of a multi-axis bone anchoring device, the cross-section being taken in a plane including the central longitudinal axis of the receiving member and perpendicular to the rod axis of the inserted rod.

[0022] Figure 4 : shows a Figures 1 to 3 receiving member of

[0023] Figure 5 : shows a Figures 1 to 4 receiving member of

[0024] Figure 6 : shows a Figure 4 and Figure 5 top view of the receiving member shown.

[0025] Figure 7 : shows Figure 4 and Figure 5 a cross-sectional view of the receiving member of Figure 6 along the center line A-A.

[0026] Figure 8 : shows a cross-sectional view of the receiving member without the expansion limiting member installed.

[0027] Figure 9 : shows a Figure 8 cross-sectional view of the receiving member shown in

[0028] Figure 10 : shows a Figure 8 and Figure 9 cross-sectional view of the receiving member, where the expansion limiting member is in a second position to allow insertion of the head.

[0029] Figures 11a to 11e : shows the steps of assembling a multi-axis bone anchor and Figures 1 to 10 the receiving member to form a multi-axis bone anchoring device.

[0030] Figures 12a to 12d : shows a cross-sectional view of the steps of locking a multi-axis bone anchoring device, Figures 12b to 12d also showing an enlarged partial view.

[0031] Figure 13 : shows according to Figures 1 to 12dCross-sectional view of a multi-axis bone anchoring device having a two-piece locking device and an inserted rod having a first diameter.

[0032] Figure 14 : Shows Figures 1 to 1 Cross-sectional view of a multi-axis bone anchoring device of 2 and a one-piece locking device and a rod having a second diameter, wherein the second diameter is greater than the first diameter.

[0033] Figure 15 : Shows the Figures 1 to 14 Front portion of the outer sleeve of an instrument used with a receiving member of

[0034] Figure 16 Shows Figure 15 Cross-sectional view of the outer sleeve of an instrument of , taken in a plane including the sleeve axis and extending through the center of an arm formed by an elongated recess in the outer sleeve.

[0035] Figure 17 : Shows the Figures 1 to 14 Perspective view of the front portion of the inner sleeve of an instrument used with a receiving member of

[0036] Figure 18 : Shows Figure 17 Top view of the rear end portion of the inner sleeve shown in

[0037] Figure 19 : Shows a Figure 18 Cross-sectional view of the front portion of the inner sleeve of an instrument taken along line B-B in

[0038] Figures 20a to 20c : Shows the Figures 15 to 19 Steps of attaching the instrument of to a Figures 1 to 14 receiving member and spreading the legs of the receiving member.

[0039] Figure 21 : Shows Figure 20c Enlarged portion of , which more particularly shows the mating surfaces of the instrument and the receiving member.

[0040] Figure 22 : Shows a cross-sectional view of an instrument mounted to a receiving member with an inserted head, an inserted rod, and a locking element of a bone anchor, the cross-section including the central longitudinal axis of the receiving member and being perpendicular to the rod axis.

[0041] Figure 23 : Shows a perspective view of a second embodiment of an instrument for use with the multi-axis bone anchoring device of the first embodiment.

[0042] Figure 24: A cross-sectional view of a system of a multi-axis bone anchoring device of a first embodiment and an instrument according to a second embodiment is shown, wherein the cross-section is taken in a plane including the central longitudinal axis of the receiving member and perpendicular to the shaft axis of the inserted shaft.

[0043] Figure 25 : A perspective view of a front portion of a third embodiment of an instrument to be used with a multi-axis bone anchoring device is shown.

[0044] Figure 26 : Shown is attached to a receiving member according to a modified embodiment Figure 25 of the instrument's perspective view.

[0045] Figure 27 : Shown is Figure 26 a cross-sectional view of a system of an instrument, a receiving member, and a bone anchor, wherein the cross-section is taken in a plane including the central longitudinal axis of the receiving member and perpendicular to the shaft axis of the inserted shaft. DETAILED DESCRIPTION

[0046] Figures 1 to 3 A multi-axis bone anchoring device according to a first embodiment is shown, which includes a bone anchor 1, the bone anchor including a shank 2 having a threaded portion and a head 3. The head 3 has an outer spherical surface portion and a recess 4 at the free end for engagement with a screwdriver. The size of the outer spherical outer surface portion can be designed such that it includes a region having a spherical maximum diameter. The bone anchoring device further includes a receiving member 5 for receiving the head 3 of the bone anchor 1 and a receiving shaft 100 for coupling the shaft 100 to the bone anchor 1. More specifically, the receiving member 5 is designed to selectively accommodate shafts 100, 101 of different diameters. Finally, the bone anchoring device may include a locking device 7 configured to lock the inserted shaft in the receiving member 5. More specifically, the receiving member 5 is designed such that it can be selectively used with locking devices 7, 8 having different designs. The locking device 7 can be, for example, a two-piece locking device, and the locking device 8 can be a one-piece locking device.

[0047] Now turning additionally to Figures 4 to 7, in this embodiment, the receiving member 5 is a one-piece member. It includes a first or upper end 5a and an opposite second or lower end 5b. A central axis C longitudinally passes through the first end 5a and the second end 5b. The overall shape of the receiving member may be generally cylindrical. A passage 50 extends from the first end 5a to the second end 5b. The passage 50 may have several portions with different diameters. In a first portion 51 adjacent to the upper end 5a, the passage may be formed as a coaxial hole having a first diameter, and in a central portion 52, the passage may be formed as a coaxial hole having a second diameter smaller than the first diameter. There is a transition portion 53 between the first portion 51 and the second portion 52, which tapers towards the second portion 52 and provides an inclined surface 53a. The inclined surface 53a forms an abutment for a part of the locking devices 7, 8. Adjacent to the lower end 5b, the passage is surrounded by a seat 54 of the head 3. The seat 54 tapers towards the lower end 5b and has a shape such that the head 3 can pivot therein. In this embodiment, the seat 54 has a truncated spherical shape that matches the spherical shape of the head 3. However, the seat 54 may have any other shape, preferably narrowing towards the second end 5b, which enables the head 3 to pivot therein. The seat 54 is open towards the second end 5b through an opening 55. The seat 54 surrounds the inserted head 3 up to a position above the maximum diameter of the head to prevent the head 3 from moving towards the upper end 5a.

[0048] A plurality of slits 57 are formed in a portion of the receiving member adjacent to the lower end 5b. The slits make the lower part of the receiving member flexible. More specifically, when the head 3 enters through the lower opening 55, the head receiving portion expands slightly to latch onto the head 3 until the head is seated in the seat 54. In this embodiment, four slits 57 are arranged in the circumferential direction at a distance of 90° from each other. The slits 57 may have widened end portions 57a for increasing the flexibility at the lower end 5b. In the axial direction, the end portions 57a of the slits may be located above the seat 54.

[0049] To receive the rods 100, 101, a recess 58 extends from the upper end 5a towards the lower end 5b. The recess 58 may have a substantially straight side wall and a substantially V-shaped bottom, thereby forming a support surface 58a for the rods 100, 101. The support surface 58a is formed by two inclined surfaces that are oriented in a generally triangular manner such that the inserted rod is supported substantially along two contact lines where the inserted rod contacts the inclined surfaces respectively. Thus, when any rod 100, 101 of different diameters is seated on the rod support surface, the rod can be prevented from sliding in a direction transverse to the rod axis. The width of the recess 58 is such that various rods of different diameters up to the maximum diameter can be accommodated therein. The bottom of the recess 58 terminates at a distance above the end portions 57a of the slits 57.

[0050] The recess 58 forms a passage for the rod. Specifically, two open legs 59 are formed by means of the recess 58. In the first part 51 of the passage 50, the legs include internal threads 60. The internal threads 60 can extend from the upper end 5a to the start of the transition part 53. In other words, the internal threads terminate above the transition part. The thread form of the internal threads 60 can be, for example, square threads or V-threads or any other thread form.

[0051] The arrangement of the slit 57 and the recess 58 relative to each other is such that a pair of opposite slits is aligned with the recess 58, and the other pair of opposite slits can be arranged at an angle of 90° with respect to the longitudinal axis L of the recess 58.

[0052] Finally, two opposite engaging projections 61 are respectively formed on the outer surface of the receiving member 5, on the legs 59. The engaging projections 61 are substantially positioned at the center of each leg in the circumferential direction and at a certain distance from the free end 5a. Specifically, the engaging projections 61 can have a trapezoidal outer contour, where the longer base faces the second end 5b in the axial direction.

[0053] More generally, the receiving member is divided into: an upper part including the recess 58, thus forming a rod receiving part; and a lower part including the seat part 54, thus forming a head receiving part. Due to the slits 57, the head receiving part is expandable and allows the head 3 of the bone anchor to enter through the lower opening 55 and be seated in the seat part 54. In addition, the head receiving part can also be compressible so as to clamp by friction and finally lock the inserted head 3 in the seat part 54. When a pair of opposite slits 57 is in a position aligned with the recess 58, the opening of the legs 59 will cause the slits 57 aligned with the recess 58 to narrow. In this way, the head receiving part is compressed, thus locking the inserted head 3. When the force affecting the opening of the legs 59 is removed, the legs 59 move back to their unopened position, thus releasing the compression of the head receiving part.

[0054] In addition, the receiving member 5 includes substantially triangular recesses 62 on each outer edge of the legs 59. The recesses 62 can extend from the upper end 5a to an axial height above the V-shaped bottom 58a of the recess 58. The outward-facing surface 62a of each recess 62 is configured to form an abutment surface for a part of the instrument, which will be described below. The abutment surface extends substantially parallel to the central longitudinal axis. The receiving member 5 has four such recesses 62. However, at least two recesses on opposite sides of the passage formed by the recess 58 are also possible.

[0055] Refer again to Figures 1 to 3, the receiving member 5 further includes an expansion limiting member 6 which is configured to surround the head receiving portion on the outside of the head receiving portion. The expansion limiting member 6 in this embodiment is a ring. The ring may have an axial length that allows the ring to move along the head receiving portion towards the rod receiving portion to a position where it no longer surrounds the head receiving portion. The cross-section of the ring may be substantially rectangular, with its height greater than the thickness of the ring. However, the ring may also have other dimensions. The inner diameter of the ring is such that when the head receiving portion is compressed and the head 3 is not in the seat portion 54 (i.e., in the unloaded configuration of the receiving member), the ring can slide from the lower end 5b to the outside of the receiving member 5. In the unloaded configuration, when the ring 6 surrounds the head receiving portion, the ring is slightly held by friction. As Figures 3 to 5 shown, the outer diameter of the receiving member slightly decreases from the larger diameter of the upper portion of the receiving member 5 to the smaller diameter of the lower portion, thereby forming a stop portion 6a. When the ring is mounted on the receiving member 5 and moved towards the upper end 5a, the stop portion serves as an abutting portion for the ring. The axial position of the stop portion 6a is located in the region of the rod receiving portion of the receiving member 5. Additionally, a stop portion 6b is formed at a height slightly lower than the enlarged end of the slit 57. The stop portion 6b prevents the expansion limiting member 6 from being removed towards the second end 5b after the expansion limiting member 6 is installed.

[0056] The locking device 7 includes an outer locking member 70 and an inner locking member 75. The outer locking member 70 is formed as a cylindrical set screw having an external thread 71 which is configured to cooperate with the internal thread 60 on the leg 59. On the side facing the second end 5b of the receiving member in the installed state, the outer locking member 70 includes a substantially cylindrical threadless portion 72. The lower outer edge 72a of the threadless portion 72 is configured to cooperate with the inclined surface 53a in the receiving member 5. The outer edge 72a may be circular. As Figure 3 specifically shown, the axial length of the outer locking member 70 is such that when the outer locking member 70 is screwed into the space between the legs 59, the outer edge 72a contacts the inclined surface 53a, thereby applying an opening force by the outer locking member 70 which tends to cause the legs 59 to open apart from each other. The outer locking member 70 further includes a threaded hole 73 having an internal thread which is configured to cooperate with the inner locking member 75. Additionally, on the upper side of the outer locking member 70 opposite to the edge 72a, a plurality of engagement recesses 74 for engaging with a driving tool may be provided.

[0057] The inner locking member 75 is formed as a positioning screw that is screwed into the outer locking member 70. The external thread 76 of the inner locking member 75 can have any thread form, and preferably can be a square thread as shown in the embodiment. This can improve the load distribution. At the side of the inner locking member 75 facing the second end 5b of the receiving member 5 in the installed state, the inner locking member 75 includes an annular protrusion 77 that is configured to abut against the lowermost turn of the thread of the external thread 76. In the installed state, this prevents the inner locking member 75 from being accidentally unscrewed from the outer locking member 70. Finally, the inner locking member 75 includes a tool engagement recess 78 that can have any suitable shape for form - fitting tool engagement, such as a torque shape or a hexagonal shape.

[0058] The locking device 7 is configured to achieve independent locking of the head 3 and the stem 100. With the outer locking member 70, the head 3 can be locked in the seat 54. With the inner locking member 75, the stem 100 can be locked in the recess 58.

[0059] As Figure 1 shown, as indicated by the arrow, the one - piece locking device 8 can be used interchangeably with the two - piece locking device 7. The one - piece locking device 8 can be formed as a cylindrical positioning screw having an external thread 81 and a threadless lower portion 82, and the lower portion has a lower side 85 facing the stem. The threadless lower portion 82 includes an edge 82a (see Figure 14 ) that is configured to cooperate with the inclined surface 53a in the receiving member to apply an opening force on the leg 59. The side of the locking device 8 opposite the threadless portion 82 can have a structure for engaging with a driving tool. In this embodiment, provided are: a central coaxial hole 83 that extends a certain distance from the free end; and a plurality (four in this embodiment) of radial slots 84. However, the shape of the engagement structure can be different to cooperate with various tools.

[0060] The components and parts of the bone anchoring device can be made of any material, but preferably are made of titanium or stainless steel or any biocompatible metal or metal alloy or plastic material. As a biocompatible alloy, nitinol can be used, such as Nitinol. Other materials can be magnesium or magnesium alloys. The biocompatible plastic materials used can be, for example, polyetheretherketone (PEEK) or polyl - lactic acid (PLLA). The components can be made of the same or different materials from each other.

[0061] Figures 8 to 10 The assembly of the expansion limiting member 6 and the receiving member 5 in the form of a ring is shown. Figure 8 The expansion limiting member 6 placed at the side of the lower end 5b of the receiving member 5 before installation is shown. Then, as Figure 9As shown, the expansion limiting member is moved onto the receiving member. Since in the unloaded configuration, the inner diameter of the loop in the region of the head receiving portion is slightly smaller than the outer diameter of the receiving member 5, during installation, the expansion limiting member may slightly compress the head receiving portion. As a result, the legs 59 are slightly opened. In Figure 10 In the next step shown, the expansion limiting member can be slid upward until it abuts against the stop 6a. In this position, the expansion limiting member no longer compresses the head receiving portion. When the expansion limiting member is above the head receiving portion and in any case when the expansion limiting member is in the highest position defined by the stop 6a, the head receiving portion can be expanded to allow the head 3 of the bone anchor 1 to enter the seat 54.

[0062] Next, the assembly of the bone anchor and the receiving member 5 will be described with reference to Figures 11a to 11e wherein the receiving member is provided with an expansion limiting member in the form of a loop mounted thereon. It should be noted that the assembly steps can be carried out before the multi-axis bone anchoring device is implanted into the patient's body. Alternatively, the assembly can be carried out when the bone anchor 1 has already been inserted into the bone. Then, the receiving member with the loop mounted thereon will be mounted onto the head 3 protruding from the bone.

[0063] First, as Figure 11a shown, the head 3 of the bone anchor 1 is oriented towards the opening 55 of the receiving member 5. The expansion limiting member 6 is in the highest position of the stop 6a. As Figure 11b further shown, the head 3 enters the passage 50 of the receiving member 5 through the opening 55. When the head 3 enters the passage, the head receiving portion of the receiving member 5 is slightly expanded, as Figure 11c shown. During insertion, the legs 59 move slightly towards each other. Since the loop is not around the head receiving portion, the loop does not prevent expansion during insertion. When the region of the head 3 having the maximum diameter has moved through the opening 55, the head 3 can be placed in the seat 54 as Figure 11d shown. At the same time, the head 3 cannot move further upward because the seat 54 extends beyond the region having the maximum outer diameter and prevents such movement. Finally, as Figure 11e shown, the loop is moved downward until it abuts against the stop 6b so that the loop surrounds the head receiving portion in the correct position. Due to its size, the loop exerts a small compressive force on the head receiving portion, and the small compressive force clamps the head 3 in the seat 54 by friction. Thus, before the final locking of the head, the angular position of the bone anchor relative to the receiving member can be held at the desired angular position. At the same time, the expansion limiting member prevents the head 3 from being removed through the lower opening. Thus, the head is pre-locked in the receiving member 5. In Figure 11e the configuration shown, several correction steps can be performed on the bone, bone portion or vertebra in which the multi-axis bone anchoring device is implanted or to be implanted.

[0064] Now referring to Figures 12a to 12d , the locking of the multi-axis bone anchoring device will be described. As Figure 12a shown, the rod 100 is inserted into the recess 58, and the locking device 7 is also inserted through the upper end 5a. In the example shown, the diameter of the rod 100 is such that it can touch the side wall of the channel.

[0065] Next, in Figures 12b to 12d , an enlarged view of the engagement of the edge 72a of the locking device 7 and the inclined surface 53a of the receiving member 5a is shown separately in the upper part of the drawing. In Figure 12b , the locking device is further screwed in and the rod is moved towards the rod support surface 58a. The edge 72a of the locking device 7 contacts the upper region of the inclined surface 53a. Next, as Figure 12c shown, when the edge 72a further moves along the inclined surface 53a, an outward force component is generated, and the outward force component causes the legs 58 to open, as indicated by the arrow above the receiving member 5. The head receiving portion is compressed around the inserted head 3. This is indicated by the arrow in the lower part of the receiving member 5. The ring remains held by friction and surrounds the head receiving portion. When the pressure applied to the head locks the head, the legs may not open further. Finally, as Figure 12d shown, in the configuration where the head 3 is locked by the compression of the head receiving portion, the rod 100 can be locked individually by the inner locking member 75 by screwing the inner locking member 75 downward so that it applies a locking force to the rod 100. This results in a further increase in the component force indicated by the inclined arrow in Figure 12d to the force that causes the legs to open, and results in an additional locking force applied to the head.

[0066] With the two-piece locking device, rods of 7 different diameters can be fixed. As Figure 13 shown, a rod 101 with a diameter smaller than the aforementioned rod 100 is inserted. The fixing of the rod in the recess 58 can be achieved by screwing the inner locking element 75 towards the rod 101 until it presses on the upper surface of the rod 101. The locking of the head 3 is achieved in the same manner as described with reference to Figures 12a to 12d . Thus, with the two-piece locking device 7, the applicability of the multi-axis bone anchoring device is greatly improved.

[0067] Figure 14Illustrated is the use of a bone anchoring device with a rod 100 and a one-piece locking device 8, the diameter of the rod 100 being greater than that of the rod 101. The one-piece locking device is configured to be used with a rod of a specific diameter. When the locking device 8 is screwed between the legs 59, the edge 82a contacts the inclined surface 53a, causing the legs 59 to open and thereby compressing the head receiving portion and locking the head 3. At this time, the lower surface 85 of the locking device 8 contacts the upper surface of the rod 100 and presses the rod 100 against the rod support surface 58a to fix the position of the rod.

[0068] It should be noted that although the legs 59 open during head locking, the locking devices 7, 8 can lock the entire device, i.e., it will not become loose.

[0069] In use, two bone anchoring devices are inserted into vertebrae (e.g., the pedicles of vertebrae) or other bone parts and connected via a rod. A variety of adjustment and correction steps can be performed, and the above multi-axis bone anchoring devices are used to facilitate the variety of adjustment and correction steps.

[0070] Now referring to Figures 15 to 19 , an instrument forming a system with the multi-axis bone anchoring device will be described.

[0071] The instrument includes an outer sleeve 30 and an inner sleeve 40. Although only the front portions of the outer sleeve 30 and the inner sleeve 40 are shown in the figure, the outer sleeve 30 and the inner sleeve 40 also have end portions and a mechanism for displacing the inner sleeve relative to the outer sleeve. Referring in more detail to Figure 15 , Figure 16 and Figure 22 , the outer tube 30 is designed to be placed on the receiving member 5 when the rod is located in the recess 58. To allow this, the outer sleeve has a recess 31 that extends from the front end 3a a certain distance from the front end. Two opposing arm portions 32 are formed by the recess 31. The width and depth of the recess are such that when the outer sleeve engages the receiving member, the recess matches or has a greater width than the width of the rod recess 58 of the receiving member. By this, the rod 100 can extend through the recess 31 and move along the rod axis and in the axial direction. The inner diameter of the outer sleeve 30 is such that the outer sleeve 30 can engage the outer surface of the receiving member 5. The recess 31 is also used to snap the outer sleeve onto the receiving member, whereby the arm portions 32 open slightly. A second recess 36 can be provided above the recess 31, and the second recess also extends in the longitudinal direction and is separated from the recess 31 by a bridging portion 37. The recess 36 may make the front portion of the outer sleeve more flexible.

[0072] There is a joint portion 33 adjacent to the front end 3a of the outer sleeve 30. The joint portion includes a notch 34, and the size and shape of the notch are designed such that a protrusion 61 on the outer surface of the leg 59 can extend therethrough. The protrusion 61 and the notch 34 provide a form-fit connection between the outer sleeve and the receiving member 5. Further, there may be a portion 35 adjacent to the front end 3a which has a slightly larger inner diameter compared to the outer diameter of the receiving member 5. As Figure 22 shown, a small gap 35a is thus formed between the outer surface of the receiving member 5 and the inner surface of the outer sleeve 30. The gap 35a provides space for a slightly outward movement of the leg. Further, when the instrument is removed, the gap 35a can facilitate the disassembly of the outer sleeve.

[0073] The inner sleeve 40 has a front end 4a and an inner diameter such that when the inner sleeve is placed inside the outer sleeve 30 and onto the receiving member 5, the front end 4a can be placed on the upper end 5a of the receiving member 5. A generally rectangular or U-shaped recess 41 extends from the front end 4a towards the rear end (not shown). The recess 41 divides the front portion of the inner sleeve 40 into two arm portions 42. The size and depth of the recess 41 are such that the inner sleeve can be placed on the rod 100, as Figure 22 shown. More specifically, the width of the recess 41 corresponds to the width of the recess 58 of the receiving member.

[0074] At either end of the arm portion 42, longitudinal protrusions 43 are provided to extend beyond the front end 4a. More specifically, four protrusions 43 are each formed adjacent to the U-shaped recess 41. The protrusions 43 are configured to engage recesses 62 provided at the outer edges of the legs 59 of the receiving member 5. As Figure 19 and Figure 21 best shown, the surface 43a of each protrusion 42 facing away from the U-shaped recess 41 is inclined such that the thickness of the protrusion 43 increases from the free end of the protrusion towards the front end 4a of the inner sleeve 4a. The inclined surface 43a is configured to engage the outwardly facing surface 62a of the recess 62 on the leg 59. Since the inclined surface 43a is inclined relative to the substantially vertical surface 62a, the protrusion 43 applies an opening force component to the leg 59 of the receiving member 5. Thus, the engagement tends to open the leg.

[0075] Referring to Figures 20a to 20c will describe the use of the multi-axis bone anchoring device and the instrument. In the first step, as Figure 20aAs shown, the outer sleeve 30 is mounted to the receiving member 5. The engaging portion 33 is snapped onto the projection 61 so as to form a form-fitting connection between the outer sleeve and the receiving member. The recess 31 is aligned with the recess 58 in the receiving member. Moreover, the inner sleeve 40 is oriented such that the recess 41 is aligned with the recess 58 of the receiving member 5. The front end 4a of the inner sleeve has not yet touched the upper end 5a of the receiving member, and the projection 43 has not yet pressed against the surface 62a of the recess 62. In this configuration, the head is held in the desired angular position by friction and can be pivoted by overcoming the frictional force (e.g., manually). Moreover, the head is securely locked in the seat portion since the expansion restricting member 6 restricts the expansion of the head receiving portion such that the head cannot escape. The rod 100 can be in a high position away from the bottom of the recess 58. This allows various surgical steps to be performed, such as pulling the vertebra or bone portion in which the bone anchor is anchored toward the rod 100.

[0076] Next, as Figure 20b shown, the inner sleeve 40 is moved downward until the inclined surface 43a of the projection 43 contacts the outwardly oriented surface 62a of the recess 62, thereby causing the legs 59 of the receiving member 5 to open. The projection 61 can enter slightly deeper into the notch 34 of the outer sleeve 30. In addition, the enlarged diameter portion 35 of the outer sleeve 30 provides space for the slight opening of the legs, and the enlarged diameter portion creates the gap between the outer sleeve and the receiving member. When the legs open, the head is locked by the compression of the head receiving portion.

[0077] Finally, as Figure 20c shown, the locking device can be inserted through the inner sleeve 40. The rod 100 and the locking device are moved further downward, and the locking device is operated to effect the opening of the legs to maintain the locking of the head 3. Finally, the instrument can be removed.

[0078] Figure 21 The engagement of the inclined surface 43a and the outwardly oriented surface 62a is depicted in more detail, which results in the opening of the legs to compress the head receiving portion. Figure 22 Shown is Figure 20c a cross-sectional view of the configuration of

[0079] Now turning to Figure 23 and Figure 24 a second embodiment of the instrument will be described. Again, the multi-axis bone anchoring device is slightly modified. The same or highly similar parts are labeled with the same reference numerals as in the previous embodiment. As particularly in Figure 24As can be seen, the protrusion 61 is omitted. Instead, a recess 61' is provided on the leg for engagement with the instrument. The instrument includes an outer sleeve 30', which has a recess 31' for the rod, the recess forming two arm portions 32', the two arm portions having inwardly directed protrusions 34' configured to engage the recess 61'. Additional recesses 36' may be provided to enhance the flexibility of the arm portions. The inner sleeve 40' includes a generally U-shaped recess 41 and has a reduced outer diameter in the region of the arm portions 42' such that the arm portions 42' are configured to extend into the passage 50 of the receiving member. The length of the arm portions 42' is such that when the inner sleeve 40' abuts against the free end 5a with its upper portion 4b, the arm portions 42' press against the inserted head 3 with their free end surfaces 41a'. The surface 42a' of the free end may have a spherical shape matching the spherical shape of the head.

[0080] In use, the inner sleeve 40' temporarily locks the head 3 in the seat 54'. When the inner sleeve 40' is withdrawn, the head can pivot again in the seat. Thus, with the instrument, the head 3 can be temporarily locked only by the instrument. After removing the instrument, the multi-axis bone anchoring device is finally locked by inserting the locking devices 6, 7.

[0081] Another embodiment of the instrument is shown in Figures 25 to 27 For this instrument, the receiving member 5'' is slightly modified in that it includes a recess 61'' for laterally engaging the head with the instrument from the outside of the receiving member. The shape of the recess is adapted to the shape of the instrument. In the example shown, the recess 61'' has a rectangular cross-section and has a width that gradually increases from the passage 50 towards the outside. The recess 61'' is inclined to allow the passage of the pincer-like arm portions 400 of the instrument. The pincer-like arm portions shown in the figure have a straight or vertical portion 401 and an inclined portion 402 with a spherical end surface 400a. Each of the arm portions 400 is configured to extend through the recess 61'' with the inclined portion 402 and is configured to press against the inserted head 3 with the end surface 400a. The instrument also includes an actuation mechanism (not shown) that actuates the arm portions 400 to enter the recess and press against the head and / or to release the head and then remove it from the recess 61''. Thus, the actuation mechanism acts in a pincer-like manner. Using this instrument, the head can be engaged and temporarily locked in the receiving member while allowing the insertion of the locking device 7. In use, after temporarily locking the head, the instrument is removed and the rod is finally locked using the locking device as in the first embodiment.

[0082] Modifications of the described embodiments are possible. The features of one embodiment may also be combined with the features of other embodiments to yield various other embodiments. The components are not limited to their detailed shapes depicted in the embodiments. Although the bone anchoring device has been described and shown as a bottom-loading bone anchoring device (wherein the bone anchor is inserted from the bottom end of the receiving member), the present invention may also be used with a top-loading bone anchoring device, in which the bone anchor is inserted from the top end of the receiving member.

[0083] Although the rod is shown as a rigid rod with a smooth surface, the term "rod" shall denote any elongate connecting member configured to be received in the rod receiving portion of the receiving member and configured to be fixed in the rod receiving portion by a locking means. In particular, various shapes, diameters, surface characteristics, etc. will be included therein.

[0084] Various other modifications may be made without departing from the present invention. In particular, the recess 62 for the instrument in the first embodiment may also be omitted. The receiving member is not limited to the specific shape described in the embodiments. Although the receiving member is shown as an integral member, it may also be two-piece. The number and shape of the slits may vary. The outer profile of the receiving member may be different. The expansion limiting member may be different from the ring, for example, it may be two clamp-type half rings mounted and fixed to the receiving member from opposite sides.

[0085] For the bone anchor, all types of bone anchors may be used, such as screws, nails, and the like.

Claims

1. A receiving member for coupling a rod to a bone anchor, the receiving member including a head receiving portion that includes an internal seat (54, 54') for pivotally receiving a head (3) of the bone anchor (1), the head receiving portion being expandable to permit insertion of the head and compressible to lock the inserted head in the seat; a rod receiving portion that includes a recess (58) forming a channel having a bottom for receiving a rod (100, 101), the recess forming two open legs (59); and an expansion limiting member (6) that at least partially surrounds the head receiving portion at an outer side thereof; wherein when the legs (59) are opened, the head receiving portion is compressed to apply a locking force to the inserted head (3); and wherein the receiving member further includes an engagement surface in the rod receiving portion, the engagement surface including an inclined surface (53a) or an abutment surface (62a), the engagement surface being configured to be engaged by an opening member such that when the opening member engages the engagement surface and moves in a direction of the bottom of the recess (58), the legs (59) are opened.

2. The receiving component according to claim 1, wherein The expansion limiting member (6) is a ring.

3. The receiving component according to claim 1 or 2, wherein The head receiving portion includes an expandable and compressible opening (55) for inserting and receiving the head (3) therethrough.

4. The receiving component according to claim 3, wherein The expansion limiting member (6) is configured to limit expansion of the opening (55) such that the inserted head cannot be removed through the opening (55).

5. The receiving component according to claim 1 or 2, wherein The expansion limiting member (6) is configured to apply a compressive force to the head receiving portion such that the inserted head (3) is clamped in the seat (54, 54') by friction before final locking.

6. The receiving component according to claim 1 or 2, wherein The expansion limiting member is movable from a first position in which the expansion limiting member surrounds the head receiving portion toward the rod receiving portion to a second position, and wherein when the expansion limiting member is in the second position, the head receiving portion is expandable to permit insertion of the head.

7. The receiving component according to claim 6, wherein A first stop (6a) is provided at the receiving member (5) for limiting further movement of the expansion limiting member away from the head receiving portion toward an upper end (5a) of the receiving member.

8. The receiving component according to claim 7, wherein, A second stop (6b) is provided for limiting further movement of the expansion limiting member toward a lower end (5b) of the receiving member.

9. The receiving component according to claim 1 or 2, wherein The engagement surface is the inclined surface (53a) formed on the legs (59), and wherein the opening member is formed by an edge (72a) of a locking device (7, 8) configured to be inserted between the legs, or vice versa.

10. The receiving component according to claim 9, wherein, The legs include internal threads (60) and the locking device (7, 8) is screwed between the legs.

11. The receiving component according to claim 1 or 2, wherein, The engagement surface is the abutment surface (62a) provided circumferentially at at least one side of the legs (59), and wherein the opening member is formed by an end portion (43) of an instrument.

12. The receiving component according to claim 11, wherein, The abutment surface (62a) is provided circumferentially on each side of the leg portion (59).

13. The receiving component according to claim 1 or 2, wherein The seat portion (54) is shaped to limit further movement of the head (3) towards the rod receiving portion.

14. The receiving component according to claim 13, wherein, When the head is in the seat portion, the seat portion extends above the maximum outer width of the head (3).

15. The receiving component according to claim 13, wherein, The head includes a spherical outer surface portion that includes the maximum outer diameter of the sphere.

16. The receiving member according to claim 1 or 2, further comprising a rod support surface (58a) in the rod receiving portion, the rod support surface being configured to support rods of different diameters.

17. The receiving component according to claim 16, wherein, The rod support surface has a substantially V-shaped cross-section.

18. The receiving component according to claim 1 or 2, wherein the receiving component further comprises: Adjacent a first end of the rod receiving portion; adjacent a second end of the head receiving portion; And a central axis (C) extending through the first end and the second end, a passageway (50) extending axially from the first end to the second end.

19. The receiving component according to claim 18, wherein, The passageway does not have any separate compression member acting on the inserted head (3).

20. A multi-axis bone anchoring device comprising a bone anchor and a receiving member according to any one of claims 1 to 19, the bone anchor (1) comprising a head (3) and a shank (2) to be anchored in bone.

21. A system of a receiving member according to any one of claims 1 to 19 or a multi-axis bone anchoring device according to claim 20 and an instrument, the instrument comprising an engagement portion (42’, 402) configured to directly engage the inserted head (3) for temporarily locking the head in the seat portion through the engagement portion.

22. The system according to claim 21, wherein, The instrument includes an outer sleeve (30’) configured to be attached to the leg portion (59) and an inner sleeve (40’) configured to extend between the leg portions (59) to press against the inserted head (3) in the seat portion (54’), and / or wherein the leg portion (59) includes at least one recess (61”) on at least one leg portion, and wherein the instrument includes a pressing member.

23. The system according to claim 22, wherein, The leg includes an opening at each leg.

24. The system according to claim 23, wherein, The instrument includes a pressing member in the form of a clamp (401, 402), wherein each clamp member is configured to extend through an opening and press against the inserted head (3).

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