Bone Fixation Devices

Abstract

To provide a bone anchoring device which improves various surgical orthopedic operations, especially those for treating spondylopathy, diseases and / or illnesses, and / or further expands the applicability of bone anchoring devices.SOLUTION: An anchoring element includes a shank 2 for anchoring to a bone and a head portion 3. The head portion has a spherical outer surface. The shank 2 and the head portion 3 are separate parts configured to be coupled to one another. The head portion 3 includes a drive structure for engagement with a drive tool.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to bone fixation devices that are generally applicable to orthopedic and trauma surgery, and more particularly to spinal surgery. [Background technology]

[0002] In spinal surgery, one or several motion joints of the spine are connected by rods. The rods are fixed to the vertebrae by monoaxial or polyaxial bone fixation devices. Such bone fixation devices typically include bone fixation elements that are fixed to, for example, the pedicles of the vertebrae. In the case of polyaxial bone fixation devices, the bone fixation elements are pivotally connected to a receiving part. The receiving part includes a recess for receiving the rod and a fixation member for fixing or locking the structure.

[0003] For example, US6835196B2 describes a polyaxial bone fixation device having a screw with a threaded portion and a spherical head, and a receiving portion for connecting the screw to a rod. The threaded portion and the spherical head of the screw are separate components. With this device, the threaded portion can be shortened to a desired length before or after inserting the device, and then the threaded portion can be connected to the head and receiving portion.

[0004] US2008 / 0132957A1 describes a bone fixation device including a shank to be fixed to a bone or vertebra, a head, and a receiving part for receiving the head and connecting the shank to a rod. The shank and the head are separate parts. Since the shank and the head are separate parts, when using the bone fixation device, the bone fixation device can be formed by selecting an appropriate shank depending on the application and connecting it to the head. Specifically, shanks of different lengths can be combined with heads.

[0005] US2014 / 0277158A1 describes a bone anchor assembly including a multi-element bone anchor configured to allow the shank of the bone anchor to be loaded into a receiving member from the bottom, the bone anchor assembly including a shank having a distal threaded portion and a proximal head, a ball having a spherical outer surface and a central lumen sized to receive the head of the shank, and a clip configured to lock the ball in engagement with the shank by engaging between the head and the ball. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US6835196B2 [Patent Document 2] US2008 / 0132957A1 [Patent Document 3] US2014 / 0277158A1 Summary of the Invention [Problem to be solved by the invention]

[0007] It is an object of the present invention to provide a bone fixation device that improves and / or further broadens the applicability of various orthopedic surgical procedures, particularly those procedures for treating spinal disorders, diseases and / or disorders. [Means for solving the problem]

[0008] This object is solved by a bone anchoring device according to claim 1. Further developments are described in the dependent claims.

[0009] According to one embodiment, the bone fixation device comprises a fixation element including a shank for fixation to bone and a head, the head having a spherical outer surface, the shank and the head being separate pieces configured to be coupled to each other, and the head including a drive structure for engaging a drive tool.

[0010] The drive structure has a larger size compared to known fixation elements with a ball-shaped head, which allows the bone fixation element to be inserted and screwed into bone with a larger torque.

[0011] In a further development, a receiving part is provided for receiving the head and connecting the bone anchoring element to the rod. The bone anchoring element and the receiving part can thus form a polyaxial bone anchoring device, which can pivot the shank at various angles relative to the receiving part and be fixed at a specific angular position. A pressure member can be provided to transmit the pressure applied by the anchoring element to the head. Alternatively, the pressure can be transmitted directly to the head via the rod.

[0012] The shank includes an engagement portion for engaging with a drive tool. Therefore, the shank can be inserted into the bone first, and then the receiver with the head attached can be placed on the shank. Because the shank can be inserted without being connected to the receiver, the visibility and available space at the surgical site can be improved, and the insertion process can be facilitated. Furthermore, if the insertion depth of the shank needs to be adjusted or the bone fixation device needs to be removed, the necessary steps can be efficiently performed by engaging the drive structure of the head.

[0013] In certain embodiments, the shank may have a large outer diameter, and the engagement portion of the shank may be designed to allow for the application of high torque.

[0014] Furthermore, the bone anchoring device is robust, and the receiving part with the head inserted therein can be easily connected to the shank.

[0015] Alternatively, the head and shank can be assembled before connecting the head to the receiver.

[0016] Various heads with different drive configurations can be paired with a particular shank. The different drive configurations can be, for example, Torx®-shaped or Mortorque®-shaped. Furthermore, a modular system can be provided in which various heads can be paired with various shanks having different lengths, different diameters, different thread or bone-engaging configurations, or different other characteristics.

[0017] In a further specific embodiment, the bone anchoring device comprises a position indicating structure that indicates a specific angular position of the head and shank relative to the receiving part, for example a zero angular position.

[0018] The bone fixation device may also include a bone plate, which includes holes for seating the heads of the bone fixation elements and, optionally, locking members for locking the heads within the holes.

[0019] Further features and advantages of the present invention will become apparent from the following description of the embodiments, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is an exploded perspective view showing a bone fixing device according to a first embodiment. [Figure 2] 2 is a perspective view of the assembled bone anchoring device of FIG. 1; FIG. [Figure 3] 3 is a cross-sectional view showing a cross section of the polyaxial bone anchoring device of FIGS. 1 and 2 along a plane extending through the center of the receiving part and the head and containing the shank axis; FIG. [Figure 4] FIG. 4 is a perspective view of the shank of the bone anchoring element of the bone anchoring device of FIGS. 1 to 3, as seen from above. [Figure 5] FIG. 5 is a side view showing the upper part of the shank of FIG. 4. [Figure 6] FIG. 6 is a top view of the shank of FIGS. 4 and 5. [Figure 7] FIG. 4 is a perspective view of the head of the bone fixing device of FIGS. 1 to 3 as viewed from above. [Figure 8] FIG. 8 is a perspective view of the head of FIG. 7 as seen from below. [Figure 9] FIG. 9 is a top view of the head of FIGS. 7 and 8. [Figure 10] 7 to 9 taken along line AA in FIG. 9. FIG. [Figure 11] FIG. 4 is a perspective view of the receiving part of the bone fixing device of FIGS. 1 to 3 as viewed from above. [Figure 12] 12 is a perspective view of the receiving portion of FIG. 11 as seen from below. FIG. [Figure 13] FIG. 13 is a top view of the receiving part of FIGS. 11 and 12. [Figure 14] 11 to 13 taken along line BB in FIG. 13. FIG. [Figure 15] FIG. 4 is a perspective view of a pressure member of the bone fixing device of FIGS. 1 to 3 as viewed from above. [Figure 16] FIG. 16 is a perspective view of the pressure member of FIG. 15 as seen from below. [Figure 17] FIG. 17 is a top view of the pressure member of FIGS. 15 and 16. [Figure 18a] 18 is a cross-sectional view showing the pressure member of FIGS. 15 to 17 taken along the line DD in FIG. 17. FIG. [Figure 18b] FIG. 18b is an enlarged view of a detail of FIG. 18a. [Figure 19a] 10 is a perspective view from above of a step of attaching the head of the bone anchoring element to the shank. FIG. [Figure 19b] 10 is a perspective view from above of a step of attaching the head of the bone anchoring element to the shank. FIG. [Figure 19c] 10 is a perspective view from above of a step of attaching the head of the bone anchoring element to the shank. FIG. [Figure 20a] 19b is a cross-sectional view showing the process of FIG. 19a along a plane including the shank axis and the central axis of the head. [Figure 20b] 19b taken along a plane including the shank axis and the central axis of the head. FIG. [Figure 20c] 19c taken along a plane including the shank axis and the central axis of the head. FIG. [Figure 21a]10A to 10C are cross-sectional views showing a process of assembling the head portion to the pressure member and the receiving portion. [Figure 21b] 10A to 10C are cross-sectional views showing a process of assembling the head portion to the pressure member and the receiving portion. [Figure 21c] FIG. 21b is an enlarged view of a detail of FIG. [Figure 21d] 10A to 10C are cross-sectional views showing a process of assembling the head portion to the pressure member and the receiving portion. [Figure 21e] 10A to 10C are cross-sectional views showing a process of assembling the head portion to the pressure member and the receiving portion. [Figure 22a] 10 is a cross-sectional view showing a step of attaching a pre-assembled head, pressure member, and receiving portion to a shank. FIG. [Figure 22b] 10 is a cross-sectional view showing a step of attaching a pre-assembled head, pressure member, and receiving portion to a shank. FIG. [Figure 22c] 10 is a cross-sectional view showing a step of attaching a pre-assembled head, pressure member, and receiving portion to a shank. FIG. [Figure 22d] 10 is a cross-sectional view showing a step of attaching a pre-assembled head, pressure member, and receiving portion to a shank. FIG. [Figure 23a] 4 shows a cross-sectional view of the bone anchoring device of FIGS. 1 to 3 with the anchoring element in a pivoted position and without a rod inserted therein; FIG. [Figure 23b] 23b shows a cross-sectional view of the polyaxial bone anchoring device of FIG. 23a with the rod and the anchoring member inserted in the receiving part and locked in a pivotal position. [Figure 24] 10 is a cross-sectional view showing a modified example of a bone anchoring device with a rod and an anchoring member inserted therein; FIG. [Figure 25] 1 is a perspective view of an embodiment of a system including a shank and two interchangeable heads for forming the bone fixation elements of a bone fixation device. FIG. [Figure 26] FIG. 10 is an exploded perspective view showing a bone fixing device according to a second embodiment. [Figure 27] FIG. 27 is a perspective view of the assembled bone anchoring device of FIG. 26. [Figure 28] FIG. 28 is a perspective view from above of the head of the bone anchoring device of FIGS. 26 and 27. [Figure 29] FIG. 29 is a perspective view of the head of FIG. 28 as seen from below. [Figure 30] FIG. 30 is a top view of the head of FIGS. 28 and 29. [Figure 31] 31 is a cross-sectional view showing the head of FIGS. 28 to 30 taken along line FF in FIG. 30. FIG. [Figure 32] 28 is a perspective view from above of the receiving part of the bone anchoring device of FIGS. 26 and 27. FIG. [Figure 33] 33 is a perspective view of the receiving part of FIG. 32 as seen from below. FIG. [Figure 34] FIG. 34 is a top view of the receiver of FIGS. 32 and 33; [Figure 35a] 35 is a cross-sectional view showing the receiving part of FIG. 34 taken along line GG of FIG. 34. [Figure 35b] FIG. 35b is an enlarged view of a detail of FIG. 35a. [Figure 36a] 28A to 28C are cross-sectional views showing steps for assembling the bone anchoring devices of FIGS. 26 and 27. [Figure 36b] 28A to 28C are cross-sectional views showing steps for assembling the bone anchoring devices of FIGS. 26 and 27. [Figure 36c] 28A to 28C are cross-sectional views showing steps for assembling the bone anchoring devices of FIGS. 26 and 27. [Figure 36d] 28A to 28C are cross-sectional views showing steps for assembling the bone anchoring devices of FIGS. 26 and 27. [Figure 37a] 10 is a cross-sectional view showing the bone fixation element being pivoted relative to the receiving part and the fixation member locking the pivoted position after the rod is inserted. FIG. [Figure 37b] 10 is a cross-sectional view showing the bone fixation element being pivoted relative to the receiving part and the fixation member locking the pivoted position after the rod is inserted. FIG. [Figure 37c] 10 is a cross-sectional view showing the bone fixation element being pivoted relative to the receiving part and the fixation member locking the pivoted position after the rod is inserted. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 to 3, the bone anchoring device of the first embodiment comprises a bone anchoring element 1, which includes a shank 2 and a separate head 3. The bone anchoring element 1 is pivotally connected to a receiving part 5 via the head 3. The receiving part 5 receives a pressure member 6 for transmitting pressure applied by a fixation member 7 to the head 3. A rod 100 is used to connect at least two bone anchoring devices together. The bone anchoring device is of a polyaxial type, i.e., the bone anchoring element can assume various angular positions of the shank axis relative to the receiving part and can be locked in any angular position.

[0022] As shown in more detail in FIGS. 4-6 , the shank 2 includes a first end 2a, an opposite end 2b, and a bone screw 21 located along at least a portion of the length of the shank. The bone screw 21 is configured to engage bone. In the illustrated embodiment, the bone screw 21 extends substantially the entire length of the shank from a tip 22 at the second end 2b to a neck 23. An engagement portion 24 is formed at the first end 2a. The engagement portion 24 has an outer surface configured to engage with a drive tool, e.g., a star-shaped, Torx-shaped, or polygonal outer surface. The maximum outer diameter of the engagement portion 24 may be smaller than the maximum outer diameter of the bone screw portion 21. Thus, in this embodiment, the shank has a relatively large diameter. More specifically, the maximum outer diameter of the bone screw portion 21 may be larger than the maximum outer diameter of the head 3. The engagement portion 24 may be limited by a substantially cylindrical portion 25 to form an annular ring that functions as a stop for the drive tool.

[0023] 7 to 10, the head 3 includes a first end 3a, an opposite second end 3b, and a spherical outer surface 30 between the first and second ends. The spherical shape refers to a shape in which the outer surface 30 includes the maximum diameter E of the head in a direction perpendicular to a central axis C that coincides with the shank axis when the head 3 is attached to the shank 2. The distance between the maximum diameter E and the first end 3a may be shorter than the distance between the maximum diameter E and the second end 3b. More specifically, the axial height of the upper portion of the head 3, i.e., the height of the portion between the maximum diameter E and the first end 3a, is as small as possible to allow for rotation and provide a sufficiently large space for forming the drive structure 31 on the first end. In this embodiment, the drive structure 31 includes a recess extending from the first end 3a axially toward the second end 3b to a distance greater than the maximum diameter E. The recess includes a star-shaped inner profile, more specifically, a torx-shaped inner profile including six radially extending longitudinal grooves 31a. The six longitudinal grooves 31a have rounded ends and are spaced apart at regular intervals. When viewed from the central axis C, the radially outermost distances of the grooves 31a are configured such that the drive structure 31 extends over substantially the entire first end 3a, leaving only a small periphery 32 on the spherical outer surface 30. This design allows the drive structure 31 to engage the head and apply greater torque to the shank 2.

[0024] A circumferential groove 33 is formed in the spherical outer surface 30 remote from the first end 3a. The groove 33 may extend completely around the central axis C. Alternatively, the groove 33 may be located closer to the first end 3a than the axial location of the maximum diameter E. As shown in Figures 7 and 10, the radial depth of the groove 33 is configured so that the groove 33 extends to the groove 31a of the drive structure 31.

[0025] The second end 3b is formed with a mating engagement portion 34. The mating engagement portion 34 is a recess configured to receive the engagement portion 24 of the shank 2. In other words, the inner contour of the mating engagement portion 34 is substantially similar to the outer contour of the engagement portion 24 of the shank. The depth of the recess forming the mating engagement portion 34 is substantially similar to the axial length of the engagement portion 24. Furthermore, the recess has a slightly tapered inner wall that tapers toward the second end 3b. The drive structure 31 and the mating engagement portion may be in communication. A shoulder 34a between the recess and the drive structure 31 forms a stop for preventing insertion of the engagement portion 24 of the shank.

[0026] The head 3 is at least partially flexible in the region adjacent the second end 3b. This partial flexibility is achieved by a plurality of longitudinal slits 35 that open at the second end 3b and extend at least to the maximum diameter E, preferably to the circumferential groove 33. The number and width of the slits 35 are selected so that the lower part of the head 3 adjacent the second end 3b exhibits sufficient flexibility to allow the insertion of the engaging portion 24 in a snap-on manner and to retain the engaging portion 24 in the recess. The tapered inner wall of the recess allows for a tight engagement with the engaging portion 24.

[0027] The receiving portion 5 will be described in more detail with reference to FIGS. 11 to 14. The receiving portion 5 may have a generally cylindrical outer shape. The receiving portion 5 has a first or upper end 5a, a second or lower end 5b, and a passage 50 extending completely through the receiving portion 5 from the first end 5a to the second end 5b. When the head 2 is placed in the zero position in the receiving portion 5, the longitudinal center axis C of the receiving portion 5 overlaps with the longitudinal center axis C of the head 3. The opening 51 provided in the second end 5b may be sized to allow at least a portion of the lower end of the head 3 to pass through the opening. The passage 50 adjacent to the second end 5b forms an accommodation space for accommodating at least a portion of the head 3. More specifically, a seat 52 for supporting the head 3 is formed adjacent to the second end 5b. The seat 52 may have a hollow spherical shape similar to the spherical shape of the head 3. When the head 3 is received in the lower part of the receiver adjacent the second end 5b, it is supported by a seat 52 and is configured to pivot in the receiver like a ball and socket joint. The seat providing this function may have any other shape.

[0028] The passage 50 adjacent the seat 52 expands into a main portion 53 having a substantially constant inner diameter. A substantially U-shaped recess 54 is formed starting from the first end 5a, forming two free legs 55. The substantially U-shaped recess 54 forms a channel configured to receive a rod 100. Furthermore, the leg 55a adjacent the first end 5a is internally threaded. This internal thread is configured to cooperate with a fixing member 7, such as a set screw. The internal thread may be any type of thread. Preferably, the internal thread is a thread that reduces the expansion of the legs 55, such as a square thread or a flat thread. A transverse through-hole 57 is formed in the circumferential center of each leg 55. The transverse through-hole 57 is formed axially above the bottom surface of the generally U-shaped recess 54 and below the threads 56. The through-hole 57 is configured to receive a pin 4 configured to extend through the through-hole 57 and into the passage 50. A circumferential groove 58 or undercut is formed in each leg 55 at the lowermost end of the internal thread 56. An upper surface 58a of this circumferential groove 58 or undercut abuts a portion of the pressure member 6. An additional recess 59 may be provided in the outer surface of each leg 55 for engagement with a tool.

[0029] 15 to 18b, the pressure member 6 has a first end 6a and an opposite second end 6b. The pressure member 6 is configured to be placed in the receiving portion 5 so that the second end 6b faces the second end 5b of the receiving portion. The upper portion 60 of the pressure member 6 is substantially cylindrical. This allows the upper portion 60 to fit into the cylindrical portion 53 of the passage 50 of the receiving portion and to move to some extent along the axial direction within the cylindrical portion 53. Therefore, when the pressure member 6 is placed in the receiving portion 5, the central axis C of the cylinder overlaps with the longitudinal central axis of the receiving portion 5. Two legs 62, which are opposed at 180°, stand upright and away from the upper surface 61 of the cylindrical portion 60. The legs 62 can have flat inner walls facing each other and a cylindrical outer wall corresponding to the shape of the cylindrical portion 60. At the first end 6a, each leg includes an outwardly protruding edge 63 that extends radially beyond the outer surface of the cylindrical portion 60. The legs 62 are at least partially flexible in the region of their free ends and have a length and thickness such that they can be compressed towards each other and flexibly return to an upright position. The upper surface of the protruding edge 63 forms the first end 6a of the pressure member 6. Each leg 62 is provided with an axially elongated slot 64 for receiving part of the pin 4.

[0030] The pressure member 6 is further configured to support the rod 100 and includes a recess 65 extending perpendicular to the central axis C of the cylindrical portion 60. The recess 65 forms a support surface for supporting the inserted rod 100. The cross section of the recess 65 may be substantially V-shaped, preferably with a rounded bottom, as particularly shown in FIG. 18a. This allows rods of different diameters to be securely supported and substantially prevents movement of the rod laterally along the rod axis. A bore 66, coaxial with the central axis of the cylindrical portion 60, extends from the upper surface 61 of the cylindrical portion to the second end 6b and provides access to the head 3 for a drive tool. The inner diameter of the bore 66 is therefore configured to be at least equal to the maximum diameter of the recess containing the drive structure 31 of the head, so that a drive tool can pass through the bore 66 and engage the drive structure 31. A substantially spherical recess 67 is formed away from the second end 6b. The shape of the spherical recess 67 is the same as the external spherical shape of the head 3. The axial height of the spherical recess 67 is configured so that when the head 3 is inserted into the pressure member 6 and the receiving part 5 and seated on the seat 52 of the receiving part at the zero angle position of the shank 2, the upper part of the head 3 between the groove 33 and the first end 3a is located within the spherical recess 67. Furthermore, as shown particularly in Figures 23 and 24 , the spherical recess 67 and the seat 52 together form a spherical pivot support for supporting the head 3.

[0031] The pressure member 6 includes a protrusion 68 extending along the inner circumference between the spherical recess 67 and the second end and projecting inward toward the central axis C. The protrusion 68 has a position and shape that matches the position and shape of the circumferential groove 33 of the head 3 when the head 3 is inserted into the spherical recess 67 of the pressure member. The protrusion 68 may be rounded to enable engagement with and disengagement from the groove 33. Furthermore, the protrusion 68 is configured to engage with the groove 33 when the head 3 is supported by the seat 52 of the receiving part 5. Because the groove 33 and the protrusion 68 extend perpendicular to the central axis C, engagement is achieved when the head 3 is positioned at the shank's zero angle position relative to the receiving part 5. Upon engagement, audible or tactile feedback can be generated. Thus, the groove and protrusion form a position indicating structure configured to indicate a specific position of the shank relative to the receiving part. As a specific example, the specific position is the zero position when the shank 2 is coaxial with the receiving part 5. To facilitate insertion of the head 3 into the pressure member 6, a tapered portion 68a that tapers outward may be provided between the protrusion 68 and the second end 6b. The tapered portion 68a forms a slope for the head 3. Therefore, when the head 3 is turned, the protrusion 68 can easily slip out of the groove 33.

[0032] The step 69a can be formed by slightly tapering the outer surface 69 between the second end 6b and a fixed distance above the spherical recess 67 towards the second end 6b, thereby allowing the wall thickness to be slightly reduced and the protrusion 68 to fit more easily into the groove 33.

[0033] The components and parts of the bone fixation device and rod may be made of any material, but preferably titanium or stainless steel, or any biocompatible metal, metal alloy, or plastic material. Biocompatible alloys may include NiTi alloys, such as Nitinol. Other materials may include magnesium or magnesium alloys. Biocompatible plastic materials may be, for example, polyetheretherketone (PEEK) or poly-L-lactide acid (PLLA). These components may be made of the same material as other components or different materials from other components.

[0034] The process of attaching the head to the shank will be described with reference to Figures 19a to 20c. The bone fixation element may be used for many purposes. For example, the assembled bone fixation element can be integrally inserted into the receiving portion of a polyaxial bone anchor or into a bone plate including a fixation screw. As shown in the figures, first, the head 3 is oriented so that the mating engagement portion 34 of the head 3 and the engagement portion 24 of the shank 2 face each other and the recesses of both are aligned along the rotational direction (Figures 19a and 20a). Next, the head 3 is pressed against the engagement portion 24 of the shank 2 so that the lower portion of the head 3 spreads within the recess 34 and the engagement portion 24 enters the recess 34 (Figures 19b and 20b). Thereafter, the engagement portion 24 moves within the recess until the end surface 2a abuts against the shoulder 34a of the recess 34a, and the mating engagement portion 34 closes around the engagement portion 24. The head 3 is fixed against rotation by the form-fitting between the engagement portion of the shank and the engagement portion of the head. The shank 2 is held in the recess to some extent by axial frictional forces.

[0035] 21a to 21e show the process of assembling the pressure member 6 and head 3 to the receiving part 5. As shown in FIGS. 21a to 21c, the first end 3a of the tip of the head 3 is inserted into the pressure member 6 from the second end 6b until the groove 33 of the head 3 engages with the protrusion 68 of the pressure member 6. Therefore, the protrusion 68 and the groove 33 form a holding structure for holding the pressure member 6 and the head 3. Then, the assembled pressure member 6 and head 3 are inserted into the receiving part 5 from the first end 5a, with the second end 3b of the head 3 facing the opening 51. The recess 54 of the receiving part 5 for receiving the rod and the recess 65 of the pressure member 6 are aligned.

[0036] When inserting the pressure member 6 assembled with the head 3, the outer edge 63 abuts against the crest of the internal thread 56 of the receiving part 5, slightly compressing the legs 62 of the pressure member 6 toward each other. As shown in FIG. 21e, when the outer edge 63 is positioned at the crest of the thread directly above the groove 58, the slot 64 overlaps with the through hole 57, allowing the pin 4 to be inserted. The pin 4 also forms a blocking structure that prevents the pressure member from rotating within the receiving part. In this position, the head 3 is accommodated within the receiving space but is not yet positioned in the seat 52. This position is defined by the top of the pressure member 6, and is the insertion position where the pressure member 6 abuts against the lower end of the slot 64 against the stop formed by the pin 4. The lower part of the head 3 expands, leaving enough space between the outer spherical surface 30 of the head 3 and the seat to allow the engagement part 24 of the shank 2 to be inserted. The head may protrude slightly from the opening 51.

[0037] 22a-22d, which illustrate the process of attaching a pre-assembled pressure member 6, head 3, and receiving portion to a shank 2. In FIG. 22a, the engaging portion 24 of the shank 2 and the receiving portion 5 are rotationally aligned relative to each other so that the engaging portion 24 of the shank 2 can be inserted into the recess of the mating engaging portion 34 of the head 3 (FIG. 22b). The lower portion of the head 3 is flexible and can expand to allow insertion of the engaging portion 24. The pin 4 prevents upward movement of the pressure member 6 during the insertion process. FIG. 22c illustrates the process of fully inserting the engaging portion 24 into the recess of the mating engaging portion 34 until it abuts against the shoulder 34a.

[0038] Finally, as shown in FIG. 22d, the pressure member 6 moves toward the second end 5b of the receiving part so that the head 3 contacts and rests against the seat 52 of the receiving part. At the same time, the outer edge 63 snaps into the groove 58. The upper surface 58a of the groove abuts the upper surface 6a of the pressure member at the foot 62. This holds the head 3 in place in the seat 52. The spherical recess 67 of the pressure member abuts against a portion of the upper part of the head 3, thereby frictionally holding the head 3 in place. The strength of the frictional force holding the head 3 varies depending on the dimensions of the part. Preferably, the frictional force can be overcome manually to pivot the receiving part 5 relative to the head 3 and shank 2. At the same time, the lower part of the head 3 is compressed within the seat 52, firmly holding the engaging portion 24 of the shank.

[0039] As shown in Figure 23a, when the receiving part 5 is pivoted relative to the shank 2, the protrusion 68 breaks free from the groove 33, allowing the head 3 to pivot within the spherical seat 52 held by a portion of the spherical recess 67. When the pivot position of the shank 2 relative to the receiving part 5 is changed to the zero angle position, i.e., the position where the axis of the shank is coaxial with the central longitudinal axis C of the receiving part, the protrusion 68 snaps into the groove 33, thereby providing audible or tactile feedback indicating that a defined position, in this case the zero angle position, has been reached.

[0040] Once the desired angular position is reached, the rod 100 is inserted and held by the support surface 65 of the pressure member 6. As shown in FIG. 23b, the locking member 7 is inserted between the legs 55 of the receiving part and tightened. The locking member 7 thus applies pressure to the rod, and via the pressure member to the head, thereby locking the head in the angular position relative to the receiving part. The locking member 7 may have a protrusion 71. When the legs 62 are not in contact with the locking member, the protrusion 71 presses against the rod.

[0041] For clinical use, at least two bone fixation devices are inserted into the bone and connected via a rod. The bone fixation devices can be used in several ways. For example, the shank 2 can be already inserted into the bone, and the receiver 5, pre-assembled with the pressure member 6 and head 3, can be attached to the engagement portion of the already inserted shank. Alternatively, the head 3 and pressure member 6 can be pre-assembled with the receiver 5 and then attached to the shank 2 before the shank 2 is inserted into the bone. Both methods can be used when the shank is large enough to pass through the opening 51. If the shank used has a small outer diameter that can pass through the opening 51, the head 3 and shank 2 can be pre-assembled and inserted into the receiver 5 from the top end until the head 3 seats in the seat 52, as shown in Figures 19a-20c. The pressure member 6 can then be inserted and secured with the pin 4.

[0042] It should be noted that a variety of shanks can be used and that a variety of shanks can be connected to the head and receiving portion, and thus the bone fixation device can provide a modular system that allows for the use of many different shanks in combination with heads and receiving portions.

[0043] When the shank is inserted into bone before the receiving part with the pressure member and head assembled is attached, the engagement portion 24 of the shank 2 provides a drive structure for engagement with a drive tool. Because the engagement portion is relatively large, a higher torque can be applied. On the other hand, as shown in FIG. 22d, once the bone fixation device is fully assembled, the drive structure 31 of the head 3 is relatively large, so a higher torque can be applied via the head 3. This is useful when inserting the bone fixation device of FIG. 22d into bone, when adjusting the position of the shank inserted into the bone, or finally when completely removing the bone fixation device.

[0044] FIG. 24 shows a modified bone anchoring device. This modified bone anchoring device differs from the first embodiment shown in FIGS. 1 to 23b in that the bone anchoring element can be pivoted to one side at a greater maximum angle relative to the receiving part than to the opposite side. The receiving part 5000 has a lower end 5b'. A plane P defined by the opening 5100 extends at an angle relative to the central axis C. This plane can be created, for example, by cutting the end of the receiving part at an angle. The seat 5200 for supporting the head 3 is enlarged in the axial direction, providing a sufficient support surface for supporting the head 3 at a greater pivot angle. As shown in FIG. 24, the bone anchoring device 1 can be pivoted to one side at a greater maximum angle. This pivoting is limited by the abutment of a portion of the shank with the lower end 5b' of the receiving part. Note that the receiving part and / or the shank may be formed in other geometric shapes to allow the shank to be pivoted at a greater angle in one or more directions than in other directions.

[0045] Different heads can also be used to form a modular system. In addition to the head 3 described above, other heads 3' having different drive configurations can be assembled to the shank 2, as shown in Figure 25. Due to the many ways in which the bone anchoring device can be assembled and used, different heads having different properties, such as different drive configurations, different materials, different flexibility, or other properties, can be selectively assembled to the shank.

[0046] The head 3' shown in Figure 25 includes a drive structure 31' that is the same as or similar to a Mortorque® drive. Depending on the size of the drive structure 31', the head 3' can be used with the receiving part 5 and pressure member 6 of the first embodiment instead of the head 3.

[0047] 26 to 37c, the head 3' may be part of the bone fixation device of the second embodiment. The same or very similar parts to those of the first embodiment are denoted by the same reference numerals, and their description will not be repeated. This bone fixation device includes a bone fixation element 1', which includes a shank 2 similar to that of the first embodiment or another shank, a head 3', and a receiving portion 5'. The bone fixation device of the second embodiment differs from the first embodiment in that it does not include a pressure member, and the rod 100 directly transmits the pressure applied by the fixation member 7 to the head 3'.

[0048] Referring to Figures 28-31, the upper portion of the head 3' is substantially solid and has a spherical outer surface 30a at the upper portion. The spherical outer surface 30a may have a radius similar to that of the spherical outer surface 30 at the lower portion. In other words, the head 3' may have a completely spherical outer surface except for the second end 3b, which is substantially flat. The drive structure 31' on the upper outer surface 30a is provided in the form of a groove 31a' that forms wings or lobes that curve outward from a center that coincides with the apex, i.e., the highest point of the spherical outer surface 30a. More specifically, the groove 31a forms four wings 36, all of which curve toward the same side and have similar shapes, sizes, and regular distances. This design is known as a Mortorque® drive. Each wing of the groove includes a substantially vertical or slightly angled portion 36a and a rounded portion 36b, the two portions connected at the tip of the wing. As shown in FIG. 28, the groove 31a' opens outward at the tip of the wing 36. This drive structure, like various other drive structures, is configured to transmit higher torque. The groove 33 and the engagement portion 34 are similar to those in the first embodiment. To enhance the flexibility of the head 3', a second central recess 37 may be provided adjacent to the engagement recess 34 in the direction toward the spherical upper surface 30a. The central recess 37 has a smaller inner diameter than the engagement recess 34 so as to form a shoulder 34a. To further increase flexibility, the slit 35' may terminate at a certain distance from the groove 33 and continue into the inner transverse slit 35a. However, because the slit 35 and the central recess 37 are located in a region including the maximum outer diameter E of the head 3, the entire head 3' can be slightly compressed toward the central axis C.

[0049] 32 to 35b, the receiving part 5′ has an accommodation space 500 for accommodating the head 3′. The head 3′ can assume an insertion position and a final pivot position in the accommodation space 500. To achieve this, the accommodation space 500 includes a lower seat 52′ near the second end 5b, more specifically, a hollow spherical portion having a radius similar to that of the lower spherical outer surface 30 of the head 3′. The height of the lower spherical seat 52′ is configured so that, when the spherical outer surface 30 of the head 3′ is seated on the lower seat 52′, the lower seat 52′ extends slightly beyond the maximum outer diameter E of the head 3′. This allows the head 3′ to be held in a pivoted position within the lower seat 52′ by frictional force. Therefore, when the head 3′ is positioned in a pivoted position and the rod and fixing member are not yet inserted and fixed, the head 3′ is prevented from inadvertently slipping out of the lower seat 52′. To facilitate insertion of the head 3', the lower seat 52' can be widened at a smaller portion 52a' toward the second end 5b. The opening 51' at the second end 5b is sized so that the head 3' can be introduced from the second end by slightly compressing the head 3'. The receiving space 500 also includes an upper seat 520 separated from the lower seat 52' by an inner circumferential groove 510 having a diameter larger than the maximum diameter E of the head 3'. The inner circumferential groove 510 allows the head 3' to pass through the upper seat 520 and reach the pivot position of the lower seat 52'. The upper seat 520 has a spherical shape similar to the outer surface 30a, 30 of the head 3' and is configured to receive a portion of the outer surface of the head 3' that extends from the groove 33 to a certain extent below the maximum diameter E when the head 3' is within the upper seat 520. Because the head 3' is compressible to some extent, frictional forces can hold the head 3' within the upper seat 520. The end of the upper seat 520 toward the first end 5a is formed with an annular inner protrusion 521 that narrows the passage 50'. The protrusion 521 is configured to engage with the groove 33 when the head 3' is in the upper seat 520. The protrusion 521 may also have a flat bottom surface facing the second end 5b. When the protrusion 521 engages with the groove 33 of the head 3', the flat bottom surface forms a stop. The circumferential protrusion 521 defines the insertion position of the head. The passage 50' widens from the protrusion 521 and has a substantially constant diameter.

[0050] In this embodiment, the diameter of the internal thread 56 may be larger than that of the first embodiment to accommodate a larger fixing member. Because this embodiment does not have a pressure member, there is no need to provide a groove on the inner wall below the thread, as in the first embodiment. The recess 54' for receiving the rod 100 has a channel diameter that is substantially the same as or slightly larger than the diameter of the rod so as to guide the rod 100 into the recess 54'. The size of the accommodating space 500 and the depth of the substantially U-shaped recess 54' are configured so that the head 3' is seated within the lower seat 52' in the pivoted position, and the apex of the upper spherical surface 30a is positioned axially substantially above the bottom of the U-shaped recess 54'. This allows the head 3' to engage with the bottom surface of the rod 100, and the rod 100 can apply pressure to the head 3', as shown in FIGS. 37b and 37c.

[0051] The assembly of the head 3' and the receiving part 5' is shown in Figures 36a to 36d. First, as shown in Figure 36a, the head 3' is oriented so that the upper spherical surface 30a faces the opening 51' of the receiving part 5'. Then, insert the head 3' into the receiving space 500 through the opening 51'. To achieve this, slightly compress the head 3' as it passes through the opening 51'. As shown in Figure 36b, the head 3' can move into the upper seat 520 until the annular protrusion 521 engages with the lower part of the groove 33. This engagement prevents further upward movement. This is the shank insertion position. The head 3' is held in the upper seat 520 by frictional force. This prevents the head 3' itself from moving from the insertion position to the pivot position. Then, as shown in Figure 36c, the lower part of the head 3' is spread apart by the engaging part 24, allowing the shank 2 to be inserted into the recess of the mating engaging part 34. Finally, as shown in Figure 36d, the engaging portion 24 of the shank 2 abuts against the stopper 34a, and the shank 2 is held in the head 3' by friction. The stopper formed by the annular protrusion 521 prevents the head from coming off the receiving portion in the direction toward the first end 5a when the shank is inserted.

[0052] Referring to Figures 37a to 37c, when the head 3' and the receiving part 5' are attached to the shank 2, the head 3' is moved from the insertion position into the lower seat 52'. The protrusion 521 is rounded toward the first end 5a, allowing it to easily slip out of the groove 33. In Figure 37a, the axis of the shank 2 and the longitudinal center axis C of the receiving part 5' are coaxial. Next, as shown in Figure 37b, the receiving part 5' can be pivoted relative to the shank 2, and frictional force can hold the receiving part 5' in the pivoted position within the lower seat 52'. Finally, as shown in Figure 37c, a rod is inserted into the substantially U-shaped channel 54', and the fixing member 7 is threaded between the legs 55 of the receiving part 5'. When the fixing member 7 is tightened, it presses against the rod, causing the rod 100 to press against the spherical surface 30a of the head 3', locking the rod and the head together.

[0053] As with the first embodiment, for clinical use, the shank can be inserted into the bone first, and then the pre-assembled receiving portion 5' and head 3' can be attached to the shank. Alternatively, the bone fixation device including the shank 2, head 3', and receiving portion 5' can be pre-assembled and then inserted into the bone. In either case, a drive tool can access the drive structure 31' through the passageway 50', which provides a large drive surface for applying high torque.

[0054] Variations of the above embodiment are contemplated. While the receiving portion and pressure member are shown as a single member, they may be formed from two or more components. All types of shanks can be used, including partially threaded shanks, nails, cannulated shanks, and various other shanks. It is contemplated that the engaging portion of the shank may include a recess, and the mating engaging portion of the head may include a protrusion that engages with the recess of the shank. The engaging portion of the shank or the head may have various other drive structures.

[0055] The position indicating structure can be designed to indicate a predetermined angle other than a zero angle. The pressure member may have legs that extend above the rod to allow for the use of a two-part fixation member, where, for example, an inner fixation member acts on the rod and an outer fixation member acts on the legs of the pressure member.

[0056] Although the rods are shown as cylindrical rods, the rods may have any other cross section. The rod support surface may have a cylindrical or flat profile or any other suitable profile for supporting the rods.

[0057] Furthermore, the particular features, structures, or properties of one embodiment may be combined in any suitable manner with other embodiments to produce numerous additional embodiments. The particular shapes of the elements are not limited to the particular shapes shown in the drawings and may have other shapes. [Explanation of symbols]

[0058] 1,1′ bone fixation element, 2 shank, 2a first end, 2b second end, 3,3′ head, 3a first end, 3b first end, 5,5′ receiving portion, 6 pressure member, 7 fixation member, 24 engagement portion, 30 spherical outer surface, 31,31′ drive structure, 32 periphery, 33 groove, 34 counter engagement portion, 36 wing, 50,500 receiving space, 51,51′ opening, 52,52′ seat, 100 rod.

Claims

1. 1. A bone fixation device comprising: A fixing element (1, 1'), The fixation element comprises a shank (2) for fixation in a bone and a head (3, 3'), The shank (2) has a first end (2a) and an opposite second end (2b); The head has a spherical outer surface (30); the shank (2) and the head (3, 3') are separate parts adapted to be connected to each other; the shank (2) includes an engagement portion (24) at the first end (2a) for engaging with the head, the engagement portion (24) being configured to engage with a drive tool; The head (3, 3') comprises a first end (3a, 30a) including a drive structure (31, 31') for engaging a drive tool, and an opposite second end (3b) including a mating engagement portion (34) for cooperating with the engagement portion (24) of the shank.

2. a receiving portion (5, 5') having an accommodation space (50, 52; 500, 52') for pivotably receiving the head portion (3, 3'), 2. The bone anchoring device according to claim 1, wherein the head (3, 3') is connectable to the receiving part (5, 5') before being connected to the shank (2).

3. 3. The bone anchoring device according to claim 2, wherein the receiving portion (5, 5000, 5') comprises an opening (51, 51') configured to allow passage of at least a portion of the shank (2) to connect the shank (2) to the head (3, 3').

4. The shank (2) has a maximum outer diameter smaller than the diameter of the opening (51, 51'), Alternatively, the shank (2) has a maximum outer diameter which is larger than the diameter of the opening (51, 51').

5. the head (3, 3') is configured to take an insertion position in the receiving part (5, 5000, 5') in which the shank is connected to the head (3, 3') along an insertion direction, Bone anchoring device according to claim 2 or 3, wherein the axial movement of the head (3, 3') along the insertion direction is stopped directly or indirectly by a stop (64, 4; 521, 520).

6. 6. The bone anchoring device according to any one of claims 2 to 5, further comprising a pressure member (6) configured to transmit a pressure applied by a fixation member (7) to the head (3) and to lock the head in the receiving space.

7. The pressure member (6) at least partially surrounds the head (3); 7. The bone anchoring device according to claim 6, wherein the pressure member (6) comprises a protrusion (68) for temporarily attaching the head (3) to the pressure member (6) by releasably engaging with a recess (33) provided in the head.

8. 8. The bone anchoring device according to claim 7, wherein the protrusion (68) is configured to engage with the head (3) only at predefined pivotal positions of the head (3) relative to the pressure member (6).

9. The bone anchoring device according to any one of claims 2 to 8, wherein the drive structure (31) comprises a star-shaped recess.

10. The bone fixation device of claim 9, wherein the star shape is a Torx (registered trademark) shape.

11. A bone fixation device as described in claim 9, wherein the recess extends substantially over the entire free end face (32) of the head (3).

12. 6. The bone anchoring device according to any one of claims 2 to 5, wherein the head (3') is adapted to be directly locked into the receiving space (500) by a single intermediate member such as a fixing member (7) or a rod.

13. The head (3) includes a rounded free end face (30a) opposite the shank (2); 7. The bone anchoring device according to any one of claims 2 to 6, wherein the drive structure (31') comprises a groove in the form of a plurality of curved wings (36) arranged around a center of the free end face (30a) and diverging therefrom.

14. 6. The bone anchoring device according to claim 5, wherein in the insertion position the head (3') is further held in the receiving part (5') by frictional forces.

15. 15. Bone anchoring device according to any one of claims 2 to 14, wherein the accommodation space (50; 500) comprises a seat (52, 5200, 52') for directly supporting the head (3, 3') so as to allow the head to pivot.

16. A bone fixation device as described in claim 15, wherein the head (3') is sized relative to the seat (52') so as to be retained in the seat (52') by frictional force.

17. The head (3, 3') includes a longitudinal central axis (C), 17. The bone anchoring device according to any one of the preceding claims, wherein at least a part of the head (3, 3') is compressible along its longitudinal axis.

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