BLADE-LIKE OSTEOSYNTHESIS DEVICE

Abstract

An osteosynthesis device for the fixation of bone components and bone fragments is disclosed including a bone anchor having a shaft which extends along a central axis and thereby defines a distal and a proximal direction, and includes at least one blade area with a first and a second wing, and proximally adjoins a neck area and further has a head with at least one spherical segment, and the bone anchor has a central and continuous cannula opening with a diameter. The blade area at least one window with an opening width is provided. The window interacts with the cannula opening, and the head area has an opening with an opening diameter, which also interacts with the cannula opening. The diameter of the cannula opening is smaller than the opening width of the window and the diameter of the cannula opening is also smaller than the opening diameter at the head and the shaft is formed in one piece with the blade area, the neck area and the head with spherical segment.

Claims

1. An osteosynthesis device for the fixation of bone components and bone fragments, in particular vertebrae, comprising a bone anchor, wherein the bone anchor has a shaft which extends along a central axis and thereby defines a distal and a proximal direction, and the shaft has at least one blade area with a first and a second wing, and proximally adjoins a neck area and further has a head with at least one spherical segment, and the bone anchor has a central and continuous cannula opening with a diameter, and in the blade area at least one window with an opening width is provided, and the window interacts with the cannula opening, and the head area has an opening with an opening diameter, which also interacts with the cannula opening, characterized in that the diameter of the cannula opening is smaller than the opening width of the window and the diameter of the cannula opening is also smaller than the opening diameter at the head and the shaft is formed in one piece with the blade area, the neck area and the head with spherical segment.

2. The osteosynthesis device according to claim 1, wherein the opening width of the window is at least equal to or greater than the opening diameter at the head.

3. The osteosynthesis device according to claim 1, wherein the cannula has at least one tapering in distal direction.

4. The osteosynthesis device according to claim 1, wherein the shaft has fenestration openings in the blade area that interact with the cannula and are formed along a surface normal of the wing surfaces.

5. The osteosynthesis device according to claim 1, wherein the blade area the wings have at least one thickening in sections which runs mainly parallel to the central axis and increases the bending stiffness of the osteosynthesis device.

6. The osteosynthesis device according to claim 1, wherein the thickenings are located at the top edge of the wings and have a greater thickness than the area distance of the wing areas.

7. The osteosynthesis device according to claim 1, wherein the top edges have at least one convex curve and these curves approximate an oval at least in sections.

8. The osteosynthesis device according to claim 1, wherein the thickness of the thickenings varies along the central axis at least in sections.

9. The osteosynthesis device according to claim 1, wherein the thickness of the thickenings at the proximal area is greater than the thickness of the thickenings at the distal area.

10. The osteosynthesis device according to claim 1, wherein the area distance of the wing areas within the blade area varies along the central axis at least in sections.

11. The osteosynthesis device according to claim 1, wherein within the blade area the core diameter of the shaft increases in the proximal blade area.

12. The osteosynthesis device according to claim 1, wherein the blade width decreases in the proximal blade area and joins the core diameter of the shaft towards the neck area.

13. The osteosynthesis device according to claim 1, wherein a threaded bush with a bone thread is rotationally movably mounted in said window, characterized in that the threaded bush has a central opening.

14. The osteosynthesis device according to claim 13, wherein the diameter of the central lateral opening is approximately equal to the cannula diameter of the shaft.

15. The osteosynthesis device according to claim 1, wherein the window is positioned within the blade area and is located closer to the proximal end of the blade area than to the distal end of the blade area.

16. The osteosynthesis device according to claim 1, wherein the threaded bush has a distal area and this distal area is in direct contact with a contact surface of the window and this contact serves as a stop.

17. The osteosynthesis device according to claim 1, wherein the threaded bush has a proximal area and this proximal area is in direct contact with a contact surface of the window and this contact serves as a stop.

18. The osteosynthesis device according to claim 1, wherein the threaded bush has a thread core diameter which is approximately equal to the outer diameter of the shaft.

19. The osteosynthesis device according to claim 1, further comprising a coupling element having a head and a tool attachment point therein, and the coupling element has an elongated shaft, and this shaft is mounted in the cannula of the shaft and in the threaded bush.

20. The osteosynthesis device according to claim 1, wherein the coupling element at the shaft area has in sections at least one profile and the threaded bush has in sections at least one profile congruent therewith, which are in engagement with one another and are suitable for transmitting a torque from the tool attachment point to the threaded bush.

21. The osteosynthesis device according to claim 1, wherein the coupling element is axially insertable into the threaded bush and into the shaft.

22. The osteosynthesis device according to claim 1, wherein the shaft of the coupling element protrudes distally from the threaded bush and this protruding distal shaft end is mounted in the cannula of the shaft in the blade area.

23. The osteosynthesis device according to claim 22, wherein the shaft of the coupling element protrudes proximally from the threaded bush and this proximal shaft portion is also mounted in the cannula of the shaft.

24. The osteosynthesis device according to claim 1, wherein the coupling element provides a head, said head having an outer diameter which is approximately equal to or smaller than the thread outer diameter of the threaded bush.

25. The osteosynthesis device according to claim 1, wherein the coupling element has a cannula and said cannula is connected to the cannula opening of the shaft.

26. The osteosynthesis device according to claim 1, wherein the at least one elastic locking element is provided inside the blade area or outside the blade area, which is locked to the coupling element, which on the one hand enables the tool-free assembly of the coupling element and on the other hand provides a retainer of the coupling element in axial direction.

27. The osteosynthesis device according to claim 1, wherein the at least one elastic locking element is provided on the coupling element, which is locked to the shaft.

28. The osteosynthesis device according to claim 1, wherein the blade area, with the two wings defines a width between the top edges of the wings, and a thread outer diameter of the threaded bush is defined, wherein the form factor, from the ratio of the width and the thread outer diameter, is between 1.3 to 2.5.

29. The osteosynthesis device according to claim 1, wherein the osteosynthesis device has a polyaxially pivotable head which in side view has a u-shaped cutout formed by two legs for receiving a connecting rod and an internal proximal thread therein.

30. The osteosynthesis device according to claim 1, wherein the blade area, with the two wings at the proximal area, has a first wing orientation and the wings at the distal end have a second wing orientation which is different from the first wing orientation, this difference being determinable by means of a crossing angle and, viewed from the proximal viewing direction, the crossing is directed counterclockwise.

31. The osteosynthesis device according to claim 1, wherein the blade area, with the two wings at the proximal area, has a first wing orientation and the wings at the distal end have a second wing orientation which is different from the first wing orientation, this difference being determinable by means of a crossing angle, and, viewed from the proximal viewing direction, the crossing is directed clockwise.

32. The osteosynthesis device according to claim 30, wherein the osteosynthesis device has a marking or label providing an indication of the direction of crossing or an indication of anatomic positioning.

33. A system comprising at least two osteosynthesis devices according to claim 1, wherein at least one of the osteosynthesis devices has a clockwise crossing of the wing orientations and at least one further osteosynthesis device has a counterclockwise crossing of the wing orientations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS SHOW

[0022] FIG. 1 the osteosynthesis device according to the invention in an oblique view.

[0023] FIG. 2 the sole bone anchor of the osteosynthesis device according to the invention in a side view and with various sectional views. For reasons of better visualization, the twisting of the wings has been omitted.

[0024] FIG. 3 shows an exploded view of the osteosynthesis device of FIG. 1.

[0025] FIG. 4 the threaded bush with inserted coupling element without the bone anchor.

[0026] FIG. 5: Side view and Sectional view of the complete osteosynthesis device according to the invention. Again, the wings have not been twisted for visual reasons.

[0027] FIG. 6 an alternative embodiment in which the latch is provided at the head portion.

[0028] FIG. 7 the osteosynthesis device according to the invention in another oblique view.

[0029] FIG. 8. an alternative embodiment with additional web and two threaded bushes in the window to increase stiffness.

[0030] FIG. 9 shows two osteosynthesis devices according to the invention, which have a different orientation of the wing twist.

[0031] FIG. 10 shows the assembly of different osteosynthesis devices into a construct as used in spinal surgeries.

DESCRIPTION

[0032] For the osteosynthesis device (10), space-allocating coordinate references are defined, such as the proximal direction (101), the distal direction (102), which extend along a central axis (103). The radial propagation (104) is defined extending outward from the central axis (103). The circumferential spread is defined by a constant radius and along a variable circumferential angle (FIG. 1). The osteosynthesis device (10) is mainly intended for the fixation of bone components and bone fragments, in particular vertebrae. It comprises a bone anchor (1), and this bone anchor (1) comprises a shaft (13) which extends along the central axis (103) and thereby defines a distal (102) and a proximal (101) direction. The bone anchor (1) has at least one blade area (14) with a first (15) and a second wing (16), and is proximally (101) adjacent to a neck area (12) and further to a head (11) with at least one spherical segment (111). An essential feature according to the invention is that the shaft (13) is formed in one piece with the blade area (14), the neck area (12) and the head (11) with spherical segment (111). The osteosynthesis device (10) is further characterized in that the blade area (14), with the two wings (15, 16) at the proximal area (101), has a first wing orientation (105) and the wings (15, 16) at the distal end (102) have a second wing orientation (106) which is different from the first wing orientation (105), this difference being determinable by means of a crossing angle (107).

[0033] FIG. 2 shows that the bone anchor (1) of the osteosynthesis device (10) has a central and continuous cannula opening (18) with a diameter (183), and in the blade area (14) at least one window (17) with an opening width (171) is provided, and the window (17) interacts with the cannula opening (18), and the head area (11) has an opening (112) with an opening diameter (113), which also interacts with the cannula opening (18). The diameter of the cannula opening (183) is smaller than the opening width of the window (171) and the diameter of the cannula opening (183) is also smaller than the opening diameter at the head (113). Furthermore, it is preferable if the opening width of the window (171) is at least equal to or larger than the opening diameter at the head (113). This applies in particular if threaded bushes with a larger diameter are required. At least one wall section or row of wall sections (116) runs between the opening at the head (112) and the cannula opening (18), connecting the two openings to one another, and these wall sections (116) are located within the head region (11).

[0034] The central cannula (18) can be used to accomplish two tasks. On the one hand, the osteosynthesis device (10) according to the invention can be implanted into the bone in a minimally invasive manner guided by a guide wire and, on the other hand, bone cement can be injected through the cannula (18) from proximal. To prevent cement leakage distally, it is preferable if the cannula (18) has at least one tapering (181, 182) in the distal direction (102). The cement can escape into the bone tissue via fenestration openings (184) in the blade area (14). These fenestration openings (184) interact with the cannula (18) and are formed along a secant or surface normal of the wing surfaces (151, 152, 161, 162).

[0035] The window (17) provided in the blade area (14) structurally weakens the osteosynthesis device (10), especially in the bending direction. To balance the bending stiffness of the shaft with blade area (14), it is preferable that the wings (15, 16) within the blade area (14) have at least one thickening (155, 165) in sections, which runs mainly parallel to the central axis (103) and increases the bending stiffness of the osteosynthesis device (10). The thickening can be formed as a longitudinal profile along a parallel to the central axis (103) within the wing areas. For example, elongated struts extending along the wings and spaced at any distance from the central axis are possible. FIG. 2 shows a preferred embodiment of the osteosynthesis device (10) according to the invention, in which these thickenings (155, 165) are located at the top edge (154, 164) of the wings (15, 16) and have a greater thickness (157) than the area distance of the wing areas (153). This results in the greatest increase in stability. Furthermore, it is preferable that the top edges (154, 164) have at least one convex curve and that these curves approximate an oval at least in sections. With the approximated oval, the top edges (154, 164) create a homogenized contact zone with reduced contact stresses to the cortical pedicle bone in the cranial-caudal direction. This allows the osteosynthesis device according to the invention to be supported on the cortical pedicle wall and thus better absorb forces.

[0036] Since the proximal structures of the osteosynthesis device (10) are subjected to the highest loads during bending, it is advantageous from a mechanical point of view that the thickness (157) of the thickenings (155, 165) at the proximal area (101) is greater than the thickness (157) of the thickenings (155, 165) at the distal area (102). The same applies to the area distance of the wing areas (153) within the blade area. This can also vary along the central axis (103), at least in sections, in order to contribute specifically to the bending stiffness.

[0037] It is also advantageous for increasing the bending stiffness of the osteosynthesis device (10) that the core diameter (131) of the shaft (13) increases in the proximal blade area (134) within the blade area (14). It is also beneficial that the blade width (1516) decreases in the proximal blade area (144) and joins the core diameter of the shaft in the neck area (12) to prevent stress peaks at the transition from the blade area (14) to the neck area (12). To reduce stress concentrations in the window area, optional curves or otherwise provided transitions (174) can be provided at the window cutout.

[0038] For better insertion into the vertebra, it is advantageous if the distal tip of the blade area has a cutting edge (142) at each wing area, which has either a symmetrical or asymmetrical gate. Optimally, the cutting edge (142) has an acute cutting angle. Orthogonally to this, it is preferable if the cutting edges of both wing areas are at an obtuse angle to each other. It is also desirable if the distal tip (141) of the shaft (13) protrudes in the distal direction. This allows the osteosynthesis device (10) to be guided into a drill channel in the bone with the distal shaft tip (141) as the first contact element. Without this feature, such guidance is more difficult.

[0039] FIG. 3 shows the osteosynthesis device (10) according to the invention with the window (17) and that the window (17) is positioned within the blade area and is closer to the proximal end (144) of the blade area than to the distal end (141) of the blade area (102). A threaded bush (2) having a bone thread (25) is rotatably mounted in the window (17). The bone thread (25) may have at least one cutting edge (26) to provide the thread with a self-tapping property. The position of the window (17) is selected so that the threaded bush (2) is mainly interlocked with the cortical bone in the pedicle region once the osteosynthesis device (10) is fully implanted. The threaded bush (2) has a central opening (23), wherein the diameter of the central opening (23) is approximately equal to the cannula diameter (183) of the shaft (13). This makes it possible for a coupling element (3) to be plugged into the shaft (13) and the threaded bush (2). The coupling element (3) has a head (35) and a tool attachment point (36) therein and an elongated shaft (31). The elongated shaft (31) is supported in the cannula (18) of the shaft (13) and in the threaded bush (2, 23) after being plugged together. Furthermore, it can be seen that the coupling element (3) at the shaft area (31) has in sections at least one profile (34) and the threaded bush (2) has in sections at least one profile (24) congruent therewith, which are in engagement with each other and are suitable for transmitting a torque from the tool attachment point (36) to the threaded bush.

[0040] FIG. 4 shows, without the bone anchor (1), how the threaded bush (2) and the coupling element (3) are assembled. An essential feature is that the shaft (31) of the coupling element protrudes distally (102) from the threaded bush (2) and this protruding distal shaft end is supported in the cannula (18) of the shaft (13) of the bone anchor (1). Thus, the shaft (31) has at least two bearing positions within the cannula (18) of the shaft (13), distal and proximal to the threaded bush (2). This allows the coupling element (3) to additionally absorb a bending stress of the shaft (13). As also shown, the coupling element (3) has a cannula opening (32) which interacts with the cannula opening (18) of the shaft (13) in the assembled state (FIG. 5). This is the only way to ensure that the entire osteosynthesis device (10) is cannulated.

[0041] FIG. 5 shows that the threaded bush (2) has a distal area (22) and this distal area (22) is in direct contact with a contact surface (172) of the window (17) and this contact serves as a stop. Furthermore, it is shown that the threaded bush (2) has a proximal area (21) and this proximal area (21) is in direct contact with a contact surface (173) of the window (17) and this contact serves as a stop. With these stops, it is possible for the pull-out forces absorbed by the threaded bush (2) to be transmitted to the blade area (14) and then to the bone anchor (1) and finally to the spherical segment (111). Preferably, these stops are designed as concentric planar contact surfaces which simultaneously allow free rotation of the threaded bush (2). Important for the configuration of the osteosynthesis device (10) according to the invention are various dimensional relationships, i. e. that the threaded bush (2) has a thread core diameter (251) which corresponds approximately to the outer diameter of the shaft (131). Furthermore, it must be ensured that the coupling element (3) provides a head (35) and that this head has an outer diameter (351) which is approximately equal to or smaller than the thread outer diameter (252) of the threaded bush (2). Only in this way it is possible to provide a portfolio of osteosynthesis devices (10) with different threaded bush outer diameters (252), which also fit the patient-specific different pedicle sizes. Considering the size variance of the osteosynthesis devices (10), it is preferable if the coupling element (3) as well as the size of the neck area (12) and the head area (11) always remain the same size. Thus, the same tulip heads (4) can be used for adaptation for the different osteosynthesis devices (10). With the variance of the threaded bush outer diameter (252), the size of the blade area must also be adjusted so that the relation of threaded bush outer diameter (252) and blade width (1516) is anatomically consistent. It must be noted that the blade area (14), with the two wings (15, 16) defines a width (1516) between the top edges (154, 164) of the wings, and a thread outer diameter (252) of the threaded bush (2) is defined, wherein the form factor, from the ratio of 1516/252, is between 1.3 to 2.5, preferably 1.4 to 2.2, preferably 1.6 to 2.0.

[0042] In FIG. 5, as previously mentioned, it can be seen that the coupling element (3) has a cannula (32) and this cannula (32) interacts with the cannula opening (18) of the shaft (13). Furthermore, a latching mechanism is shown here, in which at least one elastic locking element (132) is provided inside the blade area (14) (FIG. 5) or outside the blade area (115, 11) (FIG. 6), which is latched to the coupling element (3, 33), which on the one hand enables the tool-free assembly of the coupling element (3) and on the other hand provides a retainer of the coupling element (3) in axial direction. Alternatively, but not shown, at least one elastic locking element can also be provided on the coupling element (3), which is latched to the shaft (13) in any way. Latching mechanisms known from the prior art will not be discussed here.

[0043] FIG. 6 shows an alternative embodiment of the latching mechanism, wherein the elastic locking element (115) is configured as a spring element which is created by two slots (114). A hook profile is formed on the inside of the elastic locking element (115), which can be latched with a latching groove (33) on the head (35) of the coupling element (3). A converse variant is also possible, in which the elastic locking element is provided on the head (35) of the coupling element (3) and a groove is provided in the head (11).

[0044] FIG. 7 shows a finally assembled osteosynthesis device (10). The tool attachment point (36), which is provided in the head (35) of the coupling element (3), can be seen. Rotation of the tool attachment point with a suitable instrument forces rotation of the threaded bush (2). Apart from this, the bone anchor (1) is rigid and formed in one piece to provide maximum stability.

[0045] FIG. 8 shows an alternative embodiment in which two threaded bushes (2) are provided which are separated by a bar (135). The width of the bar (135) must be in the factorial range of the thread pitch of the threaded bushes (2) so that the proximal threaded bush runs in the same thread groove during screw-in as the distal threaded bush created during screw-in. The web (135) has the function of providing an additional bearing for the coupling element (3) and thereby increasing the bending stiffness of the bone anchor (1).

[0046] FIG. 9 shows, as mentioned above, that the osteosynthesis device (10) can be used in combination with a polyaxially swivelling tulip head (4). The polyaxially swivelling tulip head (4) has a u-shaped cutout (42) formed by two legs (44, 45) in side view, which is suitable for receiving a connecting rod (6) and has an internal proximal thread (46) for a fixation element (5).

[0047] It was also mentioned at the outset that the pedicle canals have different left and right pedicle profiles in section. It is therefore preferable to provide a left and a right version of a bone anchor (1, 90) in a portfolio of osteosynthesis devices (9, 10). More precisely that means that the blade area (14), with the two wings (15, 16) at the proximal area (101), has a first wing orientation (105) and the wings (15, 16) at the distal end (102) have a second wing orientation (106), which is different from the first wing orientation (105), wherein this difference can be described via a crossing angle (107), and viewed from a proximal direction of view, the crossing is directed against the clockwise direction (94). In addition, the blade area (14) with the two wings (15, 16) at the proximal area (101) has a first wing orientation (105) and the wings (15, 16) at the distal end (102) have a second wing orientation (106) which is different from the first wing orientation (105), this difference being determinable by means of a crossing angle (107), and, viewed from the proximal viewing direction, the crossing is directed in the clockwise direction (93). It is preferable if the osteosynthesis device has a marking or label that provides an indication of the crossing direction or an indication of the anatomic positioning (91, 92). FIG. 9 shows an example of how the different versions are marked with “R” and “L” for right and left (91, 92). Alternative markings or color schemes are also possible.

[0048] When assembling a system of at least two osteosynthesis devices (9, 10), it must be noted that at least one of the osteosynthesis devices (9) has a crossing of the wing orientations in the clockwise direction (93) and at least one other osteosynthesis device (10) has a crossing of the wing orientations against the clockwise direction (94) (FIG. 9 and FIG. 10).

[0049] The osteosynthesis device can be used in combination with a polyaxial tulip head to allow two or more osteosynthesis devices with tulip head to be assembled together into a rigid construct using connecting rods to stabilize the bony structures (FIG. 10).