Support Member and Bone Fixation System

Abstract

In the present invention, inside a housing provided with an opening part capable of accommodating a head of a bone screw, a C ring can be fitted to a groove to support the head part, has an inner diameter that is smaller than the outer diameter of the head part, and is provided with a protrusion protruding outward in the radial direction or a recess recessed inward in the radial direction.

Description

[Technical field]

[0001] The present disclosure relates to a support member for supporting a mounting member mountable to a bone, and a bone fixing system including the support member. [Background technology]

[0002] Spinal implants for holding fixation rods that secure a plurality of vertebrae together are known, the head of the spinal implant includes a support member for supporting a bone screw, and a bone anchor assembly for stabilizing the bone is described. Summary of the Invention

[0003] A support member according to one embodiment of the present disclosure is a support member for supporting an installation member that can be installed on a bone, and is arranged at one end of the installation member, and is capable of supporting the head by fitting into a groove provided in the circumferential direction near the open end of the inner surface of the opening of the housing, the support member being C-ring shaped, the inner diameter of the C-ring shape being smaller than the outer diameter of the head, and the support member being provided with a protrusion that protrudes radially outward on the outer surface and fits into a hole provided in the groove, or a recess that is recessed radially inward and fits into a protrusion provided in the groove.

[0004] A bone fixing system according to one embodiment of the present disclosure includes a C-ring shaped support member, an installation member that can be installed on a bone and that has a head at one end that is shaped to include a portion of a sphere, and a housing that has an opening that can accommodate the head, wherein the inner diameter of the C-ring shape is smaller than the outer diameter of the head, and the support member has, on an outer peripheral surface of the C-ring shape, a protrusion that protrudes radially outward or a recess that is recessed radially inward, and the housing has a groove that is provided in the circumferential direction near the open end, and the groove has a hole that fits into the protrusion or a protrusion that fits into the recess. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a perspective view of a spinal implant according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is an exploded perspective view of the spinal implant. [Diagram 3] FIG. 2 is a front view of the spinal implant. [Figure 4] FIG. 2 is a cross-sectional view of the spinal implant. [Diagram 5] FIG. 2 is an enlarged view of a portion of the cross section of the spinal implant. [Figure 6] FIG. 2 is a top view of a C-ring. [Figure 7] FIG. 4 is a cross-sectional view of the C-ring. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] 13 is a bottom view of the C-ring engaged with the housing, as viewed from below. FIG. [Figure 11] FIG. 11 is a top view of a C-ring according to a second embodiment of the present disclosure. [Figure 12] FIG. 4 is a bottom view of the housing according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Embodiment 1] Hereinafter, one embodiment of the present disclosure will be described in detail. In this embodiment, a spinal implant 1 will be described as an example of a bone fixing system. The present disclosure is not limited to the spinal implant 1.

[0007] Fig. 1 is a perspective view of a spinal implant 1. As shown in Fig. 1, the spinal implant 1 includes a bone screw 10 and a housing 30. In the following, the axial direction of the bone screw 10 is referred to as the z direction, the direction in which the tabs of the housing 30 face each other is referred to as the x direction, and the direction perpendicular to x and z is referred to as the y direction. In addition, in the spinal implant 1, the housing 30 side is also referred to as the upper side, and the bone screw 10 side is also referred to as the lower side.

[0008] Hereinafter, the spinal implant 1 will be described with reference to Figs. 2 to 5. Fig. 2 is an exploded perspective view of the spinal implant 1. Fig. 3 is a front view of the spinal implant 1. Fig. 4 is a cross-sectional view of the spinal implant 1. Fig. 5 is an enlarged view of a portion of the cross section of the spinal implant 1.

[0009] The spinal implant 1 is an instrument used in spinal fixation surgery. As shown in FIG. 2, the spinal implant 1 includes a bone screw 10, a C-ring 20, and a housing 30. In the spinal implant 1, the head 11 of the bone screw 10 is housed in the housing 30, and the head 11 is supported by the C-ring 20 so that it does not come off from inside the housing 30. Therefore, the C-ring 20 can be said to be a support member. In this embodiment, an example will be described in which the spinal implant 1 includes the bone screw 10, but it may be a hook instead of a bone screw. In addition, any member that is installed in a bone may be used, and is not limited to a bone screw or a hook.

[0010] The bone screw 10 has a male thread formed on the outer periphery of the body, and a head 11 formed in a substantially spherical shape. In addition, a neck portion 12 having a smaller diameter than the head 11 is provided between the head 11 and the male thread. The bone screw 10 is set in the spine by inserting the male thread portion into the spine during spinal fixation surgery. Therefore, the bone screw 10 can be said to be a setting member that can be set in a bone.

[0011] The C-ring 20 is a C-shaped ring with a part of the ring shape missing. The C-ring 20 will be described in detail later.

[0012] The housing 30 accommodates the head 11 of the bone screw 10. The details of the housing 30 will be described later. In this embodiment, the bone screw 10, the C-ring 20, and the housing 30 are made of a biocompatible metal material, such as pure titanium, a titanium alloy, a cobalt chrome alloy, stainless steel, or the like.

[0013] 4 shows a cross section of the spinal implant 1 taken along line III-III in FIG. 3. As shown in FIG. 4, in the spinal implant 1, the head 11 of the bone screw 10 is housed in the housing 30, and the head 11 is fixed by the C-ring 20 so that it cannot be removed from the housing 30. Specifically, the head 11 of the bone screw 10 housed in the housing 30 is supported by the C-ring 20 which is then inserted from the opening 31 of the housing 30. The C-ring 20 is engaged with the groove 32 of the housing 30, so that the C-ring 20 is fixed to the housing 30. Since the inner diameter of the C-ring 20 is smaller than the outer diameter of the head 11 of the bone screw 10, the fixed C-ring 20 prevents the head 11 of the bone screw 10 from being removed from the housing 30.

[0014] Fig. 5 shows an enlarged view of the portion IV in Fig. 4. As shown in Fig. 5, the C-ring 20 engages with the groove 32 of the housing 30 and supports the head 11 of the bone screw 10 on its inner circumferential surface.

[0015] [Details of C-Ring 20] Next, the C-ring 20 will be described with reference to Figures 6 and 7. As described above, the C-ring 20 is a member for reducing the possibility that the head 11 of the bone screw 10 will come off from the housing 30. The C-ring 20 is engaged with a groove 32 provided on the inner peripheral surface of the housing 30 within the housing 30.

[0016] 6 and 7 show details of the C ring 20. Fig. 6 is a top view of the C ring 20 seen from above, i.e., from the z direction, and Fig. 7 is a cross-sectional view showing a cross section of the C ring 20 taken along line VI-VI shown in Fig. 6.

[0017] The C-ring 20, which is a support member, is capable of supporting the head 11 of the installation member, is substantially C-shaped with an opening 22 that is a portion of the ring shape that is missing, and is made of an elastic body such as metal. Also, it has a protrusion 21 that protrudes outward in the circumferential direction. More specifically, as shown in FIG. 6, in a plan view, i.e., when viewed from the +z side, at least a portion of the protrusion 21 is disposed at a position away from an axis V that is a straight line passing through the center U of the C-ring 20 and the center of the opening 22 of the C-ring 20. Also, the protrusion 21 is not axially symmetrical with respect to the axis V.

[0018] Furthermore, in a plan view, the protrusion 21 is disposed at a position where the angle θ between the axis V and a straight line passing through the tip of the protrusion 21 (the center of the protrusion 21) and the center U is equal to or greater than 1° and equal to or less than 45°. The tip of the protrusion 21 refers to the position farthest from the center U in the protrusion direction. As a result, the protrusion 21 is positioned substantially opposite the opening 22 of the C-ring 20 across the center U of the C-ring 20, and can be positioned in a thick wall portion 33 of the housing 30 described below.

[0019] The protrusion 21 fits into a hole 35 provided in the groove 32 of the housing 30. In the process of assembling the spinal implant 1, a worker performs the assembly so that the protrusion 21 of the C-ring 20 fits into the hole 35 of the housing 30.

[0020] Since the C-ring 20 is made of an elastic material such as metal, the opening 22 enables the C-ring 20 to be compressed to a state with a smaller diameter. In this embodiment, the C-ring 20 can be in an unloaded state having an unloaded outer diameter (hereinafter referred to as DO1) and an unloaded inner diameter (hereinafter referred to as DI1), and in a compressed state having a compressed outer diameter (hereinafter referred to as DO2) and a compressed inner diameter (hereinafter referred to as DI2).

[0021] The unloaded outer diameter (DO1) and the unloaded inner diameter (DI1) represent the respective diameters measured when the C-ring 20 is not loaded with a contraction stress or an expansion stress. A contraction stress is a stress that makes the opening portion 22 smaller, and an expansion stress is a stress that makes the opening portion 22 larger.

[0022] The compressed outer diameter (DO2) and compressed inner diameter (DI2) represent the respective diameters measured when the C-ring 20 is under contraction stress and the aperture 22 is in a closed state.

[0023] The no-load outer diameter (DO1) is larger than the diameter of the opening 31 of the housing 30 and is also larger than the diameter of the groove 32. Moreover, the no-load inner diameter (DI1) is smaller than the maximum diameter of the head 11.

[0024] The compressed outer diameter (DO2) is smaller than the diameter of the opening 31 of the housing 30. The compressed inner diameter (DI2) is larger than the diameter of the neck portion 12.

[0025] The C-ring 20 deforms due to expansion stress, but in a state of elastic deformation before reaching plastic deformation, the inner diameter thereof can be made larger than the maximum diameter of the head 11 .

[0026] As shown in FIG. 7, the inner circumferential surface of the C-ring 20 includes an upper inner circumferential surface 23 and a lower inner circumferential surface 24. The upper inner circumferential surface 23 is tapered so that the inner diameter of the C-ring 20 increases in the +z direction on the upper side (+z side) of the inner circumference of the C-ring 20. The upper inner circumferential surface 23 supports the head 11 of the bone screw 10 from the lower side (-z side). In order to support the head 11 of the bone screw 10 on the upper inner circumferential surface 23, the inner diameter of the C-ring 20 on the upper inner circumferential surface 23 is smaller than the outer diameter of the head 11 of the bone screw 10 even at its largest point. Therefore, after the head 11 of the bone screw 10 is accommodated in the housing 30, the C-ring 20 is engaged with the groove 32 on the inner circumferential surface of the housing 30 to fix it, thereby reducing the risk that the head 11 of the bone screw 10 will come off the housing 30.

[0027] In order to increase the range of motion of the bone screw 10 relative to the housing 30, the lower inner surface 24 is formed with a tapered shape on the lower side (-z side) of the inner circumference of the C-ring 20 so that the inner diameter of the C-ring 20 increases as it progresses in the -z direction.

[0028] The upper inner peripheral surface 23 is formed in a tapered shape with a taper angle matching the spherical shape of the head 11, or in a concave spherical shape matching the spherical shape of the head 11. In other words, the upper end of the upper inner peripheral surface 23 and the lower end of the lower inner peripheral surface 24 of the C-ring 20 have different inner diameters. This allows the upper inner peripheral surface 23 to support the head 11 while increasing the range of motion of the bone screw 10 relative to the housing 30. "Matched to the spherical shape of the head 11" does not mean a completely identical shape, but means a shape that is approximately compatible.

[0029] By using such a C-ring 20, an operator can identify the upper and lower surfaces of the C-ring 20 and assemble it appropriately by aligning the position of the protrusion 21 with the hole 35 of the housing 30, thereby enabling the spinal implant 1 to achieve the specified function and strength.

[0030] [Details of Housing 30] The housing 30 is formed in a substantially cylindrical shape. A pair of tabs extending in the z-direction from a portion of the side wall are provided, and a slit is formed between the tabs and in which a rod (not shown) is disposed. A female thread is formed on the inner peripheral surface of the tab to be screwed with a set screw (not shown).

[0031] Moreover, the housing 30 accommodates the head 11 of the bone screw 10 therein, and is attached so that the bone screw 10 can freely rotate relative to the housing 30. Furthermore, an insert (not shown) may be provided that is disposed above the head 11 of the bone screw 10 inside the housing 30 and presses the head 11 of the bone screw 10 downward under the pressure of a rod pressed by a set screw screwed into the housing 30, thereby fixing the housing 30 and the head 11.

[0032] 8 and 9 show details of the housing 30. Fig. 8 is a bottom view of the housing 30 as viewed from the lower side (-z side). Fig. 9 is a cross-sectional view taken along line IX-IX in Fig. 8.

[0033] As shown in Fig. 9, a groove 32 is formed in the circumferential direction on the inner peripheral surface of the housing 30 near the opening 31. The groove 32 is capable of engaging with the C-ring 20. Also, as shown in Figs. 8 and 9, a hole 35 is provided in the groove 32. The hole 35 is connected to the groove 32 from the lower surface of the housing 30, and the protrusion 21 of the C-ring 20 described above can be inserted therethrough.

[0034] 8, the housing 30 has a thick wall portion 33, which is a thick portion of the side wall formed by the inner and outer surfaces of the housing 30, and a thin wall portion 34, which is a thin portion. In this embodiment, the thin wall portion 34 is located at two positions in the direction of the opening of the slit that receives the rod (not shown), and the thick wall portion 33 is located at two positions in a direction perpendicular to the direction of the opening of the slit.

[0035] Fig. 10 shows the state in which the C-ring 20 is engaged with the housing 30. Fig. 10 is a bottom view of the state in which the C-ring 20 is engaged with the housing 30, seen from the bottom (-z side). In the spinal implant 1, as shown in Fig. 4, after the head 11 of the bone screw 10 is housed in the housing 30, the C-ring 20 is engaged with the groove 32 of the housing 30, but the bone screw 10 is not shown in Fig. 10.

[0036] 10, when the C-ring 20 is engaged with the housing 30, the opening 22 of the C-ring 20 is located in the thick wall portion 33 of the housing 30. This allows the opening 22, which is weaker than other portions of the C-ring 20, to maintain sufficient strength. In other words, if the opening 22 is located in the thin wall portion 34, there is a risk that the housing 30 will be damaged starting from the thin wall portion 34, which has a relatively low strength, when an excessive load is applied to the spinal implant 1, but this can be prevented.

[0037] Furthermore, when the C-ring 20 engages with the housing 30, the protrusion 21 of the C-ring 20 is also positioned in the thick wall portion 33 of the housing 30. This maintains the strength of the portion that the protrusion 21 contacts. In other words, if the hole 35 corresponding to the protrusion 21 is positioned in the thin wall portion 34, there is a risk that the housing 30 will break starting from the thin wall portion 34, which has a relatively low strength, when an excessive load is applied to the spinal implant 1, but this can be prevented.

[0038] [Assembly method] The method of assembling the spinal implant 1 will be described. As described above, the unloaded inner diameter (DI1) of the C-ring 20 is smaller than the outer diameter of the head 11 of the bone screw 10. Therefore, if the C-ring 20 is inserted into the housing 30 first, the head 11 of the bone screw 10 cannot be accommodated therein. In the assembly process of the spinal implant 1, a worker first applies expansion stress to the C-ring 20 to expand the inner diameter, and then inserts the bone screw 10 through the C-ring 20 from the tip of the head 11 so that the C-ring 20 is positioned at the position of the neck portion 12. Then, the head 11 of the bone screw 10 is accommodated in the housing 30. Next, the worker moves the C-ring 20 toward the opening 31 of the housing 30.

[0039] When the C-ring 20 is moved close to the opening 31 of the housing 30, the worker applies a force (contraction stress) from the outside to the inside of the C-ring 20. Since the C-ring 20 is literally C-shaped, the outer diameter can be easily reduced by applying a force from the outside to the inside. Since the compressed outer diameter (DO2) with the opening 22 closed is smaller than the diameter of the opening 31 of the housing 30, the worker reduces the outer diameter of the C-ring 20, aligns the protrusion 21 with the position of the hole 35, and inserts the C-ring 20 into the housing 30.

[0040] After the C-ring 20 is inserted into the housing 30, it is moved to the position of the groove 32 and engaged with the groove 32, thereby fixing the C-ring 20 to the housing 30. Since the protrusion 21 is engaged with the hole 35, the rotational movement of the C-ring 20 in the circumferential direction is also restricted.

[0041] As a result, the head 11 of the bone screw 10 cannot be detached from the housing 30 and is supported by the C-ring 20.

[0042] [Embodiment 2] Other embodiments of the present disclosure will be described below. For convenience of explanation, the same reference numerals will be given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0043] In the above-described embodiment, the protrusion 21 is provided on the C-ring 20, and the hole 35 is provided on the housing 30. In the present embodiment, on the contrary, the recess 26 is provided on the C-ring 20', and the protrusion 36 is provided on the housing 30'.

[0044] Description will be given with reference to Figures 11 and 12. Figure 11 is a top view showing the C-ring 20' as viewed from the upper side (+z side). Figure 12 is a bottom view showing the housing 30' as viewed from the lower side (-z side).

[0045] As shown in Fig. 11, the C-ring 20' has a recess 26. The recess 26 is provided at a position corresponding to the protrusion 21 of the C-ring 20 in the first embodiment. Furthermore, as shown in Fig. 12, the housing 30' has a protrusion 36. The protrusion 36 is provided at a position corresponding to the hole 35 of the housing 30 in the first embodiment.

[0046] Therefore, when the C-ring 20' is engaged with the housing 30', the protrusion 36 fits into the recess 26.

[0047] In this manner, in this embodiment, the recesses 26 and the protrusions 36 can achieve the same effects as the protrusions 21 and the holes 35 in the first embodiment.

[0048] As described above, the C-ring 20 (20') according to the present disclosure supports the bone screw 10 that can be installed in a bone, and can support the head 11 by fitting into the groove 32 provided in the circumferential direction near the open end of the inner peripheral surface of the opening 31 of the housing 30 (30') that is provided with the opening 31 arranged at one end of the bone screw 10 and capable of accommodating the head 11 having a shape including a part of a spherical surface. The C-ring 20 has a C-ring shape, the inner diameter of the C-ring 20 is smaller than the outer diameter of the head 11, and the outer peripheral surface is provided with a protrusion 21 that protrudes radially outward and fits into a hole 35 provided in the groove 32. Alternatively, the C-ring 20 has a recess 26 that recesses radially inward and fits into a protrusion 36 provided in the groove 32.

[0049] According to this configuration, the attachment position of the C-ring 20 to the housing 30 can be uniquely determined by the protrusion 21 that fits into the hole 35 of the housing 30, or the recess 26 that fits into the convex portion 36 of the housing 30', thereby reducing the risk of the C-ring 20 rotating after attachment.

[0050] In addition, the spinal implant 1 of the present disclosure includes a bone screw 10 that can be installed in a bone and has a C-ring 20 (20') in a C-ring shape, a head 11 having a shape including a portion of a sphere at one end, and a housing 30 (31') having an opening 31 capable of accommodating the head 11, wherein the inner diameter of the C-ring 20 (20') is smaller than the outer diameter of the head 11, and the C-ring 20 (20') has, on its outer circumferential surface, a protrusion 21 that protrudes radially outward or a recess 26 that is recessed radially inward, and the housing 30 (30') has a groove 32 provided in the circumferential direction near the open end, and the groove 32 has a hole portion 35 that fits into the protrusion 21 or a protrusion 36 that fits into the recess 26.

[0051] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present disclosure also includes embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Furthermore, new technical features can be formed by combining the technical means disclosed in the respective embodiments. [Explanation of symbols]

[0052] 1 Spinal implants (bone fixation systems) 10 Bone screw (installation component) 11 Head 12 Neck 20 C-ring (support member) 21 Protrusion 22 Opening part 23 Upper inner surface 24 Lower inner surface 26 Recess 30 Housing 31 Opening 32 Groove 33 Thick wall section 34 Thin wall section 35 Hole 36 Convex

Claims

1. The head can be supported by fitting into a groove provided in a circumferential direction in a housing having an opening capable of accommodating a head having a shape including a part of a spherical surface, the housing being disposed at one end of an installation member that can be installed on a bone, It is in the shape of a C-ring. The inner diameter of the C-ring shape is smaller than the outer diameter of the head, On the outer surface, A protrusion protruding radially outwardly and fitted into a hole provided in the groove, or a recess recessed inward in the radial direction, the recess being adapted to mate with a protrusion provided in the groove; the housing includes a thick-wall portion having a thick wall thickness between the opening and an outer surface of the housing, and a thin-wall portion having a thin wall thickness; A support member, wherein the C-ring shaped opening portion is positioned in the thick wall portion when the protrusion portion is fitted into the hole portion or when the recess portion is fitted into the convex portion.

2. The support member according to claim 1 , wherein the groove is disposed near an open end of an inner circumferential surface of the opening of the housing.

3. 3. The support member according to claim 1 or 2, wherein, in a plan view, at least a portion of the protrusion or recess is positioned at a position away from an axis that is a straight line passing through the center of the C-ring shape and the center of the opening of the C-ring shape, and is not axially symmetrical with respect to the axis.

4. The support member according to claim 3 , wherein an angle formed between a central portion of the protrusion or recess and a line passing through a center of the C-ring shape and the axis is greater than or equal to 1° and less than or equal to 45° in a plan view.

5. The support member according to any one of claims 1 to 4, wherein the protrusion or the recess is located in the thick wall portion when the protrusion is fitted into the hole portion or the recess is fitted into the convex portion.

6. The support member according to any one of claims 1 to 5, wherein an inner diameter of a surface of the C-ring shape that supports the head portion is different from an inner diameter of a surface opposite to the surface.

7. The support member according to any one of claims 1 to 6, wherein the installation member has a neck portion having a smaller diameter than the head portion, and the inner diameter of the C-ring shape is larger than the neck portion.

8. The support member of claim 7 , wherein the C-ring shaped opening has an inner diameter when closed that is greater than the neck portion.

9. The support member according to any one of claims 1 to 8, wherein an outer diameter of the C-ring shape is greater than a diameter of the groove when no contraction stress or expansion stress is applied.

10. The support member according to any one of claims 1 to 9, wherein the outer diameter of the C-ring shape is larger than the diameter of the opening of the housing when no contraction stress or expansion stress is applied.

11. The support member according to any one of claims 1 to 10, wherein the C-ring shaped opening can be closed by contraction stress, and the outer diameter of the C-ring shaped opening when closed is smaller than the diameter of the opening of the housing.

12. The support member according to any one of claims 1 to 11, wherein the inner diameter of the C-ring shape is deformable to be larger than the maximum diameter of the head when elastically deformed by the load of expansion stress.

13. A C-ring shaped support member; An installation member that can be installed on a bone and has a head portion having a shape including a part of a sphere at one end; a housing having an opening capable of receiving the head; The inner diameter of the C-ring shape is smaller than the outer diameter of the head, The support member has an outer circumferential surface of the C-ring shape, and the outer circumferential surface of the support member has a protrusion protruding radially outward or a recess recessed radially inward, the housing includes a groove provided in a circumferential direction, the groove including a hole portion that fits into the protrusion portion or a protrusion portion that fits into the recess portion, the housing includes a thick-wall portion having a thick wall thickness between the opening and an outer surface of the housing, and a thin-wall portion having a thin wall thickness; A bone fixing system, wherein the C-ring shaped opening portion is located in the thick wall portion when the protrusion portion is fitted into the hole portion or when the recess portion is fitted into the protrusion portion.

14. The mounting member is a bone screw or a hook. The bone fixing system of claim 13.

15. The bone screw or the hook is for a spinal implant; The bone fixing system of claim 14.

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