Bone fixation device

Abstract

This invention provides a bone fixation device with enhanced versatility and a method for manufacturing such a device. [Solution] A bone fixation device for connecting a rod to a bone is provided. The device comprises a fixing element 1 including a shank 2 and a head 3 to be fixed to the bone, a receiving section 5 including a first end and a second end, a channel 54 for receiving the rod 100, a passage extending from the first end to the second end and defining a central axis, and a receiving space for accommodating the head 3 of the fixing element 1, and a pressure element 6. The pressure element 6 is positioned in the passage and surrounds the head 3 laterally, and when the head 3 and the pressure element 6 are positioned in the receiving section 5, pressure is applied to the head 3 from the free end 4 of the head 3, making the head 3 rotatable relative to the receiving section 5 and lockable at a certain angle relative to the receiving section 5.

Description

[Technical Field]

[0001] The present invention relates to a bone fixation device including a bone fixation element and a receiving portion for connecting a rod to the bone fixation element. In particular, the present invention relates to a uniplanar modular bone fixation device that allows the bone fixation element to rotate relative to the receiving portion in a single plane. [Background Art]

[0002] A bone fixation device including a bone fixation element and a receiving portion is used in orthopedic surgery, particularly spinal surgery, to connect a rod to the bone fixation element fixed to bone or vertebra, and connect a plurality of bone fixation devices via the rod. In the case of a polyaxial bone fixation device, since the head of the bone fixation element is rotatably received in the receiving portion, the receiving portion can adopt various angular positions in a plurality of planes relative to the bone fixation element. In the case of a uniplanar bone fixation device, the bone fixation element can rotate in only a single plane within the receiving portion. In both polyaxial and uniplanar bone fixation devices, the bone fixation element is locked at a desired angular position relative to the receiving portion by a pressure element acting on the head.

[0003] Various uniplanar bone fixation devices are known in the art. For example, US7749258B2 describes a uniplanar bone fixation device. The bone fixation device includes a bone fixation element, which is rotatable in a single plane around the central axis of the receiving portion within the receiving portion. Rotation of the bone fixation element before fixation is limited to a single plane by a form-fitting connection between the head of the bone fixation element and the pressure element.

[0004] US7892259B2 describes a bone fixation device. The bone fixation device includes a receiving portion and a bone fixation element, the bone fixation element having a head with a spherical surface and a recess recessed from the spherical surface. A pin that engages with the recess of the head is provided in a bore of the receiving portion. Thereby, the bone fixation element is rotatable about a single axis of rotation relative to the receiving portion.

[0005] US2008 / 0195159A1 describes a pedicle screw having a shank and a ball head. The ball head has two parallel flat surfaces, each corresponding to a surface of the screw head, to determine its mobility or to prevent free rotation. [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a bone fixation device with increased versatility and a method for manufacturing such a bone fixation device. A further object is to provide such a bone fixation device and a modular system including further receiving parts, which allows for the selective combination of bone fixation elements with appropriate receiving parts according to clinical applications.

[0007] This objective is achieved by the bone fixation device described in claim 1, the method described in claim 13, and the system described in claim 15. Further developments are described in the dependent claims. [Means for solving the problem]

[0008] According to one embodiment, a bone fixation device for connecting a rod to a bone comprises a fixing element including a shank and a head for fixation to the bone; a receiving section including first and second ends, a channel for receiving a rod, a passage extending from the first end to the second end and defining a central axis, and a receiving space for housing the head of the bone fixation element; and a pressure element, the pressure element being positioned in the passage and surrounding the head laterally, and configured to apply pressure to the head from the free end of the head when the head and pressure element are positioned within the receiving section, thereby making the head rotatable relative to the receiving section and lockable at a certain angle relative to the receiving section. The fixing element comprises a first cooperating surface, and the receiving section comprises a projection provided on the inner wall of the receiving space, the projection providing a second cooperating surface for cooperating with the first cooperating surface to restrict the rotation of the head to a single plane.

[0009] The head of the bone fixation element can be inserted into the receiving part from the bottom surface of the receiving part. Therefore, a single-planar modular bone fixation device is provided that allows for the selection of the appropriate bone fixation element and its combination with the receiving part before or during surgery. In particular, the bone fixation element can be inserted into the bone or vertebra in situ, and the receiving part can be attached to the head of the bone fixation element.

[0010] Furthermore, bone fixation elements having enlarged heads that cannot be inserted into the first or upper end of the receiving portion can be used together with the receiving portion. Therefore, the overall lateral dimensions of the receiving portion can be kept small. At the same time, a robust bone fixation device can be provided by increasing the holding force between the head of the bone fixation element within the pressure element and the receiving portion.

[0011] Furthermore, the maximum rotation angle of the bone fixation element relative to the receiving portion can be increased. In a further embodiment, the modular system comprises a first receiving portion having a first pressure element, a second receiving portion having a second pressure element, and a bone fixation element. The first receiving portion includes a second coordinating surface, while the second receiving portion does not include a second coordinating surface. Therefore, a single-plane bone fixation device can be provided by selectively combining the bone fixation element with the first receiving portion, or a multi-axis bone fixation device can be provided by selectively combining the bone fixation element with the second receiving portion.

[0012] The receiving portion may be manufactured using an additive manufacturing method. This allows for the easy formation of a second cooperative surface within the receiving portion, and in particular, a projection having the second cooperative surface can be integrally formed with the inner wall of the receiving portion.

[0013] Further features and advantages will become apparent from the description of the embodiments with reference to the attached drawings. [Brief explanation of the drawing]

[0014] [Figure 1] This is an exploded perspective view of a bone fixation device according to the first embodiment. [Figure 2] It is a perspective view of the bone fixation device of FIG. 1 in an assembled state. [Figure 3] It is a cross-sectional view of the bone fixation device of FIGS. 1 and 2, taken along a plane extending through the central axis and perpendicular to the rod axis of the inserted rod. [Figure 4] It is a cross-sectional view of the bone fixation device of FIGS. 1 and 2, taken along a plane extending through the central axis and including the rod axis of the inserted rod. [Figure 5] It is a perspective view from above of the receiving portion of the bone fixation device of FIGS. 1 to 4. [Figure 6] It is a perspective view from the bottom surface of the receiving portion of FIG. 5. [Figure 7] It is a top view of the receiving portion of FIGS. 5 and 6, showing the cross-sectional line A-A. [Figure 8] It is a cross-sectional view of the receiving portion of FIGS. 5 to 7, taken along the line A-A of FIG. 7. [Figure 9] It is a top view of the receiving portion of FIGS. 5 and 6, showing the cross-sectional line B-B. [Figure 10] It is a cross-sectional view of the receiving portion of FIGS. 5 to 9, taken along the line B-B of FIG. 9. [Figure 11] It is a perspective view from above of the pressure element of the bone fixation device of FIGS. 1 to 4. [Figure 12] It is a perspective view from the bottom surface of the pressure element of FIG. 11. [Figure 13] It is a top view of the pressure element of FIGS. 11 and 12, showing the cross-sectional line D-D. [Figure 14] It is a cross-sectional view of the pressure element of FIGS. 11 to 13, taken along the line D-D of FIG. 13. [Figure 15] Shows the step of assembling the bone fixation device of FIGS. 1 to 4. [Figure 16] Shows the step of assembling the bone fixation device of FIGS. 1 to 4. [Figure 17] Shows the step of assembling the bone fixation device of FIGS. 1 to 4. [Figure 18] Shows the step of assembling the bone fixation device of FIGS. 1 to 4. [Figure 19]It is a cross-sectional view of the bone anchoring device according to a further embodiment, taken along a plane extending through the central axis and perpendicular to the longitudinal axis of the rod support surface. [Figure 20] It is a cross-sectional view of the bone anchoring device according to the further embodiment of Figure 19, taken along a plane extending through the central axis and including the longitudinal axis of the rod support surface. [Figure 21] It is a cross-sectional view of the bone anchoring device according to a further embodiment, taken along a plane extending through the central axis and perpendicular to the longitudinal axis of the rod support surface. [Figure 22] It is a perspective view of a modular system of a bone anchoring device including a first receiving portion having a first pressure element and a second receiving portion having a second pressure element shown in Figures 1 to 21. [Figure 23] It is a cross-sectional view of the system of Figure 22. DETAILED DESCRIPTION OF EMBODIMENTS

[0015] Referring to Figures 1 to 4, the bone anchoring device comprises a bone anchoring element 1, the bone anchoring element 1 includes a shank 2 for anchoring to a bone or vertebra, and a head 3. The shank 2 has a bone engaging structure such as a bone thread, and defines a screw axis S. The head 3 is shaped as a part of a sphere, and thus includes a spherical outer surface 3a which may include a region having the maximum outer diameter E of the head 3. Further, the head 3 is provided at the free end 4 thereof, and includes an engaging portion 4a for engaging with a tool such as a driver. Two opposing flat portions 30 are provided on both sides of the head 3. The flat portions 30 may be circular. The size of the flat portions 30 may be such that the spherical outer surface 3a still exists between each flat portion 30 and the free end of the head 3 including the engaging portion 4, and between each flat portion 30 and the shank. That is, the flat portions 30 are recessed from the spherical outer surface 3a. Further, the maximum outer diameter E of the head preferably extends through the axial center of the two flat portions 30.

[0016] Furthermore, the bone fixation device includes a receiving section for receiving the head 3 of the bone fixation element 1 and a rod 100 configured to connect at least two or more bone fixation devices. The receiving section 5 is provided with a pressure element 6 for applying pressure to the head 3 of the bone fixation element 1 and for supporting the rod 100. A locking element 7 in the form of an internal thread or set screw can be provided to lock the head 3 and the rod 100 into the receiving section 5.

[0017] The receiving section 5 will be described in more detail with further reference to Figures 5-10. The receiving section 5 has a first end or upper end 5a and a second end or lower end 5b opposite the upper end 5a. Generally, the receiving section 5 can have a substantially cylindrical shape with a central longitudinal axis C extending through the upper end 5a and the lower end 5b. Coaxial with the central axis C, a passage 51 is provided that extends from the upper end 5a to the lower end 5b and forms an opening 52 at the lower end 5b. At a position spaced apart from the upper end 5a, the passage 51 extends into a receiving space 53 configured to accommodate the head 3 and at least a portion of the pressure element 6. The receiving section 5 further has a substantially U-shaped recess 54 extending in the direction from the upper end 5a to the lower end 5b. The U-shaped recess 54 forms two free legs 55 that open toward the first end 5a and define a channel for receiving the rod 100. Female threads 56 are formed on the inner surface of the leg portion 55. In an exemplary embodiment, the female threads 56 are square threads or other flat threads.

[0018] In particular, as shown in Figures 6, 8, and 10, a portion of the passage 51 starting from the upper end 5a is formed by a bore 51a that is substantially cylindrical and preferably has an inner diameter smaller than the maximum outer diameter E of the head 3. The bore 51a may extend axially below the bottom surface 54a of the U-shaped recess 54. Following the bore 51a, the passage widens in the widened section 51b into a cylindrical section 51c that is substantially cylindrical. The inner diameter of the cylindrical section 51c is larger than the maximum outer diameter E of the head 3 and larger than the outer diameter of the pressure element 6 into which the head 3 is inserted. Following the cylindrical section 51c, the passage 51 narrows from the constricted section 51d toward the lower end 5b, for example, in a conical shape. Since the maximum inner diameter of the opening 52 located at the lower end 5b is larger than the maximum outer diameter of the head 3, the head 3 can be inserted into the receiving section 5 from the lower end 5b. Since the maximum inner diameter of the bore 51a is smaller than the maximum outer diameter E of the head 3, the bone fixation element 1 can be inserted into the receiving part only through the opening 52 located at the lower end 5b.

[0019] A projection 57 is formed at a circumferential position corresponding to the center of each leg portion 55 and substantially adjacent to the lower end opening 52. The projection 57 has a flat portion 57a ​​that extends substantially parallel to the central axis C along the axial direction. Thus, two opposing projections 57 having flat portions 57a are formed. The flat portion 57a ​​may include a circular upper end 57b and substantially linear side ends. The area formed by the flat portion 57a ​​of the projection may be configured to substantially cover the area of ​​the flat portion 30 provided on the head portion 3. The flat portion 57a ​​may extend along the axial direction to the middle portion 51c of the accommodation space 53. Each projection 57 is surrounded by a thin base portion 57c that extends axially along the axial direction toward the upper end 5a to the widened portion 51b of the passage 51.

[0020] As can be seen in particular from Figure 3, the distance between the planar portions 57a is such that when the head 3 is inserted into the receiving portion 5 through the lower end opening 52, with the planar portions 57a of the receiving portion and the corresponding planar portions 30 of the head 3 facing each other, each planar portion 57a ​​engages with the corresponding planar portion 30 of the head 3. Therefore, the planar portions 30 on both sides of the head 3 each form a first cooperative surface, and the planar portions 57a on both sides of the receiving portion each form a second cooperative surface configured to cooperate with the corresponding first cooperative surface of the head 3. The projection 57 is integral with the inner wall of the housing space of the receiving portion 5.

[0021] A first circumferential groove 58a can be provided on the inner wall of the leg portion 55 at a position spaced apart from the bottom surface 54a of the U-shaped recess 54. The first groove 58a can function as a stopper to restrict the upward movement of the pressure element 6 toward the upper end 5a when the pressure element 6 is assembled with the receiving portion 5 and the pressure element 6 is in the insertion position. A second circumferential groove 58b can be provided on the inner wall between the first circumferential groove 58a and the bottom surface of the axial U-shaped recess 54a. The second groove 58b engages with a portion of the pressure element 6 to fix the pressure element 6 in a pre-locked position.

[0022] Furthermore, a circumferential tool engagement groove 500 for engaging with a tool or instrument can be formed on the outer surface of each leg portion 55 at a position away from the upper end 5a. Two opposing planar areas 501 are provided on the outer surface of the receiving portion 5, which is aligned with the U-shaped recess, thereby reducing the overall width of the receiving portion.

[0023] The pressure element 6 will be described with further reference to Figures 11-14. Preferably, the pressure element 6 is a single component configured to be positioned within the passage 51. The pressure element 6 is further configured to laterally surround the head 3 when the head 3 and the pressure element 6 are positioned within the receiving portion, and to apply pressure to the head 3 from its free end. This allows the head 3 to be locked in place so that the shank axis S and the central axis C of the receiving portion form a desired angle. More specifically, the pressure element 6 has a first end or upper end 6a and a second end or lower end 6b. Adjacent to the upper end, the receiving portion 6 includes a first portion 61, the first portion 61 having a substantially cylindrical outer surface with an outer diameter that allows the pressure element 6 to move axially within the bore 51a of the passage 51 of the receiving portion 5. The upper end 6a has a rod receiving recess 62 with a rod support surface 62a. The rod support surface 62a may have a substantially V-shaped cross-section having a longitudinal axis l that extends substantially perpendicular to the cylindrical axis of the first portion 61, which coincides with the central axis C of the receiving portion 5 when the pressure element 6 is placed within the receiving portion 5. The depth of the rod receiving recess 62 may be less than the diameter of the rod 100. Thus, as shown in Figure 3, for example, when the rod 100 is placed on the rod support surface 62a, the rod 100 protrudes beyond the upper end 6a of the pressure element 6. The V-shape of the rod support surface 62a allows for the use of rods of different diameters.

[0024] The rod receiving recess 62 is formed to have two free upright legs 63. Each upright leg 63 is spaced apart from the rod support surface 62a by a groove 64. This allows the legs 63 to bend slightly in a direction perpendicular to the longitudinal axis l of the rod support surface 62a. The free end of each leg 63 is provided with an outer edge 63a projecting radially outward. The upper surface of the outer edge 63a forms the upper end 6a of the pressure element 6. To fix the insertion position of the pressure element 6, the radially outward projecting outer edge 63a is configured to engage with a first groove 58a provided on the inner surface of the leg 55 of the receiving portion 5. To fix the pressure element 6 in a pre-locked position within the receiving portion 5, the radially outward projecting outer edge 63a is configured to engage with a second groove 58b provided on the inner surface of the leg 55.

[0025] The second portion 65 of the pressure element 6 has a substantially cap-like shape configured to receive the head 3 of the bone fixation device fixing element 1. The second portion 65 of the pressure element 6 includes a hollow head receiving portion 66, the head receiving portion 66 having an opening at its lower end 6b for inserting the head 3. The head receiving portion 66 may have a lower substantially spherical spherical portion 66a and an upper substantially spherical spherical portion 66b, molded to match the spherical outer surface 3a of the head 3. To facilitate the insertion of the head 3, the intermediate portion 66c may have a larger diameter. In addition, a plurality of axial slits 67 are formed. The plurality of axial slits 67 open at the second end 6b and may have enlarged, preferably rounded, ends 67a. The plurality of axial slits 67 extend along an axial length that at least covers the intermediate portion 66c having the largest inner diameter. Generally, the number, shape, and size of the slits are selected to achieve the desired flexibility, which allows for expansion of the head receiving section 66 and compression around the inserted head 3 when the head 3 is inserted through the lower end 6b. The size of the head receiving section 66 may be determined so that friction holds the head 3 in the receiving section before the head 3 is finally locked into the receiving section 5.

[0026] The outer surface 68 of the head receiving portion 66 may be rounded and may have an outer diameter larger than the outer diameter of the cylindrical first portion 1. Adjacent to the lower end 6b, the outer surface 68 has a constricted portion 68a, for example, a constricted portion 51d on the bottom surface of the receiving space 53 of the receiving portion 5, which is configured to engage with the constricted portion 68a.

[0027] The slit 67 divides the wall of the head receiving portion 66 into wall portions 69 spaced apart in the circumferential direction. Two opposing slits are aligned with the longitudinal axis l of the rod receiving recess 62, and four slits are paired and symmetrically arranged in the circumferential direction with respect to the center of the leg portion 63, forming opposing wall portions. By partially removing these wall portions, a notch 600 is formed between the slits that constitute the wall portion 69a. The remaining portion 69a of the wall portion may have a concave lower edge 69b. The lower edge 69b fits with the convex upper edge 57b of the projection 57 having a flat portion 57a ​​of the receiving portion 5. When the pressure element 6 is positioned within the receiving portion 5 and the rod receiving recess 62 is aligned with the U-shaped recess 54 of the receiving portion 5, the projection 57 having a flat portion 57a ​​is configured to extend through the notch 600 into the hollow head receiving portion 66 and contact the flat portion 30 of the head 3. As can be seen from Figure 11, the circumferential width of the notch 600 may be smaller than the circumferential width of one wall portion 69.

[0028] Furthermore, the pressure element 6 includes a coaxial opening or bore 601 that allows access to the tool engagement recess 4a of the head 3 into which a tool such as a screwdriver is inserted.

[0029] Components or parts of the bone fixation device may be made from any material, but preferably from titanium or stainless steel, biocompatible metals or alloys, or plastic materials. As a biocompatible alloy, NiTi alloy, such as nitinol, can be used. Other materials that can be used include, for example, magnesium, magnesium alloys, and biocompatible plastic materials, such as polyetheretherketone (PEEK) or poly-L-lactic acid (PLLA). Components may be made from the same material or from materials that are different from each other.

[0030] A method for manufacturing a bone fixation device includes manufacturing at least a receiving portion 5 using an additive manufacturing method, more specifically, an additive layer manufacturing method. In such a method, the receiving portion is formed by depositing the material layer by layer and solidifying or melting the material of each layer at positions corresponding to the receiving portion and the cross-section of each layer. Preferred methods include, for example, selective laser sintering (SLS) or selective laser melting (SLM). In this case, the material is a powder, such as metal powder or plastic powder, and a laser is used to melt the powder. The material for the continuous layers is applied to the support surface or the previous layer, and the laser beam is irradiated at positions in the layer corresponding to the cross-section of the receiving portion within each layer. Thus, the receiving portion is formed in an additive manner. The material may preferably be titanium powder, stainless steel powder, or a suitable metal alloy. Alternatively, an electron beam may be used to melt the material. Furthermore, other known methods, such as powder-based 3D printing methods that deposit multiple layers of powder material by applying a binder material to positions corresponding to the receiving area and then solidifying the layers of powder material, can also be used. In addition, other additive manufacturing methods, such as fused deposition modeling (FDM), can also be used.

[0031] When using additive manufacturing, the protrusions 57 of the receiving part can be easily formed based on a three-dimensional computer-aided design (CAD) model of the receiving part to be manufactured.

[0032] Furthermore, additive manufacturing, particularly additive layering, affects the external shape of the received parts manufactured by this method. For example, even after polishing, edging, coating, or other post-processing, the layered structure may be visible on the surface of the finished part. Also, when inspecting the manufactured parts, traces of laser or electron beam may be identifiable. Therefore, compared to conventional machining methods, it is possible to identify the use of additive manufacturing, especially additive layering, based on the finished part.

[0033] Refer to Figures 15-18 to describe the steps for assembling the bone fixation device. As shown in Figure 15, the rod receiving recess 62 of the fixing element 6 and the U-shaped recess 54 of the receiving portion 5 are aligned, and the pressure element 6 and the receiving portion 5 are pre-assembled so that the pressure element 6 can be inserted into the insertion position. In the insertion position, the outer edge 63a of the pressure element 6 engages with the upper wall of the first groove 58a, so that when the head 3 is inserted into the head receiving portion 66 of the pressure element 6, the pressure element 6 does not move toward the upper end 5a of the receiving portion 5. One possibility for pre-assembling the pressure element 6 and the receiving portion 5 is to insert the pressure element 6 from the upper end 5a of the receiving portion 5 by slightly compressing the head receiving portion 66 and leg portion 63 of the pressure element.

[0034] At the insertion position, the head receiving portion 66 of the pressure element 6 is located within the widened portions 51b and 51c of the housing space 53. The notch 600 is aligned circumferentially with the projection 57 of the receiving portion 5.

[0035] Referring further to Figure 15, the receiving portion 5 and the pressure element 6 are positioned relative to the bone fixation element 1 such that the flat portion 30 of the head 3 aligns with the projection 57 when the head 3 is inserted. The head 3 is inserted through the lower end opening into the receiving space 53 of the receiving portion 5 and into the head receiving portion 66 of the pressure element 6.

[0036] Next, as shown in Figure 16, the receiving section 5 and the pressure element 6 are attached to the head section 3. As shown in Figure 17, by pulling the receiving portion 5 against the bone fixation element 1, the outer edge 63a engages with the second groove 58b. Because the leg portion 63 of the pressure element 6 has slight flexibility, the outer edge 63a can disengage from the first groove 58a and engage with the second groove 58b. The pressure element 6 takes a pre-locked position in which the constricted outer surface 68a of the pressure element 6 engages with the constricted inner surface 51d of the receiving portion 5. As a result, in the pre-locked position, the lower end opening 52 is reduced by the pressure element 6, preventing the head 3 from coming out through the lower end opening 52. The head 3 is rotatable only in a single plane including the longitudinal axis and central axis of the rod support surface.

[0037] Figure 18 shows a bone fixation device having an inserted rod 100 and a locking element 7. Once the appropriate angular position of the receiving portion 5 is established relative to the bone fixation element 1, the head 3 and rod 100 are locked to the receiving portion 5 by inserting the rod 100 and then inserting and tightening the locking element 8.

[0038] In clinical use, the bone fixation device can be used in one of the following ways: In the first method, the fixation element 1 is pre-assembled with a connecting device including a receiving portion 5 and a pressure element 6 outside the patient's body. In the second method, the fixation element 1 is already inserted into the bone or vertebra, and the receiving portion and pressure element are attached in situ to the head 3 of the bone fixation element 1. When attached in situ, the flat portion 30 of the head 3 must be properly oriented relative to the flat portion 57a ​​of the receiving portion 5. This can be achieved, for example, by using an instrument (not shown) configured to indicate the position of the plane.

[0039] Typically, multiple multi-axis bone fixation devices are inserted into the bone or vertebra, particularly into the pedicle of the vertebra. The receiving portion 5 is then aligned so that the rod 100 is inserted into the U-shaped recess 54 of two or more bone fixation devices.

[0040] Due to the design of the receiving section and pressure element, the bone fixation element 1 can be used in combination with a head 3 having a larger outer diameter. For example, a bone fixation element with a head having a maximum outer diameter of 8 mm can be used instead of a head with a maximum outer diameter of 7 mm. Furthermore, the fixation element 1 can rotate at a larger maximum angle within the receiving section compared to bone fixation devices with smaller heads. The maximum rotation angle that can be formed by the shank axis S and the central axis C may be 35° or more. A larger head can increase the retention force and provide a stable and robust implant.

[0041] Figures 19 and 20 show further embodiments of the receiving section and pressure element of the bone fixation device. Parts or components identical or similar to those in the embodiments described above are denoted by the same reference numerals and their descriptions are omitted. In this embodiment, the receiving section 5' and pressure element 6' are manufactured as a single component using additive manufacturing. Therefore, the 3D CAD model is a model of a composite component including the receiving section 5' and pressure element 6'. Cross-sectional data of the composite component in each layer is used to control the solidification device, such as a laser, in each layer. Laser sintering, laser melting, or electron beam melting can be used. However, this method may require the additive manufacturing of support structures to enable the production of complex shapes, including overhangs. These support structures are later removed.

[0042] Furthermore, an additive lithography-based metal fabrication method (LMM) may be used, which enables manufacturing without the use of support structures. The raw material consists of metal particles dispersed in an organic binder phase. At room temperature, the raw material is a solid block. Thin layers of the raw material can be deposited on a build platform by applying heat, for example, with a heating blade. Then, photopolymerization of the organic binder phase is induced by selectively irradiating each layer of the raw material with light. The layer-by-layer heating and photopolymerization process can be repeated to manufacture the entire part layer by layer. The surrounding uncured raw material is solidified by active cooling. The part thus printed is finally incorporated into the block of raw material as a green part. Since the unused raw material supports the green part, no additional support structures are required. Subsequently, the green part can be separated by liquefying the block of raw material and removing the organic binder. The green part is then sintered in a sintering furnace to produce the final part.

[0043] Figure 21 shows a further embodiment in which the design of the receiving portion differs from the embodiment described above. The receiving portion 5'' does not have a projection 57 having a flat portion 57a ​​integrally formed with the wall of the housing space 53. Instead, the receiving portion 5'' has two opposing lateral through holes 570 formed adjacent to the lower end 5b and at the circumferential center of the leg portion 55. The size and shape of these through holes 570 are formed to receive pins 571, for example, in a press-fit manner. Each pin 571 has a flat front surface 571a configured to cooperate with the flat portion 30 of the head 3. The axial length of the pin 571 may be set so that the front surface 571a abuts against the flat portion 30 of the head 3 and restricts the rotational movement of the head 3 to a single plane.

[0044] Referring to Figures 22 and 23, a modular system is shown comprising a bone fixation element 1, a first receiving section 5 including a first pressure member 6, and a second receiving section 5'''' including a second pressure member 6''''. The bone fixation element 1 is the same as the bone fixation element 1 in the previously described embodiment, and the first receiving section 5 including the first pressure member 6 is the same as the receiving sections 5, 5'', 5'' including the pressure members 6, 6'', 6'' shown in Figures 1-21. The second receiving section 5'''' including the second pressure member 6'''' is configured together with the bone fixation element 1 to form a multi-axis bone fixation device. For this purpose, the second receiving section 5'''' does not have a projection 57. Instead, the widened sections 51b, 51c and narrowed sections 51b of the receiving space 53 are rotationally symmetric. As a result, the receiving section 5'''' does not have a second cooperating surface that restricts the rotation of the head to a single plane. The second pressure member 6'''' does not have a notch 600. Instead, the second pressure member 6'''' has two opposing full wall portions 69.

[0045] Therefore, the head can rotate in multiple planes within the receiving portion 5'''', which includes the pressure member 6''''. Depending on clinical requirements, the user can select a single-plane bone fixation device from the modular system by combining the bone fixation element 1 with the first receiving portions 5, 5'', 5'' and the first pressure elements 6, 6'', 6'', or by combining the bone fixation element 1 with the second receiving portion 5'''' and the second pressure element 6''''. This allows the surgeon a wide range of implant options.

[0046] Modifications of the bone fixation device of the first embodiment are also possible. For example, the projection 57 having the flat portion 57a ​​may be positioned at a different location in the circumferential direction. For example, the projection 57 may be aligned with the U-shaped recess 54 of the receiving portion 5. In this case, the single plane of rotation is perpendicular to the rod axis. In other words, the single plane of rotation is perpendicular to the longitudinal axis of the U-shaped recess 54 or the rod receiving recess 62 of the pressure element 6.

[0047] The cooperating surfaces do not necessarily have to be flat; they may have other shapes. For example, one surface may be flat while the other is convex. Other shapes are also possible.

[0048] In further modifications, the system may also include a second bone fixation element (not shown) having an additional opposing planar portion spaced 90° apart from the planar portion 30, and a third receiving portion and a third pressure member (not shown) having an additional projection 57 spaced 90° apart in the circumferential direction. The corresponding pressure member (not shown) may have an additional notch spaced 90° apart from the notch along the circumferential direction. By combining the second bone fixation element with the third receiving portion and the third pressure member, a uniaxial bone fixation device can be provided in which rotation of the bone fixation element within the receiving portion is prohibited.

[0049] Instead of the locking member 7, which is a set screw, all other types of locking assemblies known in the art can be used. As bone fixation elements, all types of bone fixation elements suitable for fixation to bone or vertebrae, such as bone screws and bone nails, can be used. The term “rod,” as used herein and in the appended claims, should be understood to include any elongated member, regardless of the cross-sectional shape of the elongated member. Specifically, the spinal stabilization rods used herein may have substantially circular, elliptical, or angular cross-sections. This cross-section may further vary along the length of the rod. The rod may be rigid or flexible.

[0050] Furthermore, the receiving portion and the housing space for the pressure element may be designed to allow the bone fixation element to rotate to a larger angle of rotation on one side compared to the other side.

[0051] The shape of the part is not limited to the detailed shape shown in the drawings. Deviations are possible and are included in this disclosure.

Claims

1. A bone fixation device for connecting a rod to a bone, A fixing element (1) including a shank (2) and a head (3) for fixing to the bone, A receiving section (5) including a first end (5a) and a second end (5b), a channel (54) for receiving the rod (100), a passage (51) extending from the first end to the second end and defining a central axis (C), and a receiving space (53) for accommodating the head (3) of the bone fixation element (1), The device comprises a pressure element (6), the pressure element (6) being positioned within the passage (51) and surrounding the head (3) laterally, and when the head (3) and the pressure element (6) are positioned within the receiving portion (5), pressure is applied to the head (3) from the free end (4) of the head (3), making the head (3) rotatable relative to the receiving portion (5) and lockable at a certain angle relative to the receiving portion (5). A bone fixation device comprising: a fixing element having a first cooperating surface (30); a receiving portion having a projection (57) provided on the inner wall of the housing space (53); the projection (57) cooperating with the first cooperating surface (30) to provide a second cooperating surface (57a) for restricting the rotation of the head (3) to a single plane.

2. The head (3) includes a spherical outer surface (3a), The bone fixation device according to claim 1, wherein the first cooperating surface (30) is a recessed portion from the spherical outer surface (3a).

3. The bone fixation device according to claim 1 or 2, wherein the second cooperating surface (57a) is integral with the inner wall of the housing space (53).

4. The bone fixation device according to any one of claims 1 to 3, wherein each of the first cooperating surface (30) and the second cooperating surface (57a) includes a flat portion, and the flat portions cooperate to restrict rotation to a single plane.

5. The bone fixation device according to claim 1 or 2, wherein two first cooperative surfaces (30) and two second cooperative surfaces (57a) are provided, respectively, that are located on opposite sides of each other.

6. The passage (51) includes an opening (52) provided at the second end (5b), The bone fixation device according to any one of claims 1 to 5, wherein the opening (52) has a width that allows insertion of the head (3) through the opening (52) only when the first cooperating surface (30) and the second cooperating surface (57a) are facing each other.

7. The bone fixation device according to any one of claims 1 to 6, wherein the second cooperating surface (57a) is provided adjacent to the opening (52).

8. The pressure element (6) includes a head receiving portion (66) that extends from the upper part of the inserted head (3) toward the shank (2) beyond the portion having the maximum outer diameter (E) of the head (3), The bone fixation device according to any one of claims 1 to 7, wherein the head receiving portion (66) is provided with at least one opening (600) that allows the first cooperating surface (30) to come into contact with the second cooperating surface when the head (3) is housed within the head receiving portion (66).

9. The bone fixation device according to claim 8, wherein the wall defining the head receiving portion (66) includes a slit (67) for making the wall flexible, and the opening (600) is formed by a notch between two adjacent slits (67).

10. The pressure element (6) includes a rod support surface (62a) that defines the orientation of the rod axis, The bone fixation device according to claim 8 or 9, wherein the at least one opening (600) is oriented in a direction perpendicular to the rod axis.

11. The bone fixation device according to any one of claims 8 to 10, wherein the projection (57) is configured to extend through the opening (600).

12. The receiving portion (5) has a constricted portion (51d) provided near the opening (52), The coupling device according to any one of claims 8 to 11, wherein the constricted portion (51d) is configured to cooperate with the corresponding constricted portion (68a) of the pressure element (6) to clamp the head (3).

13. A method for manufacturing a bone fixation device according to any one of claims 1 to 12, the method comprising manufacturing at least the receiving portion (5) using an additive manufacturing method, wherein the steps are: The steps include providing computer data of a three-dimensional (3D) model of the receiving unit (5), The steps include manufacturing the receiving portion (5) layer by layer from the molding material according to the cross-section of a portion of the receiving portion (3) in the corresponding layer, based on the computer data, Preferably, the additive manufacturing method comprises one of laser sintering (SLS), laser melting (SLM), electron beam melting (EBM), or lithography-based metal fabrication (LMM).

14. The method according to claim 13, wherein the receiving portion (5) and the pressure element (6) are preferably manufactured together without the use of a support structure, such that the pressure element (6) is located within the receiving portion (5).

15. A system comprising a bone fixation device according to any one of claims 1 to 12, The receiving section (5) is the first receiving section, The aforementioned pressure element (6) is a first pressure element, A second receiving section (5′′′) having a second pressure element (6′′′) is provided. The system is configured such that the second receiving portion (5′′′) does not have a second cooperating surface (57), thereby allowing the bone fixing element (1) to rotate in a plurality of planes.

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