Intervertebral fusion device

Abstract

An intervertebral fusion device includes a structural ceramic body. The structural ceramic body has a bottom surface, a top surface, an outer peripheral surface connecting the bottom surface and the top surface, and at least one through hole passing through the bottom surface and the top surface. An inner surface of the through hole is a convexly curved surface or the through hole is a funnel-shaped through hole. In the through hole having the convexly curved surface, a hole diameter of the through hole gradually increases from a center of the through hole toward the bottom surface and the top surface. In the funnel-shaped through hole, the hole diameter of the through hole gradually increases from the bottom surface toward the top surface. The outer peripheral surface of the structural ceramic body is wavy or zigzag.

Description

Technical Field

[0001] This invention relates to a device implanted between the vertebrae, and more particularly to an intervertebral fusion device with low stiffness and uniform internal stress distribution. Background Technology

[0002] The spine is the most important skeleton in the human body. It generally consists of 26 vertebrae, including 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae. Together with muscles and ligaments, the spine provides support for the entire body weight.

[0003] Between the vertebrae of vertebrates are intervertebral discs. These discs are relatively soft and provide lubrication for sliding between the vertebrae. This sliding between the vertebrae gradually causes wear and tear on the discs, which can lead to collapse or deformation, compressing nerves and causing pain. Therefore, implanting intervertebral fusion cages between the vertebrae is a common method to alleviate patient suffering.

[0004] Metals such as titanium alloys or stainless steel are traditionally used as materials for interbody fusion cages. However, because stainless steel may release toxic ions (such as nickel) into the bloodstream, titanium alloy cages are more commonly used clinically. However, the elastic modulus of titanium alloy is approximately 114 GPa, higher than that of bone. To reduce stiffness, titanium alloy interbody fusion cages typically have a large, through-hole in the center. This through-hole can be used to insert autologous or artificial bone grafts.

[0005] Although the rigidity of the titanium alloy interbody fusion cage is reduced due to its central through-hole, vertebral subsidence can still occur some time after implantation because all stress is concentrated at the edges of the cage. Furthermore, because titanium alloy is a metallic material, it interacts with electromagnetic waves, resulting in blurred images around the implanted titanium alloy interbody fusion cage when observed using X-rays, MRI, and CT scans, making postoperative observation difficult.

[0006] Another type of polymer interbody fusion cage has also been developed. The materials used in polymer interbody fusion cages are typically polymethyl methacrylate (PMMA) or polyetheretherketone (PEEK). PEEK has an elastic modulus of approximately 5 GPa, close to the stiffness of bone. PEEK also has high strength; however, PMMA and PEEK are manufactured using polymer monomers, and over time, trace amounts of toxic monomers are released into the human body.

[0007] Therefore, the clinical need for interbody fusion devices remains:

[0008] 1. The stiffness is matched with that of the nearby vertebrae;

[0009] 2. The interbody fusion cage is strong enough to support the body weight;

[0010] 3. A perforation is required to allow for the placement of bone fillers;

[0011] 4. It does not affect electromagnetic waves such as X-rays, MRI, and CT scans. Summary of the Invention

[0012] This invention relates to an interbody fusion device that can meet the above requirements, and in particular, can adjust its stiffness to suit the needs of individual patients.

[0013] According to an embodiment of the present invention, an intervertebral fusion device includes a structural ceramic body having a bottom surface, a top surface, an outer peripheral surface connecting the bottom surface and the top surface, and at least one through-hole penetrating the bottom surface and the top surface, wherein the inner surface of the through-hole is an inwardly convex curved surface or the through-hole is a funnel-shaped through-hole. In the case of a through-hole with an inwardly convex curved surface, the diameter of the through-hole gradually increases from the center of the through-hole towards the bottom surface and the top surface. In the case of a funnel-shaped through-hole, the diameter of the through-hole gradually increases from the bottom surface to the top surface. The outer peripheral surface of the structural ceramic body is wavy or serrated.

[0014] In the intervertebral fusion device according to an embodiment of the present invention, the material of the above-mentioned structural ceramic body includes zirconium oxide (ZrO2), aluminum oxide (Al2O3), cerium oxide (CeO2), yttrium oxide (Y2O3), magnesium oxide (MgO), titanium oxide (TiO2), silicon oxide (SiO2), zinc oxide (ZnO), bioglass, silicon nitride, silicon carbide, or composite materials of the foregoing.

[0015] In the intervertebral fusion device according to an embodiment of the present invention, the material of the above-mentioned structural ceramic body includes yttria-tetragonal zirconia polycrystal (Y-TZP), cerium-tetragonal zirconia polycrystal (Ce-TZP), a composite material of yttria-tetragonal zirconia and alumina (Y-TZP / Al2O3), or a composite material of cerium-tetragonal zirconia and alumina (Ce-TZP / Al2O3).

[0016] In the intervertebral fusion device according to an embodiment of the present invention, the bottom surface and top surface of the above-mentioned structural ceramic body are parallel to each other.

[0017] In the intervertebral fusion device according to an embodiment of the present invention, the bottom surface and top surface of the above-mentioned structural ceramic body are not parallel to each other.

[0018] In the intervertebral fusion device according to an embodiment of the present invention, the above-mentioned structural ceramic body has a thin side and a thick side, the average diameter of the through hole is smaller closer to the thin side, and the average diameter of the through hole is larger closer to the thick side.

[0019] In the intervertebral fusion device according to an embodiment of the present invention, the corners of the outer peripheral surface and the top and bottom surfaces are all rounded, and the corners of the inner surface of the through hole and the top and bottom surfaces are also rounded.

[0020] In the intervertebral fusion device according to an embodiment of the present invention, the through-holes of the above-mentioned structural ceramic body are filled with bone graft.

[0021] In the intervertebral fusion device according to an embodiment of the present invention, the total opening area of ​​the through holes on the top surface accounts for more than 10% of the area fraction of the top surface.

[0022] In the intervertebral fusion device according to an embodiment of the present invention, the total opening area of ​​the through holes on the top surface accounts for more than 50% of the area of ​​the top surface.

[0023] In the intervertebral fusion device according to an embodiment of the present invention, the outer peripheral surface of the above-mentioned structural ceramic body is arc-shaped.

[0024] In the intervertebral fusion device according to an embodiment of the present invention, the bottom surface and the top surface of the above-mentioned structural ceramic body are both wavy or serrated.

[0025] In the intervertebral fusion device according to an embodiment of the present invention, the aforementioned at least one through hole is a plurality of through holes, and the plurality of through holes are uniformly distributed in the structural ceramic body.

[0026] Based on the above, this invention uses a structural ceramic body as the basic material for the intervertebral fusion device, and designs at least one through-hole with a specific shape therein. Therefore, the stiffness of the intervertebral fusion device can be adjusted to approximate the stiffness of bone. Furthermore, the stiffness of the intervertebral fusion device can be changed or adjusted according to the needs of each patient by varying the number and size of the through-holes. Since the material of the intervertebral fusion device is ceramic, it is not only harmless to the human body but also sufficient to withstand the body's weight, and it does not interfere with electromagnetic waves such as X-rays, MRI, and CT scans, facilitating postoperative monitoring. Because the outer peripheral surface of the structural ceramic body of this invention is wavy or serrated, it can prevent slippage of the intervertebral fusion device after implantation between the vertebrae, increasing the fit between the intervertebral fusion device and the vertebrae. Attached Figure Description

[0027] Figure 1 This is a top view of an intervertebral fusion device according to a first embodiment of the present invention.

[0028] Figure 2A yes Figure 1 A side view of an intervertebral fusion device.

[0029] Figure 2B yes Figure 1 Another side view of the intervertebral fusion device.

[0030] Figure 2C yes Figure 1 Another side view of the intervertebral fusion device.

[0031] Figure 2D yes Figure 1 Another side view of the intervertebral fusion device.

[0032] Figure 3 This is a top view of an intervertebral fusion device according to a second embodiment of the present invention.

[0033] Figure 4 This is a top view of an intervertebral fusion device according to a third embodiment of the present invention.

[0034] Figure 5 This is the top view of the structure in comparison group 1.

[0035] Figure 6 This is the top view of the structure in comparison group 2.

[0036] Figure 7 This is the top view of the structure in Experiment Example 1.

[0037] Figure 8 This is the top view of the structure in Experiment Example 2.

[0038] Explanation of reference numerals in the attached figures

[0039] 10, 30, 40: Interbody fusion device

[0040] 100, 300, 400: Structural ceramic bodies

[0041] 102: Bottom

[0042] 104, 300a, 400a: Top surface

[0043] 104a, 304a: Thin-sided

[0044] 104b, 304b: Thick side

[0045] 106, 302, 402: outer peripheral surface

[0046] 108, 110, 306, 308, 310, 312: Through holes

[0047] 112: Inner surface

[0048] 402a: Corner

[0049] C1, C2: Center

[0050] R: Rounded corner

[0051] s1, s2: Distance

[0052] t1: Thickness Detailed Implementation

[0053] Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same element symbols are used in the drawings and description to denote the same or similar parts.

[0054] The exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention may be implemented in many different forms and should not be construed as limited to the embodiments described below. In the drawings, for clarity, the sizes of various regions, parts, and through holes, as well as the length and width of the device, may not be drawn to scale. For ease of understanding, the same elements will be labeled with the same reference numerals in the following description.

[0055] Figure 1 This is a top view of an interbody fusion device according to an embodiment of the present invention. Figure 2A yes Figure 1 A side view of an intervertebral fusion device. Figure 2B yes Figure 1 A side view of another interbody fusion device. Figure 2C yes Figure 1 A side view of another interbody fusion device. Figure 2D yes Figure 1 A side view of another type of intervertebral fusion device.

[0056] Please refer to the following at the same time Figure 1 and Figure 2A , Figure 2B , Figure 2C or Figure 2DThe intervertebral fusion device 10 of this embodiment includes a structural ceramic body 100. The material of the structural ceramic body 100 is basically selected to be harmless to the human body and safe in the human body. Moreover, although bone is a hard tissue inside the human body, the elastic modulus of bone is relatively low. For example, the elastic modulus of cortical bone is about 7 GPa to 30 GPa. Therefore, the stiffness of the intervertebral fusion device 10, which is implanted between the vertebrae and in close contact with the cortical bone, should be as close as possible to that of the cortical bone.

[0057] Therefore, the structural ceramic body 100 of the intervertebral fusion device 10 is fabricated to have a bottom surface 102, a top surface 104, an outer peripheral surface 106 connecting the bottom surface 102 and the top surface 104, and a plurality of through holes 108 and 110 penetrating the bottom surface 102 and the top surface 104. The design of the through holes 108 and 110 is such that the rigidity of the intervertebral fusion device 10 is close to that of cortical bone. From the viewpoint of preventing the intervertebral fusion device 10 from slipping between the vertebrae, the outer peripheral surface 106 is preferably wavy or serrated. In addition, from the viewpoint of avoiding stress concentration, the corners between the bottom surface 102 and the outer peripheral surface 106, and the corners between the top surface 104 and the outer peripheral surface 106 of the aforementioned structural ceramic body 100 can all be designed as rounded corners R. The corners of the outer peripheral surface 106 can also be designed as rounded corners R, and the corners at the openings of each through hole 108 and 110 at the bottom surface 102 and the top surface 104 are also rounded corners R. This design avoids sharp corners within the entire interbody fusion device 10. The absence of sharp corners prevents stress concentration and improves the stress uniformity of the interbody fusion device 10 when bearing the body weight.

[0058] In one embodiment, the material of the structural ceramic body 100 may include ceramic materials such as zirconium oxide (ZrO2), aluminum oxide (Al2O3), cerium oxide (CeO2), yttrium oxide (Y2O3), magnesium oxide (MgO), titanium oxide (TiO2), silicon oxide (SiO2), zinc oxide (ZnO), bioactive glass, silicon nitride, and silicon carbide, and composite materials of the aforementioned materials may also be used. To adjust the stiffness of the structural ceramic body 100 to suit the needs of each patient while bearing the weight of the human body, for example, the material of the structural ceramic body 100 may be yttrium-stabilized tetragonal zirconium oxide (Y-TZP), cerium-stabilized tetragonal zirconium oxide (Ce-TZP), a composite material of yttrium-stabilized tetragonal zirconium oxide and aluminum oxide (Y-TZP / Al2O3), or a composite material of cerium-stabilized tetragonal zirconium oxide and aluminum oxide (Ce-TZP / Al2O3).

[0059] Regarding the detailed design of through holes 108 and 110, the upper and lower limits of the stiffness of the structural ceramic body 100 can be estimated first based on the following mathematical formula (from "Elastic behavior of a model two-phase material" by CLHsieh, WHTuan, TTWu, published in the Journal of the European Ceramic Society, Vol. 24, pp. 3789-3793, 2004):

[0060] 1. Upper limit of stiffness of structural ceramic bodies

[0061] Stiffness of structural ceramic body = (volume fraction of ceramic) × (stiffness of ceramic) + (volume fraction of through hole) × (stiffness of air) ... Equation (1).

[0062] Since the stiffness of air is zero, equation (1) above can be simplified to:

[0063] Stiffness of structural ceramic body = (volume fraction of ceramic) × (stiffness of ceramic) ... Equation (2).

[0064] 2. Lower limit of stiffness of structural ceramic bodies

[0065] 1 / (stiffness of structural ceramic body) = (volume fraction of ceramic) / (stiffness of ceramic) + (volume fraction of through hole) / (stiffness of air)... Equation (3).

[0066] Since the stiffness of air is zero, a value cannot be obtained from equation (3) above. The lower limit of the stiffness of the structural ceramic body can be estimated by using an extremely low value of 0.01 GPa as the stiffness of air.

[0067] From the above mathematical formulas (2) and (3), it can be seen that the stiffness of the structural ceramic body 100 decreases rapidly with the increase of the number of through holes. Therefore, the number of through holes can be one or, as in this embodiment, multiple through holes 108 and 110 evenly distributed in the structural ceramic body 100. For example, a total opening area fraction of 10% for through holes 108 and 110 can reduce the stiffness of the structural ceramic body 100 by more than 10%. Therefore, changing the number and diameter of through holes 108 and 110 can adjust the stiffness of the structural ceramic body 100.

[0068] In addition to stiffness, the interbody fusion device 10 should be strong enough to withstand the weight of a person. Especially when a person runs or jumps, the interbody fusion device 10 must be strong enough to withstand the impact. For the interbody fusion device 10, its external load is mainly along the direction of the spine, so the central axis of each through-hole 108, 110 is preferably parallel to the extension direction of the spine.

[0069] Please continue to refer to Figure 2A The top surface 104 is an inclined surface. The inner surface 112 of the through holes 108 and 110 can be an inwardly convex curved surface. Furthermore, the diameter of the through hole 108 gradually increases from its center C1 towards the bottom surface 102 and the top surface 104; similarly, the diameter of each through hole 110 gradually increases from its center C2 towards the bottom surface 102 and the top surface 104. Additionally, from the viewpoint of avoiding stress concentration, the corners of the inner surface 112 of the through holes 108 and 110 with the top surface 104 and the bottom surface 102 can also be rounded. Since the bottom surface 102 and the top surface 104 are the parts that contact the vertebrae, the actual contact area between the structural ceramic body 100 and the vertebrae is relatively small, thus reducing the effective stiffness of the structural ceramic body 100. For example, the area fraction of the total opening area of ​​the through holes 108 and 110 on the top surface 104 can be 10% or more, such as 10%, 20%, 30%, 40%, 50%, 60%, etc.; preferably, it is 50% or more. Moreover, as described above, the modulus of elasticity can be adjusted by the number and diameter of the through holes 108 and 110, thereby further reducing the stiffness of the structural ceramic body 100.

[0070] Furthermore, the smaller apertures of the through holes 108 and 110 at their centers C1 and C2 increase the ability of the interbody fusion device 10 to withstand external loads. Moreover, to conform to the shape of the vertebrae, the interbody fusion device 10 does not have uniform thickness; therefore, the thin side 104a of the top surface 104 is the thinner part of the structural ceramic body 100, while the thick side 104b is the thicker part. Consequently, among the through holes 108 and 110, the average diameter of the through holes 108 closer to the thin side 104a of the top surface 104 is smaller, and the average diameter of the through holes 110 closer to the thick side 104b of the top surface 104 is larger. For example, the average diameter of the through holes 108 may be smaller than the average diameter of the through holes 110, and the number of through holes 108 may also be less than the number of through holes 110. Furthermore, from the viewpoint of structural strength, the distance s1 between the inner surface 112 at the center C1 of the through hole 108 and the thinnest point of the thin side 104a is preferably greater than the thinnest thickness t1 of the structural ceramic body 100.

[0071] In another embodiment, please refer to Figure 2B The bottom surface 102 and top surface 104 of the structural ceramic body 100 are parallel to each other, therefore Figure 2BThe structure can be either thick or thin. The through holes 108 and 110 can also be funnel-shaped, and the diameter of the through holes 108 and 110 gradually increases from the bottom surface 102 to the top surface 104. Due to the funnel-shaped through holes, in addition to reducing the contact area between the top surface 104 of the structural ceramic body 100 and the vertebra, thus reducing the effective stiffness of the structural ceramic body 100, it also facilitates the subsequent unidirectional filling of bone filler (not shown). Furthermore, as mentioned above, the elastic modulus can be adjusted by the number and opening size of the through holes 108 and 110, thereby further reducing the stiffness of the structural ceramic body 100.

[0072] In another embodiment, please refer to Figure 2C The bottom surface 102 and top surface 104 of the structural ceramic body 100 can also be wavy or serrated to strengthen the fixation of the upper and lower vertebrae.

[0073] In another embodiment, please refer to Figure 2D The outer peripheral surface 106 of the structural ceramic body 100 can also be arc-shaped to disperse the stress in the structural ceramic body 100.

[0074] In another embodiment, the bottom surface 102 and the top surface 104 of the structural ceramic body 100 may both be inclined surfaces, and the bottom surface 102 and the top surface 104 are not parallel to each other. For example, the intervertebral fusion device 10 may be similar to... Figure 2A The structure is similar, but the bottom surface 102 of the structural ceramic body 100 is also inclined, sloping from the thick side 104b to the thin side 104a, so its thinnest thickness will be greater than that of the other side. Figure 2A The t1 is small, and the average diameter of the through hole 108 closer to the thin side 104a is smaller, while the average diameter of the through hole 110 closer to the thick side 104b is larger. On the other hand, the bottom surface 102 of the structural ceramic body 100 can also be inclined from the thin side 104a to the thick side 104b to match the curvature of the vertebra. Therefore, the intervertebral fusion device 10 of the present invention is not limited to the contents of the drawings, and can also be structurally modified according to requirements.

[0075] In the first embodiment, the bone filler (not shown) filling the through-holes 108 and 110 of the structural ceramic body 100 is, for example, autologous bone filler or synthetic bone filler. Synthetic bone fillers include, but are not limited to, hydroxyapatite, tricalcium phosphate, or calcium sulfate, or solid solutions of the aforementioned materials, or composite materials of the aforementioned materials. The bone filler can be filled into the through-holes 108 and 110 before surgery, allowing it to come into close contact with the vertebrae after surgery and slowly release ions and substances that assist bone healing, achieving bone fusion. For example, the bone filler may contain ions or growth factors to enhance bone healing and fusion; for example, strontium ions can promote bone formation and inhibit bone resorption. The transport of strontium ions in the vertebral region can be accomplished using a solid solution of calcium salts and strontium solute. The degradation of calcium-strontium solid solution takes months or even years, therefore the use of this bone filler can contribute to the long-term rigidity of the vertebrae. The calcium-strontium solid solution can be used as a bone filler to fill the aforementioned through-holes 108 and 110 before surgery.

[0076] The following methods may be used to manufacture the intervertebral fusion device 10, but are not limited to them.

[0077] First, in one embodiment, zirconium oxide can be selected as the main raw material of the structural ceramic body 100, and yttrium oxide or cerium oxide can be added to stabilize the crystalline phase. To avoid aging in a humid environment (in the human body), the content of yttrium oxide is preferably 3 mol% or more. For example, the content of yttrium oxide in zirconium oxide can be in the range of 3 mol% to 8 mol%. The content of cerium oxide is preferably 5 mol% or more. Because the rigidity of alumina is about twice that of zirconium oxide, the addition of alumina particles can restrain the volume expansion of zirconium oxide, thus limiting the volume expansion of zirconium oxide due to aging, and increasing the aging resistance of zirconium oxide. Therefore, based on the total weight of the structural ceramic body 100, the content of alumina is preferably 30 wt% or less, of which less than 0.1 wt% of alumina can be dissolved in zirconium oxide.

[0078] In another embodiment, Ce-TZP / Al2O3, which is not easily aged at room temperature, can be used as the material of the structural ceramic body 100, the raw material of which contains 70 vol% (ZrO2-10 mol% CeO2) and 30 vol% Al2O3.

[0079] In another embodiment, the raw material for the structural ceramic body 100 may be a composite material comprising 67.9 wt% ZrO2, 10.6 wt% CeO2, 21.5 wt% Al2O3 and less than 0.1 wt% other oxides (MgO and / or TiO2).

[0080] The raw materials are then formed into green bodies using molding techniques including, but not limited to, die-pressing, isostatic pressing, slip casting, and injection molding. Subsequently, a debinding treatment is performed at a temperature below 600°C to remove all binders from the green body, thereby extending its storage time.

[0081] Once the size and shape of the interbody fusion device 10 required by the patient are known, a milling machine (e.g., a five-axis milling machine) can be used to machine the blank into the shape of the interbody fusion device 10. The size and shape of the interbody fusion device 10 required by the patient can be obtained by X-ray, MRI, or CT scans, and the scan files can be converted into digital data files and then sent to the milling machine for further processing.

[0082] Next, a sintering process is performed. During sintering, the green body is expected to undergo approximately 10% to 20% linear shrinkage, therefore the size of the green body is larger than the sintered intervertebral fusion device 10. Since the shrinkage of the green body is relatively uniform in each direction, the size of the green body can be estimated once the final size and shape of the intervertebral fusion device 10 are determined.

[0083] Figure 3 This is a top view of an intervertebral fusion device according to a second embodiment of the present invention, wherein the technical terms of the first embodiment are used to refer to the same components, and the description of the same components can be referred to the relevant content of the first embodiment above, and will not be repeated here.

[0084] exist Figure 3In the intervertebral fusion device 30, the outer peripheral surface 302 of the structural ceramic body 300 is wavy or serrated, which increases the contact area with the surrounding tissues of the human body, making the intervertebral fusion device 30 less prone to slippage after implantation into the vertebrae. Furthermore, the top surface 300a and bottom surface (not shown) of the structural ceramic body 300 can also be wavy to further secure the upper and lower vertebrae. The thin side 304a is the thinner part of the structural ceramic body 300, and the thick side 304b is the thicker part. Therefore, the through hole 306 closest to the thin side 304a is the smallest, the central through hole 308 is the largest, and the through hole 310 between 306 and 308 is between the two. The through holes 312 on both sides of the through hole 308, near the thick side 304b, are slightly smaller than the central through hole 308 but larger than the through hole 310. Furthermore, to avoid stress concentration at any point, the corners of the intervertebral fusion device 30 are rounded along its entire circumference (outer circumferential surface 302), and the corners of the openings at the top surface 300a and the bottom surface (not shown) are also rounded.

[0085] Figure 4 This is a top view of an intervertebral fusion device according to a third embodiment of the present invention, wherein the component symbols and technical terms of the first embodiment are used to represent the same components, and the description of the same components can be referred to the relevant content of the first embodiment above, and will not be repeated here.

[0086] exist Figure 4 In the interbody fusion device 40, the distance s2 between the outer peripheral surface 402 of the ceramic body 400 and the nearest through holes 108 and 110 is consistent, and the outer peripheral surface 402 maintains a rounded corner shape, that is, the corner 402a of the outer peripheral surface 402 is also rounded. Furthermore, to prevent the interbody fusion device 40 from slipping out after implantation between the vertebrae and to increase the fit between the interbody fusion device 40 and the vertebrae, it can be as follows: Figure 4 As shown, the outer peripheral surface 402 of the interbody fusion device 40 is designed to be wavy (or serrated). Furthermore, the top surface 400a and bottom surface (not shown) of the interbody fusion device 40 can also be wavy to strengthen the fixation of the upper and lower vertebrae.

[0087] The following are some simulation experiments to verify the efficacy of the present invention, but the present invention is not limited to the following content. Because the waves or serrations of the bottom surface 102 and the top surface 104 will fit into the upper and lower vertebrae after implantation, the force is still on the main body of the intervertebral fusion device, so the following simulation will only analyze the main body of the intervertebral fusion device.

[0088] <Comparison Group 1>

[0089] Structure: Square structure, such as Figure 5The top view shown has a square hole in the center. The top and bottom surfaces of the square structure are both 12mm × 12mm, and the thickness is 9mm; the square hole measures 8mm × 8mm (the inner surface is flat). The top surface area of ​​the square structure is 80mm². 2 The area of ​​the through-hole opening accounts for 44% of the top surface area.

[0090] Simulation method: The above structure was analyzed by simulation. A normal force of 30,000 N was applied to the top surface, and then the maximum equivalent stress (von Mises stress) and mean stress that occurred during the compression process were calculated.

[0091] Simulation results: The maximum stress is 805 MPa, and the average stress is 361 MPa. The maximum stress occurs at the four outer corners of the bottom of the square structure, indicating that the stress is concentrated in the right-angled parts.

[0092] <Comparison Group 2>

[0093] Structure: Square structure, such as Figure 6 The top view shown has three circular through holes. The top and bottom surfaces of the square structure are both 12mm × 12mm, and the thickness is 9mm; the diameter of each circular through hole is 3mm (the inner surface is flat). The top surface area of ​​the square structure is 123mm². 2 The total opening area of ​​the through holes accounts for 15% of the top surface area.

[0094] Simulation method: The above structure is analyzed by simulating the structure. A normal force of 30,000 N is applied to the top surface, and then the maximum equivalent stress and average stress that occur during the simulated compression process are calculated.

[0095] Simulation results: The maximum equivalent stress is 552 MPa, and the average stress is 233 MPa. This control group indicates that as the area of ​​the structure increases, both the maximum equivalent stress and the average stress decrease. However, the maximum stress still occurs at the four outer corners of the bottom of the square structure, indicating that stress concentration remains in the right-angled areas.

[0096] <Experimental Example 1>

[0097] Structure: Wave-shaped structures, such as Figure 7 The top view shown depicts three circular through-holes with convex curved surfaces. The two larger through-holes have an outer diameter of 4 mm and a center diameter of 2 mm, while the smaller through-hole has an outer diameter of 3 mm, a center diameter of 1.5 mm, and a thickness of 9 mm. The top surface area of ​​the structure is 73 mm². 2 The total open area of ​​the through holes accounts for 42% of the top surface area. In this structure, all corners are rounded.

[0098] Simulation method: The above structure was analyzed by using a simulation structure. A normal force of 30,000 N was applied to the top surface, and then the maximum equivalent stress and average stress that occurred during the compression process were calculated.

[0099] Simulation results: The maximum equivalent stress is 568 MPa, and the average stress is 255 MPa. Compared with comparison group 2, even with the top surface area reduced from 123 mm², the stress is significantly lower. 2 Reduced to 73mm 2 The maximum equivalent stress and average stress hardly increase. According to the simulation results, there should be no right angles anywhere in the structure to reduce stress concentration. Moreover, because the through hole protrudes inward, the internal stress inside the through hole is significantly lower. Therefore, the opening area can be enlarged to reduce the contact area with the spine, effectively reducing the rigidity of the structure. Furthermore, the inward protrusion design of the through hole reduces the chance of internal stress concentration, and the reduction of right angles on the surface of the through hole further reduces the chance of stress concentration.

[0100] <Experimental Example 2>

[0101] Structure: The exterior is a wave-shaped structure, such as... Figure 8 The top view shown shows three circular through holes with convex curved surfaces. The two larger through holes have an outer diameter of 4 mm and a center diameter of 2 mm, while the smaller through hole has an outer diameter of 3 mm, a center diameter of 1.5 mm, and a thickness of 9 mm. The top surface area of ​​the structure is only 56 mm². 2 The total open area of ​​the through holes accounts for approximately 54% of the top surface area. In this structure, all corners are rounded.

[0102] Simulation method: The above structure was analyzed by using a simulation structure. A normal force of 30,000 N was applied to the top surface, and then the maximum equivalent stress and average stress that occurred during the compression process were calculated.

[0103] Simulation results: The maximum equivalent stress is 738 MPa, and the average stress is 303 MPa. Compared with comparison group 2, even with the top surface area reduced from 123 mm², the stress is significantly lower. 2 Significantly reduced to 56mm 2 The increase in average stress is limited. According to simulation results, there should be no right angles anywhere in the structure to reduce stress concentration. Moreover, because the inside of the through hole protrudes inward, the internal stress inside the through hole is significantly lower. Furthermore, the wave design can reduce the area of ​​the top and bottom surfaces, reducing the contact area with the spine and more effectively reducing the rigidity of the structure. In addition, the inward protrusion design of the through hole reduces the chance of internal stress concentration, and the reduction of right angles on the surface of the through hole further reduces the chance of stress concentration.

[0104] The above four sets of analyses illustrate that:

[0105] A. There should be no right angles at any corner of the structure in order to reduce stress concentration.

[0106] B. The smaller the area of ​​the top and bottom surfaces of the structure, the less rigid the structure can be. At the same time, the design of the through holes protruding inward reduces the chance of internal stress concentration.

[0107] In summary, this invention provides a design for an intervertebral fusion device that can be used to replace damaged intervertebral discs in the cervical or lumbar spine. The stiffness of the intervertebral fusion device can be adjusted to meet the needs of each patient. Furthermore, because the intervertebral fusion device is made of ceramic, it is not only harmless to the human body but also strong enough to withstand the body's weight. It also does not interfere with electromagnetic waves such as X-rays, MRI, and CT scans, which is beneficial for postoperative follow-up examinations.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An intervertebral fusion device, characterized in that, include: A structural ceramic body has a bottom surface, a top surface, an outer peripheral surface connecting the bottom surface and the top surface, and at least one through hole penetrating the bottom surface and the top surface, wherein the number of the at least one through hole is three or less, and the total opening area of ​​the through holes on the top surface accounts for more than 20% of the area fraction of the top surface. The inner surface of the through hole is a convex curved surface. The corners between the outer peripheral surface and the top surface, and between the outer peripheral surface and the bottom surface, are all rounded. Furthermore, the corners between the inner surface of the through hole and the top surface, and between the inner surface of the through hole and the bottom surface, are also rounded. In the through hole having the aforementioned convex curved surface, the diameter of the through hole gradually increases from the center of the through hole towards the bottom surface and the top surface, and The outer peripheral surface is wavy or serrated.

2. The interbody fusion device according to claim 1, characterized in that, The materials of the structural ceramic body include zirconium oxide, aluminum oxide, cerium oxide, yttrium oxide, magnesium oxide, titanium oxide, silicon oxide, zinc oxide, bioactive glass, silicon nitride, silicon carbide, or composite materials of the foregoing.

3. The interbody fusion device according to claim 1, characterized in that, The materials of the structural ceramic body include yttrium-stabilized tetragonal zirconia, cerium-stabilized tetragonal zirconia, a composite material of yttrium-stabilized tetragonal zirconia and alumina, or a composite material of cerium-stabilized tetragonal zirconia and alumina.

4. The interbody fusion device according to claim 1, characterized in that, The bottom surface and the top surface of the structural ceramic body are parallel to each other.

5. The interbody fusion device according to claim 1, characterized in that, The bottom surface and the top surface are not parallel to each other.

6. The interbody fusion device according to claim 5, characterized in that, The structural ceramic body has a thin side and a thick side. The average diameter of the through hole is smaller closer to the thin side and larger closer to the thick side.

7. The interbody fusion device according to claim 1, characterized in that, The outer peripheral surface is arc-shaped.

8. The interbody fusion device according to claim 1, characterized in that, The through-holes of the structural ceramic body are filled with bone filler.

9. The interbody fusion device according to claim 1, characterized in that, The total opening area of ​​the through hole on the top surface accounts for more than 50% of the area of ​​the top surface.

10. The interbody fusion device according to claim 1, characterized in that, The bottom and top surfaces of the structural ceramic body are both wavy or serrated.

11. The interbody fusion device according to claim 1, characterized in that, The at least one through hole is a plurality of through holes, and the plurality of through holes are uniformly distributed in the structural ceramic body.

Images