A cervical fusion device

Abstract

The present invention discloses a cervical fusion device, which is made of porous tantalum; the structure of the cervical fusion device is a box-type structure; the upper surface of the cervical fusion device is convex, and the lower surface is straight; the cervical fusion device includes a central part and a peripheral wall, the central part is arranged in the middle of the cervical fusion device, and the peripheral wall is arranged around the central part; the peripheral wall is made of porous tantalum with a porosity of 20%-30%; the central part is made of porous tantalum with a porosity of 70%-80%; the central part of the cervical fusion device is provided with vertically retractable barbs. The cervical fusion device provided by the present invention does not require bone grafting, has no bone grafting area, and avoids complications related to bone grafting; it is made of porous tantalum material. Porous tantalum, also known as trabecular metal, has a three-dimensional structure with interconnected pores similar to human cancellous bone, has a high porosity, can promote the exchange of nutrients in the pores, is more conducive to bone ingrowth, promotes bone integration, and increases the fusion rate.

Description

Technical Field

[0001] The invention relates to the technical field of medical equipment, and in particular to a novel bioactive trabecular metal cervical fusion device. Background Art

[0002] Degenerative cervical disease is a common and frequently occurring disease. With the changes in lifestyle (such as the increase in long-term desk workers) and the aging of the population, the prevalence of cervical spondylosis continues to rise, and more and more patients need surgical intervention. Currently, the main surgical methods include anterior cervical discectomy, decompression and fusion (ACDF) and artificial cervical disc replacement (ACDR). Since ACDR has strict indications, many contraindications and is expensive, ACDF is still the most commonly used procedure. Compared with autologous bone transplantation, the use of intervertebral fusion cages can reduce complications related to autologous bone transplantation (such as infection, chronic pain, etc.), and can immediately restore intervertebral height and cervical physiological curvature, indirectly increase the intervertebral aperture, improve bone graft fusion rate, reduce bone graft collapse, pseudoarthrosis formation, etc. Therefore, the medical industry has an increasing demand for cervical fusion cages.

[0003] From the perspective of the materials of cervical fusion cages, they mainly include metal titanium mesh, high molecular weight polymer polyetheretherketone materials, and nanohydroxyapatite / polyamide 66 composite materials. The elastic modulus of metal titanium mesh is significantly higher than that of human cortical bone, and a significant stress shielding effect may occur, leading to complications such as cage sinking and bone graft absorption; at the same time, metal materials may cause inflammatory reactions and osteolysis. Polyetheretherketone fusion cages can cause endplate damage. Clinical follow-up found that the incidence of endplate osteolysis was high, and there were reports that severe cage sinking may occur during follow-up; at the same time, most of the materials are imported and relatively expensive. Although nanohydroxyapatite / polyamide 66 interbody fusion cages have been widely used as reconstruction materials for various diseases such as cervical, thoracic, and lumbar vertebrae, the material has no biological activity and no osteogenic effect. Therefore, the use of new bioactive materials to make cervical fusion cages has attracted more and more attention.

[0004] From the structural aspect of cervical fusion cage, titanium nail plate internal fixation system is currently the most commonly used. Titanium nail plate internal fixation system has the advantages of increasing stability after cervical reconstruction, improving bone graft fusion rate, and reducing fusion cage subsidence rate. However, relevant literature also points out that anterior titanium plate can cause swallowing discomfort, esophageal injury, anterior cervical soft tissue injury, etc., and some patients may have chronic dysphagia after surgery. At the same time, in long-term follow-up, it was found that rigid titanium nail plate fixation can lead to increased stress in adjacent segments, which can accelerate the occurrence of adjacent segment degeneration and lead to adjacent segment degenerative diseases. In addition, the upper surface of the cervical fusion cage currently used in clinical practice is straight, while anatomical studies have found that the lower end plate of the vertebral body is arc-shaped. The poor matching between the two can cause a decrease in fusion rate and fusion cage subsidence. Therefore, how to design the appearance of the fusion cage to reduce or avoid short-term and long-term complications of surgery is a research hotspot for cervical fusion cages.

[0005] From the perspective of the medical market, the cervical interbody fusion devices currently used in China are mainly imported from abroad and produced domestically. The imported cervical interbody fusion devices mainly come from Europe and the United States (such as Medtronic, Johnson & Johnson, and Stryker). Most of the imported cervical interbody fusion devices are made of PEEK composite materials, which are expensive (about 30,000 yuan / set), and the design of the product is based on the anatomical structure data of the cervical spine of foreign populations. For the domestic population, its application may be limited. Summary of the invention

[0006] In order to solve the problems of the prior art, an embodiment of the present invention provides a cervical fusion device. The technical solution is as follows:

[0007] On the one hand, a cervical fusion device is provided, wherein the material of the cervical fusion device is porous tantalum; the structure of the cervical fusion device is a box-shaped structure; the upper surface of the cervical fusion device is convex, and the lower surface is flat;

[0008] The cervical fusion device comprises a central portion and a peripheral wall, wherein the central portion is arranged in the middle of the cervical fusion device, and the peripheral wall is arranged around the central portion;

[0009] The peripheral wall is made of porous tantalum with a porosity of 20%-30%; the central part is made of porous tantalum with a porosity of 70%-80%;

[0010] The central part of the cervical fusion device is provided with vertically retractable barbs.

[0011] Furthermore, the cervical fusion cage is in the shape of a solid block.

[0012] Furthermore, the upper surface of the cervical fusion device is arc-shaped and convex, the highest point of the convexity is located at the middle and rear 3 / 5 of the upper surface, and the height of the convexity is 2 mm.

[0013] Furthermore, the width of the cervical fusion device is 15 mm; the depth of the cervical fusion device is 13 mm; the rear height of the cervical fusion device is 5 mm.

[0014] Optionally, the front height of the cervical fusion cage is 6 mm.

[0015] Optionally, the front height of the cervical fusion cage is 7 mm.

[0016] Optionally, the front height of the cervical fusion cage is 8 mm.

[0017] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0018] The cervical fusion device provided by the present invention has the following advantages:

[0019] 1. This cervical fusion device does not require bone grafting and has no bone grafting area. Compared with existing fusion devices, it avoids bone grafting-related complications.

[0020] 2. Made of bioactive trabecular metal (porous tantalum material). Porous tantalum, also known as trabecular metal, has a three-dimensional structure with interconnected pores similar to human cancellous bone. It has a high porosity, which can promote the exchange of nutrients in the pores, is more conducive to bone ingrowth, promotes bone integration, and increases the fusion rate.

[0021] 3. The design of this cervical fusion device is based on the anatomical data of the Chinese cervical spine. Compared with imported fusion devices, it has stronger applicability, better matching and wider application range.

[0022] 4. The upper surface of the cervical fusion cage adopts an arc-shaped design, which can further increase the fusion rate and reduce the risk of cage subsidence compared with the existing flat-surface fusion cages.

[0023] 5. This cervical fusion device does not require anterior plate fixation. Compared with the traditional titanium plate internal fixation system, it can reduce soft tissue damage during surgery and reduce postoperative dysphagia complications.

[0024] 6. The cervical fusion device does not require screw fixation, which reduces intraoperative end plate damage and metal artifacts.

[0025] 7. The cervical fusion device can be made of domestic porous tantalum material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 is a front view of a cervical fusion device according to an embodiment of the present invention;

[0028] Figure 2 is a top view of a cervical fusion device according to an embodiment of the present invention;

[0029] Figure 3 is a side view of a cervical fusion device according to an embodiment of the present invention;

[0030] Figure 4 It is a side cross-sectional view of a cervical fusion device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] The present invention provides a cervical fusion device, wherein the material of the cervical fusion device is porous tantalum; Figure 1-4 The structure of the cervical fusion device is a box-shaped structure; the upper surface of the cervical fusion device is convex, and the lower surface is straight;

[0033] See also Figure 2 The cervical fusion device comprises a central part 1 and a peripheral wall 2, wherein the central part 1 is arranged in the middle of the cervical fusion device, and the peripheral wall 2 is arranged around the central part 1;

[0034] The peripheral wall 2 is made of porous tantalum with a porosity of 20%-30%; the central part 1 is made of porous tantalum with a porosity of 70%-80%;

[0035] A vertically retractable barb 4 is disposed at the central portion of the cervical fusion device; the barb is connected to an adjustment knob 5 for adjusting the extension and retraction of the barb.

[0036] In this embodiment, a plurality of drainage holes 3 are provided on the cervical fusion cage, and the drainage holes penetrate the cervical fusion cage.

[0037] Furthermore, the cervical fusion device is a solid block with no bone grafting area in the center;

[0038] Furthermore, the upper surface of the cervical fusion device is arc-shaped and convex, the highest point of the convexity is located at the middle and rear 3 / 5 of the upper surface, and the height of the convexity is 2 mm.

[0039] Furthermore, the width of the cervical fusion device is 15 mm; the depth of the cervical fusion device is 13 mm; the rear height of the cervical fusion device is 5 mm.

[0040] Optionally, the front height of the cervical fusion cage is 6 mm.

[0041] Optionally, the front height of the cervical fusion cage is 7 mm.

[0042] Optionally, the front height of the cervical fusion cage is 8 mm.

[0043] Specifically, this embodiment provides the design steps of the cervical fusion cage, which are as follows:

[0044] 1. Material design of fusion device

[0045] Design: Bioactive trabecular metal (porous tantalum), pore size 500-600 μm, porosity 70%-80%

[0046] reason:

[0047] 1. Porous tantalum has a three-dimensional structure with interconnected pores similar to human cancellous bone. It has a high porosity, which can promote the exchange of nutrients in the pores, is more conducive to bone ingrowth, and promotes bone integration. The elastic modulus of porous tantalum is close to that of normal bone, which can reduce stress shielding.

[0048] 2. Studies have shown that when the pore size of the material is too small (<150μm), it limits the influx of external body fluids and osteoinductive proteins, thereby preventing bone ingrowth; when the pore size of the material is between 500-700μm, it is most conducive to the ingrowth of bone tissue.

[0049] 3. The cancellous bone of natural bone tissue is composed of trabeculae to form a porous structure with a porosity of about 50%-90%. From the perspective of bionics, the porosity of porous tantalum materials should be close to that of normal bone tissue. At the same time, the literature reports that the compressive strength of porous tantalum materials with a porosity of 75%-85% is 60MPa, 5×10 6 The single-cycle compression fatigue strength is 23MPa, which can meet the biomechanical requirements of the cervical spine.

[0050] 2. Structural design of fusion device

[0051] (I) Appearance design

[0052] 1. Overall design of the fusion device: box-type design, without hollow bone grafting area (reason: porous tantalum has an osteogenesis effect, and its three-dimensional structure with interconnected pores similar to human cancellous bone can promote bone integration).

[0053] 2. Fusion device surface design: the upper surface is convex and the lower surface is straight (reason: it conforms to the anatomical morphology of the Chinese cervical spine and matches better).

[0054] 3. Fusion device wall design:

[0055] a. All around (front, back, left, and right): This is the dense part of the fusion device, made of porous tantalum (20%-30%) with low porosity.

[0056] b. Upper, lower and central areas: These are the loose parts of the fusion device and are made of porous tantalum (70%-80%) with high porosity.

[0057] (Reason: It is consistent with the mechanical strength distribution of the cervical endplate and the microscopic morphological structure of bones in Chinese people)

[0058] 4. Fixation design of the fusion device: central vertical retractable barb design, without titanium plates or screws (reason: porous tantalum has a higher friction coefficient and good stability after implantation, so titanium plates or screws are not required for fixation).

[0059] (ii) Dimension design

[0060] 1. Design of the width and depth of the fusion cage. See Table 1 for comparison of the transverse diameter, sagittal diameter, and inner diameter of the uncovertebral joint in different populations (mm);

[0061] Table 1

[0062]

[0063] (1) Data characteristics:

[0064] a. The transverse and sagittal diameters of the intervertebral disc in degenerative people are larger than those in healthy people, which may be related to the formation of osteophytes.

[0065] b. The inner diameter of the uncovertebral joint in degenerative people is smaller than that in healthy people, which may be related to the hyperplasia and cohesion of the uncovertebral joint.

[0066] (2) Design reasons:

[0067] a. The inner diameter of the uncovertebral joint reflects the width of the anterior intervertebral decompression. The width of the fusion device should be designed with full consideration of the inner diameter of the uncovertebral joint. At the same time, the fusion device is mainly used in the degenerative population, so the inner diameter of the uncovertebral joint of the degenerative population should be used as a reference. Therefore, the width of the fusion device was initially designed to be 15 mm.

[0068] b. The depth of the fusion device should be designed with full consideration of the sagittal diameter of the cervical intervertebral space, and the influence of osteophyte hyperplasia should be excluded. Therefore, the sagittal diameter of the cervical intervertebral space in healthy people should be used as a reference. In addition, 1.5mm and 3mm of safety space should be reserved in the front and back of the fusion device, respectively. Therefore, the depth of the fusion device was initially designed to be 13mm.

[0069] (3) Design size:

[0070] The initial design of the fusion cage is 15mm in width and 13mm in depth.

[0071] 2. The height design of the fusion cage, see Table 2, comparison of the transverse diameter, sagittal diameter, and inner diameter of the uncovertebral joint in different populations (mm);

[0072] Table 2

[0073]

[0074] (1) Data characteristics:

[0075] a. The intervertebral disc height of degenerative people is smaller than that of healthy people, which is related to intervertebral disc degeneration and height loss.

[0076] b. The anterior height of the intervertebral space in healthy people is greater than the posterior height; the anterior height of the intervertebral space in men is greater than that in women, but there is no significant difference in the posterior height of the intervertebral space between men and women.

[0077] c. The middle height of the intervertebral disc reported in the literature is measured at the 1 / 2 position of the vertebral endplate, and the measured value of the middle height includes the depth of the depression of the lower endplate of the vertebral body above the intervertebral disc.

[0078] d. In the degenerative population, there is no significant difference in the average height of the intervertebral disc between males and females.

[0079] (2) Design concept:

[0080] From the measurement results of intervertebral disc height, it can be seen that there is a big difference in intervertebral disc height between normal people and degenerative people, so fusion devices with different height specifications need to be designed to meet the needs of different people.

[0081] Design ideas:

[0082] The anterior and posterior gap heights are designed separately, and then the upper and lower surfaces of the fusion device are designed according to the endplate morphology, depression depth, depression position, etc., in order to achieve the purpose of bionic vertebral lower endplate.

[0083] Design reason:

[0084] ① Literature reports show that there is indeed a large difference between the middle height of the intervertebral space and the anterior and posterior heights.

[0085] ② The literature reports that the measured value of the middle height of the intervertebral space actually includes the depth of the depression of the lower end plate of the vertebral body.

[0086] See Table 3, design dimensions (mm):

[0087] Table 3

[0088] Front height Rear height Specification 1 6 5 Specification 2 7 5 Specification 3 8 5

[0089] 3. Design of the upper and lower surfaces of the fusion cage, see Table 4, anatomical measurements of the upper and lower end plates of the cervical vertebrae;

[0090] Table 4

[0091] Upper end plate Lower end plate Depth of depression 0.9-1.2 2.1-2.7 Depression position 56％-67％ 52％-57％

[0092] (1) Data characteristics:

[0093] a. The sagittal shape of the cervical endplates was similar among age groups and genders. Most of the lower cervical endplates were flat, while the upper endplates were mostly concave.

[0094] b. There is no difference in the location of cervical endplate depression among different age groups, genders, and segments.

[0095] c. There is no difference in the depth of cervical endplate depression among different age groups, but there are differences between different genders and segments, but the difference is small (less than 1mm).

[0096] (2) Design reasons:

[0097] a. Lower surface: The upper end plate is less concave, so the lower surface of the fusion device can be designed to be a flat surface.

[0098] b. Upper surface: The bionic lower end plate is concave, and the upper surface of the fusion device is designed to be an arc-shaped convexity. The highest point of the convexity is located at the middle and posterior 3 / 5 (60%) of the upper surface, and the height of the convexity is 2mm.

[0099] (3) Design size:

[0100] The lower surface of the fusion device can be designed as a flat surface; the upper surface is designed as an arc-shaped bulge, the highest point of the bulge is located at the middle and rear 3 / 5 (60%) of the upper surface, and the height of the bulge is 2 mm.

[0101] 4. Design of the surrounding wall of the fusion device

[0102] (1) Characteristics of the compressive strength distribution of the cervical endplate:

[0103] a. The compressive strength of the cervical spine decreases gradually from top to bottom.

[0104] b. The compressive strength of the lower endplate of the cervical vertebral body is greater than that of the upper endplate.

[0105] c. The compressive strength of the lower endplate of the vertebral body on the adjacent surface of the cervical intervertebral space is greater than that of the upper endplate of the lower vertebral body.

[0106] d. As the pressure point gradually moves outward, the compressive strength of the cervical endplate gradually increases; starting from the 20% pressure point, the endplate strength increases more significantly as it moves toward the periphery.

[0107] e. The compressive strength of the posterior part of the upper end plate is greater than that of the anterior part; there is no significant difference in the compressive strength of the anterior and posterior parts of the lower end plate.

[0108] (2) Data reported in the literature:

[0109] a. Cervical vertebrae cortical bone thickness: anterior cortex 329um, posterior cortex 240um, porosity: 3%-5%.

[0110] b. The average cortical bone thickness of young people is 432.00±77.47um, and the average cortical bone thickness of the elderly is 233.70±23.41um.

[0111] (3) Design concept:

[0112] a. Since the compressive strength of the central area of ​​the end plate is lower than that of the peripheral area, the fusion device is designed to be dense on the periphery and loose in the center to reduce the compressive stress of the end plate and reduce the risk of fusion device sinking.

[0113] b. Since the end plate strength increases more significantly as it moves toward the periphery starting from the 20% pressure point, the thickness of the surrounding dense part is designed to account for 20% of the depth and width of the fusion device, and the calculated thickness is 2.5mm-3mm.

[0114] (4) Design size:

[0115] The thickness of the surrounding wall is designed to be 2.5mm.

[0116] In summary, see Table 5 for a summary of the parameters of this new cervical fusion device;

[0117] Table 5

[0118]

[0119] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0120] 1. This cervical fusion device does not require bone grafting and has no bone grafting area. Compared with existing fusion devices, it avoids bone grafting-related complications.

[0121] 2. Made of bioactive trabecular metal (porous tantalum material). Porous tantalum, also known as trabecular metal, has a three-dimensional structure with interconnected pores similar to human cancellous bone. It has a high porosity, which can promote the exchange of nutrients in the pores, is more conducive to bone ingrowth, promotes bone integration, and increases the fusion rate.

[0122] 3. The design of this cervical fusion device is based on the anatomical data of the Chinese cervical spine. Compared with imported fusion devices, it has stronger applicability, better matching and wider application range.

[0123] 4. The upper surface of the cervical fusion cage adopts an arc-shaped design, which can further increase the fusion rate and reduce the risk of cage subsidence compared with the existing flat-surface fusion cages.

[0124] 5. This cervical fusion device does not require anterior plate fixation. Compared with the traditional titanium plate internal fixation system, it can reduce soft tissue damage during surgery and reduce postoperative dysphagia complications.

[0125] 6. The cervical fusion device does not require screw fixation, which reduces intraoperative end plate damage and metal artifacts.

[0126] 7. The cervical fusion device can be made of domestic porous tantalum material.

[0127] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cervical fusion cage, characterized in that: The material of the cervical fusion device is porous tantalum; the structure of the cervical fusion device is a box-shaped structure; the upper surface of the cervical fusion device is convex, and the lower surface is straight; The cervical fusion device comprises a central portion and a peripheral wall, wherein the central portion is arranged in the middle of the cervical fusion device, and the peripheral wall is arranged around the central portion; The peripheral wall is made of porous tantalum with a porosity of 20%-30%; the central part is made of porous tantalum with a porosity of 70%-80%; The central part of the cervical fusion device is provided with vertically retractable barbs, and the barbs are connected with adjustment knobs for adjusting the extension and retraction of the barbs; the cervical fusion device is a solid block with no bone grafting area in the center.

2. A cervical fusion cage according to claim 1, characterized in that: The upper surface of the cervical fusion device is arc-shaped and convex, the highest point of the convexity is located at the middle and rear 3 / 5 of the upper surface, and the height of the convexity is 2mm.

3. A cervical fusion cage according to claim 2, characterized in that: The width of the cervical fusion cage is 15 mm; the depth of the cervical fusion cage is 13 mm; and the rear height of the cervical fusion cage is 5 mm.

4. A cervical fusion cage according to claim 3, characterized in that: The front height of the cervical fusion cage is 6 mm.

5. The cervical fusion cage according to claim 3, characterized in that: The front height of the cervical fusion cage is 7 mm.

6. The cervical fusion cage according to claim 3, characterized in that: The front height of the cervical fusion cage is 8 mm.

Images