A dynamic bending fatigue testing device and testing method for vertebral plate fixation plates

Abstract

The present invention relates to the technical field of medical devices, and relates to a dynamic bending fatigue test device and test method for a lamina fixing plate. The present invention includes: a base, a bracket test block, a connecting block, and a fatigue testing machine. A sliding groove for the movement of the bracket test block is provided inside the base, and a locking bolt for fixing the bracket test block is provided on the base; Two groups of bracket test blocks are symmetrically arranged and slidably arranged in the sliding groove. There is an intermediate groove between the bracket test blocks. Two groups of lamina fixing plates are symmetrically arranged in the intermediate groove. The lower end of the lamina fixing plate is fixed to the upper end of the bracket test block, and a groove is provided inside the lamina fixing plate; The connecting block is fitted in the groove and the upper end surface of the connecting block is fixedly connected to the lamina fixing plate. A loading hole is provided on the upper surface of the connecting block; The loading block of the fatigue testing machine is fixedly connected to the loading hole, and the connecting plate of the fatigue testing machine is fixedly connected to the base. By applying a dynamic load to simulate the situation of the postoperative opening lamina being squeezed, the service life and corresponding fatigue performance of the lamina fixing plate are measured.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and relates to a dynamic bending fatigue test device and test method for a lamina fixing plate. Background Art

[0002] Cervical laminoplasty was initially applied to patients with myelopathic cervical spondylosis secondary to ossification of the posterior longitudinal ligament. This surgery has the characteristics of protecting the cervical spine structure, maintaining cervical spine stability, and reducing complications while decompressing the spinal canal. The indications for cervical laminoplasty include spinal nerve root disease, cervical spondylosis, myelopathic cervical spondylosis secondary to ossification of the posterior longitudinal ligament, congenital spinal canal stenosis, multi-segmental disc herniation, and traumatic central spinal canal syndrome. Laminoplasty avoids extensive resection of the posterior spinal structure, takes into account spinal canal decompression and spinal stability, reduces complications such as spinal kyphosis deformity and dural scar adhesion, and this surgery can fully expose the spinal canal, perform the operation under direct vision, avoid injury to the cauda equina and nerve roots, and widely and thoroughly resect the lesions. After the patient undergoes laminoplasty, tissues such as muscles around the hinge side will contract, squeeze, and lift the lamina. If the mechanical properties of the lamina fixing plate are insufficient, a "door closing" phenomenon will occur.

[0003] At present, the experimental method for spinal implants is YY / T 0857-2011 "Test Method for Spinal Implants in Vertebrectomy Models". Among them, the test block and the loading method are not applicable to the lamina fixation system. There is currently no test method for comparing the mechanical properties of the lamina fixing plate, and the performance of different models of lamina fixing plates cannot be accurately evaluated in a state close to actual use. Summary of the Invention

[0004] In order to solve the problems of the prior art, the present invention provides a dynamic bending fatigue test device and test method for a lamina fixing plate.

[0005] The object of the present invention can be achieved by the following technical solutions: A dynamic bending fatigue test device and test method for a lamina fixing plate includes: a base, a chute for the movement of the bracket test block is provided inside the base, and a locking bolt for fixing the bracket test block is provided on the base;

[0006] Bracket test blocks, two groups of bracket test blocks are symmetrically arranged and slidably arranged in the chute. There is an intermediate groove between the bracket test blocks. Two groups of lamina fixing plates are symmetrically arranged in the intermediate groove. The lower end of the lamina fixing plate is fixed to the upper end of the bracket test block, and a groove is provided inside the lamina fixing plate;

[0007] Connecting blocks, the connecting blocks are fitted in the grooves, and the upper end surfaces of the connecting blocks are fixedly connected to the lamina fixing plates. Loading holes are provided on the upper surfaces of the connecting blocks;

[0008] Fatigue testing machine, wherein the loading block of the fatigue testing machine is fixedly connected to the loading hole, and the connecting plate of the fatigue testing machine is fixedly connected to the base.

[0009] Further improvement, the bottom of the loading hole is hemispherical, the loading block includes a cylindrical rod and a connecting rod, a pin hole for connecting with the fatigue testing machine is provided on the cylindrical rod, and a spherical part matching the shape of the bottom of the loading hole is provided at the bottom of the connecting rod.

[0010] Further improvement, the laminar plate fixing plate is bolted to the inner side surface of the top of the bracket test block, and the upper end surface of the connecting block is bolted to the laminar plate fixing plate.

[0011] Further improvement, a dovetail groove is provided at the bottom of the sliding groove, an installation table is provided in the dovetail groove, and the installation table and the fixed bracket test block are fixed by a locking bolt.

[0012] A testing method for a dynamic bending fatigue testing device of a laminar plate fixing plate, comprising the following steps:

[0013] S1: Assemble and connect the bracket test block, the connecting block, and the laminar plate fixing plate into a test sample, assemble the test sample into the base, and then assemble it onto the fatigue testing machine, aligning the center of the loading block with the center of the connecting block;

[0014] S2: Set the software environment, open the fatigue testing machine control software to edit the test plan, and zero the force value of the fatigue testing machine;

[0015] S3: Use the fatigue testing machine to preload the test sample to ensure full contact between the loading hole and the loading block, and zero the displacement at this time;

[0016] S4: Conduct a fatigue test according to the test plan in S2. Use the cyclic load generated by the fatigue testing machine to apply pressure to the test block connected to the laminar plate fixing plate testing device for fatigue testing. Apply a sinusoidal cyclic load to the spinal structure during the fatigue test, and the applied load ratio is R = 10; Stop until the number of cycles of the sample reaches 5,000,000 times or until the sample fails within 5,000,000 times. According to the results obtained from the experimental steps in S1 - S4, when the test samples of this group pass, increase the static ultimate load by 10% for the fatigue load of the experiment and conduct the next group of experiments. If they do not pass, reduce the static ultimate load by 10% and conduct the next group of experiments until the difference between the load at structural failure and the maximum fatigue load is less than 10% of the compression load limit; And the number of samples passing under the same maximum fatigue load is three groups, and at least six groups are used for the experiment; Continuously measure the changing number of cycles, displacement, and load, and continuously output the corresponding data of the number of cycles, displacement, and load; Continuously measure the changing number of cycles, displacement, and load, and continuously output the corresponding data of the number of cycles, displacement, and load;

[0017] For further improvement, the testing machine in step S2 is set with the maximum load being 60% of the static test limit load, the fatigue test frequency being 5 Hz, the maximum displacement change being 3 mm, and the change amount and range of the maximum force and the minimum force being 5 N.

[0018] Compared with the prior art, the beneficial effects of the dynamic bending fatigue testing device and testing method for the lamina fixing plate of the present invention are as follows:

[0019] It is assembled according to the positional relationship between the lamina fixing plate and the spine in actual surgery. By applying a dynamic load, it simulates the situation where the postoperative opened lamina is squeezed and "closed", determines the service life and corresponding fatigue performance of the lamina fixing plate, provides a basis for the design of the lamina fixing plate, and at the same time, for establishing a unified test scheme, according to the present invention, the fatigue performance comparison of lamina fixing plates produced by different materials, different models, and different manufacturers can be carried out. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the present invention

[0021] Figure 2 It is a cross-sectional view of the partial structure of the present invention

[0022] Figure 3 It is a curve graph of the load and the number of cycles of the present invention

[0023] In the figure, 1 - base, 11 - chute, 111 - dovetail groove, 112 - mounting table, 12 - locking bolt, 2 - support test block, 21 - intermediate groove, 3 - connecting block, 31 - loading hole, 41 - loading block, 411 - cylindrical rod, 412 - connecting rod, 413 - pin hole, 414 - spherical part, 42 - connecting plate, 5 - conical lamina fixing plate, 51 - groove. Detailed Embodiments

[0024] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0025] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0026] The following combines the embodiments and the attached Figures 1 to 3 , and further elaborates on the technical solution of the present invention.

[0027] Embodiment 1

[0028] A dynamic bending fatigue test device for a lamina fixing plate is used for testing the lamina fixing plate under the conditions close to its usage state to determine the maximum fatigue load of the lamina fixing plate and its corresponding mechanical properties, and includes:

[0029] A base 1, inside which there is a sliding groove 11 for the movement of a bracket test block 2, and a locking bolt 12 for fixing the bracket test block 2 is provided on the base 1;

[0030] Bracket test blocks 2, two groups of which are symmetrically arranged and slidably arranged in the sliding groove 11. There is an intermediate groove 21 between the bracket test blocks 2. Two groups of lamina fixing plates 5 are symmetrically arranged in the intermediate groove 21. The lower end of the lamina fixing plate 5 is fixed to the upper end of the bracket test block 2, and a groove 51 is provided inside the lamina fixing plate 5;

[0031] A connecting block 3, which is fitted in the groove 51 and the upper end surface of the connecting block 3 is fixedly connected to the lamina fixing plate 5. A loading hole 31 is provided on the upper surface of the connecting block 3;

[0032] A fatigue testing machine, the loading block 41 of which is fixedly connected to the loading hole 31, and the connecting plate 42 of which is fixedly connected to the base 1. The fatigue testing machine applies a cyclic load to the connecting block 3 of the lamina fixing plate testing device, continuously measures the changing number of cycles and the maximum and minimum loads, and outputs the corresponding data of the number of cycles and the load.

[0033] The bracket test block 2 and the connecting block 3 are made of ultra-high molecular weight polyethylene. The tensile fracture strength of the ultra-high molecular weight polyethylene should be 40 ± 3 Mpa, and each group of the bracket test block and the connecting block of the lamina fixing plate testing device is used only once;

[0034] After installing the lamina fixing plate 5 on the bracket test block 2, according to the different size specifications of the lamina fixing plate 5, the distance between the two bracket test blocks 2 can be adjusted, and the connecting block 3 between the two laminae can be connected by adjusting the distance to ensure that the loading force arms of the two laminae are in the same direction; and to ensure the unity of the devices used in the experimental method.

[0035] The connecting block 3 is shaped to mimic the surgical position of the cervical laminar fixing plate. Therefore, the upper surface of the connecting block 3 is basically horizontal, and the lower surface of the connecting block 3 is a downwardly protruding curve. Since the lower bracket test block 2 is separated, the shape of the connecting block 3 is basically fixed and the length does not need to be changed according to the working length of the used laminar fixing plate. Only the distance between the bracket test blocks 2 needs to be adjusted. Therefore, the structure of this device makes each part of the structure universal and can test different laminar fixing plates.

[0036] The present invention is assembled according to the positional relationship between the laminar fixing plate and the spine in actual surgery. By applying a dynamic load to simulate the situation where the opened lamina is squeezed and "closed" after surgery, the service life and corresponding fatigue performance of the laminar fixing plate are measured, providing a basis for the design of the laminar fixing plate. At the same time, for establishing a unified test plan, according to the present invention, the fatigue performance of laminar fixing plates produced by different materials, different models, and different manufacturers can be compared.

[0037] A test method for a dynamic bending fatigue test device of a laminar fixing plate includes the following steps:

[0038] S1: Assemble and connect the bracket test block 2, the connecting block 3, and the laminar fixing plate 5 into a test sample, and assemble the test sample into the base 1, and then assemble it onto the fatigue testing machine, aligning the center of the loading block 41 with the center of the connecting block 3;

[0039] S2: Set the software environment, open the control software of the testing machine 4 to edit the test plan, and zero the force value of the fatigue testing machine;

[0040] S3: Use the fatigue testing machine to preload the test sample to ensure that the loading hole 31 and the loading block 41 are in full contact, and zero the displacement at this time;

[0041] S4: Conduct a fatigue test according to the test plan in S2. Use the cyclic load generated by the fatigue testing machine to apply pressure to the connecting test block of the laminar fixing plate testing device for fatigue testing. During the fatigue test, a sinusoidal cyclic load is applied to the spinal structure, and the load ratio is R = 10; Stop until the number of cycles of the sample reaches 5,000,000 times or until the sample fails within 5,000,000 times. According to the results obtained from the experimental steps in S1 - S4, when the test sample of this group passes, increase the static ultimate load by 10% for the fatigue load of the experiment and conduct the next group of experiments. If it does not pass, reduce the static ultimate load by 10% and conduct the next group of experiments until the difference between the load at the time of structural failure and the maximum fatigue load is less than 10% of the compression load limit; and the number of samples passing under the same maximum fatigue load is three groups, and at least six groups are used for the experiment; At the same time, continuously measure the changing number of cycles, displacement, and load, and continuously output the corresponding data of the number of cycles, displacement, and load.

[0042] S5: According to the number of cycles and load recorded in S4, organize the load-displacement data output by the fatigue testing machine to obtain the curve of the number of compression-bending fatigue cycles of the lamina fixing plate and the maximum and minimum loads. Draw a semi-logarithmic fatigue curve relative to the number of cycles at failure based on the obtained number of cycles and load, as Figure 3 .

[0043] From Figure 3 , it can be obtained that the regression equations fitted from the six groups of test data. Through the regression equations, the relationship between the load and the number of dynamic fatigue limits can be known. Through this equation, it is convenient for experimenters to quickly obtain the results of the lamina fixing plates of the same model, thereby shortening the experimental time.

[0044] Determine the test stop condition of 5,000,000 cycles for the test termination number of cycles. Since the purpose of the lamina fixing plate implant is to provide short-term fixation during single-door and double-door laminoplasty, the test method in this experiment is to measure the number of cycles of 5,000,000 times of bearing under medium exercise intensity within two years for the sample, and ensure the maximum fatigue load without damage to the structure at 5,000,000 times. Therefore, to ensure the safety of the product, it is most reasonable to determine the test number of cycles to be 5,000,000 times, which is more suitable for the actual human movement situation.

[0045] As a further embodiment, set the testing machine 4 in step S2, with the maximum load being 60% of the static test limit load, the fatigue test frequency being 5 Hz, the maximum displacement change being 3 mm, and the change amount and range of the maximum force and minimum force values being 5 N.

[0046] The maximum load is 60% of the static test limit load. Since the fatigue limit obtained from fatigue is the maximum passing force value in the test, setting the initial maximum fatigue load to 60% of the limit load is to more quickly and conveniently experiment the fatigue limit. Through experiments and theoretical research, when the experimental value exceeds 60%, the sample is likely to be damaged. However, if the force value is too small, it will also cause the experiment to take too long and thus fail to achieve the effect of testing the fatigue limit. Therefore, it is reasonable and fast to determine the initial test force value to be 60% of the limit load.

[0047] Determine the fatigue test frequency to be 5 Hz. Determine the loading frequency of the fatigue load during the fatigue test to be 5 Hz. Since after the frequency exceeds 5 Hz during the loading process, due to factors such as fast testing and raw materials, melting or softening may occur at the connection between the fast test and the sample or at the loading holes of the loading block and the connection block, affecting the test results. However, if the test frequency is lower than 5 Hz, the time taken for the sample to pass the limit force value is too long, reducing the test efficiency. Therefore, in summary, 5 Hz is the optimal maximum frequency for this fatigue test during the fatigue test process.

[0048] Determine that the maximum displacement change is 3 mm. After the test starts, due to the cyclic process of the maximum and minimum loads of the test sample, when the applied load value is less than or equal to the ultimate fatigue load, during the loading process, when the maximum and minimum force values are loaded, the displacement is relatively stable at this time. However, when the applied load is greater than the fatigue load, initially, since not much plastic deformation has occurred in the sample, during the process of loading to the maximum and minimum loads, the displacement change amount will increase with time. To ensure that the sample stops immediately after reaching the break point to avoid affecting the judgment of the fatigue limit, it is necessary to make corresponding restrictions on the displacement change amount to determine whether the sample is damaged. If it is damaged, stop the test immediately, indicating that this force value is greater than the ultimate fatigue load. The 3-mm change range is the result obtained from the test. The maximum displacement change of 3 mm enables the sample to break before reaching 5,000,000 cycles and can be stopped immediately without continuing the test to avoid affecting the judgment of the fatigue limit.

[0049] The change amount and range of the maximum and minimum force values are 5 N. When the sample is damaged, relative fracture or cracks, etc. will occur. At this time, when the sample changes, its structure is damaged, and there will be large fluctuations during the loading process of the testing machine. When this fluctuation exceeds a certain value, it can be determined that this sample has failed. The 5-N change range enables the sample to have relative fracture or cracks before reaching 5,000,000 cycles and can be stopped immediately without continuing the test, reducing the waste of test time.

[0050] As a further embodiment, the bottom of the loading hole 31 is hemispherical. The loading block 41 includes a cylindrical rod 411 and a connecting rod 412. A pin hole 413 connected to the fatigue testing machine is provided on the cylindrical rod 411. The bottom of the connecting rod 412 is provided with a spherical portion 414 that matches the shape of the bottom of the loading hole 31.

[0051] The hemispherical loading block 41 corresponds to the corresponding hemispherical loading hole 31. The hemispherical loading hole 31 is more conducive to positioning the loading block 41. And during loading, due to the spherical fit, the fit is closer during loading, avoiding unevenness and unbalanced force at the loading point, ensuring that the loading direction is not perpendicular to the overall force direction of the device, and making the dynamic loading process more stable.

[0052] As a further embodiment, the laminar fixing plate 5 is bolted to the inner side of the top of the bracket test block 2, and the upper end surface of the connecting block 3 is bolted to the laminar fixing plate 5.

[0053] As a further embodiment, a dovetail groove 111 is provided at the bottom of the chute 11. An installation table 112 is provided in the dovetail groove 111. The installation table 112 and the fixed support test block 2 are fixed by a locking bolt 12. During the fatigue testing machine process, due to the influence of cyclic loads, to prevent relative rotation and horizontal movement in the front and rear directions of the test device, a dovetail groove 111 is provided in the chute 11 of the base 1 to cooperate with the installation table 112, which can achieve anti-rotation and front and rear movement prevention, improving the accuracy of the test.

[0054] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in this technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A dynamic bending fatigue testing device for vertebral plate fixation, characterized in that: include: A base, wherein a slide groove for moving the support test block is provided inside the base, and a locking bolt for fixing the support test block is provided on the base; A bracket test block, wherein the bracket test blocks are symmetrically arranged in two groups and are slidably arranged in a slide groove, an inter-groove is provided between the bracket test blocks, and two groups of lamina fixation plates are symmetrically arranged in the inter-groove, the lower ends of the lamina fixation plates are fixed to the upper ends of the bracket test blocks, and the lamina fixation plates are provided with grooves; A connecting block, wherein the connecting block is fitted in the groove and the upper end surface of the connecting block is fixedly connected to the lamina fixation plate, and a loading hole is provided on the upper surface of the connecting block; A fatigue testing machine, wherein the loading block of the fatigue testing machine is fixedly connected to the loading hole, and the connecting plate of the fatigue testing machine is fixedly connected to the base; Also included is a test method comprising the following steps: S1: Assemble and connect the stent test block, connecting block, and lamina fixation plate to form a test sample, assemble the test sample into the base, and then assemble it into the fatigue testing machine, aligning the center of the loading block with the center of the connecting block; S2: Set the software environment, open the fatigue testing machine control software to edit the test plan, and reset the fatigue testing machine force value; S3: Use the fatigue testing machine to preload the test sample to ensure that the loading hole and the loading block are in full contact. At this time, the displacement is reset to zero. S4: Fatigue test is conducted according to the test plan in S2. The cyclic load generated by the fatigue testing machine is used to pressurize the test block connected to the vertebral plate fixation plate test device for fatigue test. In the fatigue test, a sinusoidal cyclic load is applied to the spinal structure, and the applied load ratio is R=10. The test is stopped after the number of cycles of the sample reaches 5,000,000 or until the sample fails within 5,000,000 cycles. According to the results obtained in the experimental steps of S1-S4, when the samples of this group pass the test, the static limit load of the test is increased by 10% and the next group of tests is conducted. If the samples fail to pass the test, the static limit load is reduced by 10% and the next group of tests is conducted until the difference between the load at the time of structural failure and the maximum fatigue load is less than 10% of the compression load limit. The number of samples passing the test under the same maximum fatigue load is three groups, and at least six groups are tested. At the same time, the changing number of cycles, displacement and load are continuously measured, and the corresponding data of the number of cycles, displacement and load are continuously output. At the same time, the changing number of cycles, displacement and load are continuously measured, and the corresponding data of the number of cycles, displacement and load are continuously output. S5: Based on the number of cycles and loads recorded in S4, the load-displacement data output by the fatigue testing machine are sorted to obtain a curve of the number of compression bending fatigue cycles of the lamina fixation plate and the maximum and minimum loads, and a semi-logarithmic fatigue curve of the number of cycles to failure is drawn based on the obtained number of cycles and loads; The testing machine in step S2 was set up with a maximum load of 60% of the static test limit load, a fatigue test frequency of 5 Hz, a maximum displacement change of 3 mm, and a maximum and minimum force change and range of 5 N.

2. The dynamic bending fatigue testing device for vertebral plate fixation according to claim 1, characterized in that: The bottom of the loading hole is hemispherical. The loading block includes a cylindrical rod and a connecting rod. A pin hole connected to the fatigue testing machine is provided on the cylindrical rod. The bottom of the connecting rod is provided with a spherical portion that matches the shape of the bottom of the loading hole.

3. The dynamic bending fatigue testing device for vertebral plate fixation according to claim 1, characterized in that: The laminar plate fixing plate is bolted to the inner side of the top of the bracket test block, and the upper end surface of the connecting block is bolted to the laminar plate fixing plate.

4. A dynamic bending fatigue test device for a lamina fixing plate according to claim 1, characterized in that, A dovetail groove is provided at the bottom of the sliding groove. An installation table is provided in the dovetail groove, and the installation table is fixed to the bracket test block by a locking bolt.

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