Orthopedic implant in-vivo tensile loading experimental device and experimental method

Abstract

The application provides an orthopedic implant in-vivo tension loading experiment device and experiment method, and loading device comprises: fixed bone plate, the bottom surface of the fixed bone plate is consistent with the cortical bone surface of the measured bone, and implant holes and bone nail fixing holes are arranged on the fixed bone plate; implant model, the implant model is clamped in the implant hole; a force transmission hole is arranged in the implant model, and the opening of the force transmission hole is located on the top end surface of the implant model; a force transmission column is placed in the force transmission hole, the top end of the force transmission column extends out of the opening of the force transmission hole, and the rigidity of the force transmission column is greater than the rigidity of the implant model; a loading knob is installed in the implant hole through threads, and the bottom surface of the loading knob is in contact with the top surface of the force transmission column. The loading device of the application only needs to drill a hole on one side of the cortical bone of the experimental object during the experiment, so that the loading device can be installed, and the incidence of bone fracture and infection of the experimental object is reduced.

Description

Technical Field

[0001] This invention belongs to the field of orthopedic implant devices, and specifically relates to an in vivo tensile loading experimental device and method for orthopedic implants. Background Technology

[0002] Bone cells are force-sensitive cells that sense the surrounding mechanical environment and regulate physiological processes such as bone growth, repair, and reconstruction. Orthopedic implants are widely used in clinical practice to repair, supplement, and replace human bones, treat orthopedic diseases, and maintain normal bodily functions. Once inside the body, implants are constantly subjected to physiological loads in daily life, placing them within a mechanical environment. The implant is in close contact with the surrounding bone tissue, and forces interact at the interface, providing mechanical stimulation to the surrounding bone. Therefore, studying the mechanical stimulation of surrounding bone tissue by implants under physiological loads in vivo, and the impact of this mechanical stimulation on physiological and pathological processes such as bone growth, development, injury, and repair, is crucial for implant design and disease treatment. To gain a deeper understanding of the impact of implants on the remodeling of surrounding bone tissue under physiological loads in vivo, animal experimental models are needed. Constructing in vivo mechanical loading devices to reproduce physiological loads is the fundamental guarantee for experimental research.

[0003] Implants are subjected to complex loads within the body, such as compression, tension, bending, torsion, and combined tensile-compression-bending-torsion loads. Current in vivo loading devices primarily apply compressive and bending loads to the implant. For example, torsional loads can be applied by rotating the implant externally using a screw; bending loads can be applied by applying lateral thrust to the external portion of the implant; and compressive loads can be applied by squeezing the implant. However, current technology lacks a loading device for applying tensile loads to implants within the body. While it's possible to fix the implant at one end within the bone and then apply tension to the outer end to achieve stretching, this method inevitably requires bone-penetrating fixation screws. This undoubtedly increases the risk of fractures and infections in experimental subjects, potentially leading to experimental failure and thus failing to meet the needs of experimental research. Summary of the Invention

[0004] This application addresses the technical problem that existing implant loading devices cannot apply tensile loads, making it difficult to meet the needs of experimental research. It provides an orthopedic implant tensile loading experimental device that can apply adjustable tensile loads to implants in various modes, thus overcoming the problem of the limited loading methods in existing bone implants. This application also provides a method for conducting experiments using the loading device.

[0005] The technical method adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] An in vivo tensile loading experimental device for orthopedic implants includes:

[0007] A fixation plate is provided, the bottom surface of which matches the cortical bone surface of the bone to be tested, and an implantation hole and a bone screw fixation hole are provided on the fixation plate.

[0008] An implant model is fitted into an implantation hole; a force transmission hole is provided in the implant model, the opening of which is located on the top surface of the implant model; a force transmission column is placed in the force transmission hole, the top end of which extends out of the opening of the force transmission hole, and the stiffness of the force transmission column is greater than that of the implant model.

[0009] A loading knob is threaded into the implantation hole, with the bottom surface of the loading knob abutting against the top surface of the force transmission column.

[0010] The top outer wall of the implant model is a sloping surface that gradually slopes inward from top to bottom, forming a top with a frustum-shaped cross section; a sloping step is provided at the bottom of the implantation hole, and the top outer edge of the implant model is fitted onto the sloping step.

[0011] A limiting groove is provided on the inner wall of the implantation hole, and a limiting block is provided on the outer wall of the implant model. The limiting block is located in the limiting groove to restrict the axial rotation of the implant model.

[0012] A knob groove is provided on the top surface of the loading knob.

[0013] The knob groove is either a cross or a straight groove.

[0014] It also includes an auxiliary device, which includes a screwdriver for turning the knob recess.

[0015] The auxiliary device includes: an angle sleeve with a hollow channel and graduation lines; and a screwdriver installed in the hollow channel of the angle sleeve, suitable for rotating relative to the angle sleeve, with the top and bottom ends of the screwdriver extending above and below the angle sleeve, respectively.

[0016] Two limiting rods are provided on the outer wall of the angle sleeve, and the limiting rods extend outward from the outer wall of the angle sleeve; a stop bar is provided on the outer wall of the screwdriver, and the stop bar extends between the two limiting rods.

[0017] The implant model is an orthopedic implant with a force conduction hole.

[0018] The method for conducting a tensile loading experiment using the aforementioned orthopedic implant in vivo tensile loading experimental device is characterized by placing the implant model in the bone to be tested and fixing the fixation plate to the surface of the bone to be tested. A tensile force of N Newtons is applied by rotating the loading knob, so that the deformation of the implant under tensile load is in the elastic deformation stage. The formula for calculating the rotation angle A of the loading knob is as follows:

[0019]

[0020] Where X is the displacement of the bone screw when a tensile force of N Newtons is applied, calculated from the force and displacement loading curve of the implant model; P is the pitch of the thread of the loading knob.

[0021] The advantages of the in vivo tensile loading experimental device and method for orthopedic implants described in this invention are:

[0022] The in vivo tensile loading experimental device for orthopedic implants described in this invention, in its installed state, has the loading device fixed to the bone surface. The force transmission column contacts the bottom surface of the force transmission hole of the implant model and the lower surface of the loading knob. Rotating the loading knob downwards applies pressure to the force transmission column, which transmits the pressure to the bottom of the implant model. The bottom of the implant model moves downwards under pressure, thus applying a tensile load to the porous bone screw body. During the experiment, only one hole needs to be drilled on one side of the cortical bone of the experimental subject for installation; it does not need to penetrate the entire bone to apply the tensile load, reducing the incidence of fractures and infections in the experimental subjects. Furthermore, the shape of the fixing bone plate can be modified according to the animal experimental site to better fit the cortical bone, further improving the fixation effect and the stability of the device loading. In addition, the loading device of this invention has a simple structure, is easy to manufacture, and can be used in various parts of small animals such as rabbits, large animals such as dogs and monkeys, as well as humans, with a wide range of applications and a simple and easy-to-operate experimental process.

[0023] The loading experimental device described in this invention has a wide range of applicability for the implants being loaded. The implants are not limited by material or shape; they can be ordinary hollow structures or porous hollow structures. Because the load type and magnitude of the loading experimental device described in this invention are adjustable, both static and dynamic tensile forces can be applied to the bone implants in experimental animals. Furthermore, the magnitude of the tensile force can be changed at different time points after implantation in the animal as needed. Moreover, the experimental device described in this invention can apply a wide range of loads. Taking the porous bone screw implantation experiment as an example, based on the mechanical response characteristics of hollow porous bone screws, the applied tensile load can be several Newtons, tens of Newtons, or even hundreds of Newtons.

[0024] As a preferred embodiment, the in vivo tensile loading experimental device for orthopedic implants of the present invention provides measures to improve loading accuracy. In this invention, the limiting groove of the fixing bone plate matches the limiting block of the implant model, which can prevent the hollow porous bone nail from rotating during loading. Simultaneously, the top outer wall of the implant model is set as a slope that gradually slopes inward from top to bottom, forming a frustum shape. A sloped step is provided at the bottom end of the implantation hole of the fixing bone plate, and the top outer wall of the implant model is fitted onto the sloped step. The combination of these two features prevents the hollow porous bone nail from moving downward under force, thus avoiding affecting loading accuracy.

[0025] The in vivo tensile loading experimental device for orthopedic implants described in this invention includes the auxiliary loading device, thereby improving operational convenience. As an alternative implementation, the auxiliary loading device can be a manually controlled device or an electrically controlled intelligent device capable of controlling the load magnitude and loading frequency.

[0026] To make the technical solution of the in vivo tensile loading device and recording method for orthopedic implants of the present invention clearer, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0027] like Figure 1 The figure shown is a perspective view of the in vivo tensile loading experimental device for orthopedic implants according to the present invention;

[0028] like Figure 2 The image shown is a front view of the in vivo tensile loading experimental device for orthopedic implants according to the present invention;

[0029] like Figure 3 The figure shown is a cross-sectional view of the in vivo tensile loading experimental device for orthopedic implants according to the present invention;

[0030] like Figure 4 The image shown is a perspective view of the fixation bone plate of the in vivo tensile loading experimental device for orthopedic implants according to the present invention;

[0031] like Figure 5 The image shown is a top view of the fixation bone plate of the in vivo tensile loading experimental device for orthopedic implants according to the present invention;

[0032] like Figure 6 The diagram shown is a structural diagram of the implant of the orthopedic implant in vivo tensile loading experimental device of the present invention;

[0033] like Figure 7 The diagram shown is a structural diagram of the loading knob of the in vivo tensile loading experimental device for orthopedic implants according to the present invention;

[0034] like Figure 8The diagram shown is a structural diagram of the auxiliary loading device of the in vivo tensile loading test device for orthopedic implants described in this invention.

[0035] The attached figures are labeled as follows:

[0036] 1-Implantation hole; 11-Limiting groove; 12-Fixation hole; 2-Implant model; 20-Fixation cap; 21-Main body of the porous bone screw; 22-Bottom of the porous bone screw; 201-Limiting block; 3-Force transmission column; 4-Loading knob; 40-Cross groove; 50-Angle sleeve; 51-Screwdriver; 501-Limiting rod; 511-Handle; 510-Stop bar. Detailed Implementation

[0037] In this embodiment, the terms "top," "bottom," "up," and "down" in the orientation refer to the state of the implant model 2 when it is implanted into the animal bone. When the implant model 2 is implanted into the animal bone, in the force transmission direction of the force transmission column 3, the end that penetrates into the animal bone is the bottom end, and the end that is close to the surface of the cortical bone is the top end. The direction extending from the bottom end to the top end is the direction from bottom to top.

[0038] This embodiment provides an in vivo tensile loading experimental device for orthopedic implants, and details the device for applying tensile loads to a rabbit using a porous bone screw. The structure of the loading device is as follows: Figure 1-3 As shown, it specifically includes a fixation bone plate and an implant model 2. The bottom surface of the fixation bone plate conforms to the cortical bone surface of the bone to be tested, as shown... Figure 4 , 5 As shown, the fixation bone plate is provided with an implantation hole 1 and a fixation hole 12; wherein the implantation hole 1 is a threaded hole with a diameter of 5.5 mm, and the diameter of the inner wall at the bottom of the implantation hole 1 gradually decreases to form a sloping step. Simultaneously, a limiting groove 11 is provided on the inner wall of the implantation hole 1, and the limiting groove 11 extends vertically. In this embodiment, the fixation bone plate is provided with two fixation holes 12, each with a diameter of 1.5 mm, for inserting self-tapping screws, thereby fixing the loading device on the surface of the bone of the animal to be tested and preventing horizontal movement of the implant.

[0039] Implant Model 2, such as Figure 6As shown, the implant model 2 is fitted into the implantation hole 1. In this embodiment, the implant model 2 is a hollow porous bone screw, which includes a fixation cap 20, a main body 21, and a bottom 22 arranged sequentially from top to bottom. The outer wall of the fixation cap 20 at the top of the porous bone screw is a slope that gradually slopes inward from top to bottom. This slope matches the shape of the inner wall of the bottom of the implantation hole 1, thus fitting into the bottom of the implantation hole 1. A limiting block 201 is also provided on the outer wall of the fixation cap 20, which protrudes from the outer wall of the fixation cap 20, forming a protrusion. When the implant model 2 is installed in the implantation hole 1, the limiting block 201 is located in the limiting groove 11, preventing the implant model 2 from rotating axially when subjected to force. A force transmission hole is provided within the implant model 2. The opening of the force transmission hole is located on the top surface of the implant model 2, and the force transmission hole penetrates through the main body 21 of the porous bone screw to reach the bottom of the force transmission hole. In this embodiment, the diameter of the force transmission hole is 2 mm, and the force transmission hole is coaxially arranged with the porous bone screw. The opening of the force transmission hole is located on the top surface of the fixation cap 20. A force transmission column 3 is placed inside the force transmission hole. The force transmission column 3 is a solid cylinder with a diameter of 1.9 mm, and its length is slightly greater than the depth of the force transmission hole of the hollow porous bone screw, so that the top of the force transmission column 3 extends out of the opening of the force transmission hole, and the bottom of the force transmission column 3 abuts against the bottom of the implant model 2. After being installed in the force transmission hole, the force transmission column 3 protrudes 0.5 mm above the top surface of the bone screw fixation cap 20. The stiffness of the force transmission column 3 is greater than the stiffness of the implant model 2, thereby allowing for a stretching operation on the implant model 2.

[0040] The loading experimental device is also equipped with a loading knob 4, such as Figure 7 As shown, the loading knob 4 is threaded into the implantation hole 1, and the bottom surface of the loading knob 4 abuts against the top surface of the force transmission column 3. The diameter and thread of the loading knob 4 match the diameter and thread of the implantation hole 1 of the fixation bone plate. At the same time, there is a groove with a width of 1 mm and a depth of 3 mm on the loading knob 4. The groove is preferably a cross groove 40 for rotating the loading knob 4. As an alternative embodiment, the groove can also be set to other shapes.

[0041] To facilitate operation, this embodiment also includes an auxiliary loading device, such as... Figure 8As shown, the auxiliary loading device consists of an angle sleeve 50 and a screwdriver 51. The screwdriver 51 has a rod-shaped body at its bottom, the shape of which matches the knob groove. This rod-shaped body can be either Phillips head or flathead, used to rotate the loading knob 4. In a preferred embodiment, the upper outer wall of the angle sleeve 50 has two limiting rods 501, with a fixed angle between them. The upper part of the angle sleeve 50 is a hollow cylindrical body, and the lower part has a hollow guide tube. The cylindrical body is connected to the guide tube via a gradually tapering conical body. The screwdriver 51 includes a handle, a transition section, and a rod-shaped body, the outer diameter of which matches the inner diameter of the cylindrical body, the conical body, and the guide tube, respectively. The screwdriver 51 is installed within the hollow channel of the angled sleeve 50, wherein the bottom end of the rod-shaped body extends below the guide tube, and the top end of the handle extends above the cylindrical body. The screwdriver 51 is adapted to rotate relative to the angled sleeve 50. A handle 511 is provided on the outer wall of the handle of the screwdriver 51, and the handle 511 is located near the top end of the handle, forming a T-shaped handle structure for easy rotation of the screwdriver 51. A stop bar 510 is located on the outer wall of the middle region of the handle. The stop bar 510 is a horizontally arranged L-shaped bar that extends outward from the outer wall of the handle and then downward to between the two limiting bars 501.

[0042] During the experiment, the loading experimental device was fixed on the bone surface. In the installed state, the force transmission column 3 was in contact with the upper surface of the bottom of the hollow porous bone nail and the lower surface of the loading knob 4. By rotating the loading knob 4, it was moved downward to apply pressure to the force transmission column 3. The force transmission column 3 transmitted the pressure to the bottom of the porous bone nail. The bottom of the porous bone nail moved downward under pressure to achieve tensile load loading on the nail body of the porous bone nail.

[0043] The method for determining the load magnitude is as follows: Assuming the tensile force to be applied in the experiment is N Newtons, based on the force-displacement loading curve of the hollow porous bone nail, the displacement generated by the hollow porous bone nail when N Newtons is applied is X millimeters. The formula for calculating the angle A of rotation of the loading knob in the experiment is as follows:

[0044]

[0045] Where P is the pitch of the loading knob thread, and the units of pitch and displacement must be consistent. To ensure that the deformation of the porous bone screw under tensile load is within the elastic deformation stage, the loading data must be selected within the elastic region when choosing the loading data based on the force-displacement curve of the porous bone screw. The method described in this embodiment allows for adjustment of the load type and magnitude, enabling the application of both static and dynamic tensile forces to the experimental animal bone implant. Furthermore, the magnitude of the tensile force can be changed at different time points after implantation in the animal as needed.

[0046] The specific experimental method for applying tensile load to the porous bone screw in rabbits in this embodiment is as follows: During animal experiments, the soft tissue of the surgical area is treated according to conventional methods to expose the cortical bone at the implantation point of the bone screw. Then, a hole is drilled perpendicular to the cortical bone, without penetrating the cortical bone on the opposite side. The diameter and depth of the implantation hole match the diameter and length of the hollow porous bone screw. The fixing bone plate of the device of this invention is installed on the cortical bone of the implantation hole and fixed with a self-tapping bone screw. The hollow porous bone screw is installed through the implantation hole 1 in the middle of the fixing bone plate. The force transmission column 3 is inserted into the hole in the middle of the hollow porous bone screw. The loading knob 4 is screwed into the fixing bone plate, wherein the bottom surface of the loading knob 4 contacts the force transmission column 3 without gap. By rotating the loading knob 4 through the auxiliary loading device, the force transmission column 3 is squeezed downward to generate pressure on the bottom of the hollow porous bone screw. The upper fixing cap 20 of the hollow porous bone screw is fixed in the implantation hole 1 of the bone plate and will not move downward, thereby allowing the hollow porous bone screw body area to bear tensile force. Based on the calculation formula for rotation angle A mentioned earlier, the angle between the two limiting rods 501 on the angle sleeve 50 can be designed and processed to meet the experimental requirements, maintaining consistency with the rotation angle A of the loading knob. The screwdriver 51 is inserted into the angle sleeve 50; the L-shaped rod and the limiting rod 501 work together to ensure that the screwdriver 51 rotates at a fixed angle each time. At the set loading time point, the screwdriver 51 and angle sleeve 50 are assembled and inserted into the cross groove of the loading knob 4, fixing the angle sleeve 50 in place. The applied load is changed by rotating the screwdriver 51 and the loading knob 4. Dynamic tensile load can also be applied by rotating the screwdriver 51 in both forward and reverse directions. During both surgical and postoperative loading, all surgical instruments, loading devices, and auxiliary loading devices must undergo strict sterilization to prevent infection at the implantation site. The loading device in this embodiment has a wide applied load range; based on the mechanical response characteristics of the hollow porous bone screw, the applied tensile load can be several Newtons, tens of Newtons, or even hundreds of Newtons.

[0047] This embodiment uses a porous bone screw as an example to illustrate the loading test device, but the implant model 2 in this invention is not limited to a porous bone screw, but can also be any bone implant with force conduction holes, including but not limited to porous implants, ordinary bone screws, etc.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the claims.

Claims

1. An in vivo tensile loading experimental device for orthopedic implants, characterized in that, include: A fixation plate is provided, the bottom surface of which matches the cortical bone surface of the bone to be tested, and an implantation hole and a bone screw fixation hole are provided on the fixation plate. An implant model is fitted into an implantation hole; a force transmission hole is provided in the implant model, the opening of which is located on the top surface of the implant model; a force transmission column is placed in the force transmission hole, the top end of which extends out of the opening of the force transmission hole, and the stiffness of the force transmission column is greater than that of the implant model. A loading knob is threaded into the implantation hole, with the bottom surface of the loading knob abutting against the top surface of the force transmission column.

2. The in vivo tensile loading experimental device for orthopedic implants according to claim 1, characterized in that, The top outer wall of the implant model is a sloping surface that gradually slopes inward from top to bottom, forming a top with a frustum-shaped cross section; a sloping step is provided at the bottom of the implantation hole, and the top outer edge of the implant model is fitted onto the sloping step.

3. The in vivo tensile loading experimental device for orthopedic implants according to claim 2, characterized in that, A limiting groove is provided on the inner wall of the implantation hole, and a limiting block is provided on the outer wall of the implant model. The limiting block is located in the limiting groove to restrict the axial rotation of the implant model.

4. The in vivo tensile loading experimental device for orthopedic implants according to claim 3, characterized in that, A knob groove is provided on the top surface of the loading knob.

5. The in vivo tensile loading experimental device for orthopedic implants according to claim 4, characterized in that, The knob groove is either a cross or a straight groove.

6. The in vivo tensile loading experimental device for orthopedic implants according to claim 5, characterized in that, It also includes an auxiliary device, which includes a screwdriver for turning the knob recess.

7. The in vivo tensile loading experimental device for orthopedic implants according to claim 6, characterized in that, The auxiliary device includes: an angle sleeve with a hollow channel and graduation lines; a screwdriver installed in the hollow channel of the angle sleeve, suitable for rotating relative to the angle sleeve, with the top and bottom ends of the screwdriver extending above and below the angle sleeve, respectively.

8. The in vivo tensile loading experimental device for orthopedic implants according to claim 7, characterized in that, Two limiting rods are provided on the outer wall of the angle sleeve, and the limiting rods extend outward from the outer wall of the angle sleeve; a stop bar is provided on the outer wall of the screwdriver, and the stop bar extends between the two limiting rods.

9. The in vivo tensile loading experimental device for orthopedic implants according to claim 1, characterized in that, The implant model is an orthopedic implant with a force conduction hole.

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