Porous tibia cushion block

Abstract

According to the porous tibia cushion block, a shaft rod and a porous structure on the periphery of the shaft rod are formed into an integrated structure through the 3D printing technology, the shaft rod serves as a main force bearing structure, stress is optimized, stress is prevented from being concentrated in the porous structure, and the overall mechanical performance is improved. In addition, the shaft rod further serves as a limiting assembly of the bone cement, the action range of the bone cement between the cushion block and the tibia support is limited, and the bone cement syndrome caused by the fact that the bone cement is released into the body is effectively avoided.

Description

Technical Field

[0001] The present application belongs to the field of joint implants, and in particular relates to a porous tibial pad. Background Art

[0002] Traditional knee prostheses mainly include a femoral component for combining with the femur, a tibial base for combining with the tibia, and a pad arranged on the tibial base component. The combination of these three realizes the joint function. The tibial base is provided with a positioning rod that can be inserted into the tibial medullary cavity to ensure the stability of the connection. However, after long-term use, it was found that the contact area between the positioning rod and the medullary cavity was too small, resulting in local pressure concentration and wear, and eventually leading to aseptic loosening of the tibial plateau, requiring another surgical revision.

[0003] To this end, the existing technology proposes to increase the contact area with the tibia by adding a porous pad. The porous pad is a porous structure formed by 3D printing, and its shape can be customized to increase the contact area with the medullary cavity. When combined with the tibial base, it can improve the stability of the positioning rod; since the porous pad is a fully porous structure, in order to ensure the stable connection between the porous pad and the tibial base, the existing technology introduces bone cement for fixation; bone cement is a filling material widely used for prosthesis fixation, but with the expansion of the scope of bone cement use, its problems have gradually emerged, such as bone cement implantation syndrome (BCIS). BCIS was first discovered in artificial hip replacement surgery. Due to a series of clinical symptoms caused by bone cement implantation, including hypotension, arrhythmia, severe hypoxemia, asthma attacks, etc., BCIS is currently the main cause of death and disability during and after artificial hip replacement surgery.

[0004] The current mainstream view is that the pathogenesis of bone cement-induced cardiac arrest is due to: 1. The toxic effects of methacrylate resin. During the application of bone cement, a large amount of methyl methacrylate (MMA), a monomer of bone cement, is released. Some animal studies have shown that MMA has a myocardial depressant effect and can also cause vasodilation. Most scholars believe that during total hip replacement surgery, when bone cement is packed into the medullary cavity and the femoral stem is inserted, the pressure in the medullary cavity rapidly increases, causing the thin-walled intramedullary blood vessels to rupture, allowing air, fat, and bone marrow tissue to enter the blood circulation, causing diffuse pulmonary embolism and even death. 2. The heat generated by MMA polymerization damages the vascular endothelium, which can easily trigger localized vascular thrombosis. Furthermore, the absorption of MMA activates coagulation factors, causing the blood to become hypercoagulable, which can lead to thrombosis.

[0005] On the other hand, the actual mechanical properties of the porous pad are poor. Since the shape of the medullary cavity is not a standard cylinder, the contact between the porous pad and the medullary cavity is not absolutely uniform, so local concentration will definitely occur. In particular, the instantaneous stress generated during implantation is greater, which can easily cause damage or falling off of the porous structure, seriously affecting safety of use. Utility Model Content

[0006] The purpose of this utility model is to provide a porous tibial pad that creatively incorporates a shaft. Using 3D printing technology, the shaft and the porous structure of the peripheral portion are formed into an integrated structure. The shaft serves as the primary load-bearing structure, optimizing force distribution, avoiding stress concentration within the porous structure, and improving overall mechanical performance. Additionally, the shaft acts as a bone cement limiting component, restricting the range of action of the bone cement between the pad and the tibial tray, effectively preventing cement release into the body and causing bone cement syndrome.

[0007] A tibial pad comprises: a shaft and a peripheral portion, wherein the shaft is a tubular structure and the peripheral portion is located outside the shaft. The peripheral portion is a three-dimensional mesh structure constructed based on additive manufacturing technology with the outer wall of the shaft as a reference surface.

[0008] Furthermore, the porous structure is formed by repeatedly stacking and expanding structural units starting from a reference surface outward, wherein the structural units are polygonal unit cell structures constructed by wires.

[0009] Furthermore, the top end of the shaft extends outward to cover the top surface of the peripheral portion, and the wall thickness of the shaft is 0.3-2.0 mm.

[0010] The utility model has at least the following beneficial effects:

[0011] In order to improve the stability of the connection between the tibial base and the tibia, a pad structure reinforcement is introduced. The porous structure of the pad can fully contact the medullary cavity, increasing the contact area and greatly enhancing the stability of the tibial platform. At the same time, a shaft is provided inside the pad to replace the porous structure as a load-bearing component, avoiding the risk of failure of the porous structure of the pad.

[0012] Additionally, the shaft is located at the bone cement filling position, forming a limiting structure that blocks the bone cement. When the bone cement is pumped in under pressure, it can effectively prevent the bone cement from entering the porous structure, thus avoiding the risk of bone cement particles escaping outward and entering the human body. This indirectly reduces the occurrence of bone cement syndrome while achieving enhancement.

[0013] In addition, the reinforced structure can also serve as an auxiliary heat dissipation structure with a large contact area, effectively avoiding heat accumulation and reducing damage to blood vessels and bones at the implantation site. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1Schematically shows the use status diagram of this application;

[0015] Figure 2 The structural diagram in Example 1 is schematically shown;

[0016] Figure 3 The structural diagram in Example 2 is schematically shown;

[0017] Figure 4 The structural diagram of another preferred embodiment in Example 2 is schematically shown.

[0018] Among them: 1-tibial support, 2-positioning rod, 3-tibial pad, 31-axis rod, 32-peripheral part. DETAILED DESCRIPTION

[0019] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "horizontal", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", "tail", etc. are based on the directions or positional relationships shown in the accompanying drawings and are constructed and operated in specific directions. They are only for the convenience of describing the present technical solution and do not indicate that the devices or components referred to must have specific directions. Therefore, they should not be understood as limiting the present invention.

[0020] It should also be noted that, unless otherwise expressly specified or limited, terms such as "installed," "connected," "connect," "fixed," and "set" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integration; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal connectivity between two elements or interactions between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located above the other element, or one or more intervening elements may be present. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances. Example 1

[0021] A porous tibial pad is used in conjunction with the tibial base in a joint prosthesis. Figure 1As shown, the tibial base includes a tibial tray 1 and a positioning rod 2. The upper surface of the tibial tray 1 is connected to the tibial plateau pad, which in turn contacts the femoral condyle. The lower surface of the tibial tray 1 is provided with a positioning rod 2, which is inserted into the medullary cavity for fixation. A tibial pad 3 is provided at the connection between the tibial tray 1 and the positioning rod 2, and the tibial pad 3 is fixed to the tibial tray 1 by bone cement. Since the cross-sectional shape of the positioning rod 2 does not completely match the cross-sectional shape of the tibial medullary cavity opening, and the force direction may come from different directions when the joint is in use, it is easy to concentrate at the contact point between the tibial tray and the medullary cavity, and will cause shaking due to wear after long-term use.

[0022] To this end, the pad structure in this application can alleviate the above problems. The outer wall of the pad is in contact with the medullary cavity, the contact area is larger, the force is more uniform, the force points are dispersed, wear under long-term use is avoided, and long-term stability can be maintained.

[0023] The structure of the tibial pad 3 is as follows Figure 2 As shown, it includes a shaft rod 31 and a peripheral portion 32, wherein the peripheral portion 32 is a porous structure fixed around the outside of the shaft rod 31, and the shaft rod 31 is a tubular structure with a solid inner wall. The positioning rod 2 passes through the shaft rod 31 and is inserted into the tibial medullary cavity; the outer contour of the peripheral portion 32 is a smooth curve transition to avoid tissue damage, and is the same as the shape of the opening reserved on the tibial surface during surgery. After being inserted into the tibial medullary cavity, it is in full contact with the inner wall of the medullary cavity.

[0024] It should be noted that the outer contour of the tibial pad 3 can be flexibly adjusted based on preoperative planning, and personalized adaptation can be achieved using 3D printing technology.

[0025] The shaft 31 is also provided with multiple notches to accommodate irregular protrusions on the underside of commercially available tibial bases, allowing it to fit most commercially available tibial bases and ensure full contact between the tibial pad 3 and the underside of the tibial tray 1, effectively bearing the load. The tibial pad 3 and the tibial base are fixedly connected using bone cement, which is typically pumped under pressure into the gap between the pad and the tibial base. After exothermic solidification, the cement stabilizes the two, forming a single unit.

[0026] In order to improve the fusion of the tibia and the tibial pad 3, the existing technology uses additive manufacturing to form the entire pad. The pad has a fully porous structure, which can improve bone ingrowth and fully integrate with the tibia; but correspondingly, its compressive strength will be greatly reduced. The lower compressive strength will cause the porous structure to deform during implantation or use, and even cause serious consequences such as some porous units to break and fall off.

[0027] In contrast, the present application uses the shaft 31 as the main load-bearing component. The tubular structure of the body itself has high strength, and the porous structure of the peripheral part 32 is constructed with the outer wall of the shaft 31 as the reference surface, and radiates with the central axis to provide auxiliary load-bearing. It effectively avoids deformation or falling off of the porous structure and gives full play to the effect of the porous structure in promoting bone ingrowth.

[0028] In addition, the shaft rod 31 in the present application also has an additional technical effect, namely, the shaft rod 31 can reduce the incidence of bone cement syndrome.

[0029] It is generally believed that the occurrence of bone cement syndrome comes from the stage of pressurized pumping of bone cement. The pressure in the medullary cavity increases rapidly, causing the rupture of thin-walled intramedullary blood vessels, resulting in the entry of air, fat and bone marrow tissue into the blood circulation, activating the complement system, leading to the activation of coagulation factors and the hypercoagulable state of blood, causing thrombosis, and then causing diffuse pulmonary embolism; on the other hand, the heat generated by the exotherm of bone cement damages the vascular endothelium, which can easily induce local vascular thrombosis.

[0030] The shaft 31 of the present application is located exactly at the position where the tibial pad 3 contacts the bone cement, which blocks the diffusion of bone cement into the porous structure part, greatly reduces the exposed area of ​​bone cement, and at the same time reduces the pressure on the medullary cavity when the bone cement is pressurized and pumped into, preventing it from entering the blood circulation, thereby indirectly reducing the occurrence of bone cement syndrome.

[0031] It should be noted that the above-mentioned porous structure is not the dense through-holes commonly understood, but a three-dimensional network structure formed by stacking multiple structural units. The gaps in this structure are usually very small, and on a macroscopic level it appears similar to dense pores, so it is called a porous structure. Example 2

[0032] like Figure 3 As shown, the top end of the shaft 31 extends outward to cover the top surface of the peripheral portion 32 , thereby increasing the contact area with the tibial base, fully receiving the pressure from the tibial base, and further reducing the force on the peripheral portion 32 .

[0033] Of course, this embodiment is formed based on 3D printing technology, and the peripheral portion 32 can be flexibly adjusted based on the conditions of different patients. For example: Figure 4 In the embodiment shown, the spacer is designed with a notch to accommodate patients with different bone defects on both sides.

[0034] In the above description, for the purpose of explanation rather than limitation, specific details such as particular system structures and technologies are provided to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, and methods are omitted to avoid obscuring the description of the present invention with unnecessary detail.

Claims

1. A porous tibial pad, characterized in that: include: The shaft is a tubular structure, the peripheral part is located outside the shaft, and the peripheral part is a porous structure. The porous structure is a three-dimensional network structure constructed based on additive manufacturing technology with the outer wall of the shaft as a reference surface.

2. The porous tibial pad according to claim 1, characterized in that: The porous structure is formed by repeatedly stacking and expanding structural units starting from a reference surface outward.

3. The porous tibial pad according to claim 2, characterized in that: The structural unit is a polygonal unit cell structure constructed from wires.

4. The porous tibial pad according to claim 1, characterized in that: The top end of the shaft extends outward to cover the top surface of the outer peripheral portion.

5. The porous tibial pad according to claim 1, characterized in that: The wall thickness of the shaft is 0.3-2.0 mm.

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