Femoral stem prosthesis with torsional trabecular structure

Abstract

The present application relates to femoral stem prosthesis, specifically provides a femoral stem prosthesis with twisted trabecular structure, aims to solve the problem that although the existing femoral stem prosthesis has trabecular porous structure to promote bone growth, but still due to the high material elastic modulus and stress concentration inside the pore, leading to stress shielding effect and trabecular fracture, so it is difficult to effectively prevent long-term loosening of the prosthesis. For this purpose, a femoral stem prosthesis with twisted trabecular structure of the present application comprises a trabecular structure unit arranged on the surface layer of the prosthesis, the shape of the trabecular structure unit is a space net structure, the space net structure is provided with pores, the pores can accommodate new bone, and the space net structure is twisted from the inside of the prosthesis to the surface layer of the prosthesis. The present application introduces the mechanical regulation effect brought by structure twisting by arranging the space net trabecular structure which is twisted continuously from inside to outside on the surface layer of the prosthesis, on the basis of ensuring that the pores can be used for new bone growth and realizing bone-prosthesis biological fixation.

Description

Technical Field

[0001] This invention relates to femoral stem prostheses, specifically providing a femoral stem prosthesis with a torsional trabecular structure. Background Technology

[0002] Hip replacement surgery, which uses artificial prostheses to replace damaged hip joint structures, can effectively restore patients' motor function. The femoral stem, as the core load-bearing component of the prosthesis, directly determines the prosthesis's lifespan through its long-term performance. However, existing femoral stems are prone to aseptic loosening during long-term use, mainly due to an imbalance in the mechanical environment at the femoral stem-bone interface. On the one hand, the elastic modulus of traditional metallic femoral stem materials is much higher than that of human bone tissue, leading to a stress shielding effect. This causes bone loss and atrophy in surrounding bone tissue due to insufficient long-term load. On the other hand, cyclic dynamic loads and occasional impact loads generated by human activity may induce fatigue cracks at the femoral stem-bone interface. When the crack propagation rate exceeds the bone remodeling capacity, it can easily lead to femoral stem loosening or prosthesis failure.

[0003] To alleviate the stress shielding effect and promote bone ingrowth, existing technologies have developed biomimetic trabecular femoral stem structures. These structures control the equivalent elastic modulus of the prosthesis through porosity parameters and form a porous network internally to provide space for bone growth, achieving mechanical anchoring. However, existing trabecular femoral stems still have limitations: on the one hand, the modulus of commonly used metal materials is still too high to meet the porosity requirements for bone ingrowth, only partially alleviating stress shielding; on the other hand, stress concentration may still occur in the porous internal scaffold after bone tissue ingrowth, increasing the risk of trabecular fracture and damage to new bone, making it difficult to completely solve the problem of femoral stem loosening and failure.

[0004] Therefore, there is an urgent need in the field for a femoral stem prosthesis with a torsional trabecular structure to solve the above problems. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problem that although existing femoral stem prostheses have a porous trabecular structure to promote bone ingrowth, they still suffer from stress shielding effect and trabecular fracture due to the high elastic modulus of the material and stress concentration inside the pores, making it difficult to effectively prevent long-term loosening of the prosthesis.

[0006] In a first aspect, the present invention provides a femoral stem prosthesis with a torsional trabecular structure, the femoral stem prosthesis including trabecular structural units disposed on the surface of the prosthesis, the trabecular structural units being in the shape of a spatial mesh structure, the spatial mesh structure having pores that can accommodate new bone formation, the spatial mesh structure being torsional from the interior of the prosthesis toward the surface of the prosthesis.

[0007] In the specific implementation of the above-mentioned femoral stem prosthesis, the range of the change in the torsion angle per unit length of the spatial mesh structure from the inside of the prosthesis to the surface of the prosthesis is greater than 0 and does not exceed 25 deg / mm.

[0008] In the specific embodiments of the above-mentioned femoral stem prosthesis, the shape of the trabecular structural unit is an orthogonal lattice structure and a triple-period minimal surface lattice structure.

[0009] In the specific embodiment of the above-mentioned femoral stem prosthesis, the shape of the trabecular structural unit is a Gyroid curved lattice structure.

[0010] In a specific embodiment of the above-described femoral stem prosthesis, the prosthesis includes a plurality of the aforementioned trabecular bone structural units.

[0011] In a specific embodiment of the above-mentioned femoral stem prosthesis, the prosthesis includes a head, a neck, and a stem. The head is used to connect to the acetabulum. One end of the neck is connected to the head, and the other end is connected to the stem. The trabecular bone structural unit is disposed on the surface of the stem. The change in the torsion angle per unit length of the spatial mesh structure of the trabecular bone structural unit from the interior of the prosthesis to the surface of the prosthesis is set as A. The A of the trabecular bone structural unit closer to the head is greater than the A of the trabecular bone structural unit farther away from the head.

[0012] In a specific embodiment of the above-mentioned femoral stem prosthesis, the stem includes a torsional trabecular region and a solid region. The torsional trabecular region is located close to the head, and the solid region is located away from the head. The trabecular structural unit is only located in the torsional trabecular region.

[0013] In a specific embodiment of the above-mentioned femoral stem prosthesis, the torsional trabecular region includes a solid support region, and the trabecular structural unit is disposed on the surface of the solid support region.

[0014] With the above-mentioned technical solution, the present invention introduces a mechanical regulation effect brought about by the structural torsion by setting a spatial mesh-like trabecular bone structure that is continuously twisted from the inside to the outside on the surface of the prosthesis. This ensures that the pores can be used for new bone ingrowth and achieve bone-prosthesis bio-fixation. On the one hand, the torsion structure can effectively reduce the equivalent elastic modulus of the trabecular bone structure, making it closer to human cancellous bone, thereby reducing stress shielding. On the other hand, the torsion spatial mesh path can change the load transmission direction and extend the transmission path, promote the gradual dissipation of load, and at the same time deflect and impede the propagation of microcracks, reducing stress concentration and the risk of structural failure, thereby improving the stability of the prosthesis-bone tissue interface and long-term service performance.

[0015] Furthermore, this invention specifically constructs the trabecular bone structural units as orthogonal lattice structures or triple periodic minimal surface (TPMS) lattice structures, particularly preferably Gyroid surface lattice structures. This allows the trabecular bone structure to maintain interconnected pores to facilitate the ingrowth of new bone while possessing a more continuous and smooth spatial topology and excellent mechanical properties. Among these, the TPMS, especially the Gyroid structure, due to its characteristics of having no sharp angles and continuous curved surfaces, can effectively reduce stress concentration, improve the mechanical stability and fatigue performance of the structure, and further optimize the load transfer path, making the stress distribution more uniform. Thus, while enhancing the bonding effect at the bone-prosthesis interface, it also improves the overall damage resistance and long-term service reliability of the prosthesis.

[0016] Furthermore, this invention, by setting multiple trabecular structural units to form a continuously distributed spatial network structure on the surface of the prosthesis stem, not only improves the overall connectivity and stability of the porous structure, facilitating the uniform ingrowth of new bone over a wider area and the formation of a reliable prosthesis-bone composite structure, but also, by gradient-designing the torsional angle variation A of the spatial network structure along the prosthesis from the head to the stem, allows for a greater degree of torsion and a lower equivalent elastic modulus in the area near the head, thus better matching the higher load requirements of this area, while the area away from the head correspondingly increases structural stiffness, achieving zonal control of overall mechanical properties. This gradient control mechanism helps optimize stress distribution, reduce stress concentration, and mitigate stress shielding effects, while providing a more balanced mechanical stimulation environment for new bone, thereby significantly improving bone ingrowth and the long-term stability of the prosthesis.

[0017] Furthermore, this invention, by setting a partitioned structure of a torsional trabecular bone region and a solid region in the stem, and confining the trabecular bone structural units to the torsional trabecular bone region near the head, enables the prosthesis to have good elastic matching ability and bone ingrowth performance in the proximal region, which bears a large physiological load, while the distal solid region provides the necessary overall structural strength and support stability, thereby achieving synergistic optimization of mechanical performance and structural support. Furthermore, by setting a solid support region in the torsional trabecular bone region and arranging the trabecular bone structural units on its surface, a porous surface structure is formed while ensuring the internal load-bearing capacity. This not only facilitates the attachment and ingrowth of new bone, but also improves the interfacial mechanical environment while maintaining overall strength, reducing stress concentration and the risk of interfacial failure, thereby improving the initial stability and long-term service reliability of the prosthesis. Attached Figure Description

[0018] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the femoral stem prosthesis provided by the present invention. The spiral lines in the diagram represent the torn spatial network structure in the trabecular structural unit. Figure 2 This is a schematic diagram of the torsion trabecular bone region of the femoral stem prosthesis provided by the present invention. The spiral lines in the diagram represent the torsioned spatial network structure in the trabecular bone structural unit. Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure of section AA; Figure 4 This is a schematic diagram of the twisted spatial mesh structure in Embodiment 1 provided by the present invention; Figure 5 This is a schematic diagram of the spatial mesh structure in the unstressed state in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the spatial mesh structure under stress in Embodiment 1 provided by the present invention, where ε represents the deformation of the spatial mesh structure after being subjected to stress. Figure 7 This is a schematic diagram of the load transfer process in a spatial mesh structure provided by the present invention. The arrows in the diagram represent the direction of the load. Figure 8 This is a schematic diagram of the untwisted spatial mesh structure compared to Example 1; Figure 9 This is a schematic diagram of the twisted spatial mesh structure in Embodiment 2 provided by the present invention; Figure 10 This is a schematic diagram of the twisted spatial mesh structure in Embodiment 3 of the present invention; Figure 11 This is a schematic diagram of the twisted spatial mesh structure in Embodiment 4 of the present invention. The spiral lines in the figure represent the twisted spatial mesh structure, and the density of the spiral lines represents the change in the twist angle per unit length of the spatial mesh structure from the inside of the prosthesis to the surface of the prosthesis.

[0019] List of reference numerals in the attached diagram: 1. Head; 2. Neck; 3. Manubrium; 31. Torsional trabecular region; 311. Trabecular structural unit; 32. Solid region; 4. New bone. Detailed Implementation

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, terms such as "upper," "lower," "left," "right," "inner," and "outer," indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] To address the problem that existing femoral stem prostheses, despite possessing a porous trabecular structure to promote bone ingrowth, still suffer from stress shielding effects and trabecular fracture due to excessively high material elastic modulus and stress concentration within the pores, thus failing to effectively prevent long-term prosthesis loosening, this embodiment discloses a femoral stem prosthesis with a torsional trabecular structure, comprising a head 1, a neck 2, and a stem 3, as detailed below. Figure 1 The head 1 is used to connect to the acetabulum. One end of the neck 2 connects to the head 1, and the other end connects to the stem 3. The structure of the head 1 and neck 2 is the same as that of the femoral stem prosthesis in the prior art, and its specific structure will not be described again. The stem 3 includes a torsion trabecular region 31 and a solid region 32. The torsion trabecular region 31 is located close to the head 1, and the solid region 32 is located away from the head 1. The structure of the solid region 32 is the same as that of the femoral stem prosthesis in the prior art, and its specific structure will not be described again. (Refer to...) Figure 3 The torsional trabecular bone region 31 includes a solid support region and a porous trabecular bone structure layer, the porous trabecular bone structure layer being disposed on the surface of the solid support region. In this embodiment, the thickness of the porous trabecular bone structure layer is 2 mm; in other embodiments, the thickness of the porous trabecular bone structure layer can also be set to other thicknesses. (Refer to...) Figure 2 The porous trabecular bone structure layer includes multiple trabecular bone structural units 311. The shape of the trabecular bone structural units 311 is approximately square. In this embodiment, the side length of the square of the trabecular bone structural unit 311 is 3 mm; in other embodiments, the side length of the trabecular bone structural unit 311 can also be set to other lengths.

[0024] Reference Figure 4The trabecular structural unit 311 has a spatial mesh structure with pores within it. After the femoral stem prosthesis is implanted, newly formed bone tissue can grow into these pores, allowing the new bone tissue to form a composite structure with the prosthesis. Furthermore, this spatial mesh structure possesses a certain degree of elastic deformation capability; by adjusting the porosity of the spatial mesh structure, its equivalent elastic modulus can be adjusted. Figure 5 The shape of the spatial network structure in its unstressed state is shown. Figure 6 The shape of the spatial network structure under stress is shown. Figure 6 In this context, ε represents the deformation of the spatial network structure after being subjected to force.

[0025] The spatial mesh structure is twisted from the inside of the prosthesis towards the surface; in other words, it is twisted from near to far from the solid support area. Specifically, the direction from near to far from the solid support area is defined as the normal direction, and the cross-section of the spatial mesh structure perpendicular to the normal direction is defined as a cross section. Any two cross sections equidistant in the normal direction have identical shapes and are twisted about the normal direction. The change in the twist angle per unit length of the spatial mesh structure from the inside of the prosthesis towards the surface is defined as A, where A is greater than 0 and does not exceed 25 degrees / mm.

[0026] Compared to ordinary, non-twisted mesh structures, this twisted spatial mesh structure has a lower equivalent elastic modulus. This characteristic makes the spatial mesh structure more prone to elastic deformation, allowing the bone tissue near the mesh structure to bear more physiological loads. This provides a suitable mechanical stimulation environment for the ingrowth of new bone tissue and helps alleviate the stress shielding effect after prosthesis implantation.

[0027] As new bone tissue gradually grows into and fills the pores of the spatial network structure, the prosthesis enters the long-term stable service phase. At this time, the bone tissue and the spatial network structure together form a complex composite structure, which is similar to the Brigham's spiral hierarchical structure, that is, it has a layer-by-layer rotating arrangement feature.

[0028] During long-term service, the prosthesis must withstand periodic dynamic loads generated by activities such as walking and climbing stairs, as well as transient impact loads from falls. The aforementioned composite structure can guide and regulate the load transfer process and the microcrack propagation path: preventing the load transfer path and microcrack propagation direction from extending rapidly in a straight line, but instead forcing them to develop along a helical pore path. (Refer to...) Figure 7 , Figure 7The diagram illustrates the load transfer process from layer 5 to layer 1 of the composite structure, with arrows indicating the load direction. During load transfer, the load direction changes with the torsional direction of the spatial mesh structure. This process significantly prolongs the load transfer and crack propagation path and effectively dissipates the energy input from external loads during the reversal process, thereby protecting the interface between the prosthesis and bone tissue, reducing the risk of prosthesis loosening due to interface damage, and improving the overall damage resistance and structural stability of the prosthesis under long-term service conditions.

[0029] The specific shape of the spatial mesh structure will be illustrated below through several embodiments.

[0030] Example 1 In this embodiment, the femoral stem prosthesis is made of Ti6Al4V alloy and is integrally molded using a selective laser melting (SLM) process. (Refer to...) Figure 4 In this embodiment, the spatial mesh structure is an orthogonal lattice structure. Specifically, the orthogonal lattice structure includes multiple nodes, each node being connected to six adjacent nodes via connecting parts to form a spatial mesh structure. Apertures are formed between the nodes and connecting parts. Furthermore, the orthogonal lattice structure is twisted from near the solid support region to far away from the solid support region, with A being 10 deg / mm. For the specific shape, see [reference needed]. Figure 3 As a comparative example, Figure 8 The orthogonal lattice structure in the non-torsional state is shown.

[0031] Example 2 The difference between this embodiment and Embodiment 1 is that the femoral stem prosthesis is made of a cobalt-chromium alloy. Compared to the material in Embodiment 1, the cobalt-chromium alloy has higher material strength and stiffness properties. (Refer to...) Figure 9 In this embodiment, the value of A in the spatial mesh structure is 15 deg / mm to reduce its equivalent elastic modulus. Compared with Embodiment 1, this embodiment keeps the porosity and other parameters of the torsional trabecular region 31 unchanged, and adjusts the spatial torsion angle to adapt to the high stiffness characteristics of the cobalt-chromium alloy, thereby controlling the equivalent elastic modulus of the torsional trabecular region 31 so that its mechanical properties are close to those of cancellous bone.

[0032] Example 3 Reference Figure 10The difference between this embodiment and Embodiment 1 is that the trabecular structure unit 311 adopts a Triply Periodic Minimal Surface (TPMS) lattice structure, specifically a Gyroid TPMS lattice structure. Furthermore, the torsion angle of the Gyroid TPMS lattice structure, twisted outward from the solid support region, is 10 deg / mm.

[0033] Example 4 Reference Figure 11 The difference between this embodiment and embodiment 1 is that the A value of the trabecular structural unit 311 near the head 1 is greater than the A value of the trabecular structural unit 311 far from the head 1. Figure 11 The mid-torsion trabecular bone region 31 includes multiple trabecular bone structural units 311, i.e., small squares in the figure. The spirals within the small squares represent a torsional spatial network structure. The spirals closer to the head 11 are denser, representing a larger A value; the spirals further away from the head 11 are sparser, representing a smaller A value. This arrangement results in differentiated equivalent elastic modulus distribution characteristics of the porous trabecular bone structure layer at different locations in the prosthesis stem 3. In the initial stage of prosthesis implantation, the mechanical load borne by the femoral stem prosthesis from the head 1 towards the stem 3 exhibits a gradually decreasing distribution characteristic. In this embodiment, the torsion angle of the porous trabecular bone structure layer gradually decreases from near the head 1 to far away from the head 1, thereby gradually increasing its equivalent elastic modulus, which helps to achieve a uniform distribution of stress within the porous trabecular bone structure layer. Under the aforementioned mechanical environment, the trabecular bone structural units 311 at different locations can provide relatively consistent mechanical stimulation conditions for the newly formed bone 4, which is beneficial for guiding the newly formed bone 4 to achieve more uniform ingrowth within the porous trabecular bone structure layer. This embodiment demonstrates that by designing a gradient of the torsion angle of the trabecular structural unit 311, regional control of the mechanical properties of the torsion trabecular region 31 can be achieved without changing the pore parameters and material composition of the torsion trabecular region 31, and this can synergize with the ingrowth behavior of the new bone 4.

[0034] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A femoral stem prosthesis with a torsional trabecular bone structure, characterized in that, The prosthesis includes a trabecular bone structure unit disposed on the surface of the prosthesis. The trabecular bone structure unit is in the shape of a spatial mesh structure. The spatial mesh structure has pores that can accommodate newly formed bone. The spatial mesh structure is twisted from the inside of the prosthesis toward the surface of the prosthesis.

2. The femoral stem prosthesis according to claim 1, characterized in that, The range of the change in the torsion angle per unit length of the spatial mesh structure from the interior of the prosthesis to the surface of the prosthesis is greater than 0 and does not exceed 25 deg / mm.

3. The femoral stem prosthesis according to claim 1, characterized in that, The trabecular structural units are in the form of orthogonal lattice structures and triple-periodic minimal surface lattice structures.

4. The femoral stem prosthesis according to claim 3, characterized in that, The trabecular structural unit has a Gyroid curved lattice structure.

5. The femoral stem prosthesis according to claim 1, characterized in that, The prosthesis includes multiple trabecular structural units.

6. The femoral stem prosthesis according to claim 3, characterized in that, The prosthesis includes a head, a neck, and a stem. The head is used to connect to the acetabulum. One end of the neck is connected to the head, and the other end is connected to the stem. The trabecular bone structure unit is disposed on the surface of the stem. The change in the torsion angle per unit length of the spatial mesh structure of the trabecular bone structure unit from the interior of the prosthesis to the surface of the prosthesis is set as A. The A of the trabecular bone structure unit closer to the head is greater than the A of the trabecular bone structure unit farther away from the head.

7. The femoral stem prosthesis according to claim 6, characterized in that, The handle includes a torsional trabecular region and a solid region. The torsional trabecular region is located close to the head, and the solid region is located away from the head. The trabecular structural units are only located in the torsional trabecular region.

8. The femoral stem prosthesis according to claim 7, characterized in that, The torsional trabecular region includes a solid support region, and the trabecular structural units are disposed on the surface of the solid support region.

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