A hip joint prosthesis assembly

Abstract

The application relates to a hip joint prosthesis assembly, which comprises a acetabular cup and an inner liner, the inner liner is detachably accommodated in the acetabular cup, the inner surface of the acetabular cup comprises an annular groove extending around the inner surface, and the outer surface of the inner liner is provided with a protrusion which can be matched with the annular groove. The hip joint prosthesis assembly has the advantages of easy disassembly, stable connection, long service life and the like.

Description

Technical Field

[0001] This invention relates to orthopedic implants, specifically a hip joint prosthesis assembly. Background Technology

[0002] Total hip arthroplasty is one of the major medical inventions that has been widely used clinically since the 1960s. The design of a modern artificial hip joint consists of two main parts: the first is the acetabular cup fixed to the acetabular fossa of the pelvis and the friction liner installed inside the acetabular cup; the second is the joint stem fixed to the femoral cavity and the friction ball head installed at the upper end of the joint stem. The friction liner is prone to wear, leading to loosening or dislocation, and often requires separate replacement of the acetabular cup liner. However, the current design of hip joint prostheses often requires using tools and considerable force to pry the liner out of the acetabular cup during liner replacement, which is very difficult and can easily cause secondary injury. Commonly used polyethylene liner materials have poor wear resistance and a short service life. Furthermore, the current connection between the acetabular cup and acetabulum mainly relies on fasteners, resulting in poor fusion, especially for elderly people with bone aging; the stability of the connection between the acetabular cup and acetabulum still needs improvement.

[0003] Moreover, the porous metals used in existing hip joints have poor bone tissue regeneration capacity and low mechanical strength, making their application in hip joint prostheses with high load-bearing capacity still very difficult.

[0004] Currently, Chongqing Runze Company has independently developed a medical porous tantalum material whose product performance exceeds the international standard (ISO 13782-1996 Surgical implants—Metallic materials—Pure tantalum materials for surgical implants). However, as a medical orthopedic material used in the human body, in order to achieve the most ideal performance that perfectly matches human bone tissue, the product still needs to be continuously improved.

[0005] The applicant previously disclosed (CN108452385A) a multi-level porous material prepared by cross-weaving two diameters of polymer filaments into a mesh, simultaneously injecting slurry, and then sintering. This material has interconnected channels within its cavity walls and pores on its walls with diameters smaller than the pores enclosed by the cavity walls. The pore structure on the cavity walls is a multi-level porous structure graded according to the material's pore size, with at least two levels. The prepared porous tantalum material has an interconnected pore diameter of 550 μm, and the equivalent diameter of the interconnected channels within the cavity walls is 90 μm. The cavity walls have two levels of pores with diameters smaller than the pores enclosed by the cavity walls. The largest pore has a diameter of 20 μm, and on the cavity walls of the 20 μm pores are even smaller pores, i.e., the smallest level pores, with a diameter of 400 nm. The porous material prepared by this method can achieve rapid and uniform distribution of cells and tissue fluid within the porous material bulk. However, the method of cross-weaving polymer filaments into a web requires a relatively large diameter polymer filament. For small-diameter polymer filaments, the production operation and control of this method are quite difficult. The compressive strength of the multi-level porous material prepared in this patent is about 20 MPa. In order to meet the application of hip joints, the preparation process, pore structure, pore size distribution and cavity wall thickness of the multi-level porous material still need further improvement.

[0006] The applicant previously disclosed (CN108452386A) a porous tricalcium phosphate material prepared using polyurethane foam with an edge diameter of 25μm-50μm, achieving a compressive strength of 3.74MPa; and a porous niobium material prepared using polyurethane foam with an edge diameter of 50μm-90μm, achieving a compressive strength of 25.3MPa. The through-pore diameter was 300μm-600μm, the equivalent diameter of the channels penetrating the cavity wall was 40μm-70μm, and the first-order pores on the cavity wall had a diameter of 10μm-20μm. Smaller pores, i.e., minimum-order pores, with a diameter of 400nm-700nm, were also present on the cavity wall surrounding the 10μm-20μm pores. This patent used a foam impregnation method to prepare multi-level porous materials, but the pore structure and pore size distribution were still not sufficiently optimized. The two-level pores on the cavity wall limited the compressive strength, and it could only produce materials with a uniform porosity distribution, failing to adjust and fully simulate the morphology of bone tissue.

[0007] The applicant has previously prepared porous materials with gradient distributions. For example, CN108201635A discloses a porous metal material layer as a gradient porous metal material layer. Although the porous metal material in this patent adopts a gradient structure, its gradient is mainly formed by welding or powder sintering. The resulting porous material has interfaces between the gradient pores, and true integrated, interface-free fusion has not yet been achieved. Moreover, the aforementioned prepared gradient porous materials do not achieve multi-level pore distribution, have low three-dimensional pore connectivity, and the overall performance of the material is still not ideal. Summary of the Invention

[0008] The purpose of this invention is to provide a hip joint prosthesis assembly that has the advantages of easy disassembly, stable connection, and long service life.

[0009] The technical solution adopted in this invention is:

[0010] A hip joint prosthesis assembly includes an acetabular cup and a liner, the liner being removably housed within the acetabular cup. The inner surface of the acetabular cup includes an annular groove extending around the inner surface, and the outer surface of the liner has a protrusion that mates with the annular groove. The liner is secured within the acetabular cup by a snap-fit ​​engagement between the protrusion and the annular groove, and a perceptible feedback should be provided to the physician upon successful engagement.

[0011] The liner is hemispherical, with two symmetrically arranged protrusions on its outer surface that mate with the annular groove. The inner sidewall of the liner corresponding to the protrusions has a slit structure. By controlling the deformation of the outer sidewall of the liner into the slit, the position of the protrusions can be adjusted, causing them to disengage from the annular groove, making the liner easy to disassemble during repairs or sizing adjustments. The protrusions mate with the annular groove are preferably manufactured integrally with the liner. In this invention, the material of the protrusions is preferably the same as that of the liner; the material is a high-strength, high-wear-resistant polymer, preferably high-strength, high-stability, and high-wear-resistant polyetheretherketone (PEEK). By providing a slit structure inside the sidewall, this invention can use large-sized, high-strength protrusions, resulting in a stable connection between the acetabular cup and the liner.

[0012] The outer edge of the inner liner corresponding to the raised position has a protruding tab extending outwards, with a notch in the center of the tab. The notch makes it easy for doctors to install or remove the inner liner using their fingers or simple instruments.

[0013] The inner wall of the acetabular cup has a recess that can accommodate the inner lining protrusion. The recess also needs to have enough space for the doctor to operate.

[0014] The inner wall edge of the acetabular cup has multiple rounded grooves, and the outer periphery of the liner has multiple radial flanges corresponding to the rounded grooves to prevent relative rotation between the liner and the acetabular cup.

[0015] The acetabular cup contains a multi-level porous metal material. This multi-level porous metal material has an elastic modulus that matches that of bone tissue, and its porous structure facilitates bone ingrowth and fusion.

[0016] The porosity of multilevel porous metallic materials can be uniformly distributed or gradient distributed. The gradient distribution can be a gradient change along one direction or a three-dimensional gradient change. The pores in the radial direction of the cavity wall are single-level pores.

[0017] Three-dimensional gradient variation refers to changes in multiple directions within three-dimensional space. Single-level is the opposite of multi-level; multi-level refers to a specific multi-scale aperture structure, while single-level refers to a structure without multi-scale apertures.

[0018] Preferably, the acetabular cup may be composed of only multi-level porous metal material, with the outer surface of the acetabular cup having a high porosity and the inner surface having a low porosity; preferably, the porosity of the outer surface of the acetabular cup is 75-95%, and the porosity of the inner surface is 10-30%.

[0019] Preferably, the porosity of the multi-level porous metal material is gradient-distributed. The gradient distribution of this invention is a fused structure of interface-free gradient pores.

[0020] The gradient distribution of this invention does not require connection by means of electric welding or other methods.

[0021] The gradient distribution of this invention is a gradual gradient change, a non-gradual gradient change, or a combination of gradual and non-gradual gradient changes.

[0022] Non-gradient porosity refers to a sudden change in porosity, while gradual gradient porosity refers to a continuous change in porosity.

[0023] Optionally, the gradient distribution can be an asymptotic gradient change, a non-asymptotic gradient change, or a combination of asymptotic and non-asymptotic gradient changes in multiple directions in three-dimensional space.

[0024] When the porosity gradient distribution is used, the radial thickness gradient of the cavity wall is preferred.

[0025] Optionally, the multi-level porous metal material with non-gradually varying porosity includes 2-4 layers of multi-level porous metal structures with different porosities.

[0026] Optionally, in each layer of the porous metallic material with a non-gradually varying porosity, the porosity is either uniformly distributed or combined with a gradual gradient variation.

[0027] Optionally, the acetabular cup can be a double-layer structure, with the inner layer of the acetabular cup in contact with the liner being a dense metal and the outer layer being a multi-level porous metal. The porosity of the outer multi-level porous metal material can be uniformly distributed or gradient distributed; when uniformly distributed, the porosity is preferably 70-85%; when gradient distributed, the porosity of the outer layer is preferably 75-95%, and the porosity of the inner layer is preferably 20-40%.

[0028] Multi-level porous metals can achieve adjustable mechanical properties over a wide range by adjusting process parameters, with compressive strength of 30-90 MPa, preferably 50-70 MPa, and elastic modulus of 1.8-3.8 GPa.

[0029] Multi-level porous metal materials can be combined with a reinforcing frame composed of stiffeners on the outer surface to further improve compressive strength.

[0030] In this hierarchical porous metal material, the pores enclosed by the cavity walls are interconnected open holes. The cavity walls have an axially hollow structure and radial pores. The size of the open holes enclosed by the cavity walls is 80-850 μm, the size of the hollow pores in the cavity walls is 20-60 μm, and the size of the radial pores in the cavity walls is 0.2-10 μm. The distance between the radial pores in the cavity walls is 1-10 μm. The radial thickness of the cavity walls is 50-500 μm. The surface roughness of the outer side of the hierarchical porous metal material is 10-22 μm, and the surface roughness of the inner side is 2-6 μm. The surface roughness of the outer side of the cavity walls is 2-8 μm. In this invention, the metal is a metal or metal alloy with excellent electrical conductivity or biocompatibility, specifically nickel, titanium, tantalum, niobium, etc., or metal alloys thereof.

[0031] The axial hollow holes in the cavity wall of a multi-level porous metal material are continuous internal pores.

[0032] The multi-level porous metal material with the above-mentioned structure prepared by this invention has excellent comprehensive properties, achieving a good balance between elastic modulus, transmission performance and mechanical properties, and has a low production cost.

[0033] This invention uses the above-mentioned multi-level porous metal material as the main material and innovates the structure of the hip joint prosthesis. The prepared hip joint prosthesis component has the advantages of strong integration with bone tissue, strong bone regeneration ability, high connection stability, large joint range of motion, low wear rate, easy disassembly and long service life.

[0034] This invention, through the use of metal powder of specific sizes and polymer scaffolds, and precise control of the preparation process, yields a multi-level porous metal material that not only possesses excellent mechanical properties but also exhibits enhanced three-dimensional connectivity and fluid transport capacity due to the presence of axially and radially sized hollow pores in the cavity walls. The porous metal material contains at least two continuous channels: a three-dimensionally interconnected channel enclosed by the cavity walls and axially hollow pores within the cavity walls. When used in hip joint prostheses, the high surface roughness of the porous metal material increases the coefficient of friction with the host bone, improving early implantation stability. Furthermore, the high permeability of the porous metal material facilitates the transport of body fluids and nutrient cells within the material, promoting tissue growth and osteoconductivity. Attached Figure Description

[0035] Figure 1 Partial schematic diagram of the cross-section of the combined structure of the acetabular cup and liner;

[0036] Figure 2 Schematic diagram of the bottom structure of the acetabular cup;

[0037] Figure 3 Schematic diagram of the inner substrate surface structure. Detailed Implementation

[0038] In the attached diagram, 1 is the acetabular cup, 2 is the liner, 3 is the slit, 4 is the annular groove, 5 is the protrusion, 6 is the convex piece, 7 is the concave part, 8 is the rounded corner groove, 9 is the notch, and 10 is the radial flange.

[0039] In one embodiment, the gap structure inside the inner lining sidewall corresponding to the protrusion position is wedge-shaped.

[0040] In one embodiment, the acetabular cup is composed of only a multi-level porous metal material, with a porosity of 90% on the outer surface and 10% on the inner surface.

[0041] In one embodiment, the metal is titanium.

[0042] In one embodiment, the metal is tantalum, niobium, or a tantalum-niobium alloy.

[0043] In one embodiment, the acetabular cup has a double-layer structure. The inner layer of the acetabular cup that contacts the liner is a dense metallic tantalum, and the outer layer of the acetabular cup is a multi-level, multi-gradient porous tantalum. The porosity of the outer side of the multi-level, multi-gradient porous tantalum is 95%, and the porosity of the inner side is 30%.

[0044] The method for preparing the porous metal material of this invention is the foam impregnation method.

[0045] Specifically, the double-roller pressing foam impregnation method is adopted.

[0046] Specifically, multi-level porous metal materials were prepared at low cost by controlling the composition and proportion of raw materials and the operating conditions of the preparation process through processes such as surface treatment, slurry impregnation, roller pressing, liquid film breaking, cross-linking curing, and three-stage sintering.

[0047] Specifically, metal powder with a particle size of 5-20 μm is mixed with an aqueous dispersant solution and stirred until homogeneous. While stirring, an aqueous PVA solution, defoamer, and glyoxal are added sequentially to prepare a metal powder slurry. The polymer scaffold used has an edge diameter of 20-60 μm. After cleaning the surface of the polymer scaffold, it is immersed in the aqueous dispersant solution for surface treatment. The scaffold is then removed and dried. After drying, the surface-treated polymer scaffold is immersed in the metal powder slurry, and gently squeezed to ensure it fully absorbs the slurry. Once saturated, the polymer scaffold is removed and placed in a roller mill for pressing. During pressing, the distance between the rollers remains constant, squeezing out excess metal powder slurry. This process of immersion and roller pressing is repeated 3-5 times. The preform is then removed, and high-pressure gas is used to blow air onto its surface to break the surface liquid film. It is then left to stand in the air to allow the PVA in the preform to cross-link and solidify. This process allows for control of the pore size of porous metal materials. The metal powder slurry is fully filled into the polymer scaffold through roller extrusion, and excess slurry is removed. The cross-linking and curing process then solidifies the metal powder slurry, preventing agglomeration.

[0048] Then, the green body is placed in a vacuum drying oven to dry at a temperature of 60℃-80℃ for 4-6 hours. After drying, the green body is sintered under vacuum conditions by slowly raising the temperature from room temperature to 580-680℃ at a rate of 2-4℃ / min and holding for 6-8 hours. Then, the temperature is raised slowly to 1300-1600℃ at a rate of 2-4℃ / min and held for 6-8 hours. Then, the temperature is raised to 1800-2100℃ at a rate of 6-8℃ / min and held for 6-8 hours. Finally, the green body is cooled in the furnace.

[0049] For high-melting-point metals such as tantalum and niobium, this invention employs a three-stage sintering method. In the first stage, sintering at 580-680℃, the polymer scaffold, defoamer, and dispersant decompose and are removed through a vacuum system. In the second stage, sintering at 1300-1600℃, the porous metal material is pre-sintered and formed. In the third stage, sintering at 1800-2100℃, the porous metal material undergoes high-temperature sintering to further increase its mechanical strength. The high sintering temperature of this invention is well-matched with the hierarchical porous structure, resulting in porous metal materials with excellent mechanical properties.

[0050] The dispersant used in this invention is stearic acid, polyethylene glycol 400, or chitosan. Adding a dispersant to the metal powder slurry and surface-treating the polymer scaffold with the dispersant can ensure uniform dispersion of the metal powder. Even when using a polymer scaffold with a smaller ridge diameter, agglomeration of the metal powder can still be minimized, resulting in porous metal materials with high mechanical strength.

[0051] This invention, by appropriately controlling the heating rate and sintering temperature, creates continuous through-holes inside the cavity wall and pores of suitable diameter in the radial direction of the cavity wall, thereby increasing the mass transfer capacity.

[0052] The defoamer used in this invention is an organosilicon defoamer, preferably a trimethylsiloxy-terminated polydimethylsiloxane.

[0053] The porosity distribution of the porous metal material of this invention is mainly achieved by adjusting the radial thickness distribution of the cavity wall. Specifically, the porosity distribution of the porous metal material is adjusted by changing the shape of the polymer scaffold and the distance between the rollers during rolling. Preferably, the rollers are arranged in parallel. When preparing a porous metal material with a uniform porosity distribution, the polymer scaffold is a structure with two parallel surfaces, such as a cube or cuboid, and the rollers contact the two parallel surfaces during rolling. When preparing a porous metal material with a gradually increasing porosity gradient, the polymer scaffold can be a structure where the distance between the two opposite sides in contact with the rollers gradually changes. When the distance between the two opposite sides gradually changes along one direction, a porous metal material with a gradually increasing porosity gradient along one direction can be prepared. When the distance between the two opposite sides gradually changes along multiple directions, a porous metal material with a gradually increasing porosity gradient (three-dimensional gradually increasing gradient) along multiple directions can be prepared. Optionally, the polymer scaffold is a trapezoidal structure with two inclined sides. During rolling, the rollers can contact the two sides of the trapezoid, and through extrusion, the thickness distribution of the metal powder slurry layer on the inner surface of the polymer scaffold changes, thereby changing the thickness distribution of the cavity wall of the finally sintered porous metal material and causing a change in porosity. When preparing porous metal materials with non-gradually varying (abrupt) porosity distribution, the polymer scaffold can be a structure where the distance between the two opposite sides in contact with the rollers does not change gradually. When the distance between the two opposite sides changes non-gradually in one direction, porous metal materials with non-gradually varying porosity in one direction can be prepared. When the distance between the two opposite sides changes non-gradually in multiple directions, porous metal materials with non-gradually varying porosity in multiple directions (three-dimensional non-gradually varying porosity) can be prepared. Optionally, the polymer scaffold can be convex, have multiple stepped shapes on the sides, etc. When preparing porous metallic materials that combine gradual and non-gradual porosity changes, the polymer scaffold can be a structure where the distance between the two opposing sides in contact with the rollers simultaneously exhibits both non-gradual and gradual changes. When the distance between the two opposing sides exhibits both gradual and non-gradual changes along one direction, a porous metallic material combining gradual and non-gradual porosity changes along one direction can be prepared. When the distance between the two opposing sides exhibits both gradual and non-gradual changes, and these changes occur in multiple directions, a porous metallic material combining three-dimensional gradual and non-gradual porosity changes can be prepared.

[0054] Example 1

[0055] Mix 80g of tantalum powder with a particle size of 10μm with 20ml of polyethylene glycol 400 aqueous solution (0.1M) and stir until homogeneous. While stirring, add 50ml of PVA aqueous solution (0.2M), 0.1g of trimethylsiloxy-terminated polydimethylsiloxane and 0.3g of glyoxal in sequence to prepare tantalum powder slurry. After cleaning the surface of a cubic polyurethane polymer scaffold with an edge diameter of 30 μm, it was immersed in a 1M polyethylene glycol 400 aqueous solution for surface treatment. The scaffold was then removed and dried. After drying, the surface-treated scaffold was immersed in tantalum powder slurry, and gently squeezed to ensure full absorption of the slurry. Once saturated, the saturated scaffold was removed and placed in a roller mill for pressing. During pressing, the distance between the rollers remained constant, squeezing out excess tantalum powder slurry. This process of slurry immersion and roller pressing was repeated five times. The preform was then removed, and high-pressure gas was used to blow air onto its surface to break the surface liquid film. It was then left to stand in air to allow the PVA in the preform to cross-link and cure. After full curing, the preform was placed in a vacuum drying oven at 60℃ for 4 hours. After drying, the green body is sintered under vacuum conditions by slowly heating from room temperature to 580°C at a heating rate of 2°C / min and holding for 6 hours. Then, it is sintered by slowly heating to 1500°C at a heating rate of 2°C / min and holding for 6 hours. Then, it is sintered by slowly heating to 1900°C at a heating rate of 6°C / min and holding for 6 hours. Finally, it is cooled in the furnace.

[0056] The prepared porous tantalum has a porosity of 75% and a compressive strength of 65 MPa. The size of the openings enclosed by the cavity walls is 200-500 μm, the size of the hollow pores in the cavity walls is approximately 30 μm, and the size of the radial pores in the cavity walls is 5-10 μm. The distance between the radial pores in the cavity walls is 3-6 μm. The radial thickness of the cavity walls is 150 μm.

[0057] Example 2

[0058] The process and raw materials used in Example 1 were employed, the difference being that the metal used was niobium, with a particle size of 5 μm, and the amount added was 80 g. After drying the billet, it was sintered under vacuum conditions by slowly heating from room temperature to 580 °C at a heating rate of 3 °C / min and holding for 6 hours. Then, the temperature was further slowly increased to 1500 °C at a heating rate of 3 °C / min and held for 6 hours. Finally, the temperature was increased to 1800 °C at a heating rate of 7 °C / min and held for 6 hours, followed by furnace cooling. The prepared porous niobium had a porosity of 74%, a compressive strength of 60 MPa, and an elastic modulus of 1.8 GPa. The size of the openings enclosed by the cavity walls was 150-450 μm, the size of the hollow pores in the cavity walls was approximately 30 μm, and the size of the radial pores in the cavity walls was 2-10 μm. The distance between the radial pores in the cavity walls was 2-6 μm. The radial thickness of the cavity walls was approximately 140 μm. The surface roughness of the porous metal material was 16 μm. The roughness of the outer surface of the cavity wall is 2-6 μm.

[0059] Example 3

[0060] The process and raw materials used in Example 1 were employed, the difference being that the metal was a mixture of 40g of tantalum with a particle size of 15μm and 40g of niobium with a particle size of 15μm. After drying, the billet was sintered under vacuum conditions, slowly heated from room temperature to 580℃ at a heating rate of 4℃ / min and held for 6 hours. Then, the temperature was further slowly increased to 1600℃ at a heating rate of 4℃ / min and held for 6 hours. Finally, the temperature was increased to 1850℃ at a heating rate of 7℃ / min and held for 6 hours, followed by furnace cooling. The prepared porous tantalum-niobium alloy had a porosity of 76%, a compressive strength of 63MPa, and an elastic modulus of 1.9GPa. The size of the openings enclosed by the cavity walls was 200-700μm, the size of the hollow pores in the cavity walls was approximately 30μm, and the size of the radial pores in the cavity walls was 2-8μm. The distance between the radial pores in the cavity walls was 3-8μm. The radial thickness of the cavity walls was approximately 1.8μm. The surface roughness of the porous metal material is 20 μm. The roughness of the outer surface of the cavity wall is 2-6 μm.

Claims

1. A hip joint prosthesis assembly, characterized in that: The device includes an acetabular cup and a liner. The liner is detachably housed inside the acetabular cup. The inner surface of the acetabular cup includes an annular groove extending around the inner surface. The outer surface of the liner has protrusions that mate with the annular groove. The liner is hemispherical. There are two symmetrically arranged protrusions on the outer surface of the liner that mate with the annular groove. The inner sidewall of the liner corresponding to the protrusion has a slotted structure. A tab extends outward from the outer edge of the outer sidewall of the liner corresponding to the protrusion, and the tab has a notch in the center. The inner sidewall of the acetabular cup has a recess for receiving the tab of the liner. The inner sidewall edge of the acetabular cup has multiple rounded grooves distributed thereon, and the outer periphery of the liner has multiple grooves corresponding to the rounded grooves. Radial flange; the acetabular cup has a double-layer structure, with the inner layer of the acetabular cup in contact with the liner being a dense metal and the outer layer being a multi-level porous metal material; the porosity of the multi-level porous metal material is uniformly distributed or gradient distributed; in the multi-level porous metal material, the pores enclosed by the cavity wall are interconnected open holes, the cavity wall has an axially hollow structure, and the cavity wall has radial pores, the size of the open holes enclosed by the cavity wall is 80-850μm, the size of the hollow pores in the cavity wall is 20-60μm, the size of the radial pores in the cavity wall is 0.2-10μm; the distance between the radial pores in the cavity wall is 1-10μm; the radial thickness of the cavity wall is 50-500μm.

2. The hip joint prosthesis assembly according to claim 1, characterized in that: The protrusions that mate with the annular grooves are manufactured as a single unit with the inner lining.

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