A method for size compensation and deformation control of interbody fusion cages based on electron beam additive manufacturing

Abstract

This invention discloses a method for size compensation and deformation control of an interbody fusion cage based on electron beam additive manufacturing. The fusion cage body has a three-zone gradient porosity structure inside, which includes a core zone, a transition zone, and a osseointegration zone from the inside out. This invention effectively offsets the thermal accumulation deformation caused by porosity differences by obtaining a gradient porosity structure to alleviate stress shielding and promote bone ingrowth. This solves the problems of overall dimensional tolerance and instrument holding hole accuracy in existing electron beam additive manufacturing fusion cages.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method for size compensation and deformation control of intervertebral fusion devices based on electron beam additive manufacturing. Background Technology

[0002] Interbody fusion cages are crucial implants placed in the intervertebral space during spinal surgery to replace diseased intervertebral discs. They restore the height of the intervertebral space, maintain the normal physiological curvature of the spine, and provide structural support and growth space for bony fusion between adjacent vertebrae. Most existing interbody fusion cages are made of titanium alloy and manufactured through machining or casting processes.

[0003] However, existing technologies have the following shortcomings in practical clinical applications:

[0004] Traditional manufacturing processes cannot create a pore structure with a gradually increasing porosity from the inside out within the interbody fusion cage. The overall elastic modulus of the fusion cage is much higher than that of the surrounding bone tissue, resulting in a significant stress shielding effect after implantation, hindering bone ingrowth and integration. Therefore, we need to propose a method for size compensation and deformation control of interbody fusion cages based on electron beam additive manufacturing. Summary of the Invention

[0005] The purpose of this invention is to provide a method for size compensation and deformation control of interbody fusion devices based on electron beam additive manufacturing, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A size compensation method for interbody fusion cages based on electron beam additive manufacturing, comprising:

[0008] The fusion device body is integrally formed using electron beam additive manufacturing technology. The interior of the fusion device body has a three-zone gradient pore structure, which includes a core zone, a transition zone, and a osseointegration zone from the inside out.

[0009] Preferably, the fusion body (1) is made of titanium alloy or pure tantalum, and when the material is titanium alloy, the titanium alloy contains tantalum.

[0010] Preferably, the aperture of the core area is 0.1mm-0.2mm, the aperture of the transition area is 0.2mm-0.8mm, and the aperture of the osseointegration area is 0.4mm-1.2mm. The apertures of the three areas increase gradually from the inside to the outside, and the apertures are evenly distributed in each area.

[0011] Preferably, the core region has a density greater than 94%, and the core region extends through the entire axial length of the fusion body.

[0012] Preferably, the porosity of the transition zone is 30%-60%, and the transition zone covers the outer periphery of the core zone.

[0013] Preferably, the porosity of the osseointegration zone is 70%-80%, the osseointegration zone covers the periphery of the transition zone and forms the outer surface of the fusion device body, and the pore structure of the osseointegration zone is a biomimetic trabecular structure.

[0014] A deformation control method for size compensation of interbody fusion cages based on electron beam additive manufacturing includes the following steps:

[0015] S1. Establish a three-dimensional digital model of the fusion device body. Based on the thermal accumulation deformation law of the electron beam additive manufacturing process, perform zoned pre-compensation calculations on the fusion device body. The pre-compensation calculations include: setting differentiated shrinkage compensation amounts for the core region, transition region, and osseointegration region in the three-zone gradient porosity structure, wherein the compensation amount for the core region is 0.4%-1.0%, the compensation amount for the transition region is 1.4%-2.4%, and the compensation amount for the osseointegration region is 2.0%-2.4%.

[0016] S2. Electron beam additive manufacturing equipment is used, with tantalum powder (or tantalum-based alloy powder) as raw material, and layer-by-layer melting and deposition are carried out according to the pre-compensated model parameters to form an integral shape. During the forming process, the electron beam power, scanning speed and substrate temperature are controlled in three zones: the core zone uses high energy density parameters to make the density greater than 94%, the transition zone uses medium energy density parameters to make the porosity reach 30%-60%, and the osseointegration zone uses low energy density parameters to make the porosity reach 70%-80% and form a biomimetic trabecular pore structure.

[0017] S3. The fused body after molding is subjected to slow cooling treatment in a vacuum environment. The vacuum and high temperature preheating environment of the molding chamber of the electron beam additive manufacturing equipment (the molding chamber temperature is usually maintained at 600-700℃) is used to slowly cool it to room temperature in the furnace to further homogenize the temperature field and release any possible weak residual stress.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. This invention constructs a core region, transition region, and osseointegration region with a progressively increasing porosity from the inside out within the fusion unit. This is combined with pre-compensation calculations and energy parameter control during electron beam additive manufacturing. The core region employs high energy density to ensure a density greater than 94% for mechanical support, while the osseointegration region uses low energy density to form a biomimetic trabecular bone structure with 70%-80% porosity to match the elastic modulus of bone tissue. When pure tantalum is used, tantalum exhibits excellent biocompatibility and osseointegration capabilities. Its elastic modulus (approximately 186 GPa) is lower than that of titanium alloys (approximately 110 GPa), and is closer to that of human cortical bone, further reducing stress shielding effects.

[0020] 2. This invention provides a three-dimensional space for blood vessel and bone tissue ingrowth through the high porosity biomimetic trabeculae in the bone integration zone of the three-zone gradient pore structure, while the low porosity in the core zone ensures the compressive strength of the fusion device. This allows the fusion device to achieve a smooth transition from mechanical support to biological integration after implantation, significantly improving the long-term success rate of spinal fusion surgery. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 This is a cross-sectional structural diagram of the present invention.

[0023] In the diagram: 1. Fusion device body; 2. Core area; 3. Transition area; 4. Bone integration area. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1:

[0026] Please see Figures 1-2 The present invention provides a technical solution:

[0027] A size compensation method for interbody fusion cages based on electron beam additive manufacturing, comprising:

[0028] The fusion body 1 is made of titanium alloy or pure tantalum. When titanium alloy is used, it contains tantalum. The titanium alloy is a titanium-tantalum alloy, and the mass percentage content of tantalum is 5% to 15%, preferably 8% to 12%, and more preferably 10%. The remaining components of the titanium alloy are titanium (Ti) and unavoidable trace impurities, including but not limited to oxygen (O), nitrogen (N), carbon (C), and iron (Fe), with the mass percentage content of each trace impurity element not exceeding 0.2%. The tantalum is uniformly distributed in the titanium alloy matrix in a solid solution form. Tantalum and titanium share the same crystal structure (both are hexagonal close-packed or body-centered cubic), and the atomic radius of tantalum (0.146 nm) is extremely close to that of titanium (0.145 nm). Therefore, tantalum can completely dissolve in the titanium matrix, forming a stable Ti-Ta solid solution without producing brittle intermetallic compounds, thus ensuring alloy strength without significantly reducing plasticity. When pure tantalum is used, its purity is not less than 99.5%. Tantalum has a body-centered cubic crystal structure, a melting point as high as 3017℃, and is extremely chemically stable, exhibiting almost no corrosion in the human physiological environment and excellent biocompatibility. The elastic modulus of pure tantalum is approximately 186 GPa, which is relatively high compared to human cortical bone (10-30 GPa) and cancellous bone (0.1-2 GPa). However, through the three-zone gradient pore structure design of this invention, the overall equivalent elastic modulus can be effectively reduced to a range matching the surrounding bone tissue (2-12 GPa), thereby significantly reducing the stress shielding effect.

[0029] The fusion body 1 is integrally formed using electron beam additive manufacturing. During the electron beam additive manufacturing process, a high-energy electron beam scans the metal powder layer by layer in a vacuum environment according to the preset three-dimensional model. The metal powder is locally melted and solidified layer by layer under the action of the electron beam, and finally forms a near-net-shape part that is highly consistent with the design model. The advantages of this process lie in its high molding precision and controllable heat-affected zone, which ensures the precise realization of the complex three-zone gradient pore structure inside the fusion body 1. The fusion body 1 has a three-zone gradient pore structure, which, from the inside out, includes a core zone 2, a transition zone 3, and a osseointegration zone 4. The core zone 2 has a density greater than 94% and runs through the entire axial length of the fusion body 1. The transition zone 3 has a porosity of 30%-60% and covers the periphery of the core zone 2. The osseointegration zone 4 has a porosity of 70%-80% and covers the periphery of the transition zone 3, forming the outer surface of the fusion body 1. The pore structure of the osseointegration zone 4 is a biomimetic trabecular structure. The core zone 2 has a density greater than 95% and runs through the entire axial length of the fusion body 1. Its function is to bear the main axial load between the vertebral bodies and ensure that the fusion body does not undergo structural collapse after implantation. The transition zone 3, with a porosity of 40% to 60%, surrounds the periphery of the core zone 2. Its porosity is between that of the core zone 2 and the osseointegration zone 4, serving as a gradual transition in stiffness and preventing stress concentration between the high stiffness of the core zone 2 and the low stiffness of the osseointegration zone 4. The osseointegration zone 4, with a porosity of 70% to 80%, surrounds the periphery of the transition zone 3 and forms the outer surface of the fusion device body 1. Its pore structure is a biomimetic trabecular structure, mimicking the microscopic morphology of human cancellous bone, which is conducive to the adhesion, proliferation, and differentiation of osteoblasts, promoting the ingrowth of new bone into the pores of the fusion device and ultimately achieving osseointegration.

[0030] The design logic of the three-zone gradient porosity structure is as follows: after vertebral body implantation, the load on the fusion cage gradually decreases from the center to the periphery. Therefore, the interior needs high density for load bearing, the exterior needs high porosity to promote osseointegration, and the transition zone 3 undertakes the function of stiffness matching. This gradient design achieves a balance between the mechanical and biological performance of the fusion cage.

[0031] Workflow:

[0032] During the surgery, the fusion cage body 1 is implanted into the affected intervertebral space via a minimally invasive posterior or lateral approach. In the three-zone gradient porosity structure of the fusion cage body 1, the core zone 2 bears the axial load, the transition zone 3 achieves a gradual change in stiffness, and the biomimetic trabecular structure of the osseointegration zone 4 guides new bone ingrowth. Postoperatively, over time, the pores of the osseointegration zone 4 are gradually filled with new bone tissue, ultimately achieving bony fusion between the fusion cage and the vertebral bodies above and below, thus completing the treatment goal of intervertebral fusion.

[0033] Example 2:

[0034] The difference between Example 2 and Example 1 is that:

[0035] A deformation control method for size compensation of interbody fusion cages based on electron beam additive manufacturing includes the following steps:

[0036] S1. Establish a three-dimensional digital model of the fusion body 1. Based on the thermal accumulation deformation law of the electron beam additive manufacturing process, perform zoned pre-compensation calculations on the fusion body 1. The pre-compensation calculations include: setting differentiated shrinkage compensation amounts for the core region 2, transition region 3, and osseointegration region 4 in the three-zone gradient porosity structure, where the compensation amount for the core region 2 is 0.4%-1.0%, the compensation amount for the transition region 3 is 1.4%-2.4%, and the compensation amount for the osseointegration region 4 is 2.0%-2.4%.

[0037] S2. Electron beam additive manufacturing equipment is used, with tantalum powder (or tantalum-based alloy powder) as raw material, and layer-by-layer melting and deposition are carried out according to the pre-compensated model parameters to form an integral shape. During the forming process, the electron beam power, scanning speed and substrate temperature are controlled in three zones: the core zone 2 uses high energy density parameters to make the density greater than 94%, the transition zone 3 uses medium energy density parameters to make the porosity reach 30%-60%, and the bone integration zone 4 uses low energy density parameters to make the porosity reach 70%-80% and form a biomimetic bone trabecular pore structure.

[0038] S3. The fused body 1 after molding is subjected to slow cooling treatment in a vacuum environment. The vacuum and high temperature preheating environment of the molding chamber of the electron beam additive manufacturing equipment (the molding chamber temperature is usually maintained at 600-700℃) is used to slowly cool it to room temperature in the furnace to further homogenize the temperature field and release any possible weak residual stress.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A size compensation method for an interbody fusion device based on electron beam additive manufacturing, characterized in that, include: The fusion body (1) is integrally formed by electron beam additive manufacturing process. The interior of the fusion body (1) is a three-zone gradient pore structure, which includes a core zone (2), a transition zone (3) and a bone integration zone (4) from the inside to the outside.

2. The size compensation method for an interbody fusion device based on electron beam additive manufacturing according to claim 1, characterized in that: The fusion body (1) is made of titanium alloy or pure tantalum, and when the material is titanium alloy, the titanium alloy contains tantalum.

3. The size compensation method for an interbody fusion device based on electron beam additive manufacturing according to claim 1, characterized in that: The core area (2) has a pore size of 0.1mm-0.2mm, the transition area (3) has a pore size of 0.2mm-0.8mm, and the osseointegration area (4) has a pore size of 0.4mm-1.2mm. The pore sizes of the three areas increase gradually from the inside to the outside, and the pore sizes are evenly distributed in each area.

4. The size compensation method for an interbody fusion device based on electron beam additive manufacturing according to claim 1, characterized in that: The core region (2) has a density greater than 94%, and the core region (2) extends through the entire axial length of the fusion body (1).

5. The size compensation method for an interbody fusion device based on electron beam additive manufacturing according to claim 1, characterized in that: The porosity of the transition zone (3) is 30%-60%, and the transition zone (3) covers the outer periphery of the core zone (2).

6. The size compensation method for an interbody fusion device based on electron beam additive manufacturing according to claim 1, characterized in that: The porosity of the osseointegration zone (4) is 70%-80%. The osseointegration zone (4) covers the periphery of the transition zone (3) and forms the outer surface of the fusion body (1). The pore structure of the osseointegration zone (4) is a biomimetic trabecular structure.

7. A deformation control method for size compensation of interbody fusion cages based on electron beam additive manufacturing, characterized in that, The following steps are included: S1. Establish a three-dimensional digital model of the fusion body (1). According to the thermal accumulation deformation law of the electron beam additive manufacturing process, perform a pre-compensation calculation on the fusion body (1) in different regions. The pre-compensation calculation includes setting differentiated shrinkage compensation amounts for the core region (2), transition region (3), and osseointegration region (4) in the three-zone gradient pore structure, wherein the compensation amount for the core region (2) is 0.4%-1.0%, the compensation amount for the transition region (3) is 1.4%-2.4%, and the compensation amount for the osseointegration region (4) is 2.0%-2.4%. S2. Electron beam additive manufacturing equipment is used, with tantalum powder (or tantalum-based alloy powder) as raw material, and layer-by-layer melting deposition is carried out according to the pre-compensated model parameters to form an integral shape; during the forming process, the electron beam power, scanning speed and substrate temperature are controlled in three zones: the core area (2) adopts high energy density parameters to make the density greater than 94%, the transition area (3) adopts medium energy density parameters to make the porosity reach 30%-60%, and the bone integration area (4) adopts low energy density parameters to make the porosity reach 70%-80% and form a biomimetic bone trabecular pore structure; S3. The main body of the fused device (1) after molding is subjected to slow cooling treatment in a vacuum environment. The vacuum and high temperature preheating environment of the molding chamber of the electron beam additive manufacturing equipment (the temperature of the molding chamber is usually maintained at 600-700℃) is used to slowly cool it to room temperature in the furnace to further homogenize the temperature field and release any possible weak residual stress.

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