Individualized 3D printing tenon-and-mortise fusion cage for lumbar interarticular fusion

Abstract

The individual 3D printing mortise and tenon fusion cage comprises a fusion cage body, the fusion cage body is of a wedge-shaped hexahedron structure which is wide in the upper portion and narrow in the lower portion in the long axis direction, at least one threaded hole is formed in the upper surface of the fusion cage body, and a plurality of through type bone grafting hole channels are formed between the two opposite side faces of the fusion cage body. A mineralized extracellular matrix coating is arranged on the outer surface of the fusion cage body. According to the utility model, the wedge-shaped structural design with a wide upper part and a narrow lower part is adopted, so that good mechanical interlocking can be formed with a bone grafting groove after implantation, the stability is improved, and the risk of postoperative displacement is reduced. The fusion cage body is designed into a grid body with a microcosmic porous structure, micron holes provide an ideal space for bone cell ingrowth and vascularization, and transformation from mechanical fixation to biological fixation is achieved. The through type bone grafting hole channel provides sufficient space for implanting sufficient autologous bones, and the fusion process is further accelerated. The individualized matching degree is high, and the operation adaptability is good.

Description

Technical Field

[0001] This utility model relates to a facet joint fusion device, and more particularly to an individualized 3D-printed tenon-and-mortise fusion device for lumbar facet joint fusion. Background Technology

[0002] Degenerative diseases of the lumbar spine are a common cause of low back and leg pain. For patients who do not respond to conservative treatment or have neurological impairment and intervertebral instability, posterior lumbar discectomy, spinal canal decompression, and fusion with internal fixation and bone grafting are important surgical treatments. Among these, interbody fusion, which can restore intervertebral disc height and achieve circumferential fusion, has become a widely used standard procedure in clinical practice.

[0003] However, interbody fusion has certain limitations: for patients with relatively good disc height but whose main pathological feature is facet joint degeneration, traditional interbody fusion procedures can easily lead to iatrogenic instability. Furthermore, the height of the interbody fusion cage must be chosen with extreme caution: insufficient height makes it difficult to effectively restore physiological curvature and intervertebral foramen height, while excessive stretching may increase endplate stress, raise the risk of cage subsidence, and even exacerbate postoperative discomfort. In addition, the procedure is complex, and the proximity to important neurovascular structures means that the risk of nerve injury due to intraoperative traction cannot be ignored. Moreover, the loss of mobility at the fused segment alters the biomechanical load on the spine, potentially accelerating the degeneration of adjacent intervertebral discs, thus increasing the risk of long-term revision surgery.

[0004] For these patients, interfacetal fusion is gaining increasing attention as an alternative surgical approach. This procedure preserves some intervertebral disc tissue and achieves target segment stability by directly fusing the facet joint. Its theoretical advantages include: the rich blood supply to the subchondral bone of the facet joint provides an excellent biological environment for bone fusion; it avoids intervention in the intervertebral space, resulting in less surgical trauma, less bleeding, and helps reduce the risk of adjacent segment degeneration.

[0005] However, current facet joint fusion techniques are still in their early stages of development, lacking specially designed implants and supporting device systems, and have the following significant drawbacks:

[0006] (1) Lack of dedicated fusion device: The current clinical method is to directly fill the treated articular interarticular space with autologous bone granules obtained from decompression. This method lacks effective restraint on the bone graft material, and bone granules are prone to displacement, absorption or dislodgement under physiological load after surgery, resulting in loss of bone graft and ultimately fusion failure;

[0007] (2) Insufficient initial stability: Bone particles that rely solely on compression fixation cannot provide sufficient immediate mechanical stability. Micromovement during the healing period before achieving bone fusion may lead to fibrous tissue ingrowth, resulting in pseudoarthrosis.

[0008] Therefore, there is an urgent need in the field for a dedicated facet joint fusion device that can effectively solve the above-mentioned problems. This device should be able to accommodate bone graft material, provide sufficient initial stability, and guide the biological process of bone fusion, thereby helping surgeons to perform surgical procedures more precisely and safely, and reducing operational risks. Utility Model Content

[0009] To address the aforementioned technical problems, this utility model provides an individualized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion, comprising a fusion device body. The fusion device body is a wedge-shaped hexahedron structure, wider at the top and narrower at the bottom, along its long axis. It has an upper surface and a lower surface along the long axis, and four lateral sides along the circumference of the long axis. The upper surface has at least one threaded hole, and several through-type bone graft channels are provided between two opposite sides. The outer surface of the fusion device body is coated with a mineralized extracellular matrix. The threaded hole is used to connect screws for fixing the titanium alloy plate. The bone graft channels are used to fill with fine bone granules trimmed from autologous vertebral lamina bone. The mineralized extracellular matrix coating promotes bone ingrowth.

[0010] Furthermore, the fusion device body is a mesh with a microporous structure, the average pore size of which is 500-600 micrometers and the porosity is 50%-60%, which is used to promote bone ingrowth and vascularization; the pores of the microporous structure are connected to the bone graft channels; and the coating thickness is 20-100 micrometers.

[0011] Furthermore, the diameter of the bone graft channel is 4-6 mm, and the spacing between adjacent bone graft channels is 2-4 mm.

[0012] Furthermore, the fusion device body also includes at least one development mark, which is embedded in the non-joint contact area of ​​the fusion device body. The development mark has a diameter of 0.5-1.0 mm and a length of 5-10 mm, and is made of tantalum metal wire.

[0013] Furthermore, the junctions between the upper surface, lower surface, and each side of the fusion device body are chamfered to prevent bone damage caused by stress concentration.

[0014] The usage method and working principle of this utility model are as follows:

[0015] (1) Preoperative planning and fusion device customization: Based on the patient's lumbar spine 3D CT image data, 3D reconstruction is performed to accurately measure the morphology, angle, and bone strength of the facet joints of the target segment. Based on this, the decompression range of the vertebral laminae and the degree of preservation of the facet joints are determined, and the optimal drilling position, direction, and depth of the interfacial bone graft bed are simulated and calculated. Based on this planning data, an individualized tenon-and-mortise fusion device that perfectly matches the patient's anatomical structure is prepared by additive manufacturing technology (3D printing), namely, the individualized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion described in this utility model.

[0016] (2) Intraoperative preparation: After completing the routine posterior lumbar spine surgery and exposing the patient, laminectomy is performed, and the excised autologous lamina bone is trimmed into small bone particles for later use. A bone graft bed matching the shape of the fusion device is prepared between the facet joints to be fused using a special drill or curette.

[0017] (3) Bone grafting: The autologous fine bone particles prepared in step 2 are tightly packed into the through bone grafting channel of the fusion device of this utility model and compacted to ensure that the bone particles are fully filled.

[0018] (4) Implantation and Locking: Embed the pre-grafted fusion device into the bone graft bed prepared in step 2 along the preset direction. Gently tap it into place to ensure that the lower surface and all sides of the fusion device are fully in contact with the bottom and surrounding bone walls of the bone graft bed, forming a tight tenon-and-mortise fit. Finally, on the upper surface of the fusion device, use titanium alloy screws to pass through the titanium alloy plate and tighten them into the threaded holes on the upper surface. The fusion device and the articular process are connected and fixed by the titanium alloy screws and titanium alloy plate, thereby achieving reliable mechanical fixation and preventing the fusion device from coming out after implantation.

[0019] (5) Closing the incision: After confirming that the fusion device is stable and not loose, close and suture the surgical incision according to the routine surgical procedure.

[0020] The beneficial effects of this utility model are:

[0021] Compared with existing technologies, the personalized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion provided by this utility model has the following significant advantages:

[0022] (1) High implantation stability and effective prevention of displacement: The fusion device of this utility model adopts a wedge-shaped structure design with "wide at the top and narrow at the bottom". It utilizes the tenon and mortise principle to form a good mechanical interlock with the prepared bone graft groove after implantation, which significantly improves the initial stability of the implant and can effectively resist rotation and shear stress, greatly reducing the risk of postoperative displacement.

[0023] (2) High bone fusion efficiency and excellent bioactivity: The fusion device is designed as a mesh with a microporous structure, and its micron-sized pores provide ideal space for bone cell ingrowth and vascularization, realizing the transformation from mechanical fixation to biological fixation. In addition, the mineralized extracellular matrix coating on the surface fundamentally promotes long-term and robust bone fusion. The through-hole bone graft provides ample space for implanting sufficient autologous bone, further accelerating the fusion process.

[0024] (3) High degree of individualized matching and good surgical adaptability: The fusion device body is a solid structure integrally formed by three-dimensional reconstruction based on the patient's preoperative imaging data and additive manufacturing technology; the lower surface and each side of the fusion device body are in contact with the bone graft area between the facet joints, and the lower surface and the side are matched with the bony contact surface morphology of the target facet joint, realizing individualized close fit; it not only reduces the additional bone resection required during the operation to adapt to the standard implant, realizing minimally invasive implantation, but also increases the bone-implant contact area and improves the overall stability.

[0025] (4) This invention supplements existing fusion techniques and expands clinical options: For patients with lumbar degenerative diseases, especially those with mild intervertebral disc degeneration who need to preserve the function of the motor segment, this invention provides a novel and effective short-segment fusion scheme. This scheme avoids intervertebral fusion and achieves effective fusion with minimal trauma, which has important clinical application value. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0027] Figure 2 This is a schematic diagram of the lower surface and part of the side structure of this utility model;

[0028] 1. Fusion device body; 2. Upper surface; 3. Lower surface; 4. Side; 5. Threaded hole; 6. Bone graft channel; 7. Screw; 8. Radiographic marker. Detailed Implementation

[0029] Example 1

[0030] like Figure 1 , 2As shown in this embodiment, an individualized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion is provided, including a fusion device body 1. The fusion device body 1 has a wedge-shaped hexahedral structure that is wider at the top and narrower at the bottom along the long axis. It has an upper surface 2 and a lower surface 3 along the long axis, with the length and width of the upper surface 2 being greater than that of the lower surface 3. It has four side surfaces 4 circumferentially along the long axis. The upper surface has at least one threaded hole 5, and the depth of the threaded hole 5 in this embodiment is 6 mm. There are 4-8 circular through-holes 6 between two opposite side surfaces, and the number of bone grafts 6 in this embodiment is 6. The outer surface of the fusion device body 1 is coated with a mineralized extracellular matrix coating. The threaded hole 5 is used to connect and fix the titanium alloy plate with screws 7. In this embodiment, the diameter of the bone grafts 6 is 5 mm, which is used to fill the small bone particles trimmed from the autologous vertebral lamina. The mineralized extracellular matrix coating is used to promote bone ingrowth.

[0031] The fusion device body 1 is made of biocompatible material. In this embodiment, it is integrally formed from polyetheretherketone material using additive manufacturing technology. It is a mesh with a microporous structure. In this embodiment, the average pore size of the microporous structure is 500-600 micrometers, and the porosity is 50%-60%, which is used to promote bone ingrowth and vascularization. The pores of the microporous structure are connected to the bone graft channels 6.

[0032] The fusion device body 1 also includes one or two imaging markers 8 with a diameter of 0.7 mm and a length of 8 mm. The imaging markers 8 are embedded in the non-joint contact area of ​​the fusion device body, that is, the surface without bone graft channels 6. The imaging markers are tantalum metal wires.

[0033] The manufacturing method of this utility model:

[0034] (1) Individualized assessment of articular processes:

[0035] Based on the patient's lumbar spine 3D CT image data, 3D reconstruction is performed to accurately measure the morphology, angle and bone strength of the facet joint of the target segment. A three-dimensional model of the facet joint is constructed using 3D printing technology to plan the design scheme of the fusion device.

[0036] (2) Individualized structural design of the fusion device:

[0037] The decompression range of the lamina and the degree of preservation of the articular processes are determined by the lamina reduction method. The optimal drilling position, direction and depth of the interarticular bone graft bed are simulated and calculated. The shape and size of the fusion device body 1 are determined. The dimensions of the upper surface 2, lower surface 3 and each side 4 of the fusion device are determined. A three-dimensional model of the fusion device is constructed.

[0038] (3) Design the position and depth of the threaded hole 5 on the upper surface of the fusion device three-dimensional model, and design the through bone graft channel 6 between the two opposite sides of the fusion device.

[0039] (4) After the fusion model is designed, it is 3D printed using a 3D printer (this technology is existing technology, and the specific method will not be described here). The material is polyetheretherketone.

[0040] (5) A biomimetic mineralization method is used to coat the extracellular matrix with a mineralized coating, simulating the natural biological mineralization process. The fusion device is immersed in simulated body fluid for biomimetic mineralization coating (this technology is existing technology, and the specific method is not described here); the coating thickness is between 20-100 micrometers.

[0041] The usage method and working principle of this utility model are as follows:

[0042] (1) Preoperative planning and fusion device customization: Based on the patient's lumbar spine three-dimensional CT image data and the design plan of the fusion device, an individualized tenon and mortise fusion device matching the patient's anatomical structure is prepared by additive manufacturing technology (3D printing), namely the individualized 3D printed tenon and mortise fusion device for lumbar interfacial fusion described in this utility model.

[0043] (2) Intraoperative preparation: After completing the routine posterior lumbar spine surgery and exposing the patient, laminectomy is performed, and the excised autologous lamina bone is trimmed into small bone particles for later use. A bone graft bed matching the shape of the fusion device is prepared between the facet joints to be fused using a special drill or curette.

[0044] (3) Bone grafting: The autologous fine bone particles prepared in step 2 are tightly packed into the through bone graft channel 6 of the fusion device of this utility model and compacted to ensure that the bone particles are fully filled.

[0045] (4) Implantation and Locking: Insert the small-diameter end of the fusion device body 1, which has been grafted, into the bone graft bed prepared in step 2 along the preset direction. Gently tap it into place to ensure that the lower surface 3 and all sides 4 of the fusion device body 1 are fully in contact with the bottom and surrounding bone walls of the bone graft bed, forming a tight tenon-and-mortise fit. Finally, on the upper surface 2 of the fusion device, use titanium alloy screws 7 to pass through the titanium alloy plate and tighten them into the threaded holes 5 on the upper surface 2. The fusion device body 1 and the articular processes are connected and fixed by the titanium alloy screws 7 and the titanium alloy plate, thereby achieving reliable mechanical fixation and preventing the fusion device from coming out after implantation.

[0046] (5) Closing the incision: After confirming that the fusion device is stable and not loose, close and suture the surgical incision according to the routine surgical procedure.

[0047] Example 2

[0048] like Figure 2As shown in the figure, this embodiment provides an individualized 3D printed tenon fusion device for lumbar interfacial fusion. Based on embodiment 1, the junction between the upper surface 2, lower surface 3 and each side surface 4 of the fusion device body 1 is a chamfered structure to prevent bone damage caused by stress concentration.

Claims

1. A personalized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion, characterized in that: The device includes a fusion device body, which is a wedge-shaped hexahedron structure that is wider at the top and narrower at the bottom along the long axis. It has an upper surface and a lower surface along the long axis, and four sides along the circumference of the long axis. The upper surface has at least one threaded hole, and several through-holes for bone grafting are provided between two opposite sides. The outer surface of the fusion device body is coated with a mineralized extracellular matrix.

2. The personalized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion according to claim 1, characterized in that: The fusion device body is a mesh with a microporous structure, the average pore size of which is 500-600 micrometers and the porosity is 50%-60%; the pores of the microporous structure are connected to the bone graft channels; the coating thickness is 20-100 micrometers.

3. The personalized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion according to claim 1, characterized in that: The diameter of the bone graft channel is 4-6 mm, and the spacing between adjacent bone graft channels is 2-4 mm.

4. The personalized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion according to claim 1, characterized in that: The fusion unit body also includes at least one development mark, which is embedded in the non-joint contact area of ​​the fusion unit body. The development mark has a diameter of 0.5-1.0 mm and a length of 5-10 mm.

5. The personalized 3D-printed tenon-and-mortise fusion device for lumbar interfacial fusion according to claim 1, characterized in that: The junctions between the upper surface, lower surface, and each side of the fusion unit body are chamfered.

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