An adaptive manufacturing method of a cervical spine anterior path titanium cage

Abstract

The present application relates to the technical field of medical implant manufacturing, and particularly relates to a self-adaptive manufacturing method of a cervical spine anterior path titanium cage, which comprises the following steps: acquiring cervical spine CT data of a target object; performing three-dimensional reconstruction on the cervical spine CT data to obtain a complete three-dimensional vertebral body model, and analyzing the cervical spine CT data and the complete three-dimensional vertebral body model to obtain model correction parameters; performing ACCF simulation surgery on the three-dimensional vertebral body model based on an expected resection amount of the target object, to obtain a cervical spine subtotal resection model after simulation surgery; obtaining a primary structure model of the cervical spine anterior path titanium cage based on the cervical spine subtotal resection model and the model correction parameters; performing ACCF simulation installation using the primary structure model, and adjusting the primary structure model to obtain a secondary structure model; and manufacturing the cervical spine anterior path titanium cage of the target object based on the secondary structure model; the present application significantly increases the contact area between the titanium cage and the vertebral body, helps to disperse local stress, and reduces the titanium cage subsidence probability after ACCF surgery.

Description

Technical Field

[0001] This invention relates to the field of medical implant manufacturing technology, and in particular to an adaptive manufacturing method for anterior cervical spine titanium cages. Background Technology

[0002] ACCF (Anterior cervical corpectomy and fusion) is a classic surgical procedure for treating cervical spine diseases, including cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, cervical spine deformities, etc. It is especially widely used for cervical spine diseases with anterior compression of the spinal cord due to its good decompression effect and high fusion rate.

[0003] Vertebral reconstruction is a crucial step in ACCF surgery, impacting cervical spine stability and fusion rates. Autologous bone and allogeneic bone, used alone or in combination with a titanium mesh cage, are important reconstruction methods. However, autologous bone reconstruction is declining in use due to the risk of donor site complications. Allogeneic bone has a low usage rate due to limited availability and rejection issues. Titanium mesh cages, on the other hand, are widely used because they are readily available, provide immediate postoperative stability, and offer high fusion rates when combined with in-situ bone grafting. Despite the widespread use of titanium mesh cages in ACCF, postoperative complications still occur after years of clinical testing, particularly those related to TMC (titanium mesh cage) settlement and internal fixation failure. This is closely related to design flaws in TMC and the resulting biomechanical changes in the cervical spine.

[0004] The main drawback of TMC is that the small contact area at the TMC-endplate interface leads to uneven stress distribution and stress concentration, which in turn causes TMC subsidence and changes in stress at the internal fixation-bone interface.

[0005] Chinese patent application publication number CN110897695B discloses a lower cervical spine anatomical titanium cage, comprising: a titanium cage body, the upper end of which has a dome structure and the lower end has an oblique structure, with a mesh structure between the dome structure and the oblique structure, the mesh structure being connected to both the dome structure and the oblique structure; the mesh structure includes a first front surface, a first rear surface, a first left side surface, and a first right side surface connected together, the first front surface and the first rear surface being arc-shaped, and the first left side surface and the first right side surface being planar. Based on cervical spine anatomical data measurements, the upper end of the lower cervical spine anatomical titanium cage is designed with a dome structure, and the lower end with an oblique structure, simulating the angle of the cervical spine surgical segment, thereby increasing the contact area between the titanium cage and the cervical endplate, reducing stress concentration, and ensuring that stress is evenly distributed on the endplate surface, thus reducing the incidence of titanium cage collapse.

[0006] Therefore, the above-mentioned anatomical titanium cage for the lower cervical spine has the following problems: the contact area between its upper dome structure and lower oblique structure and the endplate is unstable for different patients, and stress concentration can still lead to the collapse of the titanium cage. Summary of the Invention

[0007] To address this issue, the present invention provides an adaptive manufacturing method for anterior cervical spine titanium cages, which overcomes the problem in the prior art where the contact area between the titanium cage and the endplate is unstable, easily leading to stress concentration and titanium cage collapse.

[0008] To achieve the above objectives, the present invention provides an adaptive fabrication method for anterior cervical spine titanium cages, comprising:

[0009] Step S1: Obtain cervical spine CT data of the target object;

[0010] Step S2: Perform three-dimensional reconstruction on the cervical spine CT data to obtain a complete three-dimensional vertebral body model, and analyze the cervical spine CT data and the complete three-dimensional vertebral body model to obtain model correction parameters;

[0011] Step S3: Based on the expected amount of cervical vertebrae to be removed from the target object, perform ACCF simulation resection on the three-dimensional vertebral model to obtain a simulated subtotal cervical vertebra resection model.

[0012] Step S4: Based on the subtotal cervical vertebra resection model and the model correction parameters, obtain the primary structural model of the anterior cervical titanium cage.

[0013] Step S5: Perform ACCF simulation installation using the primary structural model, and adjust the primary structural model based on the simulated cervical spine installation model and the model correction parameters to obtain the secondary structural model;

[0014] Step S6: Based on the secondary structure model, fabricate the anterior cervical titanium cage for the target object;

[0015] The anterior cervical titanium cage includes a titanium cage frame body, anti-sinking rings disposed at both ends of the titanium cage frame body in contact with the cervical vertebral endplates, and ear-shaped fixing parts disposed at both ends of the titanium cage frame body.

[0016] Furthermore, the anterior cervical titanium cage comprises:

[0017] The anti-sinking ring is a hollow circular ring structure whose surface is in contact with the bony endplate of the cervical vertebra. The anti-sinking ring includes an upper anti-sinking ring and a lower anti-sinking ring. The upper surface of the upper anti-sinking ring is in contact with the curved surface of the lower endplate of the bony endplate of the adjacent cervical vertebra above, and the lower surface of the lower anti-sinking ring is in contact with the curved surface of the upper endplate of the bony endplate of the adjacent cervical vertebra below.

[0018] The main body of the titanium cage frame is a hollow columnar structure with mesh. The upper end of the main body of the titanium cage frame is connected to the upper anti-sinking ring, and the lower end of the main body of the titanium cage frame is connected to the lower anti-sinking ring.

[0019] The ear-shaped fixing part includes an ear-shaped fixing plate and a connecting area. The ear-shaped fixing plate includes an upper ear-shaped fixing plate and a lower ear-shaped fixing plate, which are respectively provided with screw holes and semi-circular weight-reducing grooves. The connecting area includes an upper connecting area and a lower connecting area. The upper ear-shaped fixing plate is connected to the upper anti-sinking ring through the upper connecting area and is parallel to the vertebral surface of the adjacent cervical vertebra above. The lower ear-shaped fixing plate is connected to the lower anti-sinking ring through the lower connecting area and is parallel to the vertebral surface of the adjacent cervical vertebra below.

[0020] The anti-sinking ring, the titanium cage frame body, the connecting area, and the ear-shaped fixing plate are integrally fixedly connected.

[0021] Further, step S2 includes:

[0022] Step S21: Import the cervical spine CT data into the medical imaging control system for three-dimensional reconstruction and segmentation of the vertebral body to obtain 6 separate vertebral body models of C2 to C7.

[0023] Step S22: Import each of the split cervical spine models into reverse engineering software for model optimization and convert them into solid models;

[0024] Step S23: Import each of the aforementioned solid models into the 3D design software to generate cancellous bone, cortical bone, bony endplate, posterior structure, intervertebral disc and ligament complex, and adjust the cervical spine posture to the ACCF surgical posture to obtain the complete 3D vertebral body model.

[0025] Step S24: Analyze the cervical spine CT data and the complete three-dimensional vertebral body model to obtain the model correction parameters.

[0026] Further, step S24 includes:

[0027] Step S241: Based on the cervical spine CT data, construct the deformation trajectory of the esophagus during the swallowing cycle to obtain the minimum distance between the esophageal wall and the front edge of the titanium cage skeleton body.

[0028] Step S242: Obtain depth adjustment parameters based on the minimum interval distance and the expected amount of resection of the target object;

[0029] Step S243: Based on the bone density distribution of the bony endplate, the upper endplate and the lower endplate are divided into several partitions, and the contact area threshold of the anti-sinking ring corresponding to the upper endplate and the lower endplate in each partition is calculated.

[0030] Furthermore, in step S243, the contact area threshold is negatively correlated with the bone density of the bony endplate.

[0031] Further, step S4 includes:

[0032] Step S41: Based on the surfaces of the vertebral bodies adjacent to the upper and lower sides of the target cervical vertebrae, construct an upper ear-shaped fixation plate model and a lower ear-shaped fixation plate model respectively.

[0033] Step S42: Construct an upper anti-sinking ring model based on the lower endplate of the adjacent cervical vertebrae above the target cervical vertebrae, and construct a lower anti-sinking ring model based on the upper endplate of the adjacent cervical vertebrae below the target cervical vertebrae.

[0034] Step S43: Based on the upper ear-shaped fixing plate model and the upper anti-sinking ring model, construct the upper connecting part model; based on the lower ear-shaped fixing plate model and the lower anti-sinking ring model, construct the lower connecting part model.

[0035] Step S44: Construct the main body model of the titanium cage skeleton based on the upper anti-sinking ring model and the lower anti-sinking ring model;

[0036] Step S45: Connect and merge the upper anti-sinking ring model, the lower anti-sinking ring model, the upper ear-shaped fixing plate model, the lower ear-shaped fixing plate model, the upper connecting part model, the lower connecting part model, and the titanium cage skeleton main body model to obtain the primary structure model.

[0037] Further, step S42 includes:

[0038] Step S421: Construct a first-level upper anti-sinking ring model that is completely fitted with the lower end plate, and a first-level lower anti-sinking ring model that is completely fitted with the upper end plate.

[0039] Step S422: Calculate the ratio of the central hole area of ​​the first-level upper anti-sinking ring model and the first-level lower anti-sinking ring model to the larger area of ​​the upper end plate and the lower end plate; if the ratio is less than the ratio threshold, the central hole area is corrected so that the ratio of the central hole area to the corresponding end plate area is greater than or equal to the ratio threshold, thus obtaining the second-level upper anti-sinking ring model and the second-level lower anti-sinking ring model.

[0040] Step S423: Detect abrupt regions in the secondary upper anti-sinking ring model and the secondary lower anti-sinking ring model where the curvature is greater than the curvature threshold;

[0041] Step S424: Perform curvature correction on the abrupt change region so that the corrected curvature is less than or equal to the curvature threshold, thereby obtaining the upper anti-sinking ring model and the lower anti-sinking ring model.

[0042] Further, in step S421, the position of the anti-sinking ring on the corresponding end plate is determined according to the depth adjustment parameter, so that the contour of the recessed area formed by the titanium cage skeleton body and the ear-shaped fixing part is located outside the envelope of the esophageal deformation trajectory.

[0043] Further, step S5 includes:

[0044] Step S51: Simulate the internal fixation installation of ACCF surgery. Place the upper anti-sinking ring model, the lower anti-sinking ring model, and the titanium cage skeleton main body model from the primary structural model into the decompression groove, so that the anti-sinking ring fits against the corresponding cervical vertebral endplate. Then, fix the ear-shaped fixation plate model to the surface of the corresponding cervical vertebral body with screws to complete the ACCF simulation installation. The decompression groove is obtained by the target cervical vertebral body of the target object being removed in the ACCF simulation.

[0045] Step S52: Determine whether the contact area of ​​the upper anti-sinking ring model and the lower anti-sinking ring model in the primary structural model with the endplate corresponding to the cervical vertebrae in each of the partitions is less than the corresponding contact area threshold. If the contact area is less than the corresponding contact area threshold, then modify the surface of the corresponding partition of the anti-sinking ring so that the contact area is greater than or equal to the contact area threshold, and obtain the secondary structural model.

[0046] Further, in step S51, when the upper anti-sinking ring model, the lower anti-sinking ring model, and the titanium cage skeleton main body model in the primary structural model are placed into the decompression groove, the simulated normal contact stress between the upper anti-sinking ring model and the lower anti-sinking ring model and the cervical vertebral endplate is acquired in real time. If the simulated normal contact stress is greater than the stress safety threshold, the curvature of the corresponding anti-sinking ring is corrected so that the simulated normal contact stress between the corrected anti-sinking ring and the cervical vertebral endplate during the implantation process is less than or equal to the stress safety threshold.

[0047] The beneficial effects of this invention are as follows: Based on the patient's cervical spine CT scan data, a high-precision three-dimensional virtual model of the cervical spine is obtained through three-dimensional reconstruction technology. On this model, a virtual simulation of anterior cervical corpectomy and fusion is performed to obtain a virtual model after the corpectomy. Then, a personalized anterior cervical titanium cage is designed using virtual design software, optimizing the design structure of the titanium cage body-bone contact surface and adopting an anti-sinking ring structure to make the end face of the titanium cage and the endplate form a face-to-face anatomical matching relationship. Compared with existing clinical titanium cages, this significantly increases the contact area between the titanium cage and the vertebral body, which helps to disperse local stress, prevent excessive local stress concentration, and thus reduce the occurrence of titanium cage sinking complications after ACCF.

[0048] Furthermore, by integrating the fixing steel plate and the titanium cage body into a single design, the present invention ensures the internal fixing strength of the titanium cage while improving the stability of the internal fixing.

[0049] Furthermore, the present invention significantly reduces the contact area between the titanium cage and the esophagus through the hollowed-out recessed design of the front edge of the titanium cage, thereby reducing the irritation of the esophagus by the titanium cage, helping to reduce esophageal-related complications after ACCF surgery, and improving patients' postoperative difficulty in eating.

[0050] Furthermore, this invention constructs the deformation trajectory of the esophagus during the swallowing cycle based on CT scan data, and sets different depths of hollowed-out indentations at the anterior edge of the titanium cage for different patients to prevent compression of the esophagus caused by excessively shallow hollowed-out indentations or choking of swallowed food caused by excessively deep hollowed-out indentations.

[0051] Furthermore, this invention controls the support force distribution of the anti-sinking ring with the bone density gradient of the endplate by differentiating the contact area based on the cervical vertebral endplate partitions. This ensures that the high-density area bears more mechanical load, while the low-density area reduces the pressure per unit area through area compensation. This reduces the occurrence of titanium cage sinking complications after ACCF surgery and accelerates the long-term bony fusion process.

[0052] Furthermore, this invention corrects the curvature of the anti-sinking ring contact surface by detecting bony protrusions (such as osteophytes or calcified areas) with abrupt curvature changes on the endplate surface, resulting in a smooth transition between the corrected anti-sinking ring surface and the endplate surface. This correction avoids localized stress concentration caused by abrupt curvature changes and prevents mechanical interference between the edge of the anti-sinking ring and bony protrusions during implantation, ensuring a smooth titanium cage implantation path. By controlling the corrected curvature to not exceed the physiological curvature threshold of the endplate cartilage, the anatomical match between the anti-sinking ring and the endplate is maintained, while the risk of postoperative titanium cage subsidence is reduced.

[0053] Furthermore, during virtual implantation, the collision interference volume between the anti-sinking ring and the bony structure of the endplate is monitored in real time. By dynamically adjusting the edge curvature of the anti-sinking ring, the collision interference volume is ensured to remain below a safe threshold. This correction method optimizes the implantation path compatibility of the anti-sinking ring, avoiding endplate microfractures or cartilage damage caused by forced implantation, while also reducing the prolonged surgical time due to repeated adjustments to the titanium cage position during surgery. The corrected curvature distribution allows the anti-sinking ring to adaptively conform to the endplate surface during implantation, improving surgical safety. Attached Figure Description

[0054] Figure 1 This is a flowchart of the adaptive fabrication method of the anterior cervical titanium cage according to an embodiment of the present invention;

[0055] Figure 2 This is a perspective view of a schematic diagram of the anterior cervical titanium cage according to an embodiment of the present invention.

[0056] Figure 3 This is a cross-sectional schematic diagram of the anterior cervical titanium cage during simulated installation according to an embodiment of the present invention;

[0057] Figure 4 This is an actual image of the secondary structure model of the anterior cervical titanium cage according to an embodiment of the present invention;

[0058] Figure 5 This is an actual image of the secondary structure model of the anterior cervical titanium cage in an embodiment of the present invention during simulated installation;

[0059] In the diagram: 1-Titanium cage frame main body; 21-Upper anti-sinking ring; 22-Lower anti-sinking ring; 311-Upper ear-shaped fixing plate; 3111-Upper weight reduction groove; 3112-Upper fixing screw hole; 312-Lower ear-shaped fixing plate; 3121-Lower weight reduction groove; 3122-Lower fixing screw hole; 321-Upper connecting area; 322-Lower connecting area; 4-Cervical vertebrae; 5-Screw. Detailed Implementation

[0060] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0061] 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.

[0062] It should be noted that in the description of this invention, the terms "upper," "lower," "inner," "outer," etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0063] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0064] Please see Figures 2-5As shown, it is a perspective view of the anterior cervical titanium cage of the present invention, a cross-sectional view of the anterior cervical titanium cage of the present invention during simulated installation, an actual image of the secondary structure model of the anterior cervical titanium cage of the present invention, and an actual image of the secondary structure model of the anterior cervical titanium cage of the present invention during simulated installation, including:

[0065] The titanium cage frame body 1 includes anti-sinking rings located at both ends of the titanium cage frame body 1 that contact the endplates of the cervical vertebrae, and ear-shaped fixing parts located at both ends of the titanium cage frame body 1.

[0066] The anti-sinking ring includes an upper anti-sinking ring 21 and a lower anti-sinking ring 22. The upper surface of the upper anti-sinking ring 21 is in contact with the curved surface of the lower endplate of the adjacent cervical vertebra 4 above, and the lower surface of the lower anti-sinking ring 22 is in contact with the curved surface of the upper endplate of the adjacent cervical vertebra 4 below.

[0067] The titanium cage frame body 1 is a hollow columnar structure with diamond-shaped mesh holes. Its upper end is connected to the upper anti-sinking ring 21, and its lower end is connected to the lower anti-sinking ring 22.

[0068] The ear-shaped fixing part includes an ear-shaped fixing plate and a connecting area. The ear-shaped fixing plate includes an upper ear-shaped fixing plate 311 and a lower ear-shaped fixing plate 312. The connecting area includes an upper connecting area 321 and a lower connecting area 322. The upper ear-shaped fixing plate 311 is connected to the upper anti-sinking ring 21 through the upper connecting area 321 and is parallel to the vertebral surface of the adjacent cervical vertebra 4 above. The lower ear-shaped fixing plate 312 is connected to the lower anti-sinking ring 22 through the lower connecting area 322 and is parallel to the vertebral surface of the adjacent cervical vertebra 4 below.

[0069] The upper ear-shaped fixing plate 311 is provided with symmetrical upper fixing screw holes 3112 and a semi-circular upper weight reduction groove 3111 between the two screw holes; the lower ear-shaped fixing plate 312 is provided with symmetrical lower fixing screw holes 3122 and a semi-circular lower weight reduction groove 3121 between the two screw holes.

[0070] The upper ear-shaped fixing plate 311 and the lower ear-shaped fixing plate 312 are fixedly connected to the vertebral body by screws 5.

[0071] The anti-sinking ring, the titanium cage frame body 1, the connecting area, and the ear-shaped fixing plate are integrally fixedly connected.

[0072] In practice, the corners of the anti-sinking ring, the connecting area, and the ear-shaped fixing plate are provided with rounded chamfers. Preferably, the radius of the rounded chamfer is 0.2mm to 1mm.

[0073] Please continue reading. Figure 1 As shown, it is a flowchart of the adaptive fabrication method of the anterior cervical titanium cage according to an embodiment of the present invention, including:

[0074] Step S1: Obtain cervical spine CT data of the target object;

[0075] The implementation includes performing a supine cervical spine CT scan and a swallowing dynamic CT scan on the target subject; wherein, the swallowing dynamic CT scan requires the target subject to swallow a gel (simulating a food bolus) containing 2% diatrizoate meglumine contrast agent, and continuously acquires images at a rate of 8 frames per second for 10 seconds to obtain a complete swallowing dynamic image sequence.

[0076] Step S2: Perform three-dimensional reconstruction on the cervical spine CT data to obtain a complete three-dimensional vertebral body model, and analyze the cervical spine CT data and the complete three-dimensional vertebral body model to obtain model correction parameters;

[0077] Specifically, step S2 includes:

[0078] Step S21: Import the cervical spine CT data into the medical imaging control system for three-dimensional reconstruction and segmentation of the vertebral body to obtain 6 separate vertebral body models of C2 to C7.

[0079] In practice, the cervical spine CT data of the target object in supine position is imported into a medical imaging control system, such as MIMICS 14.0 (Materialise Corporation, Belgium). The C2 to C7 vertebral body contours are extracted through a threshold segmentation algorithm to generate a split vertebral body model containing the vertebral body, pedicle, and facet joints.

[0080] Step S22: Import each of the split cervical spine models into reverse engineering software for model optimization and convert them into solid models;

[0081] In implementation, the split vertebral body model is imported into reverse engineering software, such as Geomagic (Geomagic Studio 2021; Geomagic, NC, USA), and CT artifacts are eliminated through a surface smoothing algorithm. A solid model is generated using non-uniform rational B-spline (NURBS) surface reconstruction technology. The edge of the vertebral endplate is sharpened to preserve anatomical features.

[0082] Step S23: Import each of the aforementioned solid models into the 3D design software to generate cancellous bone, cortical bone, bony endplate, posterior structure, intervertebral disc and ligament complex, and adjust the cervical spine posture to the ACCF surgical posture to obtain the complete 3D vertebral body model.

[0083] In practice, the solid model is imported into 3D design software, such as SolidWorks 2022, and the cancellous bone and cortical bone regions are divided according to the CT grayscale values. The bony endplate, posterior structure, intervertebral disc and ligament complex are generated through the preset model. The cervical spine is adjusted to the ACCF standard surgical position (forward flexion angle 15°±3°, lateral tilt angle 0°).

[0084] Step S24: Analyze the cervical spine CT data and the complete three-dimensional vertebral body model to obtain the model correction parameters.

[0085] Specifically, step S24 includes:

[0086] Step S241: Based on the cervical spine CT data, construct the deformation trajectory of the esophagus during the swallowing cycle to obtain the minimum distance between the esophageal wall and the front edge of the titanium cage skeleton body 1.

[0087] In the implementation, MIMICS 14.0 software was used to extract the esophageal wall contour through a threshold segmentation algorithm and remove tracheal interference by combining a region growing algorithm. The middle section of the anterior esophageal wall was selected, and a continuous motion trajectory was generated by fitting B-spline curves. The esophageal motion envelope was constructed using a non-uniform rational B-spline (NURBS) surface to obtain the maximum radial displacement of the esophageal wall during swallowing.

[0088] The formula for calculating the minimum interval distance is as follows:

[0089] d min =Δd+d safe ;

[0090] Where, d min The minimum interval distance is expressed in mm; Δd is the maximum radial displacement of the esophageal wall during swallowing, expressed in mm; d safe For safety intervals, the unit is mm. Based on clinical research data, 2 mm is preferred.

[0091] Step S242: Obtain depth adjustment parameters based on the minimum interval distance and the expected amount of resection of the target object;

[0092] In practice, the calculation formula for the depth adjustment parameter is as follows:

[0093] ΔH=d min -(QeD);

[0094] Wherein, △H is the depth adjustment parameter in mm; Q is the depth of the expected resection in mm; e is the reference distance between the titanium cage skeleton body 1 and the inner wall of the decompression groove in mm, preferably 0.5 mm to 1 mm; and D is the outer diameter of the titanium cage skeleton body 1 in mm.

[0095] It is understood that the (QeD) part in the formula represents the distance between the anterior edge of the titanium cage and the esophageal wall when the titanium cage is implanted at the reference distance, which is related to the minimum interval distance d. min The difference is the distance by which the anti-sinking ring needs to be adjusted inward.

[0096] Step S243: Based on the bone density distribution of the bony endplate, the upper endplate and the lower endplate are divided into several partitions, and the contact area threshold of the anti-sinking ring corresponding to the upper endplate and the lower endplate in each partition is calculated.

[0097] Specifically, in step S243, the contact area threshold is negatively correlated with bone density.

[0098] In implementation, the endplate surface is divided into square grid zones. Preferably, the grid size is 3mm × 3mm. The bone density value of each grid is calculated based on the CT value (HU), and the contact area threshold is calculated. The specific formula for calculating the contact area threshold is as follows:

[0099]

[0100] Among them, S i Let ρ be the contact area threshold for the i-th partition. i This represents the bone mineral density value for the i-th region, in mg / cm³. 3 ;ρ min The minimum bone mineral density value of the endplate; ρ max is the maximum bone mineral density value of the endplate; 'a' is the compensation coefficient, which is calibrated through clinical bone strength testing, preferably 'a' is 0.3; S 基准 The baseline contact area threshold is expressed in mm. 2 It is calibrated through clinical bone strength testing, preferably, S 基准 Take 5.4mm 2 .

[0101] Understandably, endplate bone mineral density (quantified by CT values) directly reflects the mechanical strength of local bone tissue. Low-density areas (such as osteoporotic areas) have sparse trabeculae and weak load-bearing capacity, making them prone to microfractures due to stress concentration; high-density areas (such as sclerotic areas) are too rigid, and excessive contact may compress bone tissue and hinder bone ingrowth. When the bone density of a certain area is low, the contact area threshold for that area should be increased (up to 7.02 mm). 2 This design allows the anti-sinking ring to have a larger actual contact area in that region. The increased contact area reduces the pressure per unit area, preventing the trabecular bone of the cervical vertebral endplates from collapsing due to stress overload. When bone density is high in a certain area, the contact area threshold is reduced (down to the S-reference level, i.e., 5.4 mm). 2This allows the anti-sinking ring to form a larger gap with the endplate in this area. The gap provides a channel for osteoblast migration and blood vessel ingrowth, promoting long-term bone fusion, while reducing the compressive damage to high-density bone caused by rigid contact.

[0102] This invention uses zone-based differentiated contact area control to match the support force distribution of the anti-sinking ring with the bone density gradient of the endplate, ensuring that the high-density area bears more mechanical load, while the low-density area reduces the pressure per unit area through area compensation, resulting in a significant reduction in the overall stress peak compared to a uniform contact design. At the same time, reducing the contact area in the high-density area preserves micro-gaps, providing channels for osteoblast migration and vascularization, and accelerating the long-term bone fusion process.

[0103] Step S3: Based on the expected amount of cervical vertebrae to be removed from the target object, perform ACCF simulation resection on the three-dimensional vertebral model to obtain a simulated subtotal cervical vertebra resection model.

[0104] In practice, the ACCF simulated surgery is a simulated resection part of the ACCF procedure. Based on the expected amount of resection for the target object, the part of the vertebral body within the bilateral uncovertebral joints of the target cervical vertebral body is removed to obtain a decompression groove. The intervertebral disc between the target cervical vertebral body and the cervical vertebral bodies above and below it, as well as the corresponding anterior longitudinal ligament and posterior longitudinal ligament, are removed.

[0105] Step S4: Based on the subtotal cervical vertebra resection model and the model correction parameters, obtain the primary structural model of the anterior cervical titanium cage.

[0106] Specifically, step S4 includes:

[0107] Step S41: Based on the vertebral surfaces of the adjacent cervical vertebrae 4 above and below the target cervical vertebrae, construct an upper ear-shaped fixation plate model and a lower ear-shaped fixation plate model respectively.

[0108] In implementation, point cloud data of the anterior surface of the upper vertebral body in the subtotal cervical resection model are extracted, and the plane is fitted by least squares method to determine the reference plane of the upper ear-shaped fixation plate 311. A rectangular base plate is created on the reference plane. The upper fixing screw hole 3112 and the semi-circular upper weight reduction groove 3111 between the two screw holes are set on the rectangular base plate according to the preset size. The lower ear-shaped fixation plate 312 is constructed using the same method.

[0109] Understandably, the ear-shaped fixation plate is parallel to the anterior surface of the vertebral body, so that the axial direction of the screw hole is consistent with the direction of the principal stress of the cortical bone, thereby reducing the shear force of screw 5 and reducing the risk of screw 5 loosening.

[0110] Step S42: Construct an upper anti-sinking ring model based on the lower endplate of the adjacent cervical vertebra 4 above the target cervical vertebra, and construct a lower anti-sinking ring model based on the upper endplate of the adjacent cervical vertebra 4 below the target cervical vertebra.

[0111] Specifically, step S42 includes:

[0112] Step S421: Construct a first-level upper anti-sinking ring model that is completely fitted with the lower end plate, and a first-level lower anti-sinking ring model that is completely fitted with the upper end plate.

[0113] Specifically, in step S421, the position of the anti-sinking ring on the corresponding end plate is determined according to the depth adjustment parameters, so that the contour of the recessed area formed by the titanium cage skeleton body 1 and the ear-shaped fixing part is always located outside the esophageal motion envelope.

[0114] In practice, the implantation depth of the titanium cage skeleton body 1 is determined according to the depth adjustment parameter △H, and then the position of the anti-sinking ring on the corresponding end plate is determined; using the surface bonding tool of Geomagic Wrap, the initial anti-sinking ring surface is completely bonded to the exposed area of ​​the end plate (maximum gap ≤ 0.05mm) to obtain the first-level anti-sinking ring model.

[0115] Step S422: Calculate the ratio of the central hole area of ​​the first-level upper anti-sinking ring model and the first-level lower anti-sinking ring model to the larger area of ​​the upper end plate and the lower end plate; if the ratio is less than the ratio threshold, the central hole area is corrected so that the ratio of the central hole area to the corresponding end plate area is greater than or equal to the ratio threshold, thus obtaining the second-level upper anti-sinking ring model and the second-level lower anti-sinking ring model.

[0116] In implementation, the ratio threshold is based on clinical bone ingrowth efficiency studies, and preferably, it is set to 0.3. If the ratio of the central hole area in the primary anti-sinking ring model to the larger area of ​​the upper and lower endplates is less than the ratio threshold, the outer diameter of the anti-sinking ring is kept unchanged, and the inner diameter of the anti-sinking ring is increased in concentric circles. Preferably, the increase step size is 0.1 mm / time. After each expansion, the ratio of the central hole area to the corresponding endplate area in the primary anti-sinking ring model is recalculated until it is greater than or equal to the ratio threshold of 0.3, thus obtaining the secondary anti-sinking ring model.

[0117] Understandably, if the area of ​​the central hole is too small, the contact range between the cancellous bone particles inside the titanium cage skeleton body 1 and the endplate will be reduced, affecting the postoperative bone graft fusion effect.

[0118] Step S423: Detect abrupt regions in the secondary upper anti-sinking ring model and the secondary lower anti-sinking ring model where the curvature is greater than the curvature threshold;

[0119] In implementation, a 0.5mm × 0.5mm grid was divided on the surface of the secondary anti-sinking ring model, and the average curvature q of each node was calculated; the curvature abrupt change region was defined as the curvature difference Δq > 0.5mm between adjacent nodes. -1 Mark all mutation regions and generate a curvature-corrected heatmap.

[0120] Step S424: Perform curvature correction on the abrupt change region so that the corrected curvature is less than or equal to the curvature threshold, thereby obtaining the upper anti-sinking ring model and the lower anti-sinking ring model;

[0121] In implementation, the Laplacian operator smoothing algorithm (10 iterations, smoothing factor 0.7) is used for the abrupt change region to force the curvature gradient change rate to ≤0.5mm. -1 Thus, a three-level anti-sinking ring model was obtained.

[0122] Understandably, limiting and correcting the curvature of the anti-sinking ring model surface by using a curvature threshold can prevent the anti-sinking ring curvature mutation area from causing a cutting effect on the endplate cartilage during implantation; by using the Laplacian operator to perform a weighted average of the surface vertices, the matching with the endplate anatomical morphology can be preserved to the greatest extent while eliminating local curvature mutations.

[0123] Step S43: Based on the upper ear-shaped fixing plate model and the upper anti-sinking ring model, construct the upper connecting part model; based on the lower ear-shaped fixing plate model and the lower anti-sinking ring model, construct the lower connecting part model.

[0124] Step S44: Construct the main body model of the titanium cage skeleton based on the upper anti-sinking ring model and the lower anti-sinking ring model;

[0125] Step S45: Connect and merge the upper anti-sinking ring model, the lower anti-sinking ring model, the upper ear-shaped fixing plate model, the lower ear-shaped fixing plate model, the upper connecting part model, the lower connecting part model, and the titanium cage skeleton main body model to obtain the primary structure model.

[0126] Step S5: Perform ACCF simulation installation using the primary structural model, and adjust the primary structural model based on the simulated cervical spine installation model and the model correction parameters to obtain the secondary structural model;

[0127] Specifically, please refer to Figure 2 As shown, it is a cross-sectional schematic diagram of the anterior cervical titanium cage of the present invention during simulated installation. Step S5 includes:

[0128] Step S51: Simulate the internal fixation installation of ACCF surgery. Place the upper anti-sinking ring model, the lower anti-sinking ring model, and the titanium cage skeleton main body model from the primary structural model into the decompression groove, so that the anti-sinking ring fits against the corresponding cervical vertebral endplate. Then, fix the ear-shaped fixation plate model to the surface of the corresponding cervical vertebral body 4 with screws 5 to complete the ACCF simulation installation. The decompression groove is obtained by the target cervical vertebral body of the target object being removed in the ACCF simulation.

[0129] Specifically, in step S51, when the upper anti-sinking ring model, the lower anti-sinking ring model, and the titanium cage skeleton main body model in the primary structural model are placed into the decompression groove, the simulated normal contact stress between the upper anti-sinking ring model and the lower anti-sinking ring model and the cervical vertebral endplate is acquired in real time. If the simulated normal contact stress is greater than the stress safety threshold, the curvature of the corresponding anti-sinking ring is corrected so that the simulated normal contact stress between the corrected anti-sinking ring and the cervical vertebral endplate during the implantation process is less than or equal to the stress safety threshold.

[0130] In implementation, the primary structural model and the subtotal cervical spondylosis model data are imported into ANSYS software. The ANSYS Explicit Dynamics module is used to simulate the installation part of the ACCF procedure. Preferably, the titanium cage implantation speed is set to 2 mm / s to simulate the intraoperative percussion implantation process. The normal contact force between the anti-sinking ring and the endplate is monitored in real time. When the normal contact force is greater than the stress safety threshold, an early warning is triggered and the interference position is recorded. The stress safety threshold is based on the safety threshold of orthopedic percussion instruments, preferably 50 N.

[0131] In implementation, the location and curvature data of the interference region of the anti-sinking ring are extracted and imported into Solidworks software. The primary structural model is then modified to reduce the curvature of the anti-sinking ring's interference region. The specific formula for calculating the curvature reduction is as follows:

[0132] q 减小 =k×(F max -F);

[0133] Where, q 减小 The amount of curvature reduction is expressed in mm. -1 k is the interference adjustment coefficient, preferably 0.1; F max The peak value of the normal contact force at the interference location is expressed in N; F is the stress safety threshold, taken as 50 N.

[0134] The implantation process was re-simulated until the normal contact stress between the anti-sinking ring and the cervical vertebral endplate during the implantation process was always less than or equal to the stress safety threshold.

[0135] Understandably, the curvature correction at the interference position increases with the severity of the interference to avoid excessive correction that could reduce the fit between the anti-sinking ring and the final plate.

[0136] Step S52: Determine whether the contact area of ​​the upper anti-sinking ring model and the lower anti-sinking ring model in the primary structural model with the endplate corresponding to the cervical vertebra 4 in each of the partitions is less than the corresponding contact area threshold. If the contact area is less than the corresponding contact area threshold, then modify the surface of the corresponding partition of the anti-sinking ring so that the contact area is greater than or equal to the contact area threshold, and obtain the secondary structural model.

[0137] In implementation, the projected area of ​​the curved surface of the anti-sinking ring on each partition of the corresponding cervical vertebral endplate is determined. When the projected area is greater than or equal to 50% of the area of ​​the partition, the partition is determined to be an effective contact partition. It is then determined whether the contact area between the anti-sinking ring and the cervical vertebral endplate in each effective contact partition is greater than or equal to the corresponding contact area threshold. If the contact area is less than the corresponding contact area threshold, the curvature of the curved surface of the corresponding partition of the anti-sinking ring is corrected, and the contact area is recalculated until the contact area is greater than or equal to the contact area threshold. Preferably, when the contact area change rate is less than 2% after three consecutive corrections, or the total number of corrections is greater than 10, step S52 is terminated and the secondary structure model is output.

[0138] Step S6: Based on the secondary structure model, fabricate the anterior cervical titanium cage for the target object;

[0139] In practice, a laser selective melting 3D printer was used to process and manufacture the titanium cage for the anterior cervical spine of the target object.

[0140] 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 these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for adaptive fabrication of a cervical spine anterior approach titanium cage, characterized in that, The method comprises the following steps: Step S1, acquiring cervical vertebra CT data of a target object; Step S2, performing three-dimensional reconstruction on the cervical vertebra CT data to obtain a complete three-dimensional vertebral body model, and analyzing the cervical vertebra CT data and the complete three-dimensional vertebral body model to obtain model correction parameters, wherein a deformation trajectory of an esophagus in a swallowing action cycle is constructed based on the cervical vertebra CT data to obtain a minimum interval distance between an esophagus wall and a front edge of a titanium cage skeleton main body; a depth adjustment parameter is obtained according to the minimum interval distance and an expected resection amount of the target object; the upper endplate and the lower endplate are divided into a plurality of partitions according to the bone density distribution of the bony endplate, and the contact area threshold of the anti-sinking ring corresponding to the upper endplate and the lower endplate in each partition is calculated; Step S3, performing ACCF simulated resection on the three-dimensional vertebral body model based on the expected resection amount of the target cervical vertebra of the target object to obtain a cervical subtotal resection model after simulated resection; Step S4, obtaining a primary structure model of a cervical anterior titanium cage based on the cervical subtotal resection model and the model correction parameters; Step S5, performing ACCF simulated installation using the primary structure model, and adjusting the primary structure model based on the cervical installation model after simulated installation and the model correction parameters to obtain a secondary structure model; The step S5 comprises: Step S51, simulating internal fixation installation of ACCF surgery, placing the upper anti-sinking ring model, the lower anti-sinking ring model and the titanium cage skeleton main body model in the primary structure model into a decompression groove, making the anti-sinking ring fit the corresponding cervical vertebral body endplate, and then fixing the ear-shaped fixed plate model on the surface of the corresponding cervical vertebral body through a screw to complete the ACCF simulated installation, wherein the decompression groove is obtained by simulating resection of the target cervical vertebra of the target object; Step S52, judging whether the contact area of the upper anti-sinking ring model and the lower anti-sinking ring model in the primary structure model and the corresponding endplate of the cervical vertebral body in each partition is less than the corresponding contact area threshold, if the contact area is less than the corresponding contact area threshold, the corresponding partition of the corresponding anti-sinking ring is corrected to make the contact area greater than or equal to the contact area threshold, and the secondary structure model is obtained; Step S6, based on the secondary structure model, a cervical anterior titanium cage of the target object is manufactured; The cervical anterior titanium cage comprises a titanium cage skeleton main body, an anti-sinking ring arranged at both ends of the titanium cage skeleton main body and in contact with the endplate of the cervical vertebra, and an ear-shaped fixing part arranged at both ends of the titanium cage skeleton main body.

2. The method of adaptive fabrication of cervical spine anterior titanium cages according to claim 1, wherein, The cervical anterior titanium cage comprises: The anti-sinking ring is a hollow circular ring structure with a surface fitted to the bony endplate of the cervical vertebra, and the anti-sinking ring comprises an upper anti-sinking ring and a lower anti-sinking ring, the upper surface of the upper anti-sinking ring is fitted to the curved surface of the lower endplate of the bony endplate of the adjacent cervical vertebra above, and the lower surface of the lower anti-sinking ring is fitted to the curved surface of the upper endplate of the bony endplate of the adjacent cervical vertebra below; The titanium cage skeleton main body is a hollow columnar structure with a mesh, the upper end of the titanium cage skeleton main body is connected with the upper anti-sinking ring, and the lower end of the titanium cage skeleton main body is connected with the lower anti-sinking ring. The ear-shaped fixing part comprises an ear-shaped fixing plate and a connecting area, wherein the ear-shaped fixing plate comprises an upper ear-shaped fixing plate and a lower ear-shaped fixing plate respectively provided with screw holes and semicircular lightening grooves, and the connecting area comprises an upper connecting area and a lower connecting area; the upper ear-shaped fixing plate is connected with the upper anti-sinking ring through the upper connecting area and is parallel to the vertebral body surface of the upper adjacent cervical vertebra; and the lower ear-shaped fixing plate is connected with the lower anti-sinking ring through the lower connecting area and is parallel to the vertebral body surface of the lower adjacent cervical vertebra. The anti-sinking ring, the titanium cage framework main body, the connecting area and the ear-shaped fixing plate are integrally fixedly connected.

3. The method of claim 2, wherein, The step S2 comprises: Step S21, introducing the cervical vertebra CT data into a medical image control system for three-dimensional reconstruction and segmenting the vertebral body to obtain six segmented vertebral body models of C2-C7; Step S22, introducing each segmented vertebral body model into reverse engineering software for model optimization and conversion into a solid model; Step S23, introducing each solid model into three-dimensional design software to generate cancellous bone, cortical bone, bony endplate, posterior structure, intervertebral disc and ligament complex, and adjusting the cervical vertebra posture to the ACCF surgical posture to obtain the complete three-dimensional vertebral body model; Step S24, analyzing the cervical vertebra CT data and the complete three-dimensional vertebral body model to obtain the model correction parameter.

4. The method of adaptive fabrication of a cervical spine anterior titanium cage according to claim 3, wherein, In the step S2, the contact area threshold value is negatively correlated with the bone density of the bony endplate.

5. The method of adaptive fabrication of a cervical spine anterior titanium cage according to claim 4, wherein, The step S4 comprises: Step S41, constructing an upper ear-shaped fixing plate model and a lower ear-shaped fixing plate model according to the vertebral body surface of the upper adjacent cervical vertebra and the lower adjacent cervical vertebra near the esophagus side of the target cervical vertebra body; Step S42, constructing an upper anti-sinking ring model according to the lower endplate of the upper adjacent cervical vertebra of the target cervical vertebra body, and constructing a lower anti-sinking ring model according to the upper endplate of the lower adjacent cervical vertebra of the target cervical vertebra body; Step S43, constructing an upper connecting part model according to the upper ear-shaped fixing plate model and the upper anti-sinking ring model, and constructing a lower connecting part model according to the lower ear-shaped fixing plate model and the lower anti-sinking ring model; Step S44, constructing a titanium cage framework main body model according to the upper anti-sinking ring model and the lower anti-sinking ring model; Step S45, connecting and merging the upper anti-sinking ring model, the lower anti-sinking ring model, the upper ear-shaped fixing plate model, the lower ear-shaped fixing plate model, the upper connecting part model, the lower connecting part model and the titanium cage framework main body model to obtain the primary structure model.

6. The method of adaptive fabrication of a cervical spine anterior titanium cage according to claim 5, wherein, The step S42 comprises: Step S421, constructing a primary upper anti-sinking ring model completely fitted with the lower endplate, and a primary lower anti-sinking ring model completely fitted with the upper endplate; Step S422, calculating the ratio of the central hole area of the primary upper anti-sinking ring model and the primary lower anti-sinking ring model to the larger area of the upper endplate and the lower endplate; if the ratio is less than a ratio threshold value, the central hole area is corrected so that the ratio of the central hole area to the corresponding endplate area is greater than or equal to the ratio threshold value, to obtain a secondary upper anti-sinking ring model and a secondary lower anti-sinking ring model; Step S423, detecting a mutation region with a curvature greater than a curvature threshold in the secondary upper anti-sink ring model and the secondary lower anti-sink ring model; Step S424, performing curvature correction on the mutation region to make the corrected curvature less than or equal to the curvature threshold, to obtain the upper anti-sink ring model and the lower anti-sink ring model.

7. The method of adaptive fabrication of a cervical spine anterior titanium cage according to claim 6, wherein, In the step S421, according to the depth adjustment parameter, the position of the anti-sink ring on the corresponding endplate is determined, so that the invagination area profile formed by the titanium cage skeleton body and the ear-shaped fixing part is located outside the envelope surface of the esophageal deformation trajectory.

8. The method of adaptive fabrication of a cervical spine anterior titanium cage according to claim 7, wherein, In the step S51, when the upper anti-sink ring model, the lower anti-sink ring model and the titanium cage skeleton body model in the primary structure model are put into the decompression groove, the simulated normal contact stress of the upper anti-sink ring model and the lower anti-sink ring model with the cervical vertebral body endplate is respectively acquired in real time, and if the simulated normal contact stress is greater than a stress safety threshold, curvature correction is performed on the corresponding anti-sink ring, so that the simulated normal contact stress between the corrected anti-sink ring and the cervical vertebral body endplate in the implantation process is less than or equal to the stress safety threshold.

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