Method and system for determining implantation point and channel of sacroiliac screw

Abstract

The invention belongs to the field of auxiliary medical treatment, and provides a sacroiliac screw implantation point and channel determination method and system, and the method comprises the steps: constructing a bone structure three-dimensional model containing the sacrum and the ilium; in the three-dimensional model, based on the fracture type and the bone condition of the patient, an implantation point of a screw is selected in the sacrum S1 centrum trailing edge area, and the implantation point is located on the outer side of sacrum cortex and close to the sacroiliac joint trailing edge; in the three-dimensional model, a cross section containing the implantation point is selected as a plane where an implantation channel is located, and the cross section is an image plane perpendicular to the long axis of the body of the patient and serves as a space projection plane of the implantation channel; in the three-dimensional model, a screw path penetrating through the sacrum body or the sacroiliac joint area is constructed, the included angle between the implantation channel path and the coronal plane of the patient is measured, the included angle is used for controlling the front-back inclination degree of the screw implantation direction, and the implantation point, the cross section and the included angle jointly define a three-dimensional channel of the sacroiliac screw.

Description

Technical Field

[0001] The present invention belongs to the field of auxiliary medical treatment, and in particular relates to a method and system for determining an insertion point and a channel of a sacroiliac screw. Background Art

[0002] Sacroiliac screw fixation has been widely used to treat brittle pelvic fractures in the elderly, particularly for minimally invasive stabilization of sacral wing fractures. Because elderly patients often suffer from osteoporosis and fractures often present with multiple fissures and complex cross-sections, traditional fixation methods struggle to achieve both safety and minimal invasiveness while maintaining strong fixation. Rommens et al. have proposed that a transsacral screw approach should be used whenever possible, traversing the entire sacral body or at least the sacroiliac joint region to provide support in the contralateral region with concentrated bone density and enhance the implant's holding power.

[0003] However, existing preoperative sacroiliac screw design relies heavily on surgeon experience and lacks a standardized parameter system, leading to significant inter-surgeon variability. Frequent intraoperative fluoroscopic verification increases radiation risk, and deviations in the guide needle path often lead to serious complications such as screw extrusion and nerve damage. Therefore, establishing a scientific and repeatable three-dimensional path design method has become a key technical bottleneck in improving the safety and success rate of sacroiliac screw placement. Summary of the Invention

[0004] In order to solve the problems in the prior art, the present invention provides a method for determining the insertion point and channel of a sacroiliac screw, comprising the following steps: Obtain computed tomography images of the patient's sacroiliac region and import them into 3D medical imaging processing software to construct a 3D model of the bony structure including the sacrum and ilium. In the three-dimensional model, based on the patient's fracture type and bone condition, the screw insertion point is selected in the posterior margin of the sacral S1 vertebral body. The insertion point is located outside the sacral cortex and close to the posterior margin of the sacroiliac joint. In the three-dimensional model, a cross section including the insertion point is selected as the plane where the insertion channel is located, and the cross section is an image plane perpendicular to the long axis of the patient's torso, which serves as the spatial projection plane of the insertion channel; In the three-dimensional model, a screw path passing through the sacral body or sacroiliac joint area is constructed, and the angle between the insertion channel path and the patient's coronal plane is measured. The angle is used to control the anterior-posterior tilt of the screw insertion direction. The insertion point, the cross section and the angle together define the three-dimensional channel of the sacroiliac screw.

[0005] Furthermore, the step of selecting a screw insertion point in the posterior region of the sacrum S1 vertebral body specifically includes: Using the sectioning tool in the 3D model to generate multi-angle views of the S1 vertebra, multiple candidate screw insertion points were determined based on the fracture line shape and bone density distribution information. At each candidate point, a safe area with intact bone cortex, bone density greater than the set threshold, no more than 5 mm from the posterior edge of the sacroiliac joint, and avoiding the neural foramen was selected; Mark the points that meet the conditions as candidate points and record their three-dimensional coordinates; The nail insertion path is preliminarily simulated according to the direction of the channel, and the optimal point is selected as the insertion point.

[0006] Furthermore, the step of selecting a screw insertion point in the posterior region of the sacrum S1 vertebral body further includes: A candidate point set of the lattice structure is established in the three-dimensional model, and a unit perturbation force is applied to each candidate point to simulate the bone structure response during the screw insertion process; Based on the finite element analysis results, the strain energy density distribution caused by the disturbance force is calculated, and the stress path starting from each candidate point is extracted; Integrate the stress gradient along the path to form a path response scoring function; The candidate point with the highest score is selected from all candidate points as the response focal point, and the response focal point is used as the screw insertion point.

[0007] Furthermore, the step of selecting the cross section containing the insertion point as the surface where the channel is located includes: Constructing a cross section perpendicular to the long axis of the trunk and fixed at the height of the three-dimensional coordinates of the insertion point according to the three-dimensional coordinates of the insertion point; Extracting the bone tissue contours of the sacrum and ilium intersecting therewith in the cross section; Drawing a channel projection path on the cross section and calculating its two-dimensional direction angle and path length; The two-dimensional path is used to reflect the three-dimensional movement, which serves as the design basis for intraoperative C-arm rotation or guide positioning.

[0008] Furthermore, the steps of constructing a screw path through the sacral body or sacroiliac joint region and measuring the angle between the insertion channel path and the patient's coronal plane include: Connect the insertion point and the target end point in the three-dimensional model to construct a complete screw channel path; Setting the coronal plane as a reference plane perpendicular to the patient's anterior-posterior direction, and extracting the vector of the coronal plane normal; The angle between the path direction and the coronal plane was calculated using the vector angle calculation formula to quantify the inclination angle of the screw in the anterior-posterior direction.

[0009] Another aspect of the present invention provides a system for determining the insertion point and channel of a sacroiliac screw, comprising the following modules: An image acquisition and modeling module is used to acquire a computed tomography image of the patient's sacroiliac region and import the image into a three-dimensional medical imaging processing software to construct a three-dimensional model of the bone structure including the sacrum and ilium; an insertion point determination module, configured to select a screw insertion point in the posterior margin of the sacral S1 vertebra in the three-dimensional model based on the patient's fracture type and bone quality, wherein the screw insertion point is located outside the sacral cortex and close to the posterior margin of the sacroiliac joint; a channel plane identification module, configured to select a cross section containing the insertion point as the plane where the insertion channel is located, wherein the cross section is an image plane perpendicular to the long axis of the patient's torso and serves as the spatial projection plane of the insertion channel; a path generation module for constructing a screw path through the sacral body or sacroiliac joint region and measuring the angle between the insertion channel path and the patient's coronal plane; A path output module is used to output the insertion point, the cross section and the angle together to define a three-dimensional insertion channel for the sacroiliac screw.

[0010] Furthermore, the insertion point determination module includes: The candidate point screening submodule is used to determine multiple candidate screw insertion points located at the posterior edge of the S1 vertebra based on the fracture line shape and bone density distribution information; The condition judgment submodule is used to select candidate points with intact bone cortex, bone density greater than the set threshold, no more than 5 mm from the posterior edge of the sacroiliac joint, and avoiding the neural foramen; The coordinate recording submodule is used to mark the selected candidate points and record their three-dimensional coordinates; The path fitting submodule is used to simulate the channel direction and select the optimal point as the insertion point based on the channel fitness.

[0011] Furthermore, the insertion point determination module includes: The response simulation submodule is used to establish a set of candidate points in the 3D model and apply a unit perturbation force to each point to simulate the mechanical response of the bone structure when the screw is inserted; The stress calculation submodule is used to calculate the strain energy density distribution generated by the disturbance force based on the finite element analysis results and extract the stress path corresponding to each point; The scoring function construction submodule is used to integrate the stress gradient in the path and generate the path response scoring function; The maximum score selection submodule is used to screen the response focal point with the highest score among all candidate points, and use the response focal point as the insertion point of the sacroiliac screw.

[0012] Furthermore, the channel surface identification module includes: A surface construction submodule, configured to construct a cross-section perpendicular to the long axis of the patient's trunk and fixed at the height of the three-dimensional coordinates of the insertion point according to the three-dimensional coordinates of the insertion point; A contour extraction submodule, configured to extract the bone tissue contours of the sacrum and ilium intersecting therewith in the cross section; a channel projection submodule, for drawing a two-dimensional projection path of the channel on the cross section and calculating its two-dimensional direction angle and path length; The intraoperative docking submodule is used to use the two-dimensional path for intraoperative C-arm angle rotation setting or guide positioning design.

[0013] Furthermore, the path generation module includes: A three-dimensional channel construction submodule is used to generate a complete screw channel path based on the spatial connection between the insertion point and the target end point; An angle calculation submodule, used to set the coronal plane as a reference plane perpendicular to the patient's anterior-posterior direction and extract the normal vector of the coronal plane; The angle measurement submodule is used to obtain the inclination angle of the path in the anterior-posterior direction according to the angle calculation formula between the path direction vector and the coronal plane normal vector.

[0014] The present invention provides a method and system for determining the insertion point and channel of a sacroiliac screw. Based on three-dimensional image reconstruction and structural response simulation, a parameterized path modeling method of one point, one surface, and one corner is proposed, and a disturbance force field simulation and bone stress path inversion mechanism are introduced to realize the visualization, quantification, and personalized determination of the sacroiliac screw insertion path.

[0015] Compared with the prior art, the present invention has the following beneficial effects: Through the combined definition of the entry point, cross section and spatial angle, a complete three-dimensional path control framework is formed to improve path stability and avoid the risk of nerve foramen crossing.

[0016] In one improvement, a strain energy density inversion algorithm is used to determine the response focal point as the insertion point, combined with high bone density area modeling to improve the success rate of one-time guide needle insertion.

[0017] The output parameters can be directly connected to C-arm fluoroscopy, 3D printing guides or navigation robots, and have good surgical versatility and engineering scalability.

[0018] Frequent intraoperative angle adjustments and fluoroscopic confirmation are no longer necessary, significantly reducing cumulative X-ray exposure time and improving patient and medical staff safety. The path model provided by this invention can be stored as a standard digital parameter set, enabling multi-center path replication, postoperative path evaluation, and data accumulation, facilitating the construction of future surgical databases.

[0019] Therefore, the present invention not only achieves significant improvements in anatomical matching and surgical safety, but also provides a technical foundation for minimally invasive pelvic fixation technology with structural optimization, response drive, and precise path determination. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 is a flow chart of the method of the present invention;

[0022] Figure 2 It is a system block diagram of the present invention. DETAILED DESCRIPTION

[0023] Below, the invention is preferably described with reference to the accompanying drawings and specific embodiments.

[0024] This embodiment solves the above problem through the following steps:

[0025] In one embodiment, reference Figure 1 The present invention provides a method for determining the insertion point and channel of a sacroiliac screw. By obtaining medical imaging data of the patient's sacroiliac region before surgery, combined with three-dimensional reconstruction and spatial geometric analysis, based on the comprehensive design principles of insertion point selection, cross-sectional projection determination, and channel angle control, the method clarifies the screw insertion position, implantation direction, and spatial shape. The method aims to improve the individualization, standardization, and safety of the screw channel design, achieve one-time accurate insertion of the guide needle, and effectively avoid the neural foramen and bone cortical boundary. The method is suitable for minimally invasive screw fixation operations in elderly patients with brittle pelvic fractures or sacroiliac joint injuries. The method specifically includes the following steps:

[0026] Step S1: Obtain a computed tomography image of the patient's sacroiliac region and import it into a three-dimensional medical image processing software to construct a three-dimensional bone structure model including the sacrum and ilium.

[0027] Before performing sacroiliac screw implantation, the patient's sacral and iliac anatomy, fracture type, bone quality, and spatial position must be precisely understood. Traditional two-dimensional X-ray imaging fails to capture the complex three-dimensional structure of the sacroiliac region, which can easily lead to screw placement deviation or perforation, increasing the risk of complications such as nerve damage.

[0028] To this end, by acquiring high-resolution computed tomography (CT) images and reconstructing them using professional three-dimensional medical image processing software, a complete three-dimensional bone structure model personalized for the patient can be obtained, providing accurate, intuitive, and quantifiable anatomical basis for subsequent insertion point selection, channel path planning, and intraoperative navigation.

[0029] In the present invention:

[0030] Computed tomography images (CT images) are cross-sectional images of the human body obtained by scanning the body with an X-ray beam. They have high spatial resolution and can distinguish bone tissues of different densities. They are often used for three-dimensional reconstruction in orthopedics.

[0031] Three-dimensional medical image processing software refers to software that can read, reconstruct, segment, and model DICOM format images, such as Mimics, 3D Slicer, Materialise, Amira, etc., and supports three-dimensional visualization and quantitative measurement of bone tissue structure.

[0032] A three-dimensional bone structure model is a digital model that reconstructs the original two-dimensional CT slice image into a three-dimensional spatial entity and is used to truly reflect information such as bone shape, position, and bone density distribution.

[0033] In a specific implementation, step S4 includes two stages: an image acquisition stage and a three-dimensional modeling stage, which are implemented as follows:

[0034] Image acquisition stage

[0035] S11: Use multi-slice spiral CT to perform continuous thin-slice scans of the patient's sacroiliac region (recommended slice thickness ≤ 1 mm), covering the S1-S3 vertebrae and bilateral iliac bones;

[0036] S12: saving the obtained image data as a DICOM format file;

[0037] S13: Check the image for artifacts, occlusions, slice shifts, and other abnormalities to ensure that the image quality meets reconstruction requirements.

[0038] 2. 3D modeling stage (using Mimics software as an example)

[0039] S14: Import DICOM images into Mimics project;

[0040] S15: Use the threshold segmentation module to perform preliminary separation of the image grayscale and set the bone tissue grayscale threshold range (e.g., CT value > 226 HU);

[0041] S16: Use the mask editing module to erase irrelevant tissues in the non-sacroiliac region and retain the complete sacral and iliac structures;

[0042] S17: Use the region growing module to connect the target bone region into a closed structure;

[0043] S18: Generate a 3D bone model with a triangular mesh (STL format) using the 3D reconstruction module;

[0044] S19: Export the model for subsequent channel planning, simulated nail placement, and intraoperative navigation design.

[0045] Establishing a patient-specific three-dimensional bone structure model through CT images can achieve complete, continuous, and quantitative spatial analysis of the sacroiliac region, greatly improving the accuracy and personalization of channel design, avoiding the occlusion and misjudgment of deep structures by traditional two-dimensional evaluation methods, supporting seamless integration with intraoperative navigation systems, and assisting in the design of 3D guides for precise screw placement.

[0046] Step S2: In the three-dimensional model, based on the patient's fracture type and bone condition, a screw insertion point is selected in the posterior region of the sacral S1 vertebra. The insertion point is located outside the sacral cortex and close to the posterior edge of the sacroiliac joint.

[0047] The placement point of sacroiliac screws is a key factor in determining the success and safety of the screw channel. Located in the posterior cortical region of the S1 vertebral body, this point must meet two core clinical objectives: first, providing sufficient cortical bone support to enhance initial screw stability; second, avoiding high-risk anatomical structures such as the sacral foramen and spinal canal to minimize the risk of intraoperative complications.

[0048] Furthermore, selecting an area near the posterior edge of the sacroiliac joint facilitates screw insertion across the fracture line or the sacroiliac joint, thereby achieving stable fixation of the fracture end or joint. Furthermore, tailoring a personalized screw insertion strategy based on the patient's fracture type and bone quality can improve fixation effectiveness, extend implant life, and avoid issues such as screw loosening, screw penetration, and fracture reduction failure associated with traditional fixation methods.

[0049] In the present invention:

[0050] The S1 vertebra refers to the first vertebra in the upper part of the sacrum. It is the most common segment for sacroiliac screw placement and has the largest bone volume and clearer anatomical landmarks.

[0051] The lateral sacral cortex refers to the cortical bone layer on the lateral surface of the posterior edge of the sacrum S1. It is an area with high bone density and the strongest support, and is suitable for nail insertion.

[0052] The sacroiliac joint is the connecting structure between the sacrum and the ilium. Its posterior edge is located in the area accessible during surgery. Inserting screws through this area can achieve cross-joint stabilization.

[0053] Fracture type and bone quality are used to determine whether screw placement should cross the fracture line or avoid low-density areas. Fracture types include sacral wing fractures and sacroiliac separation; bone quality includes the degree of osteoporosis and bone density distribution.

[0054] In one implementation method, the specific implementation of step S2 includes:

[0055] S211: In the constructed 3D model, use the sectioning tool to generate multi-angle visual views of the sacrum S1 segment, including: lateral view, axial view, and 3D rotation view.

[0056] S212: Analyze the fracture line shape, mark the fracture edge and unstable area, and use the "bone density mapping tool" to mark the high-density area in green and the low-density area in red or transparent.

[0057] S213: Find a location on the posterior cortical bone of the S1 vertebra that meets the following conditions as a candidate screw insertion point:

[0058] The bone cortex is intact and without breaks;

[0059] Bone density ≥ set threshold (such as CT value > 600 HU);

[0060] Located ≤5 mm from the posterior edge of the sacroiliac joint;

[0061] Keep away from the neuroforamen imaging marker line.

[0062] S214: Record the three-dimensional coordinates of the point (x0, y0, z0) in the software and mark it as "nail entry point P0"; perform spatial visualization simulation in conjunction with the preliminary setting of the channel direction.

[0063] By integrating 3D anatomy, fracture morphology, and bone density distribution, personalized screw entry point planning ensures sufficient cortical support at the selected insertion point while avoiding intraoperative damage to the sacral nerve, perforation of the cortical bone, or deviation from the target fracture repair path. Leveraging structural models and multi-dimensional parameter control mechanisms, entry point selection becomes more scientific, visual, and quantifiable, laying the anatomical and biomechanical foundation for screw channel construction, improving both the intraoperative one-time puncture success rate and the long-term stability of the implant.

[0064] Traditional methods for determining sacroiliac screw insertion points rely primarily on imaging observations, bone density distribution, or surgeon experience, essentially based on static morphological matching of anatomical structures. However, these methods ignore the local stress perturbation response of bone tissue during screw implantation, which is often the key factor determining implant path stability, long-term fixation effectiveness, and fracture healing quality.

[0065] To this end, one implementation of step S2 moves beyond the static image analysis paradigm and introduces a mechanical function induction concept: the screw placement behavior is abstracted as a unit perturbation force acting on the bone surface. Finite element analysis is then used to simulate the stress conduction trends within the bone tissue at different candidate points under the perturbation. A small perturbation force is applied to multiple candidate points, and the strain energy propagation path of the force within the bone tissue is observed. Perturbation points with long paths, continuous stress accumulation, and significant force concentration indicate that the bone tissue has a "good mechanical flux response" in that direction. These points are areas of bone tissue that are naturally more likely to form mechanical channels and, from a functional perspective, are the most suitable locations for screw placement. This method does not rely on bone density, thresholds, image contrast, or segmentation algorithms. Instead, it utilizes a structure-function inversion mechanism to identify "actively responsive high-throughput regions" in the bone tissue, shifting placement point selection from anatomical appearance to a mechanically optimal choice driven by functional response.

[0066] Specifically, the steps include:

[0067] S221: Create a set of candidate insertion points in the 3D model , its composition is based on a spatial dot grid arrangement, covering the target area.

[0068] Specifically:

[0069] For the reconstructed sacrum model (STL format), closed repair and mesh resampling were first performed to homogenize the surface triangular facets (recommended side length 1 mm).

[0070] The Meshgrid algorithm was used to generate a three-dimensional grid in the S1 posterior cortical area. The normal distance between them and the model surface is about 2 mm.

[0071] Set the boundary range of the dot matrix area:

[0072] Left and right borders: Starting from the medial edge of the sacroiliac joint, extend inward 15 mm;

[0073] Upper and lower boundaries: including the upper and lower edges of the S1 vertebral body, each extended by 5 mm;

[0074] Perpendicular to the normal direction: extends only 1-2 mm on the outer surface of the cortex.

[0075] S222: For each point A virtual perturbation force is applied separately to simulate the mechanical response of the screw when it is pressed in.

[0076] Specifically:

[0077] At each point Apply a size of The directional load is perpendicular to the normal direction of the model surface and points to the inside of the cone.

[0078] The linear static finite element model is used for solution.

[0079] The material properties of the sacrum model can be set to an isotropic simplified model:

[0080] elastic modulus , Poisson's ratio ;

[0081] The constraints are set as:

[0082] The sacral base plane was set to be fixed;

[0083] Use free boundaries for the iliac junction area to avoid excessive rigidity;

[0084] Use platforms such as Abaqus / COMSOL / ANSYS, or build your own Python-FEM framework to complete the solution.

[0085] It is recommended to use tetrahedral elements for meshing, and the average element size should be controlled at around 1 mm.

[0086] S223: Calculate each disturbance point The resulting three-dimensional structural response forms an energy distribution map inside the bone.

[0087] Specifically:

[0088] After the solution is completed, the strain energy density of all mesh elements in the target domain is extracted:

[0089]

[0090] in:

[0091] represents the element strain tensor;

[0092] Represents the bone tissue elastic matrix (can be a 6×6 matrix);

[0093] It represents the elastic strain energy per unit volume, in J / mm³.

[0094] All Mapped to a three-dimensional scalar field and visualized as a density cloud.

[0095] Step S224: From the disturbance point Construct a three-dimensional conductive path along the stress gradient direction

[0096] Specifically:

[0097] Compute the gradient field of strain energy density in a 3D scalar field:

[0098]

[0099] Use numerical integration methods (such as Runge-Kutta 4th order) starting from the perturbation point and along Direction extension forms a straight path , until the energy density drops to 10% of the initial value or the path length reaches the preset length;

[0100] Each path records information such as node position, curvature, and traversed unit volume for subsequent flux evaluation.

[0101] Step S225: Comprehensively score the path corresponding to each point and select the nail entry point with the most concentrated mechanical response of the bone structure.

[0102] Define the path scoring function:

[0103]

[0104] in:

[0105] It indicates that the stress conduction flow is strong;

[0106] Represents the length of the path element, and the integration range is the entire path;

[0107] Represents the focus strength score, with higher values ​​indicating stronger and more continuous path response.

[0108] Select the point with the highest score among all candidate points:

[0109]

[0110] This point was set as the final sacroiliac screw insertion point.

[0111] This method breaks away from the conventional thinking of image threshold segmentation and bone density screening. Instead, it employs an inversion method based on a perturbation force-response mechanism to determine the insertion point. By simulating the stress response of bone tissue to screw insertion force, it can identify the most natural force flow entrance in bone tissue. This method better aligns with the principle of mechanical matching between implant and host tissue, facilitating long-term stable fixation. Furthermore, it completely does not rely on tissue segmentation, bone density CT value setting, or empirical anatomical comparison, thus avoiding segmentation errors and threshold ambiguity, and possesses greater adaptability and model robustness.

[0112] Step S3: In the three-dimensional model, a cross section including the insertion point is selected as the channel surface, wherein the cross section is an image plane perpendicular to the long axis of the patient's trunk and serves as the spatial projection plane of the insertion channel.

[0113] The design of the screw channel must have a clear three-dimensional spatial positioning structure, and the surgical operation is ultimately completed in a two-dimensional fluoroscopic or three-dimensional navigation system. Therefore, projecting the three-dimensional path onto a visual and measurable plane is an important bridge between preoperative design and intraoperative guidance.

[0114] Selecting a cross-section perpendicular to the long axis of the trunk as the channel plane has anatomical consistency and engineering simplicity: first, the cross-section is approximately parallel to the ground and perpendicular to the patient's anatomical configuration, and has a stable spatial reference property; second, the cross-section is coplanar with the aforementioned insertion point and can naturally carry the projection of the starting end of the screw path, so the two-dimensional channel direction, angle, width, path curvature and other parameters can be constructed on this plane.

[0115] By selecting such a cross-section as the projection plane in the three-dimensional model, the spatial slope and rotation angle of the insertion path can be converted into two-dimensional controllable geometric parameters, providing an accurate reference basis for subsequent path extension, screw angle adjustment and intraoperative guidance (such as C-arm rotation angle setting, surgical guide opening direction, etc.).

[0116] In a specific implementation, step S3 includes:

[0117] S31: Obtaining the determined insertion points in the 3D bone structure model The spatial coordinates of .

[0118] S32: Construct the anatomical coordinate system according to the patient's anatomical posture (supine position, pelvic neutral position):

[0119] Z axis: long axis of the patient's torso (cranial and caudal);

[0120] X axis: left and right direction;

[0121] Y axis: front-to-back direction.

[0122] S33: Build includes Cross section , which is defined as:

[0123]

[0124] This plane is perpendicular to the long axis of the torso and is fixed at the z-coordinate of the insertion point.

[0125] S34: A cross-section of the model data is captured on the plane, and the bone structure contour intersecting the plane is extracted as a preoperative two-dimensional planning view.

[0126] S35: In In the plane, draw the two-dimensional projection path of the screw channel:

[0127] Starting point The end point was set close to the contralateral S1 bone density area or the iliac inlet;

[0128] Path bearing Indicates the angle between the channel and the coronal plane.

[0129] S36: Calculate the length of the path within the cross section , path projection angle :

[0130]

[0131]

[0132] Step S3 provides a unified control platform for both operational and structural dimensions by projecting the path into the three-dimensional space onto a cross-section consistent with the patient's anatomy. This not only facilitates the surgeon's understanding of the path's shape on a two-dimensional image, but also facilitates the use of path parameters for navigation system calibration, guide plate design, or C-arm rotation angle setting. Furthermore, this cross-section exhibits anatomical stability, with minimal variability between patients. This significantly improves the repeatability of path planning and intraoperative control accuracy, making it particularly suitable for robotic-assisted surgery and multicenter standardized path design.

[0133] Step S4, in the three-dimensional model, construct a screw path passing through the sacrum body or sacroiliac joint area, and measure the angle between the channel path and the patient's coronal plane. The angle is used to control the anterior-posterior tilt of the screw placement direction. The insertion point, the cross section, and the angle together define the three-dimensional channel of the sacroiliac screw.

[0134] The preoperative path design for sacroiliac screws must not only ensure continuity and feasibility within the bone tissue but also ensure that the direction of the path is compatible with the anatomy of the sacrum and ilium and intraoperative operability. In clinical practice, the screw path must not only enter from the posterior edge of the S1 vertebral body but also traverse the sacral body or sacroiliac joint region at a specific angle and terminate in the contralateral bone-rich area to ensure good biomechanical fixation.

[0135] To this end, the inclination angle of the path in three-dimensional space must be clearly defined, especially the angle with the human coronal plane (anteroposterior direction), which will directly affect the intraoperative C-arm X-ray projection angle, guide needle insertion direction, and navigation control strategy.

[0136] Therefore, by constructing a complete path in the three-dimensional model and calculating the angle between the path and the coronal plane, the path can be upgraded from a straight line connection to a spatial directional channel, realizing quantitative control, precise adjustment and intraoperative reproduction of the path direction, and at the same time forming a complete three-dimensional path control system with the insertion point (spatial starting point) and the cross-section (directional projection plane).

[0137] In a specific implementation, step S4 includes:

[0138] S41: Constructing the initial path line

[0139] In the 3D reconstruction model, the insertion points selected in the previous steps are used , determine the starting point of the channel;

[0140] Combine the patient's fracture line direction and high bone density area to select the target endpoint in the model , or use the aforementioned mechanical function induction method to select a path to ensure that the path passes through the S1 vertebral body or sacroiliac joint area;

[0141] Represent this path as a space vector:

[0142]

[0143] S42: Define the coronal reference direction

[0144] In the patient’s local coordinate system, the coronal plane is set as the reference plane perpendicular to the Y axis (i.e., the X𝑍 plane, such as the ground or bed surface);

[0145] The coronal plane normal vector is set as:

[0146]

[0147] S43: Calculate the angle between the path and the coronal plane

[0148] Calculate the angle between the path direction and the coronal plane normal vector :

[0149]

[0150] in:

[0151] represents the path vector;

[0152] represents the coronal plane normal vector;

[0153] Represents the vector modulus;

[0154] It is the deviation angle of the path in the front-back direction (usually controlled between 10° and 45°).

[0155] The final parameters determined include:

[0156] Starting point coordinates, end point coordinates, path length, angle with the coronal plane, and projection angle in the transverse plane.

[0157] This parameter set can be directly used for navigation system call, 3D guide channel design, or intraoperative C-arm projection angle adjustment reference.

[0158] This step constructs a complete 3D path and incorporates the calculation of the spatial angle with the coronal plane. This not only achieves precise control of the path direction but also elevates the path design process from linear connection to spatial geometric constraint modeling, providing data support for precise intraoperative guidance. Furthermore, this angle parameter can be used in a variety of scenarios, including robotic arm navigation, C-arm rotation presets, intraoperative drilling direction control, and guide plate angle design, seamlessly integrating preoperative path planning with intraoperative execution.

[0159] Using the aforementioned method, the preoperative imaging data were reconstructed into a three-dimensional model, and the following ternary parameter system was constructed based on this:

[0160] One point: the insertion point, located at the posterior cortex of the S1 vertebral body, is the starting point of the screw channel;

[0161] One side: the cross section of the channel, which is a two-dimensional reference surface perpendicular to the long axis of the trunk and containing the insertion point;

[0162] Angle: The angle between the screw path and the coronal plane, which is used to define the degree of screw inclination in the anterior-posterior direction.

[0163] Through this method, the abstract "path" is transformed into a spatially oriented structure determined by these three parameters.

[0164] See also Figure 2 In another embodiment, the present invention further provides a system for determining the insertion point and channel of a sacroiliac screw, comprising:

[0165] An image acquisition and modeling module is used to acquire a computed tomography image of the patient's sacroiliac region and import the image into a three-dimensional medical imaging processing software to construct a three-dimensional model of the bone structure including the sacrum and ilium;

[0166] an insertion point determination module, configured to select a screw insertion point in the posterior margin of the sacral S1 vertebra in the three-dimensional model based on the patient's fracture type and bone quality, wherein the screw insertion point is located outside the sacral cortex and close to the posterior margin of the sacroiliac joint;

[0167] a channel plane identification module, configured to select a cross section containing the insertion point as the plane where the insertion channel is located, wherein the cross section is an image plane perpendicular to the long axis of the patient's torso and serves as the spatial projection plane of the insertion channel;

[0168] a path generation module for constructing a screw path through the sacral body or sacroiliac joint region and measuring the angle between the insertion channel path and the patient's coronal plane;

[0169] A path output module is used to output the insertion point, the cross section and the angle together to define a three-dimensional insertion channel for the sacroiliac screw.

[0170] In a further implementation, the insertion point determination module includes:

[0171] The candidate point screening submodule is used to determine multiple candidate screw insertion points located at the posterior edge of the S1 vertebra based on the fracture line shape and bone density distribution information;

[0172] The condition judgment submodule is used to select candidate points with intact bone cortex, bone density greater than the set threshold, no more than 5 mm from the posterior edge of the sacroiliac joint, and avoiding the neural foramen;

[0173] The coordinate recording submodule is used to mark the selected candidate points and record their three-dimensional coordinates;

[0174] The path fitting submodule is used to simulate the channel direction and select the optimal point as the insertion point based on the channel fitness.

[0175] In a further implementation, the insertion point determination module includes:

[0176] The response simulation submodule is used to establish a set of candidate points in the 3D model and apply a unit perturbation force to each point to simulate the mechanical response of the bone structure when the screw is inserted;

[0177] The stress calculation submodule is used to calculate the strain energy density distribution generated by the disturbance force based on the finite element analysis results and extract the stress path corresponding to each point;

[0178] The scoring function construction submodule is used to integrate the stress gradient in the path and generate the path response scoring function;

[0179] The maximum score selection submodule is used to screen the response focal point with the highest score among all candidate points, and use the response focal point as the insertion point of the sacroiliac screw.

[0180] In a further implementation, the channel surface identification module includes:

[0181] A surface construction submodule, configured to construct a cross-section perpendicular to the long axis of the patient's trunk and fixed at the height of the three-dimensional coordinates of the insertion point according to the three-dimensional coordinates of the insertion point;

[0182] A contour extraction submodule, configured to extract the bone tissue contours of the sacrum and ilium intersecting therewith in the cross section;

[0183] a channel projection submodule, for drawing a two-dimensional projection path of the channel on the cross section and calculating its two-dimensional direction angle and path length;

[0184] The intraoperative docking submodule is used to use the two-dimensional path for intraoperative C-arm angle rotation setting or guide positioning design.

[0185] In a further implementation, the path generation module includes:

[0186] A three-dimensional channel construction submodule is used to generate a complete screw channel path based on the spatial connection between the insertion point and the target end point;

[0187] An angle calculation submodule, used to set the coronal plane as a reference plane perpendicular to the patient's anterior-posterior direction and extract the normal vector of the coronal plane;

[0188] The angle measurement submodule is used to obtain the inclination angle of the path in the anterior-posterior direction according to the angle calculation formula between the path direction vector and the coronal plane normal vector.

[0189] It should be noted that the explanation of the aforementioned embodiment of the method for determining the insertion point and channel of the sacroiliac screw is also applicable to the device of the embodiment of the present application and will not be repeated here.

[0190] Those skilled in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented using a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0191] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0192] In the several embodiments provided in this application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of this application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), magnetic disk or optical disk, and other media that can store program code.

[0193] The above is only a specific embodiment of the present application. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in this application, which should be included in the scope of protection of this application. For some module structures that are not particularly clear in the present invention, the content recorded in the prior art shall prevail. The prior art mentioned in the above background technology section and the specific embodiment section of the present invention can be regarded as part of the present invention and is used to understand the meaning of some technical features or parameters.

Claims

1. A method for determining the insertion point and channel of a sacroiliac screw, characterized in that: The steps include: Obtain computed tomography images of the patient's sacroiliac region and import them into 3D medical imaging processing software to construct a 3D model of the bony structure including the sacrum and ilium. In the three-dimensional model, based on the patient's fracture type and bone condition, the screw insertion point is selected in the posterior margin of the sacral S1 vertebral body. The insertion point is located outside the sacral cortex and close to the posterior margin of the sacroiliac joint. In the three-dimensional model, a cross section including the insertion point is selected as the plane where the insertion channel is located, and the cross section is an image plane perpendicular to the long axis of the patient's torso, which serves as the spatial projection plane of the insertion channel; In the three-dimensional model, a screw path passing through the sacral body or sacroiliac joint area is constructed, and the angle between the insertion channel path and the patient's coronal plane is measured. The angle is used to control the anterior-posterior tilt of the screw insertion direction. The insertion point, the cross section and the angle together define the three-dimensional channel of the sacroiliac screw.

2. The method for determining the insertion point and channel of a sacroiliac screw according to claim 1, characterized in that: The step of selecting the screw insertion point in the posterior region of the sacral S1 vertebral body specifically includes: Using the sectioning tool in the 3D model to generate multi-angle views of the S1 vertebra, multiple candidate screw insertion points were determined based on the fracture line shape and bone density distribution information. At each candidate point, a safe area with intact bone cortex, bone density greater than the set threshold, no more than 5 mm from the posterior edge of the sacroiliac joint, and avoiding the neural foramen was selected; Mark the points that meet the conditions as candidate points and record their three-dimensional coordinates; The nail insertion path is preliminarily simulated according to the direction of the channel, and the optimal point is selected as the insertion point.

3. The method for determining the insertion point and channel of a sacroiliac screw according to claim 1, wherein: The step of selecting a screw insertion point in the posterior region of the sacral S1 vertebral body further comprises: A candidate point set of the lattice structure is established in the three-dimensional model, and a unit perturbation force is applied to each candidate point to simulate the bone structure response during the screw insertion process; Based on the finite element analysis results, the strain energy density distribution caused by the disturbance force is calculated, and the stress path starting from each candidate point is extracted; Integrate the stress gradient along the path to form a path response scoring function; The candidate point with the highest score is selected from all candidate points as the response focal point, and the response focal point is used as the screw insertion point.

4. The method for determining the insertion point and channel of a sacroiliac screw according to claim 1, wherein: The step of selecting the cross section containing the insertion point as the surface where the channel is located comprises: Constructing a cross section perpendicular to the long axis of the trunk and fixed at the height of the three-dimensional coordinates of the insertion point according to the three-dimensional coordinates of the insertion point; Extracting the bone tissue contours of the sacrum and ilium intersecting therewith in the cross section; Drawing a channel projection path on the cross section and calculating its two-dimensional direction angle and path length; The two-dimensional path is used to reflect the three-dimensional movement, which serves as the design basis for intraoperative C-arm rotation or guide positioning.

5. The method for determining the insertion point and channel of a sacroiliac screw according to claim 1, wherein: The steps of constructing a screw path through the sacral body or sacroiliac joint area and measuring the angle between the insertion channel path and the patient's coronal plane include: Connect the insertion point and the target end point in the three-dimensional model to construct a complete screw channel path; Setting the coronal plane as a reference plane perpendicular to the patient's anterior-posterior direction, and extracting the vector of the coronal plane normal; The angle between the path direction and the coronal plane was calculated using the vector angle calculation formula to quantify the inclination angle of the screw in the anterior-posterior direction.

6. A system for determining the insertion point and channel of a sacroiliac screw, characterized in that: The system includes the following modules: An image acquisition and modeling module is used to acquire a computed tomography image of the patient's sacroiliac region and import the image into a three-dimensional medical imaging processing software to construct a three-dimensional model of the bone structure including the sacrum and ilium; an insertion point determination module, configured to select a screw insertion point in the posterior margin of the sacral S1 vertebra in the three-dimensional model based on the patient's fracture type and bone quality, wherein the screw insertion point is located outside the sacral cortex and close to the posterior margin of the sacroiliac joint; a channel plane identification module, configured to select a cross section containing the insertion point as the plane where the insertion channel is located, wherein the cross section is an image plane perpendicular to the long axis of the patient's torso and serves as the spatial projection plane of the insertion channel; a path generation module for constructing a screw path through the sacral body or sacroiliac joint region and measuring the angle between the insertion channel path and the patient's coronal plane; A path output module is used to output the insertion point, the cross section and the angle together to define a three-dimensional insertion channel for the sacroiliac screw.

7. The system for determining the insertion point and channel of a sacroiliac screw according to claim 6, characterized in that: The insertion point determination module includes: The candidate point screening submodule is used to determine multiple candidate screw insertion points located at the posterior edge of the S1 vertebra based on the fracture line shape and bone density distribution information; The condition judgment submodule is used to select candidate points with intact bone cortex, bone density greater than the set threshold, no more than 5 mm from the posterior edge of the sacroiliac joint, and avoiding the neural foramen; The coordinate recording submodule is used to mark the selected candidate points and record their three-dimensional coordinates; The path fitting submodule is used to simulate the channel direction and select the optimal point as the insertion point based on the channel fitness.

8. The system for determining the insertion point and channel of a sacroiliac screw according to claim 6, characterized in that: The insertion point determination module includes: The response simulation submodule is used to establish a set of candidate points in the 3D model and apply a unit perturbation force to each point to simulate the mechanical response of the bone structure when the screw is inserted; The stress calculation submodule is used to calculate the strain energy density distribution generated by the disturbance force based on the finite element analysis results and extract the stress path corresponding to each point; The scoring function construction submodule is used to integrate the stress gradient in the path and generate the path response scoring function; The maximum score selection submodule is used to screen the response focal point with the highest score among all candidate points, and use the response focal point as the insertion point of the sacroiliac screw.

9. The system for determining the insertion point and channel of a sacroiliac screw according to claim 6, characterized in that: The channel surface identification module includes: A surface construction submodule, configured to construct a cross-section perpendicular to the long axis of the patient's trunk and fixed at the height of the three-dimensional coordinates of the insertion point according to the three-dimensional coordinates of the insertion point; A contour extraction submodule, configured to extract the bone tissue contours of the sacrum and ilium intersecting therewith in the cross section; a channel projection submodule, for drawing a two-dimensional projection path of the channel on the cross section and calculating its two-dimensional direction angle and path length; The intraoperative docking submodule is used to use the two-dimensional path for intraoperative C-arm angle rotation setting or guide positioning design.

10. The system for determining the insertion point and channel of a sacroiliac screw according to claim 6, characterized in that: The path generation module includes: A three-dimensional channel construction submodule is used to generate a complete screw channel path based on the spatial connection between the insertion point and the target end point; An angle calculation submodule, used to set the coronal plane as a reference plane perpendicular to the patient's anterior-posterior direction and extract the normal vector of the coronal plane; The angle measurement submodule is used to obtain the inclination angle of the path in the anterior-posterior direction according to the angle calculation formula between the path direction vector and the coronal plane normal vector.

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