Hollow nail primary nailing method based on femoral neck axial position safety target area boundary registration

Abstract

The application relates to a hollow nail primary implantation method based on femoral neck axis position safety target area boundary registration, which comprises the following steps: acquiring a femoral neck axis position safety target area, establishing a plane rectangular coordinate system YOZ and presetting the coordinates of a hollow nail guide needle, establishing a space rectangular coordinate system O-XYZ and post-inserting a central axis guide needle group, calculating the coordinates of the central axis guide needle based on image registration and establishing a new plane rectangular coordinate system UVW, calculating the coordinates of the preset hollow nail guide needle in the coordinate system UVW and implanting the hollow nail guide needle, implanting the hollow nail and verifying, etc. The front bottom edge of the femoral neck axis position safety target area is used as a reference landmark for constructing the space rectangular coordinate system and a surgical reference datum, which can help surgeons to design the space configuration of the combined screw before operation, the central axis guide needle group is used as a reference datum, the image registration and coordinate conversion of the X-CT during operation are realized, the in-out-in screw is avoided from the root, and the primary implantation of the femoral neck hollow nail is realized.

Description

Technical Field

[0001] This invention belongs to the field of orthopedic treatment technology and relates to a method for placing a cannulated screw in the femoral neck fracture treatment. Specifically, it relates to a cannulated screw placement method based on the registration of the safe target area boundary of the femoral neck screw channel axis. Background Technology

[0002] In hip-preserving treatment of femoral neck fractures, internal fixation with multiple cannulated screws remains the preferred option. The placement of the cannulated screw guide pins is the core technique and operational challenge. The current consensus is to arrange three cannulated screws (screws) in an inverted triangle, parallel to the midline of the femoral neck, diffusely distributed, and enclosed within the cortical bone. To ensure the safety of the cannulated screw trajectory, the direction and position of the cannulated screw guide pins must be accurately determined during surgery, especially their axial position (coordinates) and their relationship with the adjacent cortical boundary. This information is used to adjust the direction and distance of the cannulated screw guide pins, ensuring accurate placement of the femoral neck cannulated screws.

[0003] Since X-rays cannot directly obtain axial images of the femoral neck and the axial coordinates of the cannulated screw guide wire, it is necessary to infer the axial position (coordinates) of the cannulated screw guide wire by obtaining two-dimensional images through multiple fluoroscopic examinations during surgery. The obtained coordinates are then paired and marked within a hypothetical safe target area (the current mainstream view assumes the "safe target area is circular"). By comparing the position of the guide wire coordinate point with the boundary of the safe target area, a rough judgment is made regarding its approximate axial position and whether it has penetrated the cortex. However, increasing research indicates that 54-70% of cannulated screws located within the femoral neck bone, as determined by intraoperative fluoroscopy, penetrate the cortex, i.e., becoming in-out-in screws, as confirmed by postoperative anatomy and CT scans. The root causes of in-out-in screws include two aspects: first, the axial safe area is mistakenly assumed to be circular without basis and used as a reference background for comparison of the safe boundary; second, the uncertainty of limb positioning and intraoperative fluoroscopic direction leads to misjudgment of the screw's axial position (coordinates). The consequence is that "in-out-in" screws (including multiple screw placements and repeated adjustments during surgery) pose a significant risk of iatrogenic damage to the blood supply to the femoral head and neck and destruction of bone, and increase the incidence of later internal fixation failure, iatrogenic fractures, and femoral head necrosis.

[0004] To reduce the incidence of in-out-in screws, scholars at home and abroad have adopted improved methods such as multi-angle flip perspective, but they still cannot avoid them. In particular, there is still no feasible research approach for quantifying the screw position and judging the spatial configuration of combined screws.

[0005] Successful placement of the cannulated screw guide pin on the first attempt (referred to as "first-time placement") has always been a research hotspot and relentless pursuit for orthopedic surgeons, and is the only means to avoid iatrogenic damage to the blood supply and bone of the femoral head and neck. Intraoperative fluoroscopy is currently the most important and only means of determining screw position in clinical surgery. How to accurately determine the axial position (coordinates) of the femoral neck screw through intraoperative fluoroscopy is the key to avoiding in-out-in screws during surgery and is also a prerequisite for first-time placement technique. Current screw placement surgeries face the following pressing technical bottlenecks: 1. Lack of research ideas, methods, and clear research conclusions regarding "individualized femoral neck axial safe target area (ASTA) for directional and quantitative femoral neck screw access"; 2. No standardized spatial rectangular coordinate system for the femoral neck based on constant bony anatomical landmarks has been constructed; 3. It is not yet possible to obtain repeatable fluoroscopic images based on constant bony anatomical landmarks; 4. Image registration between intraoperative fluoroscopic X-ray images and axial CT images has not been achieved, nor has related research confirmed this; 5. There is a significant deviation between the screw axial position (coordinates) calculated from intraoperative X-ray fluoroscopic images and its actual axial coordinates, thus making it impossible to directionally and quantitatively determine the actual axial coordinates of the cannulated screw guide and screw, and accurately judge their relationship with the safe target area boundary through intraoperative fluoroscopy. Therefore, it is impossible to fundamentally avoid in-out-in screw occurrences, let alone implement first-line screw placement. Summary of the Invention

[0006] The purpose of this invention is to provide a method for pre-positioning hollow screws based on registration of the femoral neck axial safety target area boundary. Based on obtaining an individualized femoral neck axial safety target area (ASTA) with directional and quantitative femoral neck screw channels, a constant and flat bony anatomical landmark—the anterior cortex of the femoral neck base (corresponding to the anterior base of the ASTA)—is used as a reference landmark for constructing a spatial rectangular coordinate system O-XYZ and as an anatomical landmark during screw placement surgery. Repeatable anteroposterior and lateral X-ray images can be obtained parallel or perpendicular to this plane, based on which the stable position (coordinates) of the guide pin in the anteroposterior and lateral X-ray images can be calculated. Based on the registration of the anteroposterior and lateral X-ray fluoroscopic boundaries with the femoral neck axial safety target area boundary, and through coordinate transformation of the spatial orthogonal coordinate system (i.e., the transformation of guide pin coordinates between anteroposterior X-rays, lateral X-rays, and axial CT), the stable axial coordinates of all guide pins can be calculated in the axial safety target area coordinate system YOZ with the midline as the origin, for quantitative positioning of the guide pin during surgery. In addition, it can help surgeons establish new axial safety target area geometric models, design the spatial configuration of combined screws preoperatively, realize the placement of the central axis guide pin group, realize intraoperative X-CT image registration and coordinate transformation, and visually evaluate the position and spatial configuration of the hollow screw guide pin during the operation, thereby avoiding the occurrence of in-out-in screws from the root and achieving the first-line placement of femoral neck hollow screws.

[0007] It should be noted that the surgical midline (SCA) of the femoral neck has the following characteristics: 1. It is the midline of the two tangents of the superior and inferior diameters of the femoral neck in the coronal plane. 2. In the sagittal plane, the SCA is parallel to the anterior cortex of the femoral neck (AC-FN). 3. The SCA passes through the midpoint of the anteroposterior diameter (D-SI) and superior and inferior diameter (D-AP) of the ASTA. 4. The SCA can be determined intraoperatively. Furthermore, based on the concept of the surgical midline of the femoral neck and surgical requirements, the intraoperatively inserted midline guide wire group can also simultaneously determine the parallel plane of the anterior cortex at the base of the femoral neck (i.e., the anterior base of the ASTA).

[0008] In this application, the femoral neck axial safety target area includes two cases: "individualized femoral neck axial safety target area (ASTA)" and "safety target area geometric model".

[0009] In this application, the standardized orthogonal femoral neck anteroposterior X-ray refers to an X-ray obtained by fluoroscopy perpendicular to the anterior cortex of the femoral neck base. The standardized orthogonal femoral neck lateral X-ray refers to an X-ray obtained by fluoroscopy parallel to the anterior cortex of the femoral neck base.

[0010] The technical solution adopted in this invention:

[0011] A method for first-line placement of cannulated screws based on registration of the femoral neck axial safe target area boundary includes the following steps:

[0012] Step S1: Obtain the axial safe target area of ​​the femoral neck, and obtain the superior and inferior diameters and anteroposterior diameters of the axial safe target area of ​​the femoral neck, that is, the superior and inferior diameters of the isthmus in the standardized orthogonal femoral neck anteroposterior X-ray and the anteroposterior diameters of the isthmus in the standardized orthogonal femoral neck lateral X-ray.

[0013] Step S2: Using the anterior base of the femoral neck axial safety target area (the anterior cortex of the femoral neck base) as a reference, draw the circumscribed rectangle of the femoral neck axial safety target area. With the center of the rectangle as the origin O, the Y-axis is the line parallel to the anterior base of the femoral neck axial safety target area, and the Z-axis is the line perpendicular to the anterior base of the femoral neck axial safety target area. Establish a plane rectangular coordinate system YOZ. Set the femoral neck axial safety target area as the reference background for the screw placement surgery calculation. Within the femoral neck axial safety target area, pre-set the coordinates of 3 hollow screw guide pins on the plane rectangular coordinate system YOZ.

[0014] Step S3: Based on the plane rectangular coordinate system YOZ, establish a spatial rectangular coordinate system O-XYZ with the surgical midline of the femoral neck as the X-axis.

[0015] Step S4: During the operation, the central axis guide pin assembly is placed into the femoral neck, and the central axis guide pin assembly is in the same plane and parallel to the plane of the anterior cortex of the femoral neck base (on axial CT) and the plane of the anterior cortex of the femoral neck (on sagittal CT and standardized orthogonal lateral femoral neck X-ray), and parallel to the tangent of the superior and inferior diameter isthmus of the femoral neck (on coronal CT and standardized orthogonal anteroposterior femoral neck X-ray); the central axis guide pin assembly includes 1 central axis guide pin and 2 direction maintenance pins, wherein the central axis guide pin is located in the middle, and the 2 direction maintenance pins are located on both sides of the central axis guide pin.

[0016] Step S5: In the O-XYZ space rectangular coordinate system, with the anterior cortex of the femoral neck base as the reference, use standardized orthogonal fluoroscopy to obtain standardized orthogonal femoral neck anteroposterior X-rays and standardized orthogonal femoral neck lateral X-rays. That is, perform fluoroscopy along the Z-axis direction (perpendicular to the XOY plane rectangular coordinate system) (using the plane where the central axis guide pin group is located as the reference reference plane, and perform fluoroscopy perpendicular to the reference reference plane) to obtain standardized orthogonal femoral neck anteroposterior X-rays (i.e., XOY plane rectangular coordinate system); perform fluoroscopy along the Y-axis direction (perpendicular to the XOZ plane rectangular coordinate system) (using the plane where the central axis guide pin group is located as the reference reference plane, and perform fluoroscopy parallel to the reference reference plane) to obtain standardized orthogonal femoral neck lateral X-rays (i.e., XOZ plane rectangular coordinate system).

[0017] On a standardized orthogonal anteroposterior X-ray of the femoral neck, the centerline of the guide pin is drawn. Upper and lower boundary lines are drawn at the upper and lower boundaries of the femoral neck isthmus, respectively. These upper and lower boundary lines are tangent to the femoral neck isthmus and parallel to the centerline of the guide pin. The distances between the upper and lower boundary lines, between the upper boundary line and the centerline of the guide pin, and between the lower boundary line and the centerline of the guide pin are measured. Then, the Y-axis coordinate of the centerline of the guide pin (the actual insertion point coordinates) is calculated using the following formula: Y0 = (d5 - d4) )×d1 / (2×d3), where: Y0 is the Y-axis coordinate of the center line of the guide needle in the XOY plane rectangular coordinate system, d1 is the superior and inferior diameter of the femoral neck isthmus (measured by CT or assigned by a geometric model), d3 is the distance between the upper boundary line and the lower boundary line, d4 is the distance between the upper boundary line and the center line of the guide needle, and d5 is the distance between the lower boundary line and the center line of the guide needle. The unit is millimeters (mm). In the formula, d3=d4+d5. d3, d4, and d5 are all measured on a standardized orthogonal femoral neck anteroposterior X-ray.

[0018] On a standardized orthogonal lateral femoral neck radiograph, the centerline of the guide pin is drawn (at this time, the two guide pins are aligned with the centerline of the guide pin, and this centerline is consistent with the centerline drawn on the anteroposterior femoral neck radiograph). Anterior and posterior boundary lines are drawn at the anterior and posterior boundaries of the femoral neck isthmus, respectively. These anterior and posterior boundary lines are tangent to the femoral neck isthmus and parallel to the centerline of the guide pin. The distances between the anterior and posterior boundary lines, between the anterior and posterior boundary lines and the centerline of the guide pin, and between the posterior and posterior boundary lines and the centerline of the guide pin are measured. Then, the Z-axis coordinate of the centerline of the guide pin (the actual insertion point coordinate) is calculated. The formula for calculating Z0 is as follows: Z0 = (d7-d8) × d2 / (2 × d6), where: Z0 is the Z-axis coordinate of the center line of the central guide needle in the XOZ plane rectangular coordinate system (central guide needle), d2 is the anteroposterior diameter of the femoral neck isthmus (measured by CT or assigned by a geometric model), d6 is the distance between the anterior and posterior boundary lines, d7 is the distance between the posterior boundary line and the center line of the central guide needle, and d8 is the distance between the anterior boundary line and the center line of the central guide needle, all in millimeters (mm). In the formula, d6 = d7 + d8, and d6, d7, and d8 are all measured on a standardized orthogonal lateral femoral neck X-ray.

[0019] Step S6: Based on the standardized orthogonal femoral neck anteroposterior X-ray, the standardized orthogonal femoral neck lateral X-ray boundary isthmus and the boundary of the femoral neck axial safe target area, the coordinates of the central axis guide pin calculated in step 5 (i.e. the actual insertion point coordinates (Y0, Z0)) are marked in the plane rectangular coordinate system YOZ. With the coordinates (Y0, Z0) of the central axis guide pin as the origin V, the line parallel to the Y axis as the U axis, and the line parallel to the Z axis (perpendicular to the U axis) as the W axis, a new plane rectangular coordinate system UVW is established. The coordinates of the three hollow screw guides, which were set preoperatively in the YOZ Cartesian coordinate system, were transformed and calculated to obtain the coordinates of the three hollow screw guides in the UVW Cartesian coordinate system. In other words, the preset theoretical coordinates of the hollow screw guides were transformed to the coordinates in the UVW Cartesian coordinate system. This quantifies the coordinates of the hollow screw guides based on the central axis guide group as a reference, and eliminates surgical errors caused by the deviation between the theoretical placement point and the actual placement point of the central axis guides during the operation.

[0020] Step S7: During the operation, based on the pre-set coordinates of the three hollow screw guides in the Cartesian coordinate system UVW, using the previously inserted midline guide in the femoral neck as the origin and the midline guide group in the femoral neck as the reference, the insertion positions of the three hollow screw guides are marked, and then the three hollow screw guides are inserted respectively. Standardized orthogonal fluoroscopy is used again to obtain standardized orthogonal femoral neck anteroposterior and lateral X-rays. On the X-rays, the Y-axis and Z-axis coordinates of the three hollow screw guides are calculated using the same method as the above calculation of the midline guide centerline coordinates. These coordinates are then assigned (converted) to the Y-axis and Z-axis coordinates of the YOZ coordinate system in the femoral neck axial safe target area, marked in the coordinate system, and compared with the boundary of the femoral neck axial safe target area to ensure that the screws will not penetrate the bone cortex and meet the pre-operative design requirements; otherwise, fine adjustments are required.

[0021] Step S8: Following standard procedures, enlarge the bone tunnel along the hollow screw guide pin using a hollow drill and insert the hollow screw (screw); after successful insertion, obtain standardized orthogonal femoral neck anteroposterior and lateral femoral neck X-rays using standardized orthogonal fluoroscopy again, and calculate the Y-axis and Z-axis coordinates using the same method as above, assign (convert) them to the Y-axis and Z-axis coordinates on the plane rectangular coordinate system YOZ, mark them on the plane rectangular coordinate system YOZ, and compare them with the boundary of the femoral neck axial safe target area to verify and ensure the accurate realization of the hollow screw's direction, position, and spatial configuration. This allows for the determination of the reference benchmark (central axis guide pin) during surgery, standardizes orthogonal fluoroscopy and coordinate transformation, and enables accurate placement of hollow screw guide pins and hollow screws based on the pre-set position and spatial configuration. This minimizes surgical errors caused by factors such as elastic deformation of the steel pin, unstable fluoroscopy, and human operation, ensuring accurate screw placement from the first attempt.

[0022] Further, in step S1, the method for obtaining the femoral neck axial safety target area is as follows: A CT image of the femoral neck is obtained through CT scanning and 3D reconstruction. All axial CT images are then superimposed in situ. The area where all images overlap (intersect) is the femoral neck axial safety target area (Individualized Femoral Neck Axial Safety Target Area (ASTA)). Correspondingly, the method for obtaining the superior-inferior and anteroposterior diameters of the femoral neck axial safety target area is as follows: The CT image, including the femoral neck axial safety target area, is magnified to a 1:1 ratio. Using the anterior base of the femoral neck axial safety target area (i.e., the anterior cortex of the femoral neck base) as a reference, its circumscribed rectangle is drawn. Then, the length and width of the circumscribed rectangle are measured, which are the superior-inferior and anteroposterior diameters of the axial safety target area. This method is mainly used for femoral neck fractures without displacement, and can also be used for normal model bone conditions in research.

[0023] Further, in step S1, the method for obtaining the axial safe target area of ​​the femoral neck is as follows: using the axial CT image of the base of the femoral neck as a reference background, a rounded triangle geometric model (suitable for clinical surgery of patients with femoral neck fractures) or a rounded quadrilateral geometric model (suitable for experimental studies simulating femoral neck fractures using model bones) is constructed as the axial safe target area of ​​the femoral neck (safe target area geometric model), and the anterior base of the geometric model coincides with the anterior base of the axial CT image of the base of the femoral neck (the anterior cortex of the base of the femoral neck). This method is mainly used when there is displacement in the femoral neck fracture and the individualized axial safe target area of ​​the femoral neck cannot be directly obtained using axial CT images. Accordingly, in the constructed femoral neck axial safety target area (safety target area geometric model), the estimation method is used to obtain the superior-inferior diameter and anteroposterior diameter of the femoral neck axial safety target area: 1. Obtain axial CT images of the mid-section of the femoral neck, and measure the superior-inferior diameter on the images as the superior-inferior diameter of the femoral neck axial safety target area; or, obtain axial CT images of the base of the femoral neck, and measure the anteroposterior diameter on the images as the anteroposterior diameter of the femoral neck axial safety target area; based on the measured superior-inferior diameter or anteroposterior diameter, calculate another parameter using a regression equation; the regression equation is as follows: d2=0.71×d1+1.35; where: d1 is the superior-inferior diameter of the femoral neck axial safety target area, and d2 is the anteroposterior diameter of the femoral neck axial safety target area, in millimeters (mm). This method is mainly used when either the superior-inferior diameter or the anteroposterior diameter can be measured. 2. Using the constructed femoral neck axial safety target area (safety target area geometric model) as a reference background, the superior-inferior diameter and anteroposterior diameter of a normal adult hip joint are assigned to the superior-inferior diameter and anteroposterior diameter of the femoral neck axial safety target area. Preferably, the superior-inferior diameter is 26-38 mm, and the anteroposterior diameter is 17-29 mm. This method is mainly used when the superior-inferior diameter and anteroposterior diameter cannot be measured from CT images. It should be noted that there may be a large error when using the constructed safety target area geometric model. This invention corrects this error by: in the standardized orthogonal fluoroscopic X-ray after the placement of the central axis guide pin group, the distance between the steel pins on both sides is maintained at 30 mm. This can be used as a scale to accurately calculate the value of the superior-inferior diameter, and then the estimated value of the anteroposterior diameter is calculated through a regression equation; the values ​​corrected by orthogonal fluoroscopy are then reassigned to the superior-inferior diameter and anteroposterior diameter to reduce the error. Similarly, after the placement of the hollow screw guide pin, parameter correction can also be performed again. Multiple intraoperative parameter corrections can minimize surgical errors.

[0024] Furthermore, the method for inserting the central axis guide pin is the dual-plane fixed-point staggered method: 1) In the O-XYZ spatial rectangular coordinate system, taking the anterior cortex of the femoral neck base as the reference, fluoroscopy is performed along the Z-axis to obtain a standardized orthogonal femoral neck anteroposterior X-ray, and fluoroscopy is performed along the Y-axis to obtain a standardized orthogonal femoral neck lateral X-ray. The midpoint of the superior and inferior diameters of the isthmus is determined on the standardized orthogonal femoral neck anteroposterior X-ray, and the midpoint of the anteroposterior diameter of the isthmus is determined on the standardized orthogonal femoral neck lateral X-ray; 2) Simultaneously, the superior and inferior diameters of the isthmus are... The midpoint of the femoral neck and the midpoint of the anteroposterior isthmus are used as insertion points to insert the central axis guide pin, which is parallel to the anterior cortex of the femoral neck. Finally, one directional maintenance steel pin is inserted on each side of the central axis guide pin, so that the central axis guide pin group is in the same plane and this plane is parallel to the plane of the anterior cortex of the femoral neck base (axial CT) and the plane of the anterior cortex of the femoral neck (sagittal CT and standardized orthogonal lateral femoral neck X-ray), and is also parallel to the tangent of the superior and inferior isthmus of the femoral neck (on coronal CT and standardized orthogonal anteroposterior femoral neck X-ray).

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. An individualized femoral neck axial safety target area for the femoral neck cannula screw was obtained using the intersection method. Based on a large amount of data from normal hip joints and model femurs, a geometric model of the femoral neck axial safety target area was established. The anterior base of the individualized femoral neck axial safety target area (ASTA) (i.e., the anterior cortex of the femoral neck base) was used as a reference landmark to construct a spatial rectangular coordinate system. A standardized spatial rectangular coordinate system was established with the femoral neck surgical midline as the X-axis, the plane parallel to the anterior cortex of the femoral neck base as the Y-axis, and the plane perpendicular to the anterior cortex of the femoral neck base as the Z-axis. Similarly, the constant and flat bony anatomical structure of the anterior cortex of the femoral neck base was used as a positioning landmark for the placement of the midline guide pin group and standardized intraoperative orthogonal fluoroscopy. The obtained repeatable X-ray images were used to calculate the coordinates of the midline guide pin group. The stable axial coordinates of all hollow screw guide pins in a coordinate system with the pin as the origin are used for intraoperative positioning. This helps surgeons design the spatial configuration of combined screws preoperatively, achieve intraoperative placement of the midline guide pin group, realize standardized intraoperative orthogonal fluoroscopy and intraoperative X-CT image registration and coordinate transformation, and visually evaluate the position and spatial configuration of the hollow screw guide pins intraoperatively. This avoids the occurrence of in-out-in screws from the root cause. It can also quickly and visually determine the spatial configuration of the screw and its relationship with the safety boundary, thereby achieving the first-line placement of the femoral neck hollow screw.

[0027] 2. Using the central axis guide needle group as the reference benchmark for X-ray fluoroscopy, standardized orthogonal anteroposterior and lateral fluoroscopy is performed intraoperatively to obtain repeatable intraoperative femoral neck anteroposterior and lateral X-ray images. Based on the O-XYZ spatial rectangular coordinate system, the boundary of the isthmus of the X-ray can be registered with the boundary of the femoral neck axial safe target area (including direction registration and boundary registration), so as to ensure the correspondence between the coordinates calculated using the anteroposterior and lateral X-ray images and the coordinates of the femoral neck axial safe target area, and realize intraoperative X-CT coordinate conversion.

[0028] 3. Under the standardized O-XYZ spatial rectangular coordinate system, the axial coordinates of the screw are calculated using repeatable intraoperative femoral neck anteroposterior and lateral X-ray images, and marked in the plane rectangular coordinate system UVW with the central axis guide pin as the origin. The preset theoretical coordinates of the hollow screw guide pin are converted into coordinates in the plane rectangular coordinate system UVW, realizing the quantification of the preset hollow screw guide pin coordinates based on the central axis guide pin group as the reference.

[0029] 4. During the operation, the reference benchmark (central axis guide pin) is determined to accurately insert the hollow screw guide pin according to the pre-set position and spatial configuration, so as to minimize the surgical error caused by the error between the pre-set screw position and the actual screw position due to factors such as the elastic deformation of the steel pin, fluoroscopic instability and human operation, and ensure accurate screw placement. Attached Figure Description

[0030] Figure 1 This is an axial safe target area image obtained by overlaying axial CT images of the femoral neck in situ. d1 is the superior-inferior diameter of the axial safe target area of ​​the femoral neck, and d2 is the anteroposterior diameter of the axial safe target area of ​​the femoral neck.

[0031] Figure 2 The goal is to construct a rounded triangle geometric model as the axial safe target area for the femoral neck.

[0032] Figure 3 The goal is to construct a rounded quadrilateral geometric model as the axial safe target area for the femoral neck.

[0033] Figure 4 Establish a plane rectangular coordinate system YOZ on the femoral neck axial safe target area.

[0034] Figure 5 It is a spatial rectangular coordinate system O-XYZ.

[0035] Figure 6 This is an anteroposterior X-ray image of the femoral neck with a central guide pin. L2 is the central guide pin, and L1 and L3 are directional support pins.

[0036] Figure 7 This is a lateral X-ray image of the femoral neck with a central guide needle. L2 is the central guide needle (its direction maintains the alignment of L1, L3, and L2).

[0037] Figure 8 To calculate the Y-axis coordinate of the centerline guide needle in the XOY plane rectangular coordinate system. A is the upper boundary line, B is the lower boundary line, L2 is the centerline guide needle, d3 is the distance between the upper and lower boundary lines, d4 is the distance between the upper boundary line and the centerline of the centerline guide needle, and d5 is the distance between the lower boundary line and the centerline of the centerline guide needle.

[0038] Figure 9 To calculate the Z-axis coordinate of the centerline guide pin in the XOZ plane rectangular coordinate system. E is the front boundary line, F is the back boundary line, L2 is the centerline guide pin, d6 is the distance between the front and back boundary lines, d7 is the distance between the back boundary line and the centerline of the centerline guide pin, and d8 is the distance between the front boundary line and the centerline of the centerline guide pin.

[0039] Figure 10 It is to establish a new planar rectangular coordinate system UVW.

[0040] Figure 11 This is a coordinate conversion for hollow nail guide pins. S1, S2, and S3 are all hollow nail guide pins.

[0041] Figure 12 It is a standardized orthogonal femoral neck anteroposterior X-ray with a hollow screw guide.

[0042] Figure 13 It is a standardized orthogonal lateral X-ray of the femoral neck with a hollow screw guide. Detailed Implementation

[0043] The invention will be further described below with reference to examples and accompanying drawings, but this is not intended to limit the invention.

[0044] This application discloses a cannulated screw placement method based on registration of the femoral neck axial safe target area boundary. It consists of two main parts: preoperative and intraoperative, comprising eight steps in total. Steps S1-S3 are preoperative procedures, and steps S4-S8 are intraoperative procedures. The specific process is as follows:

[0045] Step S1: Obtain the axial safety target area of ​​the femoral neck, and obtain the superior-inferior and anteroposterior diameters on the axial safety target area of ​​the femoral neck, which correspond to the superior-inferior and anteroposterior diameters of the femoral neck isthmus. This includes three scenarios:

[0046] 1) For cases of non-displaced femoral neck fractures in clinical practice, or for structurally normal model bones used in research (intersection method to determine individualized femoral neck axial safe target area): A. Use 64-slice CT (Model SOMATOM, Siemens, Germany). Select the following parameters: pelvis + proximal femur, slice interval 5mm, slice thickness 5mm, FOV from the upper pelvis to 180mm below the lesser trochanter, KVp 130KV, effective mAs 106, matrix 512*512. B. After CT 3D reconstruction, acquire axial CT images of the femoral neck perpendicular to the midline, from the top of the femoral head outwards and downwards, with a slice thickness of 2mm. C. Import all axial CT images of each femoral neck into image processing software (Bridge, Photoshop CC). Stack the images sequentially in situ, removing non-intersecting areas and retaining intersecting areas. After stacking related CT images, the common area (overlapping or intersecting) of all axial CT images of the femoral neck for the same patient is the femoral neck axial safety target area (Individualized Femoral Neck Axial Safety Target Area (ASTA)). D. Enlarge the CT images, including the femoral neck axial safety target area, to a 1:1 image ratio. Using the anterior base of the femoral neck axial safety target area (i.e., the anterior cortex of the femoral neck base) as a reference, draw its circumscribed rectangle. Then measure the length and width of the circumscribed rectangle; these are the superior-inferior diameter d1 and the anteroposterior diameter d2 of the femoral neck axial safety target area. Figure 1 As shown.

[0047] 2) For cases of femoral neck fracture displacement in clinical practice where the intersection method cannot be used to obtain individualized ASTA, but one of the femoral neck regions (middle or base) remains intact on the axial CT scan: A) Using the axial CT image of the femoral neck base as a reference background, a rounded triangle geometric model is constructed as the axial safe target area for the femoral neck (safe target area geometric model), and the anterior base of the geometric model coincides with the anterior base of the axial CT image of the femoral neck base (anterior cortex of the femoral neck base). Studies have found that the axial safe target area in normal adults is a rounded triangle, while the axial safe target area of ​​the Saw bone model is a rounded quadrilateral. Based on extensive research on normal hip joints and model femurs, this invention uses a constructed safe target area geometric model to replace the real individualized axial safe target area for femoral neck fracture displacement where the axial CT scan cannot obtain the actual axial safe target area. It has good versatility and can encompass the geometric shape of the axial safe target area for both patients with femoral neck fractures and model bones simulating femoral neck fractures. B. Obtain axial CT images of the mid-section of the femoral neck and measure the superior-inferior diameter (U-C) as the superior-inferior diameter of the axial safe target area of ​​the femoral neck. Alternatively, obtain axial CT images of the base of the femoral neck and measure the anteroposterior diameter as the anteroposterior diameter of the axial safe target area of ​​the femoral neck. Based on the measured superior-inferior or anteroposterior diameter, calculate another parameter using a regression equation. The regression equation is as follows: d2 = 0.71 × d1 + 1.35; where d1 is the superior-inferior diameter of the axial safe target area image, and d2 is the anteroposterior diameter of the axial safe target area image, in millimeters (mm). Studies have shown that the U-C is often located in the mid-section of the femoral neck on anteroposterior X-ray images (i.e., the superior-inferior diameter on axial CT), and the U-C is often located at the base of the femoral neck on lateral X-ray images (i.e., the anteroposterior diameter on axial CT). Therefore, axial CT images of the mid-section of the femoral neck and the base of the femoral neck can be used for measurement, and the obtained values ​​can be used to estimate the superior-inferior and anteroposterior diameters, with errors within the allowable range for surgery. Figure 2 As shown.

[0048] 3) For femoral neck fractures with displacement in clinical practice, where the intersection method cannot be used to obtain individualized ASTA, and where both the mid-neck region and the base of the femoral neck are incomplete on the axial CT scan: A. Using the axial CT image of the femoral neck base as a reference background, construct a rounded quadrilateral geometric model (or a rounded triangle geometric model) as the safe target area for the femoral neck axial view (safe target area geometric model), with the anterior base of the geometric model coinciding with the anterior base of the axial CT image of the femoral neck base (the anterior cortex of the femoral neck base). B. Using the rounded quadrilateral geometric model as a reference background, assign the average values ​​of the superior-inferior diameter and anteroposterior diameter of the hip joint in a normal adult to the superior-inferior diameter and anteroposterior diameter of the safe target area geometric model (e.g., setting the superior-inferior diameter to 30mm and the anteroposterior diameter to 24mm). Figure 3 As shown.

[0049] Step S2: Using the anterior base of the femoral neck axial safety target area (the anterior cortex of the femoral neck base) as a reference, draw the circumscribed rectangle of the femoral neck axial safety target area. Establish a Cartesian coordinate system YOZ with the center of the rectangle as the origin O, the line parallel to the anterior base of the femoral neck axial safety target area as the Y-axis, and the line perpendicular to the anterior base of the femoral neck axial safety target area as the Z-axis. Set the femoral neck axial safety target area as the reference background for screw placement surgery calculations. Within the femoral neck axial safety target area, based on the preoperative spatial planning of the three hollow screws, pre-set the coordinates of the three hollow screw guide pins (S1, S2, S3) on the Cartesian coordinate system YOZ (they can be set to an inverted triangle, or preset to various spatial configurations such as an equilateral triangle or an inclined triangle). Figure 4 As shown. Theoretically, three cannulated screw guides positioned within the femoral neck axial safe target area should not result in "in-out-in" screws. However, due to current technological limitations, the proposed placement of three cannulated screw guides remains hypothetical. There is no theoretical support or matching surgical instruments for directional and quantitative placement of the femoral neck axial safe target area, making it impossible to achieve in actual surgery. This is because, in current surgical practice, suitable bony anatomical landmarks have not yet been found as reliable reference points, making it difficult to place screws according to the pre-set positions and directions, which can easily lead to significant errors.

[0050] Step S3: Based on the plane rectangular coordinate system YOZ, establish a spatial rectangular coordinate system O-XYZ with the surgical midline of the femoral neck as the X-axis to achieve X-CT image registration and coordinate transformation. For example... Figure 5 As shown.

[0051] In the O-XYZ Cartesian coordinate system, using the anterior cortex of the femoral neck base as a reference, fluoroscopy is performed along the Z-axis (perpendicular to the XOY plane Cartesian coordinate system) to obtain a standardized orthogonal femoral neck anteroposterior X-ray. Similarly, fluoroscopy is performed along the Y-axis (perpendicular to the XOZ plane Cartesian coordinate system) to obtain a standardized orthogonal femoral neck lateral X-ray. Theoretically, the superior-inferior diameter (d1) and anteroposterior diameter (d2) of the orthogonal fluoroscopic femoral neck anteroposterior and lateral X-rays are equal to the superior-inferior diameter and anteroposterior diameter of the femoral neck axial safety target area, respectively. This means that parameters of the same coordinate axis exhibit consistent behavior on corresponding axes in different coordinate systems. Therefore, the superior-inferior diameter and anteroposterior diameter parameters of the femoral neck axial safety target area can be assigned to the corresponding parameters on the standardized orthogonal femoral neck anteroposterior and lateral X-rays, enabling quantitative studies of these radiographs. The reverse is also true. In other words, the Y-Z coordinates of the guide pin calculated in the standardized orthogonal femoral neck anteroposterior and lateral X-rays obtained through intraoperative fluoroscopy can be equivalently assigned (converted) to the corresponding Y-Z coordinates of the hollow screw guide pin in the YOZ axial coordinate system of the femoral neck axial safety target area, and marked on the reference background of the femoral neck axial safety target area. This allows for the determination of whether the guide pin position is appropriate and how to make quantitative adjustments. It must be emphasized that, theoretically, only standardized orthogonal femoral neck anteroposterior and lateral X-rays obtained through orthogonal fluoroscopy can be registered with ASTA of axial CT.

[0052] Step S4: During the operation, the central axis guide pin assembly (including 1 central axis guide pin and 2 direction-maintaining pins) is placed into the femoral neck using the dual-plane fixed-point staggered method: 1) In the O-XYZ space rectangular coordinate system, with the anterior cortex of the femoral neck base as the reference, fluoroscopy is performed along the Z-axis to obtain a standardized orthogonal femoral neck anteroposterior X-ray, and fluoroscopy is performed along the Y-axis to obtain a standardized orthogonal femoral neck lateral X-ray. The midpoint of the superior-inferior diameter isthmus is determined on the standardized orthogonal femoral neck anteroposterior diameter isthmus is determined on the standardized orthogonal femoral neck lateral X-ray. 2) Simultaneously, insert the central axis guide pin using the midpoints of the superior and inferior diameter isthmuses and the anteroposterior diameter isthmuses as insertion points, ensuring it is parallel to the anterior cortex of the femoral neck. Finally, insert one direction-maintaining steel pin on each side of the central axis guide pin, so that the central axis guide pin assembly is in the same plane, and this plane is parallel to the plane of the anterior cortex at the base of the femoral neck (axial CT) and the plane of the anterior cortex of the femoral neck (sagittal CT and standardized orthogonal lateral femoral neck X-ray), and also parallel to the tangent of the superior and inferior diameter isthmuses of the femoral neck (on coronal CT and standardized orthogonal anteroposterior femoral neck X-ray). For the specific device and insertion method used, please refer to the invention patent (Patent No.: ZL202111029619.1; Authorization Announcement No.: CN113693701B; Title: Femoral Neck Surgical Central Axis Mechanical Navigation System Based on Individualized Safety Boundaries). Of course, after the central axis guide pin assembly is inserted, in a standardized orthogonal femoral neck anteroposterior X-ray, the distance between the two direction steel pins is equal to 30mm. Using this as a scale, the superior and inferior diameters can be calculated and corrected; the anteroposterior diameter can also be corrected according to the regression equation.

[0053] Based on the O-XYZ spatial coordinate system, the inserted central guide needle assembly is parallel to the anterior cortical plane of the femoral neck base. Therefore, standardized orthogonal anteroposterior and lateral X-ray fluoroscopy with the anterior cortical plane of the femoral neck base as a reference can be achieved. This not only provides repeatable standardized orthogonal anteroposterior and lateral femoral neck X-rays but also enables registration of X-ray fluoroscopy with the femoral neck axial safety target area, including directional and boundary registration. Furthermore, since the distance between the two directional maintaining needles is equal to 30mm, this can be used as a scale for parameter correction of the superior-inferior and anteroposterior diameters.

[0054] Step S5: In the O-XYZ rectangular coordinate system, using the anterior cortex of the femoral neck base as the reference, obtain standardized orthogonal femoral neck anteroposterior and lateral X-rays using standardized orthogonal fluoroscopy. This involves fluoroscopy along the Z-axis (perpendicular to the XOY plane rectangular coordinate system) (using the plane containing the central guide pin group as the reference plane, and fluoroscopy perpendicular to the reference plane) to obtain a standardized orthogonal femoral neck anteroposterior X-ray (i.e., XOY plane rectangular coordinate system). Figure 6As shown; fluoroscopy is performed along the Y-axis (perpendicular to the XOZ plane rectangular coordinate system) (using the plane containing the central axis guide pin group as the reference plane, and fluoroscopy is performed parallel to the reference plane) to obtain a standardized orthogonal femoral neck anteroposterior X-ray (i.e., XOZ plane rectangular coordinate system), as shown. Figure 7 As shown.

[0055] On a standardized orthogonal anteroposterior X-ray of the femoral neck, the centerline of the central guide pin is drawn. Upper and lower boundary lines are drawn at the upper and lower boundaries of the isthmus of the femoral neck, respectively. These upper and lower boundary lines are tangent to the isthmus of the femoral neck and parallel to the centerline of the central guide pin. The distances between the upper and lower boundary lines, between the upper boundary line and the centerline of the central guide pin, and between the lower boundary line and the centerline of the central guide pin are measured. Then, the Y-axis coordinate (coordinate of the actual insertion point) of the centerline (central guide pin) is calculated using the following formula: Y0 = (d5 - d4) × d1 / (2 × d3), where: Y0 is the Y-axis coordinate of the centerline (central axis guide needle) in the XOY plane rectangular coordinate system; d1 is the superior and inferior diameters of the axial safety target area (measured by CT or assigned by the geometric model of the safety target area, equal to the superior and inferior diameters of the femoral neck fluoroscopic boundary isthmus); d3 is the distance between the upper and lower boundary lines; d4 is the distance between the upper boundary line and the centerline of the central axis guide needle; d5 is the distance between the lower boundary line and the centerline of the central axis guide needle, all in millimeters (mm). In the formula, d3 = d4 + d5. d3, d4, and d5 are all measured on a standardized orthogonal femoral neck anteroposterior X-ray. Figure 8 As shown. It should be noted that when using the safe target area geometry model, in the standardized orthogonal fluoroscopic image after the central axis guide needle assembly is inserted, the distance between the steel needles on both sides is maintained at 30mm. This can be used as a scale to accurately calculate the values ​​of the superior and inferior diameters, and then the estimated values ​​of the anterior and posterior diameters can be calculated through regression equations. Reassigning the values ​​after orthogonal fluoroscopic correction to the superior and inferior diameters and the anterior and posterior diameters can minimize surgical errors to the greatest extent.

[0056] On a standardized orthogonal lateral femoral neck radiograph, draw the centerline of the central guide pin (at this time, the two guide pins are aligned with the central guide pin, and this centerline is consistent with the centerline drawn on the standardized orthogonal anteroposterior femoral neck radiograph). Draw the anterior and posterior boundary lines at the anterior and posterior boundaries of the femoral neck isthmus, respectively. The anterior and posterior boundary lines are tangent to the femoral neck isthmus and parallel to the centerline of the central guide pin. Measure the distances between the anterior and posterior boundary lines, between the anterior boundary line and the centerline of the central guide pin, and between the posterior boundary line and the centerline of the central guide pin, respectively. Then calculate the Z-axis coordinate of the centerline (central guide pin) (the actual insertion point coordinates). The calculation formula is as follows: Z0=(d7-d8)×d2 / (2×d6), where: Z0 is the Z-axis coordinate of the centerline (central axis guide needle) in the XOZ plane rectangular coordinate system; d2 is the anteroposterior diameter of the femoral neck axial safe target area (measured by CT or assigned by a geometric model, equal to the anteroposterior diameter of the fluoroscopic boundary isthmus); d6 is the distance between the anterior and posterior boundary lines; d7 is the distance between the posterior boundary line and the centerline of the central axis guide needle; d8 is the distance between the anterior boundary line and the centerline of the central axis guide needle, in millimeters (mm). In the formula, d6=d7+d8, and d6, d7, and d8 are all measured on a standardized orthogonal lateral femoral neck X-ray. Figure 9 As shown.

[0057] Repeatable X-rays obtained by standardized orthogonal fluoroscopy based on constant bony anatomical landmarks can be image registered with the femoral neck axial safety target area. This allows for accurate calculation of the coordinates of the guide pin in the coordinate system of the femoral neck axial safety target area using intraoperative orthogonal fluoroscopy images. This enables the transformation of the positional coordinates of the central axis guide pin and hollow screw guide pin on the X-ray with the coordinates of the femoral neck axial safety target area, and allows for visualization of their position, spatial configuration, and relationship with the safety boundary.

[0058] Step S6: Mark the calculated coordinates of the centerline guide pin (i.e., the actual placement point coordinates (Y0, Z0)) in the Cartesian coordinate system YOZ. Establish a new Cartesian coordinate system UVW with the coordinates (Y0, Z0) of the centerline guide pin as the origin V, the line parallel to the Y-axis as the U-axis, and the line parallel to the Z-axis (perpendicular to the U-axis) as the W-axis. Figure 10As shown. Obviously, due to factors such as patient anatomical differences, human error, and mechanical deviation, there may be a certain range of comprehensive deviations between the theoretical placement point of the central axis guide needle (i.e., the origin (0, 0) of the Cartesian coordinate system YOZ) and the actual placement point during surgery (i.e., the origin (Y0, Z0) of the Cartesian coordinate system UVW). The Cartesian coordinate system YOZ and the Cartesian coordinate system UVW are two parallel Cartesian coordinate systems with different origins (i.e., the Cartesian coordinate system UVW is obtained by translating the origin O (0, 0) of the Cartesian coordinate system YOZ to point V (Y0, Z0)). The coordinates of any point can be quantitatively converted between the two Cartesian coordinate systems (the calculation parameters are the Y-axis coordinate Y0 and Z-axis coordinate Z0 of the central axis guide needle centerline in the Cartesian coordinate system YOZ as described in step 5), so that the coordinates of the same point in different Cartesian coordinate systems can be obtained through conversion calculation. The coordinates of the three hollow guide pins, pre-set in the YOZ Cartesian coordinate system, are transformed and calculated to obtain their coordinates in the UVW Cartesian coordinate system. This converts the preset theoretical coordinates of the hollow guide pins into UVW coordinates, quantifying the hollow guide pin coordinates based on the central axis guide pin group as a reference, and eliminating surgical errors caused by deviations between the theoretical placement point and the actual placement point of the central axis guide pin during surgery. Figure 11 As shown.

[0059] Step S7: During the operation, based on the pre-set coordinates of the three hollow screw guides in the Cartesian coordinate system UVW, using the previously inserted midline guide pin in the femoral neck as the origin and the midline guide pin group in the femoral neck as the reference, the insertion positions of the three hollow screw guides are marked, and then the three hollow screw guides are inserted respectively. At this time, in order to avoid the hollow screw guides penetrating the femoral neck cortex and femoral head cartilage (especially in the case where a safe target area geometry model is used as a reference background during screw placement, it is impossible to ensure that the safe target area geometry model and the individualized femoral neck axis are aligned), The shape and boundary position of the entire target area are completely consistent. After opening the proximal femoral cortex at the coordinate point of the hollow screw, the bone tunnel of the hollow screw guide pin can be opened using the "limit pressure individualized adjustable hollow elastic channel screw opener", and the hollow screw guide pin can be inserted. This completely avoids the occurrence of in-out-in screws and hollow screw guide pins penetrating the femoral head cartilage. The specific device and insertion method are described in the invention patent (application number: ZL201911044418.1; title: limit pressure individualized adjustable hollow elastic channel screw opener). Standardized orthogonal fluoroscopy is used again to obtain a standardized orthogonal femoral neck anteroposterior X-ray (e.g., Figure 12 (as shown), standardized orthogonal lateral femoral neck X-ray (such as...) Figure 13As shown), on standardized orthogonal femoral neck anteroposterior and lateral X-rays, the Y-axis and Z-axis coordinates of the three hollow screw guides are calculated using the same method as above for calculating the coordinates of the centerline of the guide pin. These coordinates are then converted into the Y-axis and Z-axis coordinates of the YOZ coordinate system in the femoral neck axial safe target area, marked in the coordinate system, and compared with the boundary of the femoral neck axial safe target area (screw diameter is 8mm, cortical bone is 3mm, and the safe corridor (i.e., the distance from the screw edge to the inner edge of the cortical bone) is 2mm). This ensures that the screw will not penetrate the cortical bone and meets the requirements of the preoperative design; otherwise, fine adjustments are necessary.

[0060] Step S8: Following standard procedures, enlarge the bone tunnel along the hollow screw guide pin using a hollow drill and insert the hollow screw (screw). After successful insertion, obtain standardized orthogonal femoral neck anteroposterior and lateral femoral neck X-rays using standardized orthogonal fluoroscopy to verify and ensure the accurate realization of the hollow screw's direction, position, and spatial configuration. This allows for the determination of the reference benchmark (central axis guide pin) during the operation, enabling accurate insertion of the hollow screw guide pin based on the pre-set position and spatial configuration. This minimizes surgical errors caused by factors such as patient anatomical differences, elastic deformation of the steel pin, fluoroscopic instability, and human manipulation, ensuring accurate screw placement on the first attempt.

[0061] According to the design concept of this invention, the present invention can also employ a coordinate system rotation algorithm (i.e., after the central axis guide pin group is inserted, the coordinates of the central axis guide pin and the coordinates of the preset hollow nail in the central axis guide pin group coordinate system are calculated on standardized orthogonal femoral neck anteroposterior and lateral X-ray films with quantitatively changed orthogonal fluoroscopy angles). This is suitable for situations where it is inconvenient or unfamiliar to use the central axis guide pin group as a fluoroscopic reference during surgery, and also provides a convenient algorithm for coordinate system rotation studies of model bone simulating femoral neck fractures. Taking intraoperative fluoroscopy parallel or perpendicular to the proximal coronal plane of the femur as an example, the following is an explanation: the angle ∠α between the anterior cortex of the femoral neck base and the proximal coronal plane of the femur is measured and calculated in the preoperative CT film, and the ASTA coordinate system YOZ is rotated in the same direction by ∠α; this is equivalent to rotating the O-XYZ spatial rectangular coordinate system with the X-axis as the rotation axis in the required direction by ∠α, forming a new spatial rectangular coordinate system O'-X'Y'Z'. At this point, the X' axis is still the central axis (parallel to the X-axis, but the origin may be offset), the Y' axis is parallel to the coronal plane of the proximal femur (with an angle of ∠α with the Y-axis), and the Z' axis is perpendicular to the coronal plane of the proximal femur (with an angle of ∠α with the Z-axis). The coordinates of the origin O' may change, but can be obtained by the aforementioned method of calculating the circumscribed rectangle. Since the X' axis, Y' axis, and Z' axis are perpendicular to each other, they also satisfy the conditions for forming a spatial rectangular coordinate system. Orthogonal perspective along the Z' axis, orthogonal perspective along the Y' axis, and the rotated ASTA coordinate system can all achieve orientation and boundary registration (but O'-X'Y'Z' and O-XYZ have inconsistent orientations and boundaries). Therefore, the Y' and Z' axis coordinates of the central axis guide pin can be calculated using the rotated orthogonal orthogonal perspective, and converted to the axial coordinates of the Y'O'Z' coordinate system. Then, the central axis guide pin is marked on the Y'O'Z' coordinate system according to its coordinates, and the coordinates converted to the YOZ coordinate system and the UVW coordinate system are calculated in sequence. According to the aforementioned coordinate system translation method, the coordinates of the preset hollow nail based on the central axis guide pin group as the reference (in the UVW coordinate system) are calculated to achieve the first-alignment nail placement. Of course, although the coordinates of the central axis guide pin and the hollow screw guide pin can be calculated by using coordinate system rotation, it is not the optimal solution for clinical surgery (screw placement and fluoroscopy based on the base of the femoral neck are the optimal solutions). However, for quantitative research on femoral neck fractures simulating model bone fractures, coordinate system translation and coordinate system rotation are important research topics that cannot be avoided. This invention provides an efficient analysis and calculation method for this purpose.

[0062] This invention designs a method for image registration and coordinate transformation calculation of the guide needle under conditions of coordinate system translation and rotation between the central axis guide needle assembly and the anterior cortical plane at the base of the femoral neck. This method is designed to address all possible unexpected situations during surgery and various extreme assumptions in experimental studies.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for first-line placement of hollow screws based on registration of the femoral neck axial safe target area boundary, characterized in that, Includes the following steps: Step S1: Obtain the axial safety target area of ​​the femoral neck, and obtain the superior and inferior diameters and anteroposterior diameters of the axial safety target area of ​​the femoral neck, namely the superior and inferior diameters of the isthmus in the standardized orthogonal anteroposterior X-ray of the femoral neck and the anteroposterior diameters of the isthmus in the standardized orthogonal lateral X-ray of the femoral neck. Step S2: Using the anterior bottom edge of the femoral neck axial safety target area as a reference, draw the circumscribed rectangle of the femoral neck axial safety target area. With the center of the rectangle as the origin O, the line parallel to the anterior bottom edge of the femoral neck axial safety target area as the Y-axis, and the line perpendicular to the anterior bottom edge of the femoral neck axial safety target area as the Z-axis, establish a plane rectangular coordinate system YOZ. Set the femoral neck axial safety target area as the reference background for the screw placement surgery calculation. Within the range of the femoral neck axial safety target area, pre-set the coordinates of 3 hollow screw guide pins on the plane rectangular coordinate system YOZ. Step S3: Based on the plane rectangular coordinate system YOZ, establish a spatial rectangular coordinate system O-XYZ with the surgical midline of the femoral neck as the X-axis; Step S4: During the operation, the central axis guide pin assembly is placed into the femoral neck, and the central axis guide pin assembly is in the same plane and parallel to the plane of the anterior cortex of the femoral neck base and the plane of the anterior cortex of the femoral neck, and at the same time parallel to the tangent of the isthmus of the superior and inferior diameters of the femoral neck; the central axis guide pin assembly includes 1 central axis guide pin and 2 direction maintenance pins, wherein the central axis guide pin is located in the middle, and the 2 direction maintenance pins are located on both sides of the central axis guide pin; The method for inserting the central axis guide pin is the dual-plane fixed-point offset method: 1) In the O-XYZ space rectangular coordinate system, with the anterior cortex of the femoral neck base as the reference, fluoroscopy is performed along the Z-axis to obtain a standardized orthogonal femoral neck anteroposterior X-ray, and fluoroscopy is performed along the Y-axis to obtain a standardized orthogonal femoral neck lateral X-ray. The midpoint of the superior and inferior diameters of the isthmus is determined on the standardized orthogonal femoral neck anteroposterior X-ray, and the midpoint of the anterior and posterior diameters of the isthmus is determined on the standardized orthogonal femoral neck lateral X-ray; 2) The central axis guide pin is inserted simultaneously with the midpoints of the superior and inferior diameters of the isthmus and the midpoints of the anterior and posterior diameters of the isthmus as the insertion points, and is made parallel to the anterior cortex of the femoral neck. Finally, one direction-maintaining steel pin is inserted on each side of the central axis guide pin, so that the central axis guide pin group is in the same plane and the plane is parallel to the plane of the anterior cortex of the femoral neck base and the plane of the anterior cortex of the femoral neck, and is also parallel to the tangent of the superior and inferior diameters of the femoral neck isthmus; Step S5: In the O-XYZ rectangular coordinate system, with the anterior cortex of the femoral neck base as the reference, use standardized orthogonal fluoroscopy to obtain standardized orthogonal femoral neck anteroposterior and lateral femoral neck X-rays. That is, perform fluoroscopy along the Z-axis to obtain a standardized orthogonal femoral neck anteroposterior X-ray; perform fluoroscopy along the Y-axis to obtain a standardized orthogonal femoral neck lateral X-ray. On a standardized orthogonal anteroposterior radiograph of the femoral neck, the centerline of the guide pin is drawn. Upper and lower boundary lines are drawn at the upper and lower boundaries of the femoral neck isthmus, respectively. These upper and lower boundary lines are tangent to the femoral neck isthmus and parallel to the centerline of the guide pin. The distances between the upper and lower boundary lines, between the upper boundary line and the centerline of the guide pin, and between the lower boundary line and the centerline of the guide pin are measured. Then, the Y-axis coordinate of the centerline of the guide pin is calculated using the following formula: Y0 = ( d5-d4)×d1 / (2×d3), where: Y0 is the Y-axis coordinate of the center line of the guide needle in the XOY plane rectangular coordinate system, d1 is the superior and inferior diameter of the femoral neck isthmus, d3 is the distance between the upper boundary line and the lower boundary line, d4 is the distance between the upper boundary line and the center line of the guide needle, and d5 is the distance between the lower boundary line and the center line of the guide needle. The unit is millimeters. In the formula, d3=d4+d5. d3, d4, and d5 are all measured on a standardized orthogonal femoral neck anteroposterior X-ray. On a standardized orthogonal lateral femoral neck X-ray, draw the centerline of the guide pin. Draw anterior and posterior boundary lines at the anterior and posterior boundaries of the femoral neck isthmus, respectively. These boundary lines are tangent to the femoral neck isthmus and parallel to the centerline of the guide pin. Measure the distances between the anterior and posterior boundary lines, between the anterior and posterior boundary lines and the centerline of the guide pin, and between the posterior and posterior boundary lines and the centerline of the guide pin. Then calculate the Z-axis coordinate of the centerline of the guide pin using the following formula: Z0 = ( d7-d8)×d2 / (2×d6), where: Z0 is the Z-axis coordinate of the center line of the guide needle in the XOZ plane rectangular coordinate system, d2 is the anteroposterior diameter of the femoral neck isthmus, d6 is the distance between the anterior and posterior boundary lines, d7 is the distance between the posterior boundary line and the center line of the guide needle, and d8 is the distance between the anterior boundary line and the center line of the guide needle. The units are millimeters. In the formula, d6=d7+d8. d6, d7, and d8 are all measured on a standardized orthogonal lateral femoral neck X-ray. Step S6: Based on the standardized orthogonal femoral neck anteroposterior X-ray and the standardized orthogonal femoral neck lateral X-ray, register the boundary between the isthmus and the femoral neck axial safe target area. Mark the coordinates of the central axis guide pin calculated in Step 5 in the plane rectangular coordinate system YOZ. With the coordinates (Y0, Z0) of the central axis guide pin as the origin V, the line parallel to the Y-axis as the U-axis, and the line parallel to the Z-axis as the W-axis, establish a new plane rectangular coordinate system UVW. Transform and calculate the coordinates of the three hollow screw guide pins set preoperatively in the plane rectangular coordinate system YOZ to obtain the coordinates of the three hollow screw guide pins in the plane rectangular coordinate system UVW. Step S7: During the operation, based on the pre-set coordinates of the three hollow screw guides in the Cartesian coordinate system UVW, using the previously inserted femoral neck central axis guide as the origin and the central axis guide group inserted into the femoral neck as the reference, the insertion positions of the three hollow screw guides are marked, and then the three hollow screw guides are inserted respectively; standardized orthogonal fluoroscopy is used again to obtain standardized orthogonal femoral neck anteroposterior and lateral femoral neck X-rays. On the X-rays, the Y-axis and Z-axis coordinates of the three hollow screw guides are calculated using the same method as above for calculating the central axis guide coordinates. These coordinates are then assigned equal values ​​to the Y-axis and Z-axis coordinates of the YOZ coordinate system in the femoral neck axial safe target area, marked in the coordinate system, and compared with the boundary of the femoral neck axial safe target area to ensure that the screws will not penetrate the bone cortex and meet the pre-operative design requirements; otherwise, fine adjustments are required. Step S8: Following standard procedures, enlarge the bone tunnel along the hollow screw guide pin using a hollow drill and insert the hollow screw. After successful insertion, obtain standardized orthogonal femoral neck anteroposterior and lateral femoral neck X-rays using standardized orthogonal fluoroscopy. Calculate the Y-axis and Z-axis coordinates using the same method as above, assign them as equal values ​​to the Y-axis and Z-axis coordinates in the Cartesian coordinate system YOZ, mark them in the Cartesian coordinate system YOZ, and compare them with the boundary of the femoral neck axial safety target area to verify and ensure the accurate realization of the hollow screw's direction, position, and spatial configuration.

2. The pin placement method according to claim 1, characterized in that: In step S1, the method for obtaining the femoral neck axial safe target area is as follows: CT scans are used to obtain femoral neck axial CT images after three-dimensional reconstruction. All axial CT images are superimposed in situ, and the overlapping area of ​​all images is the femoral neck axial safe target area.

3. The pin placement method according to claim 2, characterized in that: The method for obtaining the superior-inferior and anteroposterior diameters of the femoral neck axial safety target area is as follows: magnify the CT image including the femoral neck axial safety target area to an image ratio of 1:1, use the anterior bottom edge of the femoral neck axial safety target area as a reference, draw its circumscribed rectangle, and then measure the length and width of the circumscribed rectangle, which are the superior-inferior and anteroposterior diameters of the axial safety target area.

4. The pin placement method according to claim 1, characterized in that: In step S1, the method for obtaining the axial safe target area of ​​the femoral neck is as follows: using the axial CT image of the base of the femoral neck as a reference background, a rounded triangle geometric model or a rounded quadrilateral geometric model is constructed as the axial safe target area of ​​the femoral neck, and the anterior base of the geometric model coincides with the anterior base of the axial CT image of the base of the femoral neck.

5. The pin placement method according to claim 4, characterized in that: Methods for obtaining the superior-inferior and anteroposterior diameters of the femoral neck axial safety target area: Obtain axial CT images of the mid-section of the femoral neck, measuring the superior-inferior diameter on the images as the superior-inferior diameter of the femoral neck axial safety target area; or, obtain axial CT images of the base of the femoral neck, measuring the anteroposterior diameter on the images as the anteroposterior diameter of the femoral neck axial safety target area. Based on the measured superior-inferior or anteroposterior diameters, calculate another parameter using a regression equation; the regression equation is as follows: d2=0.71×d1+1.35; where: d1 is the superior-inferior diameter of the femoral neck axial safety target area, and d2 is the anteroposterior diameter of the femoral neck axial safety target area, in millimeters.

6. The pin placement method according to claim 4, characterized in that: The method for obtaining the superior-inferior and anteroposterior diameters of the femoral neck axial safety target area is as follows: using the constructed femoral neck axial safety target area as a reference background, the superior-inferior and anteroposterior diameters of the normal adult hip joint are assigned to the superior-inferior and anteroposterior diameters of the femoral neck axial safety target area.

7. The pin placement method according to claim 6, characterized in that: The top and bottom diameters are 26-38 mm, and the front and back diameters are 17-29 mm.

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