Femoral tackle forming method based on 3D printing

Abstract

The invention discloses a thighbone tackle forming method based on 3D printing, and relates to the technical field of three-dimensional reconstruction. Comprising the steps of data collection, data preprocessing, three-dimensional model construction, parameter measurement, individualized reconstruction, osteotomy guide plate design and intraoperative forming, knee joint skeleton anatomy details are accurately obtained through spiral CT data collection, multi-step image processing and three-dimensional modeling, and the individualized reconstruction of the tackle groove based on patient individual anatomy is achieved. The curvature radius, the width, the depth and the articular surface angle of the reconstructed tackle groove are matched with the height of the patella, the operation accuracy is improved, and the problem that the patella is unstable due to maldevelopment of the tackle groove is solved; the design of the osteotomy guide plate realizes accurate conversion from virtual osteotomy to an actual operation, the binding surface of the osteotomy guide plate is tightly attached to the outer surface of the femur, the osteotomy channel is accurately matched with an osteotomy tool, the operation time is shortened, the design of the fixing holes ensures that the guide plate is stable, the osteotomy deviation risk is reduced, and the operation safety is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of three-dimensional reconstruction, in particular to a femoral trochlear pulley forming method based on 3D printing. BACKGROUND

[0002] In knee joint diseases, femoral trochlear dysplasia is one of the important causes of patellar instability, patellar dislocation and other conditions, which seriously affects the knee joint function and quality of life of patients. At present, the treatment of femoral trochlear dysplasia, especially the trochlear forming surgery, has many deficiencies.

[0003] Traditional trochlear forming surgery relies on the experience of the operator and two-dimensional imaging data for operation, and lacks precise three-dimensional anatomical structure guidance. Due to the significant individual differences in the morphology of the femoral trochlear and the patella, it is difficult to achieve individualized trochlear groove reconstruction by experience alone, and it is easy to cause insufficient or excessive osteotomy. For example, in the control of key parameters such as trochlear groove angle, depth and width, the traditional method cannot accurately measure and evaluate, resulting in poor matching of the postoperative trochlear groove shape and the patella, and still existing the risk of patellar dislocation, affecting the surgical efficacy.

[0004] At the same time, the horizontal distance between the tibial tuberosity and the center of the femoral trochlear groove (TT-TG value) is a key indicator for evaluating the risk of patellar dislocation, and the traditional method cannot accurately measure this value, so it cannot be adjusted in the operation, increasing the probability of postoperative complications.

[0005] Therefore, there is an urgent need for a trochlear forming algorithm based on 3D printing to solve the problems of insufficient precision, poor individual matching and unstable surgical effect in traditional surgery through precise three-dimensional data acquisition and processing, comprehensive morphological parameter measurement, individualized trochlear groove reconstruction design and adaptive osteotomy guide plate production, so as to improve the success rate of femoral trochlear forming surgery and improve the knee joint function of patients. SUMMARY

[0006] (I) Technical problems solved

[0007] In view of the deficiencies of the prior art, the present application provides a femoral trochlear forming method based on 3D printing, which solves the problems mentioned in the background art.

[0008] (II) Technical solutions

[0009] In order to achieve the above purpose, the present application is realized by the following technical solutions: a femoral trochlear forming method based on 3D printing, comprising the following steps:

[0010] Step 1, data acquisition: using spiral CT to perform tomographic scanning on the affected knee joint of the patient, and obtaining DICOM format original data containing gray scale information and spatial position information of each tissue of the knee joint;

[0011] Step two, data preprocessing: by the noise reduction algorithm based on the preset gray value threshold to retain the bone pixel points, at the same time based on region growing method, selecting seed points and setting growth threshold in femur, patella, tibia area, then according to whether the gray difference value is less than or equal to the growth threshold, to separate out the corresponding single image data of femur, patella, tibia;

[0012] Step three, three-dimensional model construction: based on the single image data of preprocessed femur, patella, tibia segmentation, construct the three-dimensional model of knee joint, which extracts the bone contour by calculating the gray gradient value of pixel points, stacks the two-dimensional contour of the section and fills the triangular facet to construct the three-dimensional model of knee joint, establishes the coordinate system with the center of tibial plateau as the origin: along the long axis of tibia as X axis (the positive direction points to the distal end of knee joint), perpendicular to the tibial plateau upward as Z axis (the positive direction points to the upper of knee joint), according to the right-hand coordinate system rule to determine Y axis (the positive direction points to the medial side of knee joint); Through the coordinate system, the spatial coordinate positioning of any point on the three-dimensional model of femur, patella, tibia is realized;

[0013] Step four, parameter measurement: measure the radius of curvature, width and height of the inner surface of patella, as well as the trochlear groove angle, depth, width and TT-TG value;

[0014] Step five, individualized reconstruction: match the radius of curvature of the inner surface of the trochlear groove with the radius of curvature of the inner surface of the patella, the width of the trochlear groove is the width of the inner surface of the patella plus a preset width compensation value, the depth of the trochlear groove is designed according to the product of the height of the inner surface of the patella and a preset depth coefficient, and the angle of the trochlear groove articular surface is adjusted;

[0015] Step six, osteotomy guide plate design: extract the osteotomy contour and design the osteotomy guide plate that fits the surface of femur;

[0016] Step seven, intraoperative shaping: after exposing the femoral trochlear groove area, the osteotomy guide plate is fixed to the femoral surface in a side-by-side state with the trochlear groove, and the osteotomy guide plate is used as a template to guide the osteotomy tool along the osteotomy channel to complete the osteotomy shaping of the trochlear groove, and then the osteotomy guide plate is removed.

[0017] As a further scheme of the application: the gray information refers to the gray value of different knee joint tissues under CT scanning, and the spatial position information refers to the coordinate position relationship of the knee joint tissues in the three-dimensional space, including the specific position, shape structure and spatial distribution of the bones such as femur, patella, tibia and the surrounding soft tissues on X, Y and Z axes; wherein, the different knee joint tissues include bones, muscles, synovial membrane and fat.

[0018] As a further scheme of the application: the determination method of bone pixel point reservation is as follows:

[0019] The gray value threshold is denoted as [H1, H2], wherein H1 is the lower limit of the gray value of the knee bone tissue, and H2 is the upper limit of the gray value of the knee bone tissue;

[0020] When the pixel gray value H satisfies H1≤H≤H2, the pixel point is reserved and is regarded as a bone pixel point; otherwise, the pixel point is removed.

[0021] As a further scheme of the present application, the separation of the single image data is as follows:

[0022] The growth threshold is denoted as T, which is the allowed range of the gray value difference between the seed point and the surrounding pixel points; the absolute value of the difference between the gray value of the seed point and the gray value of the surrounding pixel points is calculated and denoted as ΔH;

[0023] If ΔH≤T, H z is classified into the bone region; otherwise, H z is not classified into the bone region.

[0024] Through the operation, the single image data of the femur, the patella and the tibia are separated from the whole image of the knee joint.

[0025] As a further scheme of the present application, the specific way of constructing the three-dimensional model of the knee joint is as follows:

[0026] The gray gradient value of the pixel point is calculated by: wherein G T represents the gray gradient value of the pixel point, G x is the gray change rate of the pixel point in the x direction, and G y is the gray change rate of the pixel point in the y direction.

[0027] Then, a preset gradient threshold G th is extracted, and when G T ≥G th , the pixel point is a bone contour point, and all the contour points are connected to form the two-dimensional contour of the bone of the layer.

[0028] The triangular patch generation algorithm is adopted to fill the triangular patches between the adjacent two layers of contours, the two-dimensional contours of the bone of each section are stacked in the order of the scanning layer thickness to form a continuous three-dimensional model of the knee joint.

[0029] Thus, the three-dimensional models of the femur, the patella and the tibia are constructed, including the curved surface characteristics of the inner surface of the patella and the original geometric shape of the trochlear groove of the femur.

[0030] As a further scheme of the present application: the X axis is along the long axis direction of the tibia, wherein the positive direction of the X axis points to the distal end of the knee joint; the Z axis is perpendicular to the tibial plateau plane and upward, wherein the positive direction of the Z axis points to the upper side of the knee joint; the Y axis is determined according to the right-hand coordinate system rule, wherein the positive direction of the Y axis points to the medial side of the knee joint.

[0031] As a further scheme of the present application: the right-hand coordinate system rule is a standard rule for determining the direction of the coordinate axis in a three-dimensional space, which is a prior art, and the core definition thereof is that: stretch the right hand, so that the thumb, index finger and middle finger are perpendicular to each other, if the thumb points to the positive direction of the X axis, the index finger points to the positive direction of the Y axis, then the middle finger points to the positive direction of the Z axis.

[0032] As a further scheme of the present application: on the three-dimensional model corresponding to the patella, the patella shape parameter measurement method is as follows:

[0033] Curvature radius of the inner surface of the patella: select three non-collinear feature points P1(x1, y1, z1), P2(x2, y2, z2) and P3(x3, y3, z3) on the inner surface of the patella; calculate the lengths of the three sides of the triangle formed by the three points through: ; then calculate the area S of the triangle through the Heron formula: , wherein ; finally, calculate the curvature radius R of the inner surface of the patella through:

[0034] Width of the inner surface of the patella: select the innermost point P N (x N ,y N ,z N ) and the outermost point P W (x W ,y W ,z W ) on the coronal plane of the three-dimensional model of the patella; wherein the coronal plane refers to a plane perpendicular to the X axis; then calculate the distance of the two points in the Y axis direction, i.e. the width Wp of the inner surface of the patella, through: P = |y W- y N |

[0035] Height Hp of the inner surface of the patella: select the frontmost point P Q (x Q ,y Q ,z Q ) and the last point P H (x H ,y H ,z H ) on the sagittal plane of the three-dimensional model of the patella; wherein the sagittal plane refers to a plane perpendicular to the Y axis; then calculate the height Hp of the inner surface of the patella through: P ​= |x Q- x H |, calculate the distance between the two points in the X-axis direction, that is, the height of the inner surface of the patella Hp.

[0036] As a further scheme of the present application: on the corresponding three-dimensional model of the femur, the trochlear groove original morphology parameter measurement method is as follows:

[0037] Trochlear groove angle θ: on the cross section of the femoral trochlear groove, the tangent line L W of the lateral articular surface of the trochlear groove and the tangent line L N of the medial articular surface are selected, and the included angle of the two tangent lines is the trochlear groove angle; wherein the cross section is perpendicular to the plane of the femoral long axis; the direction vectors V W (a1, b1, c1) and V N (a2, b2, c2) of the two tangent lines are obtained, and according to the vector dot product formula: , the included angle of the two tangent lines is obtained as the trochlear groove angle θ;

[0038] Trochlear groove depth: at the midline position of the cross section of the trochlear groove, the bottom point P D (x D , y D , z D ) of the trochlear groove and the top edge point P T (x T , y T , z T ) of the trochlear groove are selected; wherein the top edge point of the trochlear groove refers to the midpoint of the lateral and medial top edge points; the midline position of the cross section refers to the midline along the Y-axis direction; then through: Dg = |z T- z D |, calculate the distance between the two points in the Z-axis direction, that is, the trochlear groove depth Dg;

[0039] Trochlear groove width: at the top edge of the cross section of the trochlear groove, the lateral edge point PU(x U , y U , z U ) and the medial edge point P V (x V , y V , z V ) are selected, and through: Wg = |y U- y V |, calculate the distance between the two points in the Y-axis direction, that is, the trochlear groove width Wg;

[0040] TT-TG value: in the three-dimensional model, the center of the tibial tuberosity P tt (x tt , y tt , z tt ) and the center of the femoral trochlear groove P tg(x tg ,y tg ,z tg ); and through: TT-TG=∣y tt- y tg | Calculate the distance between two points along the Y-axis, i.e., the TT-TG value.

[0041] As a further aspect of the present invention: extract the standard range corresponding to the normal pulley groove angle, compare the measured pulley groove angle θ with the standard range corresponding to the normal pulley groove angle, and determine the abnormality of the original pulley groove based on the comparison result.

[0042] As a further aspect of the present invention: abnormal situations are categorized as follows:

[0043] Type A: The trochlear groove of the femur is slightly shallower than normal;

[0044] Type B: The femoral trochlea is flattened or protruding;

[0045] Type C: Asymmetry of the articular surfaces on the inner and outer sides of the trochlear groove, with the outer side protruding and the inner side developing abnormally;

[0046] Type D: The articular surfaces on both sides of the trochlear groove are asymmetrical and malformed, with the angle of the articular surfaces being right angles or cliff-like.

[0047] When the measured pulley groove angle θ exceeds the standard range, the abnormality is initially identified as Type A.

[0048] When the measured pulley groove angle θ is abnormal or cannot be measured normally, the abnormality is initially identified as type B, C, or D.

[0049] As a further aspect of the present invention: wherein, the TT-TG value is the horizontal distance in the coronal plane from the center of the tibial tuberosity to the center of the femoral trochlear groove;

[0050] As a further aspect of the present invention, the specific method of individualized reconstruction is as follows:

[0051] Trochlear groove surface matching: Based on the radius of curvature R of the inner surface of the patella, design the radius of curvature R′ of the inner surface of the trochlear groove so that R′=R;

[0052] Trochlear groove width design: The reconstructed trochlear groove width Wg′ is matched with the patellar inner surface width Wp; the trochlear groove width is determined by: Wg′=Wp+ΔW; where ΔW is a preset width compensation value;

[0053] Troch groove depth design: according to the original depth of the troch groove Dg and the height of the inner surface of the patella Hp, the depth of the reconstructed troch groove Dg' is designed; if the abnormal condition of the original troch groove is type A, the depth of the reconstructed troch groove Dg' is determined by Dg'=Hp×k, wherein k is a preset depth coefficient; if the abnormal condition of the original troch groove is type B, type C or type D, the original irregular articular surface of the troch groove is flattened, and then Dg' is designed according to the formula: Dg'=Hp×k;

[0054] Troch groove articular surface angle design: for the original troch groove corresponding to type C or type D, the troch groove angle θ' of the reconstructed troch groove is calculated by: θ'=θ Z ±Δθ, wherein θ Z is the standard value of the normal troch groove angle, and Δθ is the angle deviation allowable value; that is, the troch groove angle of the reconstructed troch groove is obtained by adding or subtracting the angle deviation allowable value from the standard value of the normal troch groove angle.

[0055] As a further scheme of the present application, the specific way of the osteotomy guide plate design is as follows:

[0056] From the three-dimensional model of the femur, the boundary profile of the bone removal area marked in the troch groove reconstruction process is extracted, which is the osteotomy profile, including the medial and lateral boundaries, the anterior and posterior boundaries and the bottom boundary of the troch groove;

[0057] The three-dimensional profile data of the outer surface around the femoral troch groove is extracted as the design basis of the guide plate fitting surface, so that the guide plate fitting surface forms a surface contact with the outer surface of the femur;

[0058] According to the size and shape of the osteotomy tool used in the operation, the osteotomy channel on the osteotomy guide plate is designed; the position and direction of the osteotomy channel are consistent with those of the virtual osteotomy tool, and the width and depth of the channel are determined according to the diameter Z J and the osteotomy depth S J ; wherein the width of the channel Z T =Z J +0.2mm, and the depth is S T =S J +2.5mm; three fixing holes are designed on the osteotomy guide plate.

[0059] As a further scheme of the present application, the virtual osteotomy tool is a digital tool model used for simulating the operation of osteotomy in the three-dimensional modeling software, which is a virtual digital counterpart relative to the physical osteotomy tool used in the actual operation;

[0060] The osteotomy tool is a physical instrument used for removing specific bone in the femoral troch groove area and realizing the reconstruction of the shape of the troch groove in the knee joint trochoplasty operation.

[0061] As a further scheme of the present application: the specific method for forming the trochlear groove during operation is as follows:

[0062] According to the conventional knee joint operation approach, the skin, subcutaneous tissue and joint capsule are incised, and the femoral trochlear groove region is fully exposed, and the synovial tissue and hyperplastic bone in the trochlear groove are removed;

[0063] The sterilized osteotomy guide plate is placed around the femoral trochlear groove, so that the fitting surface of the osteotomy guide plate is tightly fitted with the outer surface of the femur;

[0064] The osteotomy guide plate is fixed on the femur by a fixing screw through the fixing hole on the guide plate;

[0065] According to the osteotomy channel on the osteotomy guide plate, a matching osteotomy tool is selected and inserted into the osteotomy channel, and osteotomy operation is performed along the direction and depth of the channel;

[0066] During the osteotomy process, the osteotomy tool is slowly and uniformly advanced, and physiological saline is continuously flushed in the osteotomy region to reduce the local temperature and reduce the thermal damage to the surrounding soft tissue; after the osteotomy is completed, the osteotomy tool is removed, the fixing screw is unscrewed, and the osteotomy guide plate is removed.

[0067] (Three) beneficial effects

[0068] The present application provides a femoral troch formation method based on 3D printing. Compared with the prior art, the following beneficial effects are achieved:

[0069] Firstly, in terms of precision and individualization, through spiral CT data acquisition, multi-step image processing and three-dimensional modeling, the anatomical details of the patient's knee joint bone can be accurately obtained, including the inner surface curve of the patella and the original geometric shape of the femoral troch. Based on these accurate data, morphological parameter measurement and individualized troch reconstruction are performed, so that the reconstructed troch is highly matched with the patient's patella in terms of curvature radius, width, depth and joint surface angle, etc., realizing true individualized treatment, greatly improving the operation precision and effectively solving the problem of patellar instability caused by troch dysplasia, and providing a treatment scheme more suitable for the patient's own anatomical structure.

[0070] Secondly, in terms of operation efficiency and safety, the close fitting of the guide plate fitting surface with the outer surface of the femur and the precise matching of the osteotomy channel with the osteotomy tool enable the operator to quickly and accurately perform osteotomy operation during operation, thereby shortening the operation time. At the same time, the design of the fixing hole and the fixing screw ensures the stability of the guide plate during operation, reduces the risk of osteotomy deviation, and the physiological saline flushing during osteotomy reduces the probability of thermal damage and improves the safety of the operation. This digital and individualized operation scheme also reduces the excessive dependence on the experience of the operator, which is conducive to the popularization and standardization of the technology. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1It is a flowchart of the femoral troch forming method based on 3D printing of the present application. DETAILED DESCRIPTION

[0072] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0073] Please refer to Figure 1 The embodiments of the present application provide the following technical solutions:

[0074] As an embodiment of the present application:

[0075] The present application is a femoral troch forming method based on 3D printing, comprising:

[0076] Step one, data acquisition:

[0077] The patient's affected knee joint is subjected to tomography by spiral CT. After the scanning is completed, the DICOM format original data of the patient's affected knee joint is obtained, which contains the gray scale information and spatial position information of each tissue of the knee joint;

[0078] Step two, data preprocessing:

[0079] Image noise reduction processing: a noise reduction algorithm based on gray value threshold is adopted to extract a pre-set gray value threshold [H1, H2], wherein H1 is the lower limit value of the gray scale of the knee joint bone tissue, and H2 is the upper limit value of the gray scale of the knee joint bone tissue;

[0080] In this embodiment, H1 is 200 HU and H2 is 1000 HU, and HU is the unit of CT value;

[0081] When the pixel gray value H satisfies H1≤H≤H2, the pixel point is retained;

[0082] When the pixel gray value H is less than H1 or greater than H2, the pixel point is removed;

[0083] Image segmentation: based on the gray scale difference between the bone and the surrounding soft tissue, a region growing method is adopted;

[0084] Seed points are selected in the femur, patella and tibia regions, and a growth threshold T is set, which is the allowed range of gray scale difference between the seed points and the surrounding pixel points;

[0085] In this embodiment, the value range of the region growth threshold T is 5-15 HU;

[0086] Through , calculate the gray difference value AH between the surrounding pixel point and the seed point; wherein H0 is the seed point gray value, H z is the surrounding pixel point gray value;

[0087] If AH≤T, H z is classified into the bone region;

[0088] If AH>T, H z is not classified into the bone region;

[0089] Through this operation, the separate image data of femur, patella and tibia is separated from the overall image of knee joint;

[0090] Step three, three-dimensional model construction:

[0091] Bone three-dimensional modeling: based on the pre-processed separate image data of femur, patella and tibia segmentation, the three-dimensional model of knee joint is constructed, the process is as follows:

[0092] For each bone section image after segmentation, edge detection algorithm is used to extract the bone contour;

[0093] Through: , calculate the gray gradient value G T of the pixel point;

[0094] Among them, G x is the gray change rate of the pixel point in x direction, G y is the gray change rate of the pixel point in y direction;

[0095] Then extract the pre-set gradient threshold G th , when G T ≥G th , the pixel point is the bone contour point, and all contour points are connected to form the two-dimensional contour of the bone of this layer;

[0096] Stack the two-dimensional bone contours of each section according to the scanning layer thickness sequence to form a continuous three-dimensional model of knee joint, which uses triangle patch generation algorithm to fill the triangle patch between the adjacent two layers of contour;

[0097] The triangle patch generation algorithm uses Delaunay triangulation algorithm, which can ensure the uniformity of the triangle patch and improve the smoothness of the model surface;

[0098] From this, the three-dimensional models of femur, patella and tibia are constructed, including the curved surface characteristics of the inner surface of patella and the original geometric morphology of femoral trochlear groove;

[0099] Model coordinate system establishment: take the center of the tibial plateau as the coordinate origin, the long axis direction of the tibia as the X axis, the positive direction of the X axis points to the distal end of the knee joint, the vertical direction to the tibial plateau plane and upward as the Z axis, the positive direction of the Z axis points to the upper of the knee joint, the Y axis is determined according to the right-hand coordinate system rule, and the positive direction of the Y axis points to the medial side of the knee joint; then the spatial coordinates of any point on the three-dimensional model of the femur, patella and tibia are positioned through the coordinate system;

[0100] The femoral troch shape forming method based on 3D printing of the embodiment one, through spiral CT collection knee joint DICOM data, utilize gray threshold denoising and region growing method accurate segmentation femur, patella, tibia, again through edge detection and triangular facet generation algorithm constructs containing patella inner surface curved surface, femoral troch groove original geometric shape three-dimensional model, also established with tibial plateau center as the origin coordinate system realizes spatial positioning. This scheme lays a precise three-dimensional data foundation for subsequent personalized troch reconstruction, can accurately restore the anatomical structure of the knee joint, guarantee the accuracy of subsequent model analysis, parameter measurement and surgical planning, and provide a high-precision three-dimensional visualization tool for the knee joint for the clinic.

[0101] As the embodiment two of the application:

[0102] In the specific implementation of the application, compared with the embodiment one, the technical scheme of the embodiment is only different from the embodiment one in that the embodiment further performs parameter measurement of the patella and the troch shape on the corresponding three-dimensional models of the femur, the patella and the tibia; and the parameter measurement method of the patella and the troch shape is as follows:

[0103] Step 4.1, patella shape parameter measurement:

[0104] On the three-dimensional model of the patella, the following key parameters are obtained:

[0105] The curvature radius R of the inner surface of the patella:

[0106] Select three non-collinear feature points P1(x1, y1, z1), P2(x2, y2, z2) and P3(x3, y3, z3) on the inner surface of the patella;

[0107] First, calculate the lengths of the three sides of the triangle formed by the three points by:

[0108] Then, calculate the area S of the triangle by using the Heron formula: , wherein, ;

[0109] Finally, calculate the curvature radius R of the inner surface of the patella by:

[0110] ​​In this embodiment, multiple sets of feature points are measured on different regions of the inner surface of the patella, and the average value is taken as the overall curvature radius of the inner surface of the patella, which reflects the bending degree of the inner surface of the patella.

[0111] Patellar inner surface width Wp:

[0112] On the coronal plane of the three-dimensional model of the patella, the innermost point P N (x N ,y N ,z N ) and the outermost point P W (x W ,y W ,z W ) of the inner surface of the patella are selected; wherein the coronal plane refers to the plane perpendicular to the X-axis;

[0113] Then W P =∣y W- y N ∣ is calculated to obtain the distance of the two points in the Y-axis direction, i.e. the width Wp of the inner surface of the patella;

[0114] In this embodiment, this parameter determines the width size after the reconstruction of the trochlear groove, and needs to ensure that the width of the trochlear groove matches the width of the inner surface of the patella to avoid sliding jamming.

[0115] Patellar inner surface height Hp:

[0116] On the sagittal plane of the three-dimensional model of the patella, the most anterior point P Q (x Q ,y Q ,z Q ) and the most posterior point P H (x H ,y H ,z H ) of the inner surface of the patella are selected; wherein the sagittal plane refers to the plane perpendicular to the Y-axis;

[0117] Then H P =∣x Q- x H ∣ is calculated to obtain the distance of the two points in the X-axis direction, i.e. the height Hp of the inner surface of the patella;

[0118] In this embodiment, this parameter is used to determine the front and back depth range after the reconstruction of the trochlear groove, to ensure the sliding space of the patella in the front and back directions.

[0119] Step 4.2, measurement of original morphology parameters of the trochlear groove:

[0120] On the three-dimensional model of the femur, the following key parameters of the trochlear groove region are measured to evaluate the type and degree of trochlear dysplasia:

[0121] Trochlear groove angle θ: on the cross section of femoral trochlear groove, a tangent line L of lateral articular surface of trochlear groove is selected W and a tangent line L of medial articular surface of trochlear groove N , and the included angle of the two tangent lines is the trochlear groove angle; wherein the cross section is perpendicular to the plane of the long axis of femur;

[0122] The direction vectors V W (a1, b1, c1) and V N (a2, b2, c2) of the two tangent lines are obtained, and the included angle of the two tangent lines is calculated according to the vector dot product formula:

[0123] , and the included angle of the two tangent lines is the trochlear groove angle θ;

[0124] The standard range corresponding to the normal trochlear groove angle is extracted, and the measured trochlear groove angle θ is compared with the standard range corresponding to the normal trochlear groove angle, and the abnormal condition is determined according to the comparison result;

[0125] Among them, the abnormal condition is divided into:

[0126] Type A: the femoral trochlear groove is slightly shallower than normal, and the judgment basis is that the trochlear groove angle θ exceeds the standard range;

[0127] Type B: the femoral trochlear groove is flat or convex, and the judgment basis is that the trochlear groove angle θ is abnormal or cannot be normally measured;

[0128] Type C: the medial and lateral articular surfaces of the trochlear groove are asymmetric, the lateral is convex, and the medial is deformed, and the judgment basis is that the trochlear groove angle θ is abnormal or cannot be normally measured, and accompanied by the difference in the shape of the medial and lateral articular surfaces;

[0129] Type D: the medial and lateral articular surfaces of the trochlear groove are asymmetric and deformed, and the articular surface angle is at right angles or cliff-like, and the judgment basis is that the trochlear groove angle θ is abnormal or cannot be normally measured, and the articular surface angle is in an extreme shape;

[0130] That is, when the measured trochlear groove angle θ exceeds the standard range, the abnormal condition is preliminarily determined as type A; when the measured trochlear groove angle θ is abnormal or cannot be normally measured, the abnormal condition is preliminarily determined as type B, C or D;

[0131] In this embodiment, the normal trochlear groove angle standard range is 138°±6°, which is referred to from the relevant standard of “Imaging Knowledge and Measurement Methods Related to Patellofemoral Joint”;

[0132] In this embodiment, there may also be special population differences, such as the normal trochlear groove angle standard range of adults is 138°±6°, and the normal trochlear groove angle standard range of teenagers may be 140°±5°;

[0133] Depth of the trochlear groove Dg: in the middle line position of the trochlear groove cross section, select the bottom point P D (x D ,y D ,z D ) and the top edge point P T (x T ,y T ,z T ) of the trochlear groove;

[0134] Wherein, the top edge point of the trochlear groove refers to the midpoint of the outer and inner top edge points; the middle line position of the cross section refers to the middle line along the Y axis direction;

[0135] Then pass through: Dg=∣z T- z D ∣, calculate the distance of the two points in the Z axis direction;

[0136] In this embodiment, through the parameter, it can be directly judged whether the trochlear groove is too shallow, that is, whether the abnormal condition is type A, and the smaller the depth value, the more serious the dysplasia.

[0137] Width of the trochlear groove Wg: in the top edge of the trochlear groove cross section, select the outer edge point PU(x U ,y U ,z U ) and the inner edge point P V (x V ,y V ,z V ),

[0138] Pass through: Wg=∣y U- y V ∣, calculate the distance of the two points in the Y axis direction, that is, the width of the trochlear groove Wg;

[0139] In this embodiment, compared with the width of the inner surface of the patella Wp, it can be preliminarily judged whether the width of the trochlear groove matches the patella, if Wg is much smaller than Wp, the width of the trochlear groove needs to be expanded when reconstructed.

[0140] TT-TG value: in the three-dimensional model, determine the center of the tibial tuberosity P tt (x tt ,y tt ,z tt ) and the center of the femoral trochlear groove P tg (x tg ,y tg ,z tg );

[0141] And pass through: TT-TG=∣y tt- y tg|, the distance between the two points in the Y-axis direction, i.e. the TT-TG value;

[0142] The TT-TG value is the horizontal distance between the center of the tibial tuberosity and the center of the femoral trochlear groove in the coronal plane, and is an important parameter for evaluating the risk of patellar dislocation.

[0143] When the TT-TG value is too large, it indicates that the patella has a risk of lateral dislocation, and in the design of trochlear groove reconstruction, the medial and lateral positions and shapes of the trochlear groove need to be adjusted to reduce the risk of dislocation, providing a quantitative basis for doctors to judge the patient's condition and helping to take measures in advance to prevent dislocation.

[0144] In Example Two, based on Example One, the femur, patella and tibia three-dimensional models are measured for patellar and trochlear groove shape parameters. By measuring the radius of curvature, width and height of the inner surface of the patella, the shape characteristics of the patella can be comprehensively mastered, providing key basis for the design of curve matching, width and depth of trochlear groove reconstruction; measuring the trochlear groove angle, depth, width and TT-TG value of the trochlear groove can accurately evaluate the type and degree of trochlear groove dysplasia and judge the risk of patellar dislocation. The acquisition of these parameters realizes the quantitative analysis of the anatomical shape of the trochlear region of the knee joint, provides data support for the development of individualized trochlear groove reconstruction plan, and helps to improve the pertinence and effectiveness of the operation.

[0145] As Example Three of the present application:

[0146] In the specific implementation of the present application, compared with Example One and Example Two, the technical solution of the present embodiment is to combine the solutions of Example One and Example Two, and the difference between the technical solution of the present embodiment and Example One and Example Two is that in the present embodiment, the shape of the inner surface of the patella is taken as the core basis, and the measured parameters of the patella and the trochlear groove are combined to determine the target shape after the reconstruction of the trochlear groove, i.e. individualized reconstruction and osteotomy guide plate design of the trochlear groove, wherein the osteotomy guide plate is used to provide positioning and guidance for the osteotomy tool in the operation to ensure that the actual osteotomy operation is consistent with the computer-simulated osteotomy area;

[0147] In this embodiment, the osteotomy tool is a physical instrument used to remove specific bone in the femoral trochlear groove area in the knee trochlear forming operation to realize the reconstruction of the shape of the trochlear groove, which is the core tool connecting preoperative virtual planning and actual operation in the operation, and its type needs to be completely matched with the surgical demand and the design of the osteotomy guide plate, and the specifications need to be adapted to the width and depth parameters of the osteotomy channel. The osteotomy tool includes bone saw (straight saw blade, arc-shaped saw blade), bone knife, drill (ball head drill, columnar drill), bone file, etc.

[0148] The individualized reconstruction of the trochlear groove is as follows:

[0149] Trochlear groove curve matching: according to the radius of curvature R of the inner surface of the patella, the radius of curvature R' of the inner surface of the trochlear groove is designed to make R'=R, which is used to ensure that the two curves are completely matched;

[0150] Through the design, the sliding resistance caused by the mismatch of the curve can be eliminated, and the smooth sliding of the patella is ensured.

[0151] Trochlear groove width design: match the width Wg' of the reconstructed trochlear groove with the width Wp of the inner surface of the patella;

[0152] The width of the trochlear groove is determined by Wg'=Wp+ΔW; wherein ΔW is the width compensation value, in this embodiment, the value of ΔW is 1-2mm; and the value thereof needs to be adjusted in combination with the age of the patient and the weight-bearing condition of the knee joint;

[0153] The width compensation value is set considering the operation error and the slight displacement during joint movement;

[0154] In this embodiment, the setting of ΔW can avoid the patella compression caused by the too tight width, and prevent the patella from deviating caused by the too loose width.

[0155] Trochlear groove depth design: according to the original depth Dg of the trochlear groove and the height Hp of the inner surface of the patella, the depth Dg' of the reconstructed trochlear groove is designed;

[0156] If the original depth Dg of the trochlear groove is too shallow, that is, the abnormal condition is type A, then the depth Dg' of the reconstructed trochlear groove is determined by Dg'=Hp×k, wherein k is the depth coefficient, in this embodiment, the value of k is 0.6-0.8, and it is based on clinical data statistics to ensure that the depth of the trochlear groove can accommodate the patella, and avoid excessive bone removal of the femur to reduce the strength of the femur, so that the depth of the trochlear groove can accommodate most of the area of the inner surface of the patella, while avoiding excessive removal of the femur bone;

[0157] If the original trochlear groove corresponds to abnormal conditions of type B, type C or type D, then the original irregular joint surface of the trochlear groove is flattened, and then Dg' is designed according to the formula Dg'=Hp×k;

[0158] Trochlear groove joint surface angle design: for the case that the original trochlear groove corresponds to the asymmetric condition of the medial and lateral joint surfaces of the type C and type D trochlear groove, the angle of the medial and lateral joint surfaces of the reconstructed trochlear groove is adjusted according to the medial and lateral shape of the inner surface of the patella; the way is:

[0159] Through: θ'=θ Z ±Δθ

[0160] The trochlear groove angle θ' of the reconstructed trochlear groove is calculated, that is, after the reconstruction of the trochlear groove, the included angle formed by the tangent of the lateral joint surface and the tangent of the medial joint surface on the transverse section of the trochlear groove;

[0161] Wherein, θ Z is the normal trochlear groove angle standard value, and Δθ is the angle deviation allowable value, and the value range is 5°-10°;

[0162] In this embodiment, the trochlear groove angle θ' of the reconstructed trochlear groove is a key parameter for measuring whether the medial and lateral articular surface angles of the trochlear groove are normal and symmetrical; through this design, the stress of the medial and lateral patella can be balanced to prevent the patella from tilting to one side;

[0163] The design steps of the osteotomy guide plate are as follows:

[0164] Osteotomy contour extraction:

[0165] From the three-dimensional model of the femur, the boundary contour of the marked bone removal area in the trochlear groove reconstruction process is extracted, and the contour is the osteotomy contour, including the medial and lateral boundaries, the front and rear boundaries, and the bottom boundary of the trochlear groove;

[0166] The guide plate material is medical-grade polyether ether ketone PEEK, which has good biocompatibility and mechanical strength;

[0167] Guide plate fitting surface design:

[0168] The three-dimensional contour data of the outer surface around the femoral trochlear groove is extracted as the design basis of the guide plate fitting surface, so that the guide plate fitting surface forms a surface contact with the outer surface of the femur;

[0169] Osteotomy channel design:

[0170] According to the size and shape of the osteotomy tool used in the operation, the osteotomy channel on the osteotomy guide plate is designed; the position and direction of the osteotomy channel are completely consistent with the position and direction of the virtual osteotomy tool, and the width and depth of the channel are determined according to the diameter Z J and the osteotomy depth S J ;

[0171] Wherein, the width of the channel Z T =Z J +0.2mm, and the depth is S T =S J +2.5mm;

[0172] In this embodiment, 0.2mm is the preset width gap of the channel, and 2.5mm is the preset depth allowance of the channel, which ensures that the osteotomy tool passes smoothly and completely removes the marked bone area.

[0173] The virtual osteotomy tool is a digital tool model used to simulate the operation of osteotomy in three-dimensional modeling software, which is a virtual digital counterpart relative to the physical osteotomy tool used in actual operation;

[0174] Virtual osteotomy tools are used in the preoperative planning stage to simulate key parameters such as the location, direction, depth, and extent of osteotomy based on a 3D model of the patient's knee joint. This provides a precise digital reference for the subsequent design of the physical osteotomy guide and the actual osteotomy operation during surgery. Specifically, the virtual osteotomy tool is configured with digital attributes according to the surgical requirements, including dimensions, shape, and operating path consistent with the actual osteotomy tool.

[0175] Fixing hole design:

[0176] Three fixation holes are designed on the osteotomy guide plate to prevent displacement of the osteotomy guide plate during surgery;

[0177] In this embodiment, the diameter of the fixing hole is set to 3mm to accommodate M3 fixing screws;

[0178] In this embodiment, the fixation hole is located in a region around the femoral trochlear groove where the bone is thicker and far from the osteotomy area;

[0179] Example 3 combines Examples 1 and 2, focusing on the morphology of the patella's inner surface and incorporating measurement parameters to perform individualized trochlear groove reconstruction and osteotomy guide design. Trochlear groove surface matching ensures a close fit between the patella and the trochlear groove, eliminating sliding resistance; width design matches the width of the patella's inner surface and sets compensation values ​​to avoid compression or displacement; depth design is rationally determined based on the original trochlear groove condition and patellar height to avoid excessive bone removal; articular surface angle design balances patellar stress and prevents tilting; the osteotomy guide design ensures that the osteotomy operation during surgery is consistent with computer simulation. This example achieves individualized and precise trochlear groove reconstruction, providing a precise guide tool for surgery, greatly improving the personalization and surgical precision of trochlear groove reconstruction, and ensuring postoperative knee joint function recovery.

[0180] As an embodiment of the present invention:

[0181] In specific implementation, compared with Embodiments 1, 2, and 3, the only difference between this embodiment and Embodiments 1, 2, and 3 is that this embodiment also includes an intraoperative shaping step of the trochlear groove, as detailed below:

[0182] After exposing the trochlear groove area of ​​the femur, the osteotomy guide plate is placed side by side with the trochlear groove and fixed to the outer surface of the femur. Using the osteotomy guide plate as a template, the osteotomy tool is guided along the osteotomy channel to complete the osteotomy shaping of the trochlear groove. After shaping, the osteotomy guide plate is removed.

[0183] Specifically, following the conventional knee surgery approach, the skin, subcutaneous tissue and joint capsule are incised to fully expose the femoral trochlear groove area, and the synovial tissue and hyperplastic bone in the trochlear groove are removed to ensure that the osteotomy guide plate can fit the femoral surface.

[0184] Put the sterilized osteotomy guide plate around the trochlear groove of the femur, so that the fitting surface of the osteotomy guide plate is closely fitted with the outer surface of the femur;

[0185] In this embodiment, if the osteotomy guide plate is not fitted well, check whether there is hyperplastic bone on the surface of the femur, remove it and re-fit; if there is a lot of bleeding during the osteotomy, use hemostatic cotton to stop bleeding, and continue the operation after the amount of bleeding is reduced;

[0186] Through the fixing hole on the guide plate, the osteotomy guide plate is fixed on the femur with a fixing screw, and in this embodiment, it is observed whether the guide plate is stable during the fixing process, and if there is no loosening and no displacement, the fixing is qualified;

[0187] According to the osteotomy channel on the osteotomy guide plate, select a matching osteotomy tool, insert it into the osteotomy channel, and perform osteotomy operation along the direction and depth of the channel; in this embodiment, the pushing speed of the osteotomy tool is controlled between 2-5mm / s to avoid bone collapse caused by too fast speed;

[0188] During the osteotomy process, the osteotomy tool is pushed slowly and uniformly, and the osteotomy area is continuously flushed with physiological saline to reduce the local temperature and reduce the thermal damage to the surrounding soft tissue; after the osteotomy is completed, the osteotomy tool is removed, the fixing screw is unscrewed, and the osteotomy guide plate is removed;

[0189] In this embodiment, the physiological saline flushing flow is controlled between 50-100ml / min to ensure that the temperature of the osteotomy area is controlled below 40℃;

[0190] It is particularly noted that: after the osteotomy is completed, the trochlear groove is scanned by intraoperative ultrasound or micro-CT, and the deviation between the scanning results and the morphological parameters of the preoperative reconstruction model is ≤0.5mm, which can enter the subsequent operation steps.

[0191] Example four increases the intraoperative trochlear groove shaping step on the basis of the previous examples, after exposing the operation area according to the conventional approach, the sterilized osteotomy guide plate is fitted to the surface of the femur, the guide plate is fixed to ensure the stability of the guide plate through the fixing hole, and then the osteotomy operation is performed along the osteotomy channel, while physiological saline is used for flushing to reduce thermal damage. This step applies the computer-simulated individualized trochlear groove reconstruction scheme to clinical surgery, ensures the consistency of actual osteotomy and planning through the precise guidance of the osteotomy guide plate, realizes the closed loop from three-dimensional model design to intraoperative precise implementation, effectively improves the operability and accuracy of the trochlear shaping surgery, and provides operation level guarantee for the postoperative recovery of the troch function of the patient.

[0192] As an embodiment of the present application:

[0193] Compared with the first embodiment, the second embodiment, the third embodiment and the fourth embodiment, the technical scheme of the present embodiment is to combine the schemes of the first embodiment, the second embodiment, the third embodiment and the fourth embodiment.

[0194] The fifth embodiment combines the first four embodiments and integrates the whole process of data acquisition, pretreatment, three-dimensional modeling, parameter measurement, individualized trochlear groove reconstruction, osteotomy guide plate design and intraoperative shaping. This combination realizes the complete technical chain from patient knee joint anatomical data acquisition to precise operation implementation, and the technical advantages of each link are superimposed, which not only guarantees the accuracy of the three-dimensional model and the comprehensiveness of the parameter measurement, but also realizes the individualization of the trochlear groove reconstruction and the precision of the surgical operation, forming a complete 3D printing assisted trochlear shaping technical scheme, significantly improving the overall effect of the knee trochlear shaping surgery, providing a more precise and personalized solution for the treatment of knee trochlear dysplasia and other diseases, and effectively promoting the technical progress and clinical efficacy improvement in this field.

[0195] It should be noted that the preset in the present application is a personalized parameter calculated by computer algorithm based on patient knee joint CT data and clinical diagnosis and treatment guidelines, which is not a fixed value.

[0196] All user data collected in the present application is collected with the consent and authorization of the user, and the use of user data is legal and compliant, and the use and processing of user data comply with relevant laws, regulations and standards in the relevant region.

[0197] Meanwhile, the contents not described in detail in the specification all belong to the existing technology known to those skilled in the art.

[0198] It should be noted that in this paper, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the term "include", "contain" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0199] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

[0200] Having described various embodiments of the application, it is to be understood that the above description is meant not to limit and not to encompass all of the possible embodiments. Many modifications and variations of this application can be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. It is intended that the scope of the application be defined by the scope of the patent and by the claims as allowed by the patent office, which can include adaptations based on the description, equivalents, and / or substitutions of elements individually or collectively to the entire disclosure.

Claims

1. A method of femoral troch shape forming based on 3D printing, characterized in that, The method comprises the following steps: Data acquisition: adopt spiral CT to perform tomography on the affected knee joint of the patient, and obtain original data in DICOM format containing gray scale information and spatial position information of each tissue of the knee joint; Data preprocessing: retain bone pixel points by a noise reduction algorithm based on a preset gray value threshold, and select seed points in the femur, patella and tibia regions and set a growth threshold based on a region growing method, and then separate out the individual image data of the femur, patella and tibia according to whether the gray scale difference is less than or equal to the growth threshold; Three-dimensional model construction: based on the individual image data of the preprocessed femur, patella and tibia segmentation, construct a three-dimensional model of the knee joint, which extracts the bone contour by calculating the gray scale gradient value of the pixel point, stacks the tomographic two-dimensional contour and fills the triangular facets to construct the three-dimensional model of the knee joint, and establishes a coordinate system with the center of the tibial plateau as the origin: the long axis of the tibia as the X axis, perpendicular to the tibial plateau upward as the Z axis, and the Y axis is determined according to the right-hand coordinate system rule, and the spatial coordinate positioning of any point on the three-dimensional model of the femur, patella and tibia is realized through the coordinate system; Parameter measurement: measure the radius of curvature, width and height of the inner surface of the patella, and the trochlear groove angle, depth, width and TT-TG value; Individualized reconstruction: make the radius of curvature of the inner surface of the trochlear groove equal to that of the patella, the width of the trochlear groove equal to the width of the inner surface of the patella plus a preset width compensation value, design the depth of the trochlear groove according to the product of the height of the inner surface of the patella and a preset depth coefficient, and adjust the angle of the trochlear groove articular surface; Osteotomy guide plate design: extract the osteotomy contour and design an osteotomy guide plate that fits the surface of the femur; Intraoperative shaping: after exposing the femoral trochlear groove area, the osteotomy guide plate is fixed to the femoral surface in a side-by-side state with the trochlear groove, and the osteotomy guide plate is used as a template to guide the osteotomy tool along the osteotomy channel to complete the osteotomy shaping of the trochlear groove, and the osteotomy guide plate is removed after shaping.

2. The 3D printing based femoral troch shape forming method according to claim 1, characterized in that: The data preprocessing method is as follows: The gray value threshold is denoted as [H1, H2], wherein H1 is the lower limit of the gray scale of the knee joint bone tissue, and H2 is the upper limit of the gray scale of the knee joint bone tissue; When the pixel gray value H satisfies H1≤H≤H2, the pixel point is retained and is regarded as a bone pixel point; otherwise, the pixel point is removed; The growth threshold is denoted as T; the absolute value of the difference between the gray value of the seed point and the gray value of the surrounding pixel points is calculated and denoted as ΔH; If ΔH≤T, then H is assigned to the bone region; otherwise, H is not assigned to the bone region. z If ΔH≤T, then H is assigned to the bone region; otherwise, H is not assigned to the bone region. z If ΔH≤T, then H is assigned to the bone region; otherwise, H is not Through this operation, the individual image data of the femur, patella and tibia is separated from the overall image of the knee joint.

3. The 3D printing based femoral troch shape forming method according to claim 1, characterized by: The specific method for constructing the three-dimensional model of the knee joint is as follows: The gray gradient value of the pixel point is calculated by: ; wherein, G T represents the gray gradient value of the pixel point, G x is the gray change rate of the pixel point in the x direction, G y is the gray change rate of the pixel point in the y direction; The preset gradient threshold G is extracted th When G T ≥ G th , the pixel point is a skeleton contour point, and all contour points are connected to form a two-dimensional contour of the layer skeleton. A triangular facet generation algorithm is used to fill triangular facets between adjacent two layers of contours, and the two-dimensional bone contours of each tomographic layer are stacked in the order of scanning layer thickness to form a continuous three-dimensional model of the knee joint; Thereby, the three-dimensional models of the femur, patella and tibia are constructed, including the curved surface feature of the inner surface of the patella and the original geometric morphology of the femoral trochlear groove.

4. The 3D printing based femoral troch shape forming method of claim 1, wherein: The long axis direction of the tibia is the X axis, wherein the positive direction of the X axis points to the distal end of the knee joint; the Z axis is perpendicular to the tibial plateau plane and upward, wherein the positive direction of the Z axis points upward; the Y axis is determined according to the right-hand coordinate system rule, wherein the positive direction of the Y axis points to the medial side of the knee joint.

5. The 3D printing based femoral troch shape forming method of claim 1, wherein: The patellar morphological parameter measurement method on the corresponding three-dimensional model of the patella is as follows: Radius of curvature of the patellar inner surface: Three non-collinear feature points P1(x1,y1,z1), P2(x2,y2,z2), and P3(x3,y3,z3) on the patellar inner surface were selected; [The following is a more detailed description of the patellar inner surface curvature:] Calculate the lengths of the three sides of the triangle formed by the three points; then use Heron's formula: Calculate the area S of the triangle, where, Finally passed: Calculate the radius of curvature R of the inner surface of the patella; Patellar inner surface width: the absolute value of the difference between the Y-axis coordinates of the outermost point and the innermost point of the inner surface of the patella; Patellar inner surface height Hp: the absolute value of the difference between the X-axis coordinates of the front end point and the rear end point of the inner surface of the patella.

6. The 3D printing based femoral troch shape forming method of claim 1, wherein: The trochlear groove original morphological parameter measurement method on the corresponding three-dimensional model of the femur is as follows: Trochlear groove angle θ: on the cross section of femoral trochlear groove, tangent L of lateral articular surface of trochlear groove is selected W and tangent L of medial articular surface N , and the included angle of the two tangents is the trochlear groove angle; wherein the cross section is perpendicular to the plane of femoral long axis; the direction vectors V W (a1, b1, c1) and V N (a2, b2, c2) of the two tangents are obtained, and the included angle of the two tangents is calculated according to the vector dot product formula: , to obtain the trochlear groove angle θ Trochlear groove depth: the absolute value of the difference between the Z-axis coordinates of the top edge point and the bottom point of the trochlear groove; Trochlear groove width: the absolute value of the difference between the Y-axis coordinates of the outer edge point and the inner edge point of the top of the trochlear groove; TT-TG value: the absolute value of the difference between the Y-axis coordinates of the tibial tuberosity center and the femoral trochlear groove center.

7. The 3D printing based femoral troch shape forming method according to claim 6, characterized in that: The standard range corresponding to the normal trochlear groove angle is extracted, and the measured trochlear groove angle θ is compared with the standard range corresponding to the normal trochlear groove angle, and the abnormal condition of the original trochlear groove is determined according to the comparison result.

8. The 3D printing based femoral troch shape forming method according to claim 7, characterized by: The abnormal conditions are divided into: Type A: the femoral trochlear groove is slightly shallower than normal; Type B: the femoral trochlear groove is flat or convex; Type C: the medial and lateral articular surfaces of the trochlear groove are asymmetric, with the lateral side convex and the medial side developmental deformity; Type D: the articular surfaces on both sides of the trochlear groove are asymmetric, with developmental deformity, and the articular surface angle is at right angles or cliff-like; When the measured trochlear groove angle θ exceeds the standard range, the abnormal condition is preliminarily determined as type A; when the measured trochlear groove angle θ is abnormal or cannot be normally measured, the abnormal condition is preliminarily determined as type B, C or D.

9. The 3D printing based femoral troch shape forming method according to claim 8, characterized in that: The specific method of individualized reconstruction is as follows: When designing the trochlear groove depth, if the abnormal condition of the original trochlear groove is type A, the reconstructed trochlear groove depth Dg' is the product between the patellar inner surface height and the preset depth coefficient; If the abnormal condition of the original trochlear groove is type B, C or D, the original irregular articular surface of the trochlear groove is first flattened, and then the trochlear groove depth is designed according to the product between the patellar inner surface height and the preset depth coefficient; The articular surface angle of the trochlear groove is designed for the original trochlear groove corresponding to type C or D, and the standard value of the normal trochlear groove angle is added or subtracted by the angle deviation allowable value to determine the trochlear groove angle of the reconstructed trochlear groove.

10. The 3D printing based femoral troch shape forming method of claim 1, wherein: The specific method of the osteotomy guide plate design is as follows: From the three-dimensional model of the femur, the boundary contour of the bone removal area marked in the trochlear groove reconstruction process is extracted, which is the osteotomy contour, including the medial and lateral boundaries, the anterior and posterior boundaries and the bottom boundary of the trochlear groove; The three-dimensional contour data of the outer surface around the femoral trochlear groove is extracted as the design basis of the guide plate fitting surface, so that the guide plate fitting surface forms a surface contact with the outer surface of the femur; According to the size and shape of the osteotomy tool used in the operation, the osteotomy channel on the osteotomy guide plate is designed; the position and direction of the osteotomy channel are consistent with those of the virtual osteotomy tool, and the width and depth of the channel are determined according to the diameter of the osteotomy tool and the osteotomy depth.

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