Traversal calculation method and system for acetabular cup coverage rate and acetabular top coverage rate

Abstract

The invention relates to the technical field of medical apparatus and instruments, and discloses a traversal calculation method and system for an acetabular cup coverage rate and an acetabular top coverage rate, and the method comprises the following steps: 1, constructing a pelvis model and a spherical model where an acetabular cup is located, and building a coordinate system; 2, determining parameters and a range thereof; 3, solving an intersection point of the pelvic bone model and the spherical model where the acetabular cup is located; step 4, segmenting and identifying the area embedded into the pelvis and an intersection line triangular area; step 5, identifying a pelvic bone embedding area and an intersection line triangular area on the acetabular cup; step 6, identifying the area of the acetabular cup embedded into the pelvis above the plane where the rotation center is located and an intersection line triangular area; 7, the acetabular cup coverage rate and the acetabular top coverage rate under the offset position are calculated; according to the method, the acetabular cup coverage rate and the acetabular top coverage rate under all possible mounting positions can be rapidly and accurately calculated, and doctors are helped to obtain the optimal reconstructed rotation center position in total hip replacement and the iconography abduction angle and the iconography front inclination angle of the acetabular cup.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a traversal calculation method and system for acetabular cup coverage and acetabular top coverage. Background Art

[0002] The hip joint is one of the important load-bearing joints in the human body. It is a typical "ball and socket" structure. However, for patients with severe hip arthritis, joint replacement is necessary to restore hip joint function. Hip replacement mainly replaces the patient's necrotic hip joint with an artificial acetabulum and an artificial femoral head. Hip replacement is a very successful surgical operation, and its appearance has solved the pain of thousands of patients. Hip replacement is divided into total hip replacement, hip surface replacement and double-motion total hip replacement. Regardless of the type of replacement, an artificial acetabulum is used. In theory, the center of the artificial acetabulum coincides with the center of the artificial femoral head, and the outer surface of the acetabulum is usually part of a sphere.

[0003] During hip replacement surgery, the contact area between the acetabulum and the pelvis should be increased as much as possible to improve the stability of the acetabulum. At the same time, the rotation center of the acetabulum should be made to coincide with the center of the native femoral head as much as possible, so as not to change the force arm of the muscle groups near the hip joint. Doctors are more concerned about two types of coverage. One is the conventional three-dimensional coverage, which is the ratio of the contact surface between the acetabulum and the bone to the surface area of ​​the acetabulum; the other is the acetabulum top coverage (hereinafter referred to as: acetabulum top coverage), which is the ratio of the bone contact area of ​​the acetabulum above the horizontal plane where the rotation center is located to the area of ​​the acetabulum above the horizontal plane. The acetabulum top coverage can better represent the performance of postoperative contact mechanics, and the acetabulum coverage can better represent the bone ingrowth conditions of the biological acetabulum after surgery. The currently recognized minimum coverage of the acetabular cup and acetabular top is 70%, but not every patient can reconstruct the rotation center of the prosthesis at the rotation center of the native femur and achieve a cup coverage rate and acetabular top coverage rate of more than 70%, especially for patients with developmental dysplasia of the hip (DDH). Due to the insufficient bone mass in the acetabulum, it is very difficult to achieve the above requirements while keeping the outer diameter of the acetabular cup unchanged. The common practice is to translate the rotation center of the acetabular cup toward the inner and upper sides of the human body to increase the bone coverage rate of the acetabular cup and improve the stability of the acetabular cup. However, the acetabular cup cannot be shifted to the upper side of the human body blindly. Too large a shift distance may cause the patient to have different lengths of legs, abductor muscle weakness, and medial pelvic rupture after surgery. Too small a shift distance will cause complications such as instability and loosening of the acetabular cup after surgery. Therefore, the position of the reconstructed rotation center is crucial for patients with hip dysplasia.

[0004] The position of the acetabular cup relative to the center of rotation O (e.g. Figure 1As shown in the figure, X, Y, and Z represent the top, front, and outside of the human body, respectively. It is determined by the radiographic inclination (RI) and radiographic anteversion (RA). When the rotation center is determined, the bone coverage of the acetabular cup will also change with the change of RI and RA. Therefore, when the geometric design parameters of the acetabular cup are determined, the coverage of the acetabular cup is determined by RI, RA, and the offset x, y, and z relative to the center of the native femoral head.

[0005] There are currently two methods for measuring acetabular cup coverage: 3D simulation method and 2D X-ray film evaluation method. The 3D simulation method is characterized by accuracy. The 3D simulation software or advanced surgical navigation software can accurately calculate the bone coverage and acetabular top coverage of the acetabular cup at a specific location. However, this method can only be used for a limited number of acetabular cup locations. For the tens of thousands of possible acetabular cup installation locations, this method is difficult to apply. Even if the coverage corresponding to all acetabular cup installation locations can be calculated, it is still a very labor-intensive and material-intensive task. After determining the offsets x, y, z and the upper and lower limits of RI and RA, there are many possible installation positions of the acetabular cup, such as x = -5mm ~ 5mm, y = -10mm ~ 0, z = -5mm ~ 10mm, all with an interval of 1mm; RI = 10 ~ 60°, RA = 10 ~ 40°, all with an interval of 1°. The number of all possible positions of the acetabular cup in three-dimensional space is 3060816. It is almost impossible to calculate the acetabular cup bone coverage and acetabular top coverage corresponding to these 3060816 positions using the 3D simulation method.

[0006] The two-dimensional X-ray film evaluation method estimates the coverage rate by observing the overlapping areas between the acetabulum bone and the prosthesis in the horizontal plane, coronal plane, and sagittal plane. Although this method is simple, it can only provide limited coverage information and it is difficult to accurately evaluate the bone coverage in different postures or angles, especially for patients with large differences in individual anatomical structures. It is impossible to accurately calculate the acetabular cup bone coverage in three-dimensional space. After comparison, some scholars found that the coverage rate calculated by the two-dimensional evaluation method was too large or too small. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a traversal calculation method and system for acetabular cup coverage and acetabular top coverage.

[0008] The technical solution adopted by the present invention is: a traversal calculation method for acetabular cup coverage and acetabular top coverage, comprising the following steps:

[0009] Step 1: Construct the pelvic model and the spherical model where the acetabular cup is located, and establish the coordinate system;

[0010] Step 2: Determine the upper and lower limits of the acetabular cup relative to the coordinate origin and the acetabular cup geometric parameters; transform the pelvis to the required position; determine whether the prerequisite for coverage calculation is met, if so, proceed to step 3, otherwise exit;

[0011] Step 3: Find the intersection point between the pelvic bone model and the spherical surface model where the acetabular cup is located, remove the intersection triangle where the intersection point is located in the spherical surface where the acetabular cup is located, and retain the area that does not directly intersect with the pelvic bone;

[0012] Step 4: Divide the outer surface of the sphere where the acetabular cup is located into several independent areas; determine whether each area is embedded in the pelvis and mark the area embedded in the pelvis and the intersection triangle area;

[0013] Step 5: Based on the area marked in step 4, identify the portion of the acetabular cup and the intersection triangle portion in the area where the spherical surface of the acetabular cup intersects with the pelvis, and obtain the contact area between the acetabular cup and the embedded pelvis;

[0014] Step 6: Based on the area identified in step 5, identify the area where the acetabular cup is embedded in the pelvis above the plane where the center of rotation is located and the intersection triangle area and calculate the area of ​​these areas;

[0015] Step 7: Calculate the cup coverage and acetabular top coverage at the offset position based on the results obtained in Steps 5 and 6; repeat the loop until the calculation of all offset positions is completed.

[0016] Furthermore, the coverage calculation conditions in step 2 include:

[0017] The spherical surface of the acetabulum intersects with the outer surface of the pelvis;

[0018] The spherical surface of the acetabular cup does not intersect with the inner surface of the pelvis, and the minimum distance between the two is not less than the set threshold.

[0019] Furthermore, in step 3, a ray-triangle intersection algorithm is used to solve the intersection of the pelvic model and the spherical model where the acetabular cup is located;

[0020] Identify the triangle where the intersection point is located and the triangle that shares the same side with the triangle, and mark them as intersection triangles.

[0021] Furthermore, in step 4, the common point region growing method is used to divide the outer surface of the sphere where the acetabular cup is located into several independent regions.

[0022] Furthermore, the method for identifying the portion of the acetabular cup in the area intersecting the pelvis on the spherical surface where the acetabular cup is located in step 5 is as follows:

[0023] The normal vector of the plane where the acetabular opening is located is NormalVector_Now, and the coordinates of a point on the plane are PointOnPlane_Now;

[0024] NormalVector_Now=R X (RI)·R Y (-RA) NormalVector_Initial

[0025] PointOnPlane_Now=R X (RI)·R Y (-RA) PointOnPlane_Initial

[0026]

[0027]

[0028] Where: NormalVector_Initial is the opening normal vector of the acetabular cup in the initial position, PointOnPlane_Initial is a point on the opening plane of the acetabular cup in the initial position, RI is the radiographic abduction angle of the acetabular cup, RA is the radiographic anteversion angle of the acetabular cup; R X (RI) is the rotation matrix with X as the rotation axis and the rotation degree as RI, R Y (-RA) is the rotation matrix with Y as the rotation axis and the degree of rotation as -RA; R is the radius of the sphere where the acetabular cup is located, and OpeningAngle is the angle of the acetabular cup opening;

[0029] Assume the plane equation is Ax+By+Cz+D=0, then:

[0030] A=NormalVector_Now(1)

[0031] B = NormalVector_Now (2)

[0032] C = NormalVector_Now (3)

[0033] D=-C·PointOnPlane(3)

[0034] Where: NormalVector_Now(1), NormalVector_Now(2), NormalVector_Now(3) are all components of the vector NormalVector_Now, and PointOnPlane(3) is the third component of the vector PointOnPlane_Now;

[0035] If for any point (x0, y0, z0), if Ax0+By0+Cz0+D<0, then the point is on the acetabulum.

[0036] Furthermore, the calculation method of the cup coverage rate Rate_CupCoverage in step 7 is as follows:

[0037]

[0038] Where: S Embedded is the contact area between the acetabulum and the pelvic bone, S AllCup is the total outer surface area of ​​the acetabular cup;

[0039] The calculation method of acetabular top coverage rate Rate_TopCupCoverage is as follows:

[0040]

[0041] Where: S Top_Embedded S is the area of ​​the acetabulum embedded in the pelvis above the horizontal plane of the rotation center. TopCup It is the area of ​​the outer surface of the acetabular cup above the horizontal plane where the center of rotation is located.

[0042] Furthermore, the contact area between the acetabular cup and the embedded pelvis is the area of ​​the acetabular cup embedded in the pelvis and the area of ​​the corresponding intersection triangle area;

[0043] The calculation method is as follows:

[0044]

[0045] Where: S FullEmbeddedΔ1 S is the area of ​​the acetabulum embedded in the pelvic bone, IntersectingΔ1 The area of ​​the intersection triangle corresponding to the area where the acetabulum is embedded in the pelvic bone;

[0046] The area of ​​the acetabular cup embedded in the pelvis above the plane where the rotation center is located is the area of ​​the acetabular cup embedded in the pelvis above the XOY plane and the area of ​​the corresponding intersection triangle; the calculation method is as follows:

[0047]

[0048] Where: S FullEmbeddedΔ2 S is the area of ​​the acetabulum embedded in the pelvis above the XOY plane. IntersectingΔ2 It is the area of ​​the intersection triangle corresponding to the area where the acetabulum is embedded in the pelvic bone above the XOY plane.

[0049] Furthermore, the total area of ​​the outer surface of the acetabular cup is calculated as follows:

[0050]

[0051] The area of ​​the outer surface of the acetabular cup above the horizontal plane of the center of rotation is calculated as follows:

[0052]

[0053] Where: η is the angle between the normal vector of the acetabular cup opening plane and the negative direction of the Z axis, and θ is the integral variable in the integral formula.

[0054] Furthermore, the method further comprises the following steps:

[0055] The cup coverage distribution diagram and the acetabular top coverage distribution diagram are obtained according to the calculation results of all offset positions in step 7.

[0056] A traversal calculation system for acetabular cup coverage and acetabular top coverage, comprising:

[0057] Input module: used to input the pelvic model and the spherical model where the acetabular cup is located, and input the upper and lower limit parameters and parameter step length of the moving position of the acetabular cup relative to the coordinate origin;

[0058] Acetabular cup coverage calculation module: used to calculate the acetabular cup coverage;

[0059] Acetabular coverage calculation module: used to calculate the acetabular coverage;

[0060] Output module: used to output acetabular cup coverage data and its distribution diagram and acetabular top coverage data and its distribution diagram.

[0061] The beneficial effects of the present invention are:

[0062] (1) The present invention uses the spherical model where the acetabular cup is located and the pelvis to solve the intersection area and the area embedded in the pelvis, and identifies the part of the acetabular cup in the area where the spherical surface is embedded in the pelvis according to the opening plane of the acetabular cup. Regardless of the values ​​of RI and RA of the acetabular cup, only the focus of the spherical model and the pelvis needs to be solved once, which reduces the solution time;

[0063] (2) The present invention can quickly and accurately calculate the acetabular cup coverage and acetabular top coverage in all possible installation positions, and obtain the optimal reconstructed rotation center position and the RI and RA of the acetabular cup in total hip replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a schematic diagram of acetabular cup position parameters in the background technology of the present invention.

[0065] Figure 2 It is a schematic diagram of the process of the present invention.

[0066] Figure 3 It is a schematic diagram of the coordinate system in the present invention.

[0067] Figure 4 It is a schematic diagram of the geometric parameters of the acetabular cup in the present invention.

[0068] Figure 5 It is a schematic diagram of the relative position of the acetabulum and the pelvis in the present invention.

[0069] Figure 6 It is a schematic diagram of the coverage calculation process under a certain offset in the present invention.

[0070] Figure 7 Schematic diagram of the method for dividing regions using the common point region growing method of the present invention.

[0071] Figure 8 The maximum value, minimum value, average value and standard deviation distribution diagram of the coverage rate in the range of RI=10-60° and RA=0-40° in all acetabular cup rotation positions calculated in the embodiment of the present invention.

[0072] Fig. 9 : is the coverage ratio of the acetabular cup / acetabular top when the offset x=0, y=-3mm, z=5mm in the embodiment of the present invention. DETAILED DESCRIPTION

[0073] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0074] A method for calculating the traversal of the acetabular cup coverage and the acetabular top coverage comprises the following steps: Figure 2 As shown:

[0075] Step 1: Construct the pelvic model and the spherical model where the acetabular cup is located, and establish the coordinate system;

[0076] The left hip of the human body is taken as the research object, and the rotation center of the native femoral head is taken as the origin of the coordinate system. X, Y, and Z are the front, lateral, and upper sides of the human body, respectively. Figure 3 If the patient's right hip is required, simply mirror the patient's pelvis and femur.

[0077] The pelvic model file format is STL, and the STL format model is composed of many small triangles. In order to study different pelvic postures, the pelvic position is adjusted so that the pelvic sagittal plane inclination angle PT is 0, and the line connecting the anterior superior iliac spines of the left and right pelvis is parallel to the X-axis. The femoral posture is adjusted to ensure that the line connecting the center of the native femoral head and the center of the knee joint coincides with the Z-axis, and the line connecting the internal and external condyles of the knee joint is parallel to the X-axis.

[0078] Assuming that the outer surface of the acetabular cup is a part of a sphere, its shape parameters are determined by the outer surface radius R and the acetabular cup opening angle OpeningAngle. The STL model of the sphere where the acetabular cup is located can be automatically generated according to the acetabular cup geometric parameters and resolution, such as Figure 6 shown.

[0079] Step 2: Determine the upper and lower limits of the acetabular cup relative to the coordinate origin and the acetabular cup parameters; convert the pelvic position to the required position; determine whether the coverage calculation conditions are met, if so, proceed to step 3, otherwise exit;

[0080] To determine the upper and lower limits of the acetabular cup relative to the coordinate origin, we decompose it into translations on the X, Y, and Z axes, with upper and lower limits of x and min 、x max ,y min ,y max 、z min 、z max The movement steps in the three directions are Δx, Δy, and Δz respectively. The upper and lower limits and step sizes of RI and RA of the acetabular cup relative to the reconstructed rotation center are RI min , RI max , R.A. min , R.A. max , ΔRI, ΔRA.

[0081] Rotate the pelvis PT degrees around the Y axis to simulate the inclination of the pelvis in the sagittal plane. Start to cycle the position of the acetabular cup relative to the pelvis. For example, in a certain cycle, the translation coordinates of the acetabular cup relative to the pelvis are [x, y, z], but at this time, keep the rotation center of the acetabular cup coincident with the coordinate origin, and translate the pelvis to the coordinates [-x, -y, -z] to simulate the offset of the rotation center of the acetabular cup. Therefore, the transformation relationship of the pelvis relative to the initial position is:

[0082] Position Pelvis =R Y (PT) Initial Pelvis Pelvis +T(-x,-y,-z)

[0083] Where: R Y (PT) is the rotation matrix with Y as the rotation axis and PT as the rotation degree, and T(-x,-y,-z) is the translation matrix. Pelvis InitialPelvis is the coordinate matrix of all points of the pelvis in the initial position. Pelvis is the coordinate matrix of all points of the pelvis after rotation and translation transformation.

[0084] Not all cup offset coordinates require coverage calculation. To perform coverage calculation, the following conditions must be met at the same time, such as Figure 5 As shown:

[0085] The spherical surface of the acetabulum intersects with the outer surface of the pelvis;

[0086] The spherical surface of the acetabular cup does not intersect with the inner surface of the pelvis, and the minimum distance between the two is not less than the set threshold d min . If one of the conditions is not met, exit.

[0087] Step 3: Find the intersection of the pelvic model and the spherical model where the acetabular cup is located, remove the intersection triangle in the spherical model where the acetabular cup is located, and retain the area that does not directly intersect with the pelvic bone; (The specific process of steps 3 to 6 is as follows Figure 6 (shown)

[0088] The intersection point between the pelvic model and the spherical model where the acetabular cup is located is solved by using the ray-triangle intersection algorithm;

[0089] Identify the triangle where the intersection point is located and the triangle that shares the same side with the triangle, and mark them as intersection triangles.

[0090] The essence of solving the intersection point is to identify the intersection point between a pair of surfaces by assuming that each edge of each triangular mesh represents an infinitesimal ray. The triangles where the intersection point is located and the triangles that share edges with these triangles are identified and marked as intersection triangles.

[0091] Solving the intersection point is the most time-consuming part in calculating the cup coverage. For all possible combinations of RI and RA under a certain cup offset position, the spherical model only needs to solve the intersection point once, which greatly shortens the calculation time.

[0092] Step 4: Divide the outer surface of the sphere where the acetabular cup is located into several independent areas; determine whether each area is embedded in the pelvis and mark the area embedded in the pelvis and the intersection triangle area;

[0093] After removing all the intersection triangles in the sphere and retaining the areas that do not directly intersect with the pelvis, the remaining triangles on the outer surface of the acetabular cup are divided into several independent regions using the common point region growing method. The principle of the common point region growing method is as follows: Figure 7 shown.

[0094] First, randomly select a triangle from the remaining triangles on the outer surface of the acetabular cup as the starting point, and gradually grow with the common vertex as the link until all connected triangles in the current area are attributed to the same area. After identifying a region, remove the region to retain the remaining region, and then execute the region growing method several times to naturally divide the triangles on the outer surface of the acetabular cup that do not directly intersect with the pelvis into several independent regions. Finally, in each independent region, randomly select a vertex of a triangle to detect whether it is located inside the pelvis.

[0095] If the test point is located inside the pelvis, the area where it is located is determined to be embedded in the pelvis. All areas embedded in the pelvis and the intersection triangle areas are marked and recorded to facilitate the subsequent calculation of the acetabular cup coverage.

[0096] Step 5: Based on the area marked in step 4, identify the portion of the acetabular cup and the intersection triangle portion in the area where the spherical surface of the acetabular cup intersects with the pelvis, and obtain the contact area between the acetabular cup and the embedded pelvis;

[0097] Based on step 4, the acetabular cup embedding area and the edge triangle area are identified, and the identified dividing line is the opening plane of the acetabular cup.

[0098] The normal vector of the plane where the acetabular cup opening is located is NormalVector_Now, and the coordinates of a point on the plane are PointOnPlane_Now;

[0099] NormalVector_Now=R X (RI)·R Y (-RA) NormalVector_Initial

[0100] PointOnPlane_Now=R X (RI)·R Y (-RA) PointOnPlane_Initial

[0101]

[0102]

[0103] Where: NormalVector_Initial is the opening normal vector of the acetabular cup in the initial position, PointOnPlane_Initial is a point on the opening plane of the acetabular cup in the initial position, RI is the radiographic abduction angle of the acetabular cup, RA is the radiographic anteversion angle of the acetabular cup; R X (RI) is the rotation matrix with X as the rotation axis and the rotation degree as RI, R Y (-RA) is the rotation matrix with Y as the rotation axis and the degree of rotation as -RA; R is the radius of the sphere where the acetabular cup is located, and OpeningAngle is the angle of the acetabular cup opening;

[0104] Assume the plane equation is Ax+By+Cz+D=0, then:

[0105] A=NormalVector_Now(1)

[0106] B = NormalVector_Now (2)

[0107] C = NormalVector_Now (3)

[0108] D=-C·PointOnPlane(3)

[0109] Where: NormalVector_Now(1), NormalVector_Now(2), NormalVector_Now(3) are all components of the vector NormalVector_Now, and PointOnPlane(3) is the third component of the vector PointOnPlane_Now;

[0110] If for any point (x0, y0, z0), if Ax0+By0+Cz0+D<0, then the point is on the acetabulum.

[0111] According to whether it is on the acetabulum, the area of ​​the region on the acetabulum embedded in the pelvis and the area of ​​the corresponding intersection triangle are obtained.

[0112] The calculation method is as follows:

[0113]

[0114] Where: S FullEmbeddedΔ1 S is the area of ​​the acetabulum embedded in the pelvic bone, IntersectingΔ1 It is the area of ​​the intersection triangle corresponding to the area of ​​the acetabulum embedded in the pelvic bone.

[0115] Step 6: Based on the area identified in step 5, identify the area of ​​the acetabular cup embedded in the pelvis above the plane where the rotation center is located; based on step 5, identify the area of ​​the acetabular cup embedded in the pelvis above the XOY plane and the area of ​​the corresponding intersection triangle; the calculation method is as follows:

[0116]

[0117] Where: S FullEmbeddedΔ2 S is the area of ​​the acetabulum embedded in the pelvis above the XOY plane. IntersectingΔ2 It is the area of ​​the intersection triangle corresponding to the area where the acetabulum is embedded in the pelvic bone above the XOY plane.

[0118] Step 7: Calculate the cup coverage and acetabular top coverage at the offset position based on the results obtained in Steps 5 and 6; repeat the loop until the calculation of all offset positions is completed.

[0119] The calculation method of the cup coverage rate Rate_CupCoverage is as follows:

[0120]

[0121] Where: S Embedded is the contact area between the acetabulum and the pelvic bone, S AllCup is the total outer surface area of ​​the acetabular cup;

[0122] The calculation method of acetabular top coverage rate Rate_TopCupCoverage is as follows:

[0123]

[0124] Where: S Top_Embedded S is the area of ​​the acetabulum embedded in the pelvis above the horizontal plane of the rotation center. TopCup It is the area of ​​the outer surface of the acetabular cup above the horizontal plane where the center of rotation is located.

[0125] The total external surface area of ​​the acetabular cup is calculated as follows:

[0126]

[0127] The area of ​​the outer surface of the acetabular cup above the horizontal plane of the center of rotation is calculated as follows:

[0128]

[0129] Where: η is the angle between the normal vector of the acetabular cup opening plane and the negative direction of the Z axis, and θ is the integral variable of the integral formula.

[0130] Among them, 0≤η≤90°, the acetabular roof coverage rate can better represent the performance of postoperative contact mechanics, and the acetabular cup coverage rate can better represent the bone ingrowth conditions of the biological acetabular cup after surgery.

[0131] Then, the rotation center position of the acetabular cup and the RI and RA of the acetabular cup that meet the coverage requirement are screened according to the coverage requirement, such as the rotation center position and the RI and RA of the acetabular cup with a coverage ≥ 70%.

[0132] A system for traversal calculation of acetabular cup coverage and acetabular top coverage, comprising:

[0133] Input module: used to input the pelvic model and the spherical model where the acetabular cup is located, and input the upper and lower limit parameters and parameter step length of the moving position of the acetabular cup relative to the coordinate origin;

[0134] Acetabular cup coverage calculation module: used to calculate the acetabular cup coverage;

[0135] Acetabular coverage calculation module: used to calculate the acetabular coverage;

[0136] Output module: used to output acetabular cup coverage data and its distribution diagram and acetabular top coverage data and its distribution diagram.

[0137] Example

[0138] The effects of the present invention are described below in conjunction with specific embodiments.

[0139] In this embodiment, a bone model of hip dysplasia is selected, and the upper and lower limits of the offset of the acetabulum relative to the coordinate origin, the step length, and the geometric parameters of the acetabulum are shown in Table 1.

[0140] Table 1 Upper and lower limits of the position of the acetabular cup relative to the coordinate origin and acetabular cup parameters in the embodiment

[0141]

[0142] The maximum value, minimum value, average value and standard deviation of the acetabular cup / acetabular top coverage rate corresponding to all offset positions calculated by the method of the present invention within the range of RI = 10° to 60° and RA = 10° to 30° are distributed as follows: Figure 8 shown.

[0143] Fig. 9 is the acetabular cup / acetabular top coverage rate when the offset x=0, y=-3mm, z=5mm. By using the method of the present invention, doctors can check the acetabular cup / acetabular top coverage rate at any acetabular cup installation position.

[0144] The present invention uses the spherical model where the acetabular cup is located and the pelvis to solve the intersection area and the area embedded in the pelvis, and then identifies the part of the acetabular cup in the area where the spherical surface is embedded in the pelvis based on the opening plane of the acetabular cup. No matter what the values ​​of the RI and RA of the acetabular cup are, it is only necessary to solve the intersection point of the spherical model and the pelvis once, which greatly reduces the solution time. If the acetabular cup model and the pelvis are used to solve the intersection point and the intersection triangle, then the intersection point and the intersection triangle need to be solved once the values ​​of RI and RA change once, which greatly increases the solution time. The method of the present invention can quickly and accurately calculate the coverage rate and acetabular top coverage rate of the acetabular cup in all possible installation positions, providing a reference for the doctor to determine the rotation position of the total hip replacement reconstruction and the RI and RA of the acetabular cup.

Claims

1. A method for calculating cup coverage and acetabular top coverage, characterized in that: The following steps are involved: Step 1: Construct the pelvic model and the spherical model where the acetabular cup is located, and establish the coordinate system; Step 2: Determine the upper and lower limits of the acetabular cup relative to the coordinate origin and the acetabular cup geometric parameters; transform the pelvis to the required position; determine whether the prerequisite for coverage calculation is met, if so, proceed to step 3, otherwise exit; Step 3: Find the intersection point between the pelvic bone model and the spherical surface model where the acetabular cup is located, remove the intersection triangle where the intersection point is located in the spherical surface where the acetabular cup is located, and retain the area that does not directly intersect with the pelvic bone; Step 4: Divide the outer surface of the sphere where the acetabular cup is located into several independent areas; determine whether each area is embedded in the pelvis and mark the area embedded in the pelvis and the intersection triangle area; Step 5: Based on the area marked in step 4, identify the portion of the acetabular cup and the intersection triangle portion in the area where the spherical surface of the acetabular cup intersects with the pelvis, and obtain the contact area between the acetabular cup and the embedded pelvis; Step 6: Based on the area identified in step 5, identify the area where the acetabular cup is embedded in the pelvis above the plane where the center of rotation is located and the intersection triangle area and calculate the area of ​​these areas; Step 7: Calculate the cup coverage and acetabular top coverage at the offset position based on the results obtained in Steps 5 and 6; repeat the loop until the calculation of all offset positions is completed.

2. The method for calculating the traversal of the acetabular cup coverage and the acetabular top coverage according to claim 1, characterized in that: The coverage calculation conditions in step 2 include: The spherical surface of the acetabulum intersects with the outer surface of the pelvis; The spherical surface of the acetabular cup does not intersect with the inner surface of the pelvis, and the minimum distance between the two is not less than the set threshold.

3. The method for calculating the traversal of the acetabular cup coverage and the acetabular top coverage according to claim 1, characterized in that: In step 3, a ray-triangle intersection algorithm is used to solve the intersection of the pelvic model and the spherical model where the acetabular cup is located; Identify the triangle where the intersection point is located and the triangle that shares the same side with the triangle, and mark them as intersection triangles.

4. The method for calculating the traversal of the acetabular cup coverage and the acetabular top coverage according to claim 3, characterized in that: In step 4, the common point region growing method is used to divide the outer surface of the sphere where the acetabular cup is located into several independent regions.

5. The method for calculating the traversal of the acetabular cup coverage and the acetabular top coverage according to claim 4, characterized in that: The method for identifying the portion of the acetabular cup in the area where the spherical surface where the acetabular cup is located intersects with the pelvis in step 5 is as follows: The normal vector of the plane where the acetabular opening is located is NormalVector_Now, and the coordinates of a point on the plane are PointOnPlane_Now; NormalVector_Now=R X (RI)·R Y (-RA)·NormalVector_Initial PointOnPlane_Now=R X (RI)·R Y (-RA)·PointOnPlane_Initial Where: NormalVector_Initial is the opening normal vector of the acetabular cup in the initial position, PointOnPlane_Initial is a point on the opening plane of the acetabular cup in the initial position, RI is the radiographic abduction angle of the acetabular cup, RA is the radiographic anteversion angle of the acetabular cup; R X (RI) is the rotation matrix with X as the rotation axis and the rotation degree as RI, R Y (-RA) is the rotation matrix with Y as the rotation axis and the degree of rotation as -RA; R is the radius of the sphere where the acetabular cup is located, and OpeningAngle is the angle of the acetabular cup opening; Assume the plane equation is Ax+By+Cz+D=0, then: A=NormalVector_Now(1) B = NormalVector_Now (2) C = NormalVector_Now (3) D=-C·PointOnPlane(3) Where: NormalVector_Now(1), NormalVector_Now(2), NormalVector_Now(3) are all components of the vector NormalVector_Now, and PointOnPlane(3) is the third component of the vector PointOnPlane_Now; If for any point (x0, y0, z0), if Ax0+By0+Cz0+D<0, then the point is on the acetabulum.

6. A traversal calculation method for acetabular cup coverage and acetabular top coverage according to claim 5, characterized in that: The calculation method of the cup coverage rate Rate_CupCoverage in step 7 is as follows: Where: S Embedded is the contact area between the acetabulum and the pelvic bone, S AllCup is the total outer surface area of ​​the acetabular cup; The calculation method of acetabular top coverage rate Rate_TopCupCoverage is as follows: Where: S Top_Embedded S is the area of ​​the acetabulum embedded in the pelvis above the horizontal plane of the rotation center. TopCup It is the area of ​​the outer surface of the acetabular cup above the horizontal plane where the center of rotation is located.

7. A traversal calculation method for acetabular cup coverage and acetabular top coverage according to claim 6, characterized in that: The contact area between the acetabular cup and the embedded pelvic bone is the area of ​​the acetabular cup embedded in the pelvic bone and the area of ​​the corresponding intersection triangle area; The calculation method is as follows: Where: S FullEmbeddedΔ1 S is the area of ​​the acetabulum embedded in the pelvic bone, IntersectingΔ1 The area of ​​the intersection triangle corresponding to the area where the acetabulum is embedded in the pelvic bone; The area of ​​the acetabular cup embedded in the pelvis above the plane where the rotation center is located is the area of ​​the acetabular cup embedded in the pelvis above the XOY plane and the area of ​​the corresponding intersection triangle; the calculation method is as follows: Where: S FullEmbeddedΔ2 S is the area of ​​the acetabulum embedded in the pelvis above the XOY plane. IntersectingΔ2 It is the area of ​​the intersection triangle corresponding to the area where the acetabulum is embedded in the pelvic bone above the XOY plane.

8. The method for calculating the traversal of the acetabular cup coverage and the acetabular top coverage according to claim 7, characterized in that: The total area of ​​the outer surface of the acetabular cup is calculated as follows: The area of ​​the outer surface of the acetabular cup above the horizontal plane of the center of rotation is calculated as follows: Where: η is the angle between the normal vector of the acetabular cup opening plane and the negative direction of the Z axis, and θ is the integral variable of the integral formula.

9. The method for calculating cup coverage and acetabular top coverage according to claim 1, characterized in that: The following steps are also included: The cup coverage distribution diagram and the acetabular top coverage distribution diagram are obtained according to the calculation results of all offset positions in step 7.

10. A system using the traversal calculation method for acetabular cup coverage and acetabular top coverage as claimed in any one of claims 1 to 9, characterized in that: include: Input module: used to input the pelvic model and the spherical model where the acetabular cup is located, and input the upper and lower limit parameters and parameter step length of the moving position of the acetabular cup relative to the coordinate origin; Acetabular cup coverage calculation module: used to calculate the acetabular cup coverage; Acetabular coverage calculation module: used to calculate the acetabular coverage; Output module: used to output acetabular cup coverage data and its distribution diagram and acetabular top coverage data and its distribution diagram.

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