A traversal calculation method and system for acetabular cup coverage rate and acetabular roof coverage rate

Abstract

The present invention relates to the technical field of medical devices, and discloses a traversal calculation method and system for acetabular cup coverage rate and acetabular roof coverage rate, including the following steps: Step 1: Construct a pelvic model and a spherical model where the acetabular cup is located, and establish a coordinate system; Step 2: Determine the parameters and their ranges; Step 3: Solve the intersection points of the pelvic model and the spherical model where the acetabular cup is located; Step 4: Divide and identify the area embedded in the pelvis and the intersection line triangle area; Step 5: Identify the area embedded in the pelvis and the intersection line triangle area on the acetabular cup; Step 6: Identify the area embedded in the pelvis and the intersection line triangle area of the acetabular cup above the plane where the rotation center is located; Step 7: Calculate the acetabular cup coverage rate and acetabular roof coverage rate at this offset position; The present invention can quickly and accurately calculate the acetabular cup coverage rate and acetabular roof coverage rate at all possible installation positions, helping doctors obtain the optimal reconstructed rotation center position, the radiographic abduction angle of the acetabular cup, and the radiographic anteversion angle during total hip arthroplasty.

Description

Technical Field

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

[0002] The hip joint is one of the important load-bearing joints in the human body and is a typical "ball and socket" structure. However, for patients with severe hip arthritis, joint replacement must be performed to restore the function of the hip joint. Hip joint replacement mainly uses an artificial acetabulum and an artificial femoral head to replace the necrotic hip joint of the patient. Hip joint replacement is a very successful surgical operation, and its emergence has solved the pain of thousands of patients. Hip joint replacement is divided into total hip replacement, hip surface replacement, and bipolar total hip replacement. No matter which replacement type is used, an artificial acetabular cup will be used. In theory, the center of the ball of the artificial acetabular cup coincides with the center of the ball of the artificial femoral head, and the outer surface of the acetabular cup is usually a part of a spherical surface.

[0003] During hip joint replacement, it is necessary to increase the contact area between the acetabular cup and the pelvis as much as possible to improve the stability of the acetabular cup. At the same time, it is also necessary to make the rotation center of the acetabular cup coincide with the center of the original femoral head as much as possible, so as not to change the lever arm of the muscle group near the hip joint. Doctors are more concerned about two types of coverage rates. One is the conventional three-dimensional coverage rate, that is, the ratio of the bone contact area of the acetabular cup to the surface area of the acetabular cup; the other is the acetabular roof coverage rate (hereinafter referred to as: acetabular roof coverage rate), that is, the ratio of the bone contact area of the acetabular cup above the horizontal plane where the rotation center is located to the area of the acetabular cup above the horizontal plane. The acetabular roof coverage rate can better represent the performance of postoperative contact mechanics, and the acetabular cup coverage rate can better represent the conditions for bone ingrowth after implantation of a biological acetabular cup. The currently recognized minimum coverage rates for the acetabular cup and the acetabular roof are 70%, but not every patient can reconstruct the rotation center of the prosthesis at the rotation center of the original femur and still achieve an acetabular cup coverage rate and an acetabular roof coverage rate of more than 70%. Especially for patients with developmental dysplasia of the hip (DDH), due to insufficient bone mass at the acetabulum, it is very difficult to meet the above requirements on the premise of keeping the outer diameter of the acetabular cup unchanged. A common practice is to translate the rotation center of the acetabular cup inward and upward in 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 blindly offset inward and upward in the human body. Excessive offset distance may cause consequences such as unequal leg lengths, abductor muscle weakness, and medial pelvic rupture in patients after surgery. Too small an offset 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 developmental dysplasia of the hip.

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

[0005] Currently, there are two methods for measuring the coverage rate of the acetabular cup: the 3D simulation method and the two-dimensional X-ray film evaluation method. The 3D simulation method is characterized by accuracy. In 3D simulation software or advanced surgical navigation software, the bone coverage rate and the roof coverage rate of the acetabular cup corresponding to a specific position can be accurately calculated. However, the positions of the acetabular cup that this method can target are very limited. For the tens of thousands of possible installation positions of the acetabular cup, this method is difficult to apply. Even if the coverage rates corresponding to all possible installation positions of the acetabular cup can be calculated, it is also a very labor-consuming and material-consuming thing. After determining the upper and lower limits of the offsets x, y, and z, as well as RI and RA, there are many possible installation positions of the acetabular cup. For example, x = -5 mm to 5 mm, y = -10 mm to 0, z = -5 mm to 10 mm, with an interval of 1 mm for each; RI = 10 to 60°, RA = 10 to 40°, with an interval of 1° for each. The number of all possible positions of the acetabular cup in three-dimensional space is 3,060,816. Calculating the bone coverage rate and the roof coverage rate of the acetabular cup corresponding to these 3,060,816 positions is almost an impossible task for the 3D simulation method.

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

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

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

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

[0010] Step 2: Determine the upper and lower limits of the position where the acetabular cup moves relative to the coordinate origin and the geometric parameters of the acetabular cup; transfer the pelvis to the required position; determine whether the preconditions for coverage calculation are met. If so, proceed to Step 3; otherwise, exit.

[0011] Step 3: Solve the intersection points of the pelvis model and the spherical model where the acetabular cup is located, remove the intersection line triangles where the intersection points are located in the spherical surface where the acetabular cup is located, and retain the area that does not directly intersect with the pelvis.

[0012] Step 4: Divide the outer surface of the spherical surface where the acetabular cup is located into several independent regions; determine whether each region is embedded in the pelvis and mark the regions embedded in the pelvis and the intersection line triangle regions.

[0013] Step 5: According to the regions marked in Step 4, identify the part of the acetabular cup and the intersection line triangle part in the region where the acetabular cup intersects with the pelvis on the spherical surface where the acetabular cup is located, and obtain the contact area between the acetabular cup and the part embedded in the pelvis.

[0014] Step 6: According to the regions identified in Step 5, identify the regions and intersection line triangle regions where the acetabular cup is embedded in the pelvis above the plane where the rotation center is located and calculate the areas of these regions.

[0015] Step 7: Calculate the acetabular cup coverage rate and the acetabular cup roof coverage rate at this offset position according to the results obtained in Step 5 and Step 6; perform iterative calculations until the calculations for all offset positions are completed.

[0016] Further, the coverage calculation conditions in Step 2 include:

[0017] The spherical surface where the acetabular cup is located intersects with the outer surface of the pelvis;

[0018] The spherical surface where the acetabular cup is located 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] Further, in Step 3, the ray - triangle intersection algorithm is used to solve the intersection points of the pelvis model and the spherical model where the acetabular cup is located;

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

[0021] Further, in Step 4, the common - point region growth method is used to divide the outer surface of the spherical surface where the acetabular cup is located into several independent regions.

[0022] Further, the method for identifying the part of the acetabular cup in the region where the acetabular cup intersects with 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 cup opening is located is NormalVector_Now, and the coordinates of a point on this 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 normal vector of the cup opening at the initial position, PointOnPlane_Initial is a point on the opening plane of the cup at the initial position, RI is the radiographic abduction angle of the cup, RA is the radiographic anteversion angle of the 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 rotation degree as -RA; R is the radius of the spherical surface where the cup is located, and OpeningAngle is the angle of the cup opening angle;

[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), and NormalVector_Now(3) are all components of the vector NormalVector_Now, and PointOnPlane(3) is the third component of the vector PointOnPlane_Now;

[0035] For any point (x0, y0, z0), if it satisfies Ax0 + By0 + Cz0 + D < 0, then this point is on the cup.

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

[0037]

[0038] In the formula: S Embedded is the contact area between the acetabular cup and the pelvis embedded, and S AllCup is the total area of the outer surface of the acetabular cup;

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

[0040]

[0041] In the formula: S Top_Embedded is the area where the acetabular cup is embedded in the pelvis above the horizontal plane where the rotation center is located, and S TopCup is the area of the outer surface of the acetabular cup above the horizontal plane where the rotation center is located.

[0042] Further, the contact area between the acetabular cup and the pelvis embedded is the area of the region where the acetabular cup is embedded in the pelvis and the area of the corresponding intersection line triangle region;

[0043] Its calculation method is as follows:

[0044]

[0045] In the formula: S FullEmbeddedΔ1 is the area of the region where the acetabular cup is embedded in the pelvis, and S IntersectingΔ1 is the area of the corresponding intersection line triangle region of the region where the acetabular cup is embedded in the pelvis;

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

[0047]

[0048] In the formula: S FullEmbeddedΔ2 is the area of the region where the acetabular cup is embedded in the pelvis above the XOY plane, and S IntersectingΔ2 is the area of the corresponding intersection line triangle of the region where the acetabular cup is embedded in the pelvis above the XOY plane.

[0049] Further, the calculation method of the total area of the outer surface of the acetabular cup is as follows:

[0050]

[0051] The calculation method of the area of the outer surface of the acetabular cup above the horizontal plane where the rotation center is located is as follows:

[0052]

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

[0054] Furthermore, the following steps are further included:

[0055] Obtain the acetabular cup coverage distribution map and the acetabular roof coverage distribution map according to the calculation results of all offset positions in step 7.

[0056] A traversal calculation system for acetabular cup coverage and acetabular roof coverage, including:

[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 size 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 roof coverage calculation module: used to calculate the acetabular roof coverage;

[0060] Output module: used to output the acetabular cup coverage data and its distribution map and the acetabular roof coverage data and its distribution map.

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

[0062] (1) The present invention uses the spherical model where the acetabular cup is located to solve the intersection area with the pelvis and the area embedded in the pelvis, and identifies the part belonging to 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 one intersection of the spherical model and the pelvis needs to be solved, reducing the solution time;

[0063] (2) The present invention can quickly and accurately calculate the acetabular cup coverage and acetabular roof coverage under all possible installation positions, and obtain the optimal reconstructed rotation center position and the RI and RA of the acetabular cup in total hip arthroplasty. Brief Description of the Drawings

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

[0065] Figure 2 It is a schematic diagram of the method flow 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 acetabular cup geometric parameters in the present invention.

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

[0069] Figure 6 This is a schematic diagram of the coverage rate calculation process at a specific offset in the present invention.

[0070] Figure 7 This is a schematic diagram of the method for dividing regions by the common point area growth method in the present invention.

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

[0072] Figure 9 This is the acetabular cup / acetabular roof coverage rate when the acetabular cup has an offset of x = 0, y = -3 mm, and z = 5 mm in the embodiment of the present invention. Detailed implementation manners

[0073] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments.

[0074] A traversal calculation method for acetabular cup coverage rate and acetabular roof coverage rate includes the following steps: as Figure 2 shown:

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

[0076] Taking the left hip of the human body as the research object, the rotation center of the native femoral head is used as the origin of the coordinate system, and X, Y, and Z are the front, lateral, and superior sides of the human body respectively, as Figure 3 shown. If the right hip of the patient is needed, only the pelvis and femur of the patient need to be mirrored.

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

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

[0079] Step 2: Determine the upper and lower limits of the moving position 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 rate calculation condition is met. If it is met, go to Step 3; otherwise, exit.

[0080] Determine the upper and lower limits of the translational position of the acetabular cup relative to the coordinate origin. We decompose it into translations along the X, Y, and Z axes, with the upper and lower limits being x min , x max , y min , y max , z min , z max respectively. The translational step sizes in the three directions are Δx, Δy, and Δz. 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 , RA min , RA max , ΔRI, and ΔRA.

[0081] Rotate the pelvis by PT degrees around the Y axis to simulate the inclination of the pelvis in the sagittal plane. Start cycling through the positions of the acetabular cup relative to the pelvis. In a certain cycle, if the translational 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, 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)·InitialPelvis Pelvis +T(-x,-y,-z)

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

[0084] It is not necessary to calculate the coverage rate for all acetabular cup offset coordinates. The coverage rate calculation needs to meet the following conditions simultaneously, as Figure 5 shown:

[0085] The sphere where the acetabular cup is located intersects with the outer surface of the pelvis;

[0086] The sphere where the acetabular cup is located 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: Solve the intersection points of the pelvic model and the spherical model where the acetabular cup is located, remove the intersecting triangular lines in the spherical surface where the acetabular cup is located, and retain the area that does not directly intersect with the pelvis; (The specific processes of Steps 3-6 are as Figure 6 shown)

[0088] Use the ray-triangle intersection algorithm to solve the intersection points of the pelvic model and the spherical model where the acetabular cup is located;

[0089] Identify the triangle where the intersection point is located and the triangles sharing the same side with this triangle, and mark them as intersecting triangular lines.

[0090] The essence of solving the intersection point is to identify the intersection points between a pair of surfaces by assuming that each edge of each triangular mesh component represents an infinitesimal ray. Identify the triangles where the intersection points are located and the triangles sharing the same side with these triangles, and mark them as intersecting triangular lines.

[0091] Solving the intersection point is the most time-consuming part in calculating the acetabular cup coverage rate. For all possible RI and RA combinations at a certain acetabular cup offset position, using the spherical model only requires solving the intersection point once. This greatly shortens the calculation time.

[0092] Step 4: Divide the outer surface of the spherical surface where the acetabular cup is located into several independent regions; determine whether each region is embedded in the pelvis and mark the regions embedded in the pelvis and the intersecting triangular line regions;

[0093] After removing all the intersecting triangular lines in the spherical surface and retaining the area that does not directly intersect with the pelvis, use the common-point region growth method to divide the remaining triangles on the outer surface of the acetabular cup into several independent regions. The principle of the common-point region growth method is as 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 the connected triangles in the current region are attributed to the same region. After identifying a region, remove that region, so as to retain the remaining regions. Then perform the region growth 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 and detect whether it is located inside the pelvis.

[0095] If the test point is located inside the pelvis, determine that the region where it is located is embedded in the pelvis. Mark and record all the regions embedded in the pelvis and the intersecting triangular line regions for subsequent calculation of the acetabular cup coverage rate.

[0096] Step 5: According to the regions marked in Step 4, identify the part of the acetabular cup and the intersecting triangular line part in the region where the acetabular cup intersects with the pelvis on the spherical surface of the acetabular cup, and obtain the contact area between the acetabular cup and the part embedded in the pelvis;

[0097] Based on Step 4, identify the acetabular cup embedding area and the marginal triangle area in the pelvic region. The identified demarcation line is the opening plane of the acetabular cup.

[0098] The normal vector of the plane where the acetabular cup opening lies is NormalVector_Now, and the coordinates of a point on this 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] In the formula: 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 of RI, R Y (-RA) is the rotation matrix with Y as the rotation axis and the rotation degree of -RA; R is the radius of the spherical surface where the acetabular cup is located, and OpeningAngle is the angle of the acetabular cup opening angle;

[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), and NormalVector_Now(3) are all components of the vector NormalVector_Now, and PointOnPlane(3) is the third component of the vector PointOnPlane_Now;

[0110] For any point (x0, y0, z0), if it satisfies Ax0 + By0 + Cz0 + D < 0, then this point is on the acetabular cup.

[0111] Based on whether it is on the acetabular cup, obtain the area of the region where the acetabular cup is embedded in the pelvis and the area of the corresponding intersection triangle region.

[0112] The calculation method is as follows:

[0113]

[0114] Where: S FullEmbeddedΔ1 is the area of the region where the acetabular cup is embedded in the pelvis, and S IntersectingΔ1 is the area of the corresponding intersection triangle region of the region where the acetabular cup is embedded in the pelvis.

[0115] Step 6: According to the region identified in Step 5, identify the area where the acetabular cup is embedded in the pelvis above the plane of the rotation center; on the basis of Step 5, identify the area of the region where the acetabular cup is 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 is the area of the region where the acetabular cup is embedded in the pelvis above the XOY plane, and S IntersectingΔ2 is the area of the corresponding intersection triangle of the region where the acetabular cup is embedded in the pelvis above the XOY plane.

[0118] Step 7: Calculate the acetabular cup coverage rate and the acetabular cup top coverage rate at this offset position according to the results obtained in Step 5 and Step 6; perform cyclic iteration until the calculation of all offset positions is completed.

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

[0120]

[0121] Where: S Embedded is the contact area between the acetabular cup and the pelvis where it is embedded, and S AllCup is the total outer surface area of the acetabular cup;

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

[0123]

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

[0125] The calculation method of the total area of the outer surface of the acetabular cup is as follows:

[0126]

[0127] The calculation method of the area of the outer surface of the acetabular cup above the horizontal plane where the rotation center is located is as follows:

[0128]

[0129] Where: η is the angle between the normal vector of the opening plane of the acetabular cup and the negative direction of the Z-axis, and θ is the integration variable of the integration 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 conditions for bone ingrowth after implantation of the biological acetabular cup.

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

[0132] A system for the traversal calculation method of the acetabular cup coverage rate and the acetabular roof coverage rate, 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 sizes of the moving position of the acetabular cup relative to the coordinate origin;

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

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

[0136] Output module: used to output the acetabular cup coverage rate data and its distribution map and the acetabular roof coverage rate data and its distribution map.

[0137] Embodiment

[0138] The effects of the present invention will be 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 acetabular cup relative to the coordinate origin, the step size, and the geometric parameters of the acetabular cup are shown in Table 1.

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

[0141]

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

[0143] Figure 9 It is the acetabular cup / acetabular roof coverage rate when the offset is x = 0, y = -3 mm, z = 5 mm. Using the method of the present invention, doctors can view the acetabular cup / acetabular roof coverage rate at any acetabular cup installation position accordingly.

[0144] The present invention uses the spherical model where the acetabular cup is located to solve the intersection area and the embedded area in the pelvis, and then identifies the part belonging to the acetabular cup in the area where the sphere 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 one solution of the intersection points of the spherical model and the pelvis is required, which greatly reduces the solution time. If the intersection points and the intersection line triangles are solved by using the acetabular cup model and the pelvis, then the intersection points and the intersection line triangles need to be solved once when the values of RI and RA change, which will greatly increase the solution time. By using the method of the present invention, the coverage rate of the acetabular cup and the acetabular roof coverage rate at all possible installation positions can be calculated quickly and accurately, giving doctors a reference for determining the rotational position of the reconstruction of this total hip arthroplasty and the RI and RA of the acetabular cup.

Claims

1. A traversal calculation method for acetabular cup coverage rate and acetabular roof coverage rate, characterized in that It includes the following steps: Step 1: Construct a pelvic model and a spherical model where the acetabular cup is located, and establish a coordinate system; Step 2: Determine the upper and lower limits of the movement position of the acetabular cup relative to the coordinate origin and the geometric parameters of the acetabular cup; Transform the pelvis to the required position; Determine whether the preconditions for coverage calculation are met. If met, go to Step 3; otherwise, exit; The preconditions for coverage calculation include: The spherical surface where the acetabular cup is located intersects with the outer surface of the pelvis; The spherical surface where the acetabular cup is located does not intersect with the inner surface of the pelvis, and the minimum distance between them is not less than the set threshold; Step 3: Solve the intersection points of the pelvic model and the spherical model where the acetabular cup is located, remove the intersection line triangles where the intersection points are located on the spherical surface of the acetabular cup, and retain the area that does not directly intersect with the pelvis; Step 4: Divide the outer surface of the spherical surface where the acetabular cup is located into several independent regions; Determine whether each region is embedded in the pelvis and mark the regions embedded in the pelvis and the intersection line triangle regions; Step 5: According to the regions marked in Step 4, identify the part belonging to the acetabular cup and the part of the intersection line triangle in the region where the spherical surface of the acetabular cup intersects with the pelvis, and obtain the contact area between the acetabular cup and the part embedded in the pelvis; Step 6: According to the regions identified in Step 5, identify the regions and intersection line triangle regions where the acetabular cup is embedded above the plane where the rotation center is located, and calculate the areas of these regions; Step 7: Calculate the acetabular cup coverage rate and the acetabular cup roof coverage rate at the offset position according to the results obtained in Step 5 and Step 6; Loop and iterate until the calculations for all offset positions are completed.

2. The traversal calculation method of the acetabular cup coverage rate and the acetabular roof coverage rate according to claim 1, wherein In Step 3, the ray - triangle intersection algorithm is used to solve the intersection points 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 triangles sharing the same side with this triangle, and mark them as intersection line triangles.

3. The traversal calculation method for the cup coverage rate and the dome coverage rate according to claim 2, wherein, In Step 4, the co - point region growth method is used to divide the outer surface of the spherical surface where the acetabular cup is located into several independent regions.

4. The traversal calculation method of the cup coverage rate and the dome coverage rate according to claim 3, characterized in that, The method for identifying the part belonging to the acetabular cup in the region where the spherical surface of the acetabular cup intersects with the pelvis in Step 5 is as follows: The normal vector of the plane where the acetabular cup opening lies is NormalVector_Now , and the coordinates of a point on this plane are PointOnPlane_Now ; Wherein: is the opening normal vector of the acetabular cup at the initial position, is a point on the opening plane of the acetabular cup at the initial position, RI is the radiographic abduction angle of the acetabular cup, RA is the radiographic anteversion angle of the acetabular cup; is X is the rotation axis, and the rotation degree is RI the rotation matrix of is Y is the rotation axis, and the rotation degree is -RA the rotation matrix of; R is the radius of the sphere where the acetabular cup is located, is the angle of the opening angle of the acetabular cup; Let the plane equation be , then: In the formula: , , are all components of the vector NormalVector_Now , is the vector PointOnPlane_Now 's third component; If any point , if it is satisfied, then , then this point is on the acetabular cup.

5. A traversal calculation method for the cup coverage rate and the acetabular roof coverage rate according to claim 4, characterized in that The calculation method of the cup coverage rate in step 7 is as follows: Wherein: is the contact area between the acetabular cup and the pelvis into which it is inserted, is the total outer surface area of the acetabular cup; Acetabular roof coverage The calculation method is as follows: Wherein: is the area where the acetabular cup is embedded in the pelvis above the horizontal plane where the rotation center is located, is the area of the outer surface of the acetabular cup above the horizontal plane where the rotation center is located.

6. The traversal calculation method of the cup coverage rate and the dome coverage rate according to claim 5, characterized in that The contact area between the acetabular cup and the part embedded in the pelvis is the area of the region where the acetabular cup is embedded in the pelvis and the area of the corresponding intersection line triangle region; Its calculation method is as follows: Wherein: is the area of the region on the acetabular cup that is embedded in the pelvic bone, is the area of the triangular region corresponding to the intersection line of the region on the acetabular cup that is embedded in the pelvic bone; The area where the acetabular cup is embedded in the pelvic bone above the plane where the rotation center lies is the area where the acetabular cup is embedded in the pelvic bone region above the XOY plane and the area of the corresponding intersection triangle; the calculation method is as follows: In the formula: is the area of the pelvic region where the acetabular cup is embedded above the XOY plane, is the area of the triangle corresponding to the intersection line of the pelvic region where the acetabular cup is embedded above the XOY plane.

7. A traversal calculation method for the coverage rate of the acetabular cup and the coverage rate of the acetabular dome according to claim 6, characterized in that The calculation method for the total outer surface area of the acetabular cup is as follows: The calculation method for the area of the outer surface of the acetabular cup above the horizontal plane where the rotation center is located is as follows: Wherein: is the included angle between the normal vector of the opening plane of the acetabular cup and Z the negative direction of the axis, and is the integration variable of the integral formula.

8. A traversal calculation method for cup coverage and acetabular roof coverage according to claim 1, characterized in that, It also includes the following steps: Obtain the acetabular cup coverage rate distribution map and the acetabular cup roof coverage rate distribution map according to the calculation results of all offset positions in Step 7.

9. A system adopting the traversal calculation method for the cup coverage rate and the dome coverage rate as described in any one of claims 1 to 8, characterized in that, It includes: Input module: Used to input the pelvic model and the spherical model where the acetabular cup is located, input the upper and lower limit parameters of the movement position of the acetabular cup relative to the coordinate origin and the parameter step size; Acetabular cup coverage rate calculation module: Used to calculate the acetabular cup coverage rate; Acetabular cup roof coverage rate calculation module: Used to calculate the acetabular cup roof coverage rate; Output module: Used to output the acetabular cup coverage rate data and its distribution map and the acetabular cup roof coverage rate data and its distribution map.

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