CN117860439A - Knee joint prosthesis construction method based on b spline curve - Google Patents

Abstract

The invention discloses a knee joint prosthesis construction method based on a b spline curve, which specifically comprises the following steps: acquiring a knee joint image of a patient, and determining a characteristic point set of the knee joint of the patient according to the knee joint image; constructing a first three-dimensional projection of the distal femur end in the knee joint according to the characteristic point set, and constructing a second three-dimensional projection of the tibial plateau in the knee joint according to the characteristic point set, wherein the first three-dimensional projection and the second three-dimensional projection are both determined by a plurality of b-spline curves, and the b-spline curves are determined according to the characteristic points in the characteristic point set; constructing a knee prosthesis from the first three-dimensional projection and the second three-dimensional projection. The invention solves the technical problem of low accuracy of the knee joint prosthesis constructed in the related technology.

Description

Knee joint prosthesis construction method based on b spline curve

Technical Field

The invention relates to the field of medical instruments, in particular to a knee joint prosthesis construction method based on a b-spline curve.

Background

Prior to knee prosthesis construction, doctors often use medical imaging techniques such as X-ray, magnetic Resonance Imaging (MRI), or Computed Tomography (CT) to assess the patient's knee structure in order to better customize the prosthesis. With the advancement of medical technology, there is an increasing demand for personalized and precise medical treatment. In the field of orthopaedics, knee replacement surgery is very common, and prosthesis design is a key factor affecting the effectiveness of the surgery. However, the current technology mainly depends on experience and personal judgment, and cannot accurately simulate the motion characteristics of a natural knee joint, and cannot meet the requirements of personalized medical treatment and accurate medical treatment. No effective solution has been proposed so far.

Disclosure of Invention

In order to solve the problems, the invention provides a method for constructing a knee joint prosthesis, which comprises the following steps:

and acquiring a knee joint image of the patient, and determining a characteristic point set of the knee joint of the patient according to the knee joint image. And constructing a first three-dimensional projection of the distal femur end in the knee joint according to the feature point set, and constructing a second three-dimensional projection of the tibial plateau in the knee joint according to the feature point set. The first three-dimensional projection and the second three-dimensional projection are determined by a plurality of b spline curves, and the b spline curves are determined according to the characteristic points in the characteristic point set.

Further, the set of feature points includes a first subset of feature points of the distal femur in the sagittal view of the knee joint and a second subset of feature points of the distal femur in the coronal view of the knee joint. Constructing a first three-dimensional projection of the distal femur in the knee joint from the set of feature points, comprising the steps of: determining a starting point, an ending point and at least two intermediate points from the first subset of feature points; constructing an initial two-dimensional curve corresponding to the distal femur according to the starting point, the ending point and at least two intermediate points; judging whether the positions of at least two intermediate points are accurate or not according to the coronal image information in the knee joint image; and under the condition that the middle point with the inaccurate position exists, adjusting the position of the middle point with the inaccurate position, and correcting the initial two-dimensional curve according to the adjusted middle point to obtain a first two-dimensional curve.

Further, in the case that the first two-dimensional curves are plural, the different first two-dimensional curves are constructed from different first feature point subsets, the different first feature point subsets corresponding to different knee sagittal positions. Constructing a first three-dimensional projection of the distal femur from the first two-dimensional curve and the second two-dimensional curve, comprising the steps of: constructing an initial three-dimensional projection corresponding to the distal femur according to a first two-dimensional curve and a second two-dimensional curve; detecting whether a third two-dimensional curve exists, wherein the third two-dimensional curve refers to a first two-dimensional curve which is not used when an initial three-dimensional projection is constructed; under the condition that a third two-dimensional curve exists, correcting the initial three-dimensional projection according to the third two-dimensional curve to obtain an updated initial three-dimensional projection; and repeatedly executing the step of correcting the updated initial three-dimensional projection according to the third two-dimensional curve until a preset iteration condition is reached, and determining a first three-dimensional projection according to the latest obtained initial three-dimensional projection.

Further, determining a first three-dimensional projection from the newly obtained initial three-dimensional projection comprises the steps of: acquiring a movement characteristic condition of a knee joint of a patient, wherein the movement characteristic condition comprises at least one of the following: a movement range condition, a movement speed condition; judging whether the latest obtained initial three-dimensional projection meets the motion characteristic condition or not; and under the condition that the latest obtained initial three-dimensional projection does not meet the motion characteristic conditions, adjusting the latest obtained initial three-dimensional projection according to the motion characteristic conditions to obtain a first three-dimensional projection.

Further, in the case where the motion characteristic condition includes a motion range condition, determining whether the newly obtained initial three-dimensional projection satisfies the motion characteristic condition includes the steps of: for each target two-dimensional curve, determining a control point according to a starting point, an ending point and a middle point in the target two-dimensional curve, wherein the target two-dimensional curve is a first two-dimensional curve or a third two-dimensional curve; if the middle point and the control point of the target two-dimensional curve are in the movement range defined by the movement range condition in the knee joint movement process, determining that the latest obtained initial three-dimensional projection meets the movement characteristic condition; if the middle point and the control point of the target two-dimensional curve are not in the movement range in the knee joint movement process, determining that the latest obtained initial three-dimensional projection does not meet the movement characteristic condition.

Further, the set of feature points includes a third subset of feature points of the tibial plateau in the sagittal view of the knee joint and a fourth subset of feature points of the tibial plateau in the coronal view of the knee joint. Constructing a second three-dimensional projection of the tibial plateau in the knee joint according to the set of feature points, comprising the steps of: constructing a fourth two-dimensional curve corresponding to the tibia platform according to the characteristic points in the third characteristic point subset, wherein the fourth two-dimensional curve is a b-spline curve; constructing a fifth two-dimensional curve corresponding to the tibia plateau according to the characteristic points in the fourth characteristic point subset, wherein the fifth two-dimensional curve is a b-spline curve; and constructing a second three-dimensional projection corresponding to the tibia platform according to the fourth two-dimensional curve and the fifth two-dimensional curve.

According to the invention, three-dimensional projections of the far femur end and the tibia platform of a patient are built according to a b spline curve, a knee joint prosthesis is built according to the three-dimensional projections, a knee joint image of the patient is obtained, a characteristic point set of the knee joint of the patient is determined according to the knee joint image, then a first three-dimensional projection of the far femur end in the knee joint is built according to the characteristic point set, and a second three-dimensional projection of the tibia platform in the knee joint is built according to the characteristic point set, so that the knee joint prosthesis is built according to the first three-dimensional projection and the second three-dimensional projection. The first three-dimensional projection and the second three-dimensional projection are determined by a plurality of b spline curves, and the b spline curves are determined according to the characteristic points in the characteristic point set. By utilizing the b-spline curve, the effective determination of the geometrical morphology of the distal femur and the geometrical morphology of the distal tibia according to the thought of point-to-line painting is realized, so that the curved surface information on which the knee joint prosthesis design depends can be effectively fitted. By constructing the knee joint prosthesis according to the first three-dimensional projection and the second three-dimensional projection, the knee joint prosthesis is constructed according to the curved surface information on which the knee joint prosthesis is designed, and therefore the accuracy of the knee joint prosthesis can be effectively improved. Therefore, the technical problem that the accuracy of the knee joint prosthesis constructed by the method is low due to the fact that the knee joint prosthesis is constructed by relying on artificial experience in the related technology is solved, and the technical effect of improving the accuracy of the knee joint prosthesis is achieved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:

FIG. 1 is a flow chart of an alternative method of constructing a knee prosthesis in accordance with an embodiment of the present invention;

FIG. 2 is a flow chart II of an alternative method of constructing a knee prosthesis according to an embodiment of the present invention;

FIG. 3 is a schematic illustration of an alternative b-spline curve according to an embodiment of the present invention;

FIG. 4 is a flowchart of an alternative construction of a first three-dimensional projection according to an embodiment of the invention;

fig. 5 is a formula diagram.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

As shown in fig. 1, the method comprises the steps of:

in step S101, first, a knee joint image of a patient is acquired by using the target construction system as an execution subject. These knee images may be obtained by a variety of techniques, such as 3D scanning techniques, including but not limited to CT (Computed Tomography, electronic computed tomography) and MRI (Magnetic resonance imaging ). These images may be sectioned and viewed in different planes (e.g., cross-section, sagittal, and coronal) to provide more detailed anatomical information.

In fig. 2, a flowchart of an alternative knee prosthesis construction method according to embodiments of the present invention is shown. After the knee joint images are acquired, the target construction system utilizes the images to identify a plurality of characteristic points of the knee joint, and determines coordinate values of the characteristic points to form a characteristic point set. These feature points include, but are not limited to, the medial-lateral femoral epicondylitis point, the anterior-posterior-left-right diameter point of the medial tibial plateau, the anterior-posterior-left-right diameter point of the lateral tibial plateau, the center point of the patella, the midpoint of the intercondylar axis connection, and the like.

In addition, the target construction system may employ different methods to identify feature points, including obtaining labeling information of the user for the knee image, identifying feature points using the labeling information, or automatically identifying multiple feature points from the knee image using a deep neural network model (e.g., U-Net). Through the steps, the characteristic point set of the knee joint of the patient can be accurately obtained, and key anatomical information is provided for subsequent knee joint prosthesis construction.

In step S102, three-dimensional projection construction of the knee joint is performed according to the feature point set. First, a first three-dimensional projection of the distal femur in the knee joint and a second three-dimensional projection of the tibial plateau in the knee joint are constructed. The two three-dimensional projections are determined by b-spline curves, which are defined in terms of feature points in the set of feature points.

In this process, the target construction system may selectively construct a first three-dimensional projection of the distal femur using the feature points of the set of feature points associated with the distal femur and construct a second three-dimensional projection of the tibial plateau using the feature points associated with the tibial plateau. For example, as shown in fig. 2, the target construction system may first construct a plurality of b-spline curves corresponding to the distal femur (or tibial plateau), where each curve is two-dimensional, containing b-spline curves corresponding to the sagittal and coronal positions of the knee. Because the curve corresponding to the sagittal view of the knee reflects the x-axis and z-axis coordinate information in the three-dimensional projection, and the curve corresponding to the coronal view of the knee reflects the y-axis and z-axis coordinate information, a first (or second) three-dimensional projection may be constructed from a plurality of b-spline curves corresponding to the distal femur (or tibial plateau).

In this process, the b-spline curve is a graphical mathematical curve, consisting of a start point, an end point (anchor point) and several control points in between. By adjusting the positions of these points, the shape of the b-spline curve, including the curvature and degree of curvature, can be changed. FIG. 3 shows a schematic diagram of an alternative b-spline curve of an embodiment of the present invention, in which the location of the intermediate points is determined by the control points and the end points. In this embodiment, the starting point, the ending point and at least two intermediate points separated from each other may be determined directly from the feature points, and then fitted using a b-spline curve algorithm to determine the profile of the b-spline curve. In this way, three-dimensional projection construction of the knee joint is successfully achieved.

In step S103, a knee prosthesis is constructed from the first three-dimensional projection and the second three-dimensional projection. The two projections are constructed from feature points associated with the distal femur and tibial plateau, respectively, so that the first three-dimensional projection effectively reflects the geometry of the distal femur and the second three-dimensional projection effectively reflects the geometry of the tibial plateau.

An alternative construction is for the target construction system to determine the first three-dimensional projection modality as the actual modality of the distal femur of the patient and the second three-dimensional projection modality as the actual modality of the tibial plateau of the patient after the first three-dimensional projection and the second three-dimensional projection are acquired. The distal femur prosthesis and tibial plateau prosthesis are then designed according to these two real configurations, with a metal shim having an arcuate surface disposed therebetween. The upper arc surface morphology of the metal gasket designed in this way is determined by a first three-dimensional projection, and the lower arc surface morphology is determined by a second three-dimensional projection. The provision of the metal shims helps to better accommodate the range of motion and speed of the knee joint in flexion and extension. The thickness may be selected manually based on the structural relationship between the distal femoral prosthesis and the tibial plateau prosthesis.

Alternatively, after the first and second three-dimensional projections are acquired, the target construction system may determine coverage and overlap between the first three-dimensional projection and the actual distal femur of the patient. And determining the diffraction and interference redundancy part of the first three-dimensional projection and the knee joint through difference value calculation. Further, the target construction system may determine the width and size of the distal femoral prosthesis based on the first three-dimensional projection, e.g., directly using the width and size of the first three-dimensional projection as the width and size of the distal femoral prosthesis. The width and size of the first three-dimensional projection may also be trimmed, for example, from the knee joint image, and then the trimmed width and size may be used as the width and size of the distal femoral prosthesis.

The target construction system can firstly design an initial femur distal prosthesis according to the width and the size and the first three-dimensional projection, and then obtain a final femur distal prosthesis by fine adjustment and consideration of coverage rate, overlap ratio, knee joint diffraction and interference redundancy. Similarly, tibial plateau prostheses can be designed in the same manner. Through these steps, the construction of knee joint prostheses was successfully achieved.

Prior to making the knee prosthesis, as shown in fig. 2, 3D printing additive manufacturing techniques may be utilized to verify the effectiveness of the designed prosthesis. The target construction system is used for manufacturing the designed knee joint prosthesis through a 3D printing technology, and the femur distal prosthesis and the tibia platform prosthesis are made of high polymer materials so as to improve the wear resistance and corrosion resistance of the prosthesis. And performing comparison experiments and simulation, and evaluating the performance, the elongation rate and the like of the knee joint prosthesis. After passing the evaluation, a truly usable knee prosthesis was made to ensure that it exhibited superior effects in practical applications.

In the above process, by constructing the first three-dimensional projection and the second three-dimensional projection according to the characteristic point set of the knee joint of the patient by using the b spline curve, the effective determination of the geometry of the distal femur and the geometry of the distal tibia according to the point-to-line painting concept is realized, so that the curved surface information on which the knee joint prosthesis design depends can be effectively fitted. Further, by constructing the knee joint prosthesis according to the first three-dimensional projection and the second three-dimensional projection, the knee joint prosthesis is constructed according to the curved surface information on which the knee joint prosthesis is designed, and therefore accuracy of the knee joint prosthesis can be effectively improved. Therefore, the scheme provided by the application achieves the purposes of constructing the three-dimensional projection of the distal femur and the tibial plateau of the patient according to the b-spline curve and constructing the knee joint prosthesis according to the three-dimensional projection, thereby realizing the technical effect of improving the accuracy of the knee joint prosthesis, and further solving the technical problem that the accuracy of the knee joint prosthesis constructed by relying on artificial experience in the related technology is low.

In an alternative embodiment, the feature point set includes a first feature point subset of the distal femur in the sagittal position of the knee joint and a second feature point subset of the distal femur in the coronal position of the knee joint, wherein in constructing a first three-dimensional projection of the distal femur in the knee joint from the feature point set, the target construction system may construct a first two-dimensional curve corresponding to the distal femur from the feature points in the first feature point subset, wherein the first two-dimensional curve is a b-spline curve, and then construct a second two-dimensional curve corresponding to the distal femur from the feature points in the second feature point subset, thereby constructing a first three-dimensional projection of the distal femur from the first two-dimensional curve and the second two-dimensional curve. Wherein the second two-dimensional curve is a b-spline curve.

Optionally, the feature point set in this embodiment includes a first feature point subset of the distal femur in a sagittal position of the knee joint, a second feature point subset of the distal femur in a coronal position of the knee joint, a third feature point subset of the tibial plateau in a sagittal position of the knee joint, and a fourth feature point subset of the tibial plateau in a coronal position of the knee joint, where the first feature point subset, the second feature point subset, the third feature point subset, and the fourth feature point subset may be one or more.

Specifically, the feature points in the first feature point subset and the third feature point subset are identified according to sagittal image information in the knee joint, and the feature points in the second feature point subset and the fourth feature point subset are identified according to coronal image information in the knee joint. The first feature point subset (or the third feature point subset) is different from the first feature point subset (or the fourth feature point subset) in terms of the sagittal position of the knee joint, and the second feature point subset (or the fourth feature point subset) is different from the coronal position of the knee joint. The feature points in the first feature point subset or the second feature point subset are distal femur, medial and lateral condyle anatomy bone feature points, and the first feature point subset or the second feature point subset includes but is not limited to the feature points of medial and lateral epicondylar points of femur and the like. Moreover, since the points in the feature point set are identified based on the sagittal image or coronal image of the knee joint, the coordinates of each feature point are two-dimensional coordinates. The target construction system may determine a starting point, an ending point, and at least two intermediate points from the first subset of feature points, e.g., using a feature point of the first subset of feature points located at one distal edge of the femur as a starting point, using a feature point of the first subset of feature points located at the other distal edge of the femur as an ending point, and then selecting a feature point from between the starting point and the ending point as an intermediate point. Thus, a first two-dimensional curve corresponding to the distal femur is constructed according to the starting point, the ending point and the intermediate point, and the first two-dimensional curve corresponds to the sagittal phase of the knee joint. The target construction system can determine a three-dimensional model of the knee joint according to the knee joint image, and determine the mapping relation between the first two-dimensional curve and the second two-dimensional curve and the knee joint three-dimensional model after the first two-dimensional curve and the second two-dimensional curve are obtained, so that the relative position relation of the first two-dimensional curve and the second two-dimensional curve is determined according to the mapping relation. The target construction system may then construct a first three-dimensional projection of the distal femur based on the first two-dimensional curve, the second two-dimensional curve, and the aforementioned relative positional relationship.

It should be noted that, through determining the first two-dimensional curve according to the characteristic points in the first characteristic point subset, the two-dimensional contour of the distal femur in the sagittal position of the knee joint is determined, and through determining the second two-dimensional curve according to the characteristic points in the second characteristic point subset, the two-dimensional contour of the distal femur in the coronal position of the knee joint is determined, so that when the first three-dimensional projection is constructed according to the first two-dimensional curve and the second two-dimensional curve, the irregular geometric form of the distal femur can be effectively fitted, and the basis is provided for the design of the distal femur prosthesis, such as the factors of the width of the appearance, the coverage of the curved surface, the constraint of the half package and the like.

In an alternative embodiment, in the process of constructing the first two-dimensional curve corresponding to the distal femur according to the feature points in the first feature point subset, determining a start point, an end point and at least two intermediate points from the first feature point subset, then constructing an initial two-dimensional curve corresponding to the distal femur according to the start point, the end point and the at least two intermediate points, and then judging whether the positions of the at least two intermediate points are accurate according to the coronal image information in the knee joint image, so that the positions of the intermediate points with inaccurate positions are adjusted under the condition that the intermediate points with inaccurate positions exist, and correcting the initial two-dimensional curve according to the adjusted intermediate points to obtain the first two-dimensional curve.

FIG. 4 is a flowchart illustrating an alternative construction of a first three-dimensional projection according to an embodiment of the present invention, where, as shown in FIG. 4, the target construction system may determine control points according to the determined intermediate points, starting points, and ending points in the first feature point subset, so as to calculate a plurality of points according to the starting points, ending points, and the determined control points by using a definition formula of the b-spline curve, and then construct an initial two-dimensional curve corresponding to the sagittal view of the knee joint from the calculated plurality of points.

As shown in fig. 5, a plurality of control points are first determined, and a plurality of points P0, P1, and Pn are sequentially given, i.e., P0 is a start point, pn is an end point, and P1 to Pn-1 are control points, then the coordinate values of the points for forming the initial two-dimensional curve can be calculated according to the formula of fig. 5:

where i represents the ith point location.

Further, since the initial two-dimensional curve is fitted according to the characteristic points of the distal femur in the sagittal position of the knee joint, after the initial two-dimensional curve is constructed, as shown in fig. 4, the target construction system can determine whether the initial two-dimensional curve needs to be finely tuned according to the coronal image information in the knee joint image. For example, the target construction system may determine the coordinate value of the intermediate point at the coronal position of the knee joint according to the coronal position image information in the knee joint image, and then compare the coordinate value of the intermediate point at the coronal position with the coordinate value of the intermediate point corresponding to the sagittal position, that is, compare the z-axis coordinate value, so as to determine whether the position of the intermediate point is accurate. For example, when the z-axis coordinate values of the two coordinate values are the same, the position of the intermediate point is accurately determined, otherwise, the determination is inaccurate. Under the condition that the middle point with inaccurate positions is determined, the target construction system can adjust the coordinate value corresponding to the middle point on the sagittal position according to the coordinate value of the middle point on the coronal position, the adjustment mode can be direct replacement or taking the average value of two coordinate values, then, a new control point is redetermined according to the adjusted middle point, the initial point and the end point, a plurality of point positions are obtained through calculation according to the new control point, the initial point and the end point, and then, a first two-dimensional curve is formed by the calculated plurality of point positions, so that the correction of the initial two-dimensional curve is realized.

By constructing an initial two-dimensional curve according to the characteristic points of the distal femur in the sagittal position of the knee joint and performing secondary optimization on the initial two-dimensional curve according to the coronal position image information in the knee joint image, the fitting accuracy of the first two-dimensional curve on the sagittal position of the knee joint and the coronal position of the knee joint is improved.

In an alternative embodiment, in the case that the first two-dimensional curve is a plurality of first two-dimensional curves, the different first two-dimensional curves are constructed by different first feature point subsets, and the different first feature point subsets correspond to different sagittal positions of the knee joint, where in the process of constructing the first three-dimensional projection of the distal femur according to the first two-dimensional curve and the second two-dimensional curve, the target construction system may construct an initial three-dimensional projection corresponding to the distal femur according to one of the first two-dimensional curve and the second two-dimensional curve, then detect whether a third two-dimensional curve exists, and then, in the case that the third two-dimensional curve exists, correct the initial three-dimensional projection according to the third two-dimensional curve to obtain an updated initial three-dimensional projection, so that the step of correcting the updated initial three-dimensional projection according to the third two-dimensional curve is repeatedly performed until a preset iteration condition is reached, and the first three-dimensional projection is determined according to the newly obtained initial three-dimensional projection. Wherein the third two-dimensional curve refers to the first two-dimensional curve that is not used in constructing the initial three-dimensional projection.

Optionally, in this embodiment, the second two-dimensional curve is one. The target construction system can firstly determine the mapping relation between the first two-dimensional curve and the second two-dimensional curve and the knee joint three-dimensional model, so as to determine the relative position relation of the first two-dimensional curve and the second two-dimensional curve according to the mapping relation. Wherein, since the first two-dimensional curve corresponds to the sagittal position of the knee joint and the second two-dimensional curve corresponds to the coronal position of the knee joint, the first two-dimensional curve and the second two-dimensional curve are intersected with each other, and a unique intersection point exists. Further, in the process of constructing the initial three-dimensional projection, the target construction system can control the first two-dimensional curve to deviate along the second two-dimensional curve for a plurality of times to obtain a plurality of deviation curves, so that the initial three-dimensional projection is constructed by the first two-dimensional curve, the plurality of deviation curves of the first two-dimensional curve and the second two-dimensional curve. Wherein the area of the gap between the curves can be expressed in terms of approximation based on existing heuristics. After the initial three-dimensional projection is obtained, the target construction system can detect whether a third two-dimensional curve exists, so that under the condition that the third two-dimensional curve exists, a third two-dimensional curve is selected, then the mapping relation between the third two-dimensional curve and the knee joint three-dimensional model is determined, the relative position relation between the third two-dimensional curve and the second two-dimensional curve is determined according to the mapping relation, and an offset curve which is positioned at the same position as the third two-dimensional curve is found from the initial three-dimensional projection according to the relative position relation. Further, as shown in fig. 4, the target construction system may replace the found offset curve with the third two-dimensional curve to obtain a replaced initial three-dimensional projection, and re-express the vacant areas between the curves with an approximation based on the existing heuristic, so as to obtain an updated initial three-dimensional projection, and implement projection correction. After the updated initial three-dimensional projection is obtained, the target construction system can continuously detect whether a third two-dimensional curve exists, so that a third two-dimensional curve is selected again under the condition that the third two-dimensional curve exists, the updated initial three-dimensional projection is corrected according to the mode to obtain the updated initial three-dimensional projection again, iteration is continued until a preset iteration condition is achieved, the first three-dimensional projection is determined according to the latest obtained initial three-dimensional projection, for example, the latest obtained initial three-dimensional projection is directly used as the first three-dimensional projection, and fine adjustment is performed on the latest obtained initial three-dimensional projection according to a motion characteristic condition to obtain the first three-dimensional projection. The preset iteration condition may be that a third two-dimensional curve does not exist, or that the obtained initial three-dimensional projection and the real distal femur end of the patient have a contact ratio greater than a preset value, or the like. It should be noted that, in this embodiment, the process of selecting the feature point, the process of determining the first two-dimensional curve and the second two-dimensional curve, and the process of determining the first three-dimensional projection may be iterative, for example, assuming that the preset iteration condition is that the overlap ratio between the initial three-dimensional projection and the real distal femur of the patient is greater than a preset value, if the overlap ratio between the initial three-dimensional projection and the real distal femur of the patient is still less than or equal to the preset value after the third two-dimensional curve does not exist, the target construction system may reselect the feature point, construct a new first two-dimensional curve and a new second two-dimensional curve according to the newly selected feature point, and then redetermine the first three-dimensional projection.

It should be noted that, by constructing the first three-dimensional projection according to the plurality of first two-dimensional curves and the second two-dimensional curves, and continuously correcting the initial three-dimensional projection according to the unused first two-dimensional curves in the construction process, the fitting accuracy of the finally obtained first three-dimensional projection on the sagittal position of the knee joint and the coronal position of the knee joint is improved.

In an alternative embodiment, in determining the first three-dimensional projection according to the latest obtained initial three-dimensional projection, the target construction system may acquire a motion characteristic condition of the knee joint of the patient, and then determine whether the latest obtained initial three-dimensional projection meets the motion characteristic condition, so that the latest obtained initial three-dimensional projection is adjusted according to the motion characteristic condition to obtain the first three-dimensional projection if the latest obtained initial three-dimensional projection does not meet the motion characteristic condition.

Optionally, as shown in fig. 2 and fig. 4, the newly obtained initial three-dimensional projection may be optimized according to the motion characteristics of the b-spline curve and the biomechanical constraint of the knee joint, so that the first three-dimensional projection obtained after optimization may meet the biomechanical requirements of the knee joint, including but not limited to bearing, stability, flexibility, and the like. The biomechanical constraint is the motion characteristic condition, and the motion range condition includes, but is not limited to, information for characterizing the pronation and supination angles of different joint positions during knee flexion and extension, for example, the motion range condition may be a limitation of a coordinate range.

Alternatively, after acquiring the motion characteristic condition of the knee joint of the patient, the target construction system may determine whether the newly obtained initial three-dimensional projection satisfies the motion characteristic condition. If the intermediate point exists in the latest obtained initial three-dimensional projection and is out of the movement range defined by the movement range condition, determining that the latest obtained initial three-dimensional projection does not meet the movement characteristic condition, adjusting the position of the intermediate point to be within the movement range defined by the movement range condition, and correcting the latest obtained initial three-dimensional projection according to the adjusted intermediate point, thereby obtaining the first three-dimensional projection.

In an alternative embodiment, in the case that the motion characteristic condition includes a motion range condition, in determining whether the latest obtained initial three-dimensional projection meets the motion characteristic condition, the target construction system may determine, for each target two-dimensional curve, a control point according to a start point, an end point and a middle point in the target two-dimensional curve, if the middle point and the control point of the target two-dimensional curve are in a motion range defined by the motion range condition during knee joint motion, determine that the latest obtained initial three-dimensional projection meets the motion characteristic condition, and if the middle point and the control point of the target two-dimensional curve are not in the motion range during knee joint motion, determine that the latest obtained initial three-dimensional projection does not meet the motion characteristic condition. The target two-dimensional curve is a first two-dimensional curve or a third two-dimensional curve.

Alternatively, the target construction system may simulate the motion of the initial three-dimensional projection during knee joint motion, for example, simulate the angle of the initial three-dimensional projection during knee joint flexion and extension, so as to determine the point-position motion range of the middle point and the control point of the target two-dimensional curve during knee joint motion. Further, the target construction system may determine whether the point location motion range of each intermediate point and the point location motion range of each control point are within a motion range defined by the motion range condition.

Further, if the point location motion range of each intermediate point and the point location motion range of each control point are both within the motion ranges, determining that the latest obtained initial three-dimensional projection meets the motion characteristic conditions, otherwise, determining that the latest obtained initial three-dimensional projection does not meet the motion characteristic conditions.

If the intermediate point or the control point exists in the newly obtained initial three-dimensional projection and is outside the movement range defined by the movement range condition, the point position (i.e. the intermediate point or the control point) outside the movement range can be adjusted to be within the movement range defined by the movement range condition, and the newly obtained initial three-dimensional projection is corrected according to the adjusted intermediate point or the adjusted control point, so that the first three-dimensional projection is obtained. For example, the target two-dimensional curve where the adjusted intermediate point or the adjusted control point is located is determined first, then the outline of the target two-dimensional curve is determined again according to the adjusted intermediate point or the adjusted control point, an updated target two-dimensional curve is obtained, and the updated target two-dimensional curve is used for replacing the corresponding target two-dimensional curve in the newly obtained initial three-dimensional projection, so that the first three-dimensional projection is obtained.

It should be noted that, by judging whether the latest obtained initial three-dimensional projection meets the motion characteristic condition according to the relation between the control point, the middle point and the motion range, the judgment accuracy is improved, thereby being convenient for improving the accuracy of the finally constructed knee joint prosthesis.

In an alternative embodiment, the feature point set includes a third feature point subset of the tibial plateau in a sagittal position of the knee joint and a fourth feature point subset of the tibial plateau in a coronal position of the knee joint, where in constructing the second three-dimensional projection of the tibial plateau in the knee joint according to the feature point set, the target construction system may construct a fourth two-dimensional curve corresponding to the tibial plateau according to the feature points in the third feature point subset, and then construct a fifth two-dimensional curve corresponding to the tibial plateau according to the feature points in the fourth feature point subset, so as to construct the second three-dimensional projection corresponding to the tibial plateau according to the fourth two-dimensional curve and the fifth two-dimensional curve. The fourth two-dimensional curve is a b-spline curve, and the fifth two-dimensional curve is a b-spline curve.

Alternatively, the third feature point subset and the fourth feature point subset may each be one or more. The third feature point subset or the fourth feature point subset includes, but is not limited to, feature points corresponding to anterior-posterior paths of the tibial plateau, feature points corresponding to left-right paths of the tibial plateau, and the like.

Still further, the target construction system may determine a starting point, an ending point, and at least two intermediate points from the third subset of feature points, e.g., with a feature point of the third subset of feature points located at one side edge of the tibial plateau as the starting point, a feature point of the first subset of feature points located at the other side edge of the tibial plateau as the ending point, and then select a feature point from between the starting point and the ending point as the intermediate point. And constructing a fourth two-dimensional curve corresponding to the tibia platform according to the starting point, the ending point and the middle point.

Optionally, the target construction system may further determine a starting point, an ending point, and at least two intermediate points from the fourth subset of feature points, thereby constructing a fifth two-dimensional curve corresponding to the tibial plateau from the starting point, the ending point, and the intermediate points. The method for constructing the fourth two-dimensional curve is the same as the method for constructing the second two-dimensional curve, and the method for constructing the third two-dimensional curve is the same as the method for constructing the first two-dimensional curve, so that the description thereof is omitted.

Still further, the target construction system may determine a mapping relationship between the fourth two-dimensional curve and the fifth two-dimensional curve and the knee joint three-dimensional model after the fourth two-dimensional curve and the fifth two-dimensional curve are obtained, so as to determine a relative positional relationship between the fourth two-dimensional curve and the fifth two-dimensional curve according to the mapping relationship. The target construction system may then construct a second three-dimensional projection of the tibial plateau based on the fourth two-dimensional curve, the fifth two-dimensional curve, and the aforementioned relative positional relationship. The method for constructing the second three-dimensional projection is the same as the method for constructing the first three-dimensional projection, and therefore, the description thereof will not be repeated here.

It should be noted that, through determining the fourth two-dimensional curve according to the feature points in the third feature point subset, the determination of the two-dimensional contour of the distal femur in the sagittal position of the knee joint is realized, and through determining the fifth two-dimensional curve according to the feature points in the fourth feature point subset, the determination of the two-dimensional contour of the tibial plateau in the coronal position of the knee joint is realized, so that when the second three-dimensional projection is constructed according to the fourth two-dimensional curve and the fifth two-dimensional curve, the geometric form of the tibial plateau can be effectively fitted, and the accuracy of the finally constructed knee joint prosthesis is further facilitated to be improved.

Therefore, the scheme provided by the application achieves the purposes of constructing the three-dimensional projection of the distal femur and the tibial plateau of the patient according to the b-spline curve and constructing the knee joint prosthesis according to the three-dimensional projection, thereby realizing the technical effect of improving the accuracy of the knee joint prosthesis, and further solving the technical problem that the accuracy of the knee joint prosthesis constructed by relying on artificial experience in the related technology is low.

In the description of the present invention, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present invention; the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A method of constructing a knee prosthesis, comprising:

acquiring a knee joint image of a patient, and determining a characteristic point set of the knee joint of the patient according to the knee joint image;

constructing a first three-dimensional projection of the distal femur end in the knee joint according to the characteristic point set, and constructing a second three-dimensional projection of the tibial plateau in the knee joint according to the characteristic point set, wherein the first three-dimensional projection and the second three-dimensional projection are both determined by a plurality of b-spline curves, and the b-spline curves are determined according to the characteristic points in the characteristic point set;

constructing a knee prosthesis from the first three-dimensional projection and the second three-dimensional projection.

2. The method of claim 1, wherein the set of feature points includes a third subset of feature points of the tibial plateau in a sagittal view of the knee and a fourth subset of feature points of the tibial plateau in a coronal view of the knee, wherein constructing a second three-dimensional projection of the tibial plateau in the knee from the set of feature points includes:

Constructing a fourth two-dimensional curve corresponding to the tibia platform according to the characteristic points in the third characteristic point subset, wherein the fourth two-dimensional curve is the b-spline curve;

constructing a fifth two-dimensional curve corresponding to the tibia platform according to the characteristic points in the fourth characteristic point subset, wherein the fifth two-dimensional curve is the b-spline curve;

and constructing a second three-dimensional projection corresponding to the tibia platform according to the fourth two-dimensional curve and the fifth two-dimensional curve.

3. The method of claim 1, wherein the set of feature points includes a first subset of feature points of the distal femur in a sagittal view of the knee joint and a second subset of feature points of the distal femur in a coronal view of the knee joint, wherein constructing a first three-dimensional projection of the distal femur in the knee joint from the set of feature points includes:

constructing a first two-dimensional curve corresponding to the distal femur according to the characteristic points in the first characteristic point subset, wherein the first two-dimensional curve is the b-spline curve;

constructing a second two-dimensional curve corresponding to the distal femur according to the characteristic points in the second characteristic point subset, wherein the second two-dimensional curve is the b-spline curve;

And constructing a first three-dimensional projection of the distal femur according to the first two-dimensional curve and the second two-dimensional curve.

4. The method of claim 3, wherein constructing a first two-dimensional curve corresponding to the distal femur from the feature points in the first subset of feature points comprises:

determining a starting point, an ending point and at least two intermediate points from the first subset of feature points;

constructing an initial two-dimensional curve corresponding to the distal femur according to the starting point, the ending point and the at least two intermediate points;

judging whether the positions of the at least two intermediate points are accurate or not according to the coronal image information in the knee joint image;

and under the condition that an intermediate point with an inaccurate position exists, adjusting the position of the intermediate point with the inaccurate position, and correcting the initial two-dimensional curve according to the adjusted intermediate point to obtain the first two-dimensional curve.

5. A method according to claim 3, wherein in the case of a plurality of first two-dimensional curves, the different first two-dimensional curves are constructed from different first feature point subsets corresponding to different knee sagittal positions, wherein constructing a first three-dimensional projection of the distal femur from the first two-dimensional curves and the second two-dimensional curves comprises:

Constructing an initial three-dimensional projection corresponding to the distal femur according to a first two-dimensional curve and the second two-dimensional curve;

detecting whether a third two-dimensional curve exists, wherein the third two-dimensional curve refers to a first two-dimensional curve which is not used when the initial three-dimensional projection is constructed;

correcting the initial three-dimensional projection according to the third two-dimensional curve under the condition that the third two-dimensional curve exists, so as to obtain an updated initial three-dimensional projection;

and repeatedly executing the step of correcting the updated initial three-dimensional projection according to the third two-dimensional curve until a preset iteration condition is reached, and determining the first three-dimensional projection according to the latest obtained initial three-dimensional projection.

6. The method of claim 5, wherein determining the first three-dimensional projection from the newly obtained initial three-dimensional projection comprises:

acquiring a motion characteristic condition of a knee joint of the patient, wherein the motion characteristic condition comprises at least one of: a movement range condition, a movement speed condition;

judging whether the latest obtained initial three-dimensional projection meets the motion characteristic condition or not;

and under the condition that the latest obtained initial three-dimensional projection does not meet the motion characteristic conditions, adjusting the latest obtained initial three-dimensional projection according to the motion characteristic conditions to obtain the first three-dimensional projection.

7. The method of claim 6, wherein, in the case where the motion characteristic condition includes the motion range condition, determining whether the newly obtained initial three-dimensional projection satisfies the motion characteristic condition comprises:

for each target two-dimensional curve, determining a control point according to a starting point, an ending point and an intermediate point in the target two-dimensional curve, wherein the target two-dimensional curve is the first two-dimensional curve or the third two-dimensional curve;

if the middle point and the control point of the target two-dimensional curve are in the movement range defined by the movement range condition in the knee joint movement process, determining that the latest obtained initial three-dimensional projection meets the movement characteristic condition;

and if the middle point and the control point of the target two-dimensional curve are not in the movement range in the knee joint movement process, determining that the latest obtained initial three-dimensional projection does not meet the movement characteristic condition.