Measuring tool and measuring method for measuring anteversion angle of acetabular prosthesis

Abstract

The invention discloses a measuring tool and a measuring method for measuring an anteversion angle of an acetabular prosthesis, and relates to the technical field of clinical medicines.The measuring tool comprises a bottom plate, a bottom plate acetabular aiming pattern and an intersecting edge curve, the acetabular aiming pattern comprises a semicircle and an isosceles triangle, the isosceles triangle and the semicircle share a bottom edge, and the intersecting edge curve is arranged on the bottom plate; the two waists of the isosceles triangle and the arc of the semicircle are located on the same side of the bottom edge, and the intersecting edge curve is located on the other side of the bottom edge. When the anteversion angle of the acetabular prosthesis is measured on the hip joint normal position line sheet, the bottom edge is aligned with the long axis of the acetabular ellipse, the intersecting edge curve and the unshielded part of the acetabular ellipse intersect at one point, the point and the circle center of the semicircle are connected to form a straight line, and the included angle formed by the straight line and the bottom edge of the semicircle is the imaging anteversion angle of the acetabular prosthesis. The method has the advantages that estimation, calculation and drawing on an X-ray film are not needed, the convenience and accuracy of ACA measurement can be improved, and THA operation image evaluation is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of clinical medicine, and in particular to a measuring tool and a measuring method for measuring the anteversion angle of an acetabular prosthesis. Background Art

[0002] Total hip replacement is a surgical procedure to treat end-stage hip joint disease. The specific method is to remove the hip joint that has lost its function due to the disease and implant an artificial total hip prosthesis into the body to replace the function of the hip joint, thereby achieving the purpose of relieving pain and improving function.

[0003] The hip joint is composed of the acetabulum and femur. Artificial hip prostheses consist of two parts: the femoral prosthesis and the acetabular prosthesis. Acetabular prostheses are categorized as either biocompatible or cement-based. Biocompatible prostheses are more commonly used and typically consist of a metal bowl-shaped outer cup with an inner liner. Biocompatible acetabular prostheses are installed on the acetabular bone bed with the opening facing anteroinferior and outward. Most biocompatible acetabular prostheses have a hemispherical top; a few are axially symmetrical, non-hemispherical, and a very small number are asymmetrical, irregular shapes. Most biocompatible acetabular prostheses have a perfectly circular opening. Cement-based prostheses are less commonly used and typically consist of a polyethylene plastic bowl-shaped structure, installed on the acetabular bone bed in the same orientation as the biocompatible prosthesis. Because polyethylene does not show up on X-rays, most cement-based prostheses are manufactured with a metal wire embedded around the edge of the opening to facilitate radiographic assessment of the prosthesis' orientation.

[0004] Achieving a good result with total hip arthroplasty requires proper placement and orientation of the prosthesis. Acetabular component anteversion (ACA) is the direction in which the acetabular component tilts forward. The commonly used clinical definition of ACA is the radiographic anteversion (RA), which is the angle between the opening of the acetabular component and the coronal plane.

[0005] The primary clinical method for measuring ACA is indirect measurement on conventional X-rays. ACA is a three-dimensional geometric parameter and therefore cannot be directly measured on conventional anteroposterior and lateral X-rays. The most direct imaging method for its measurement is CT, however, CT is expensive and involves high radiation exposure, making it unsuitable for routine examination after THA surgery. There are also methods for measuring ACA using continuous X-ray fluoroscopy in special body positions, but these methods are not widely used due to their complexity, high radiation exposure, and the impact of changes in pelvic tilt angle during the procedure. Anteroposterior X-rays are the most common imaging examination after THA surgery, and the commonly used ACA target value in clinical practice, the "Lewinnek safe zone," is also based on measurements on anteroposterior X-rays. Therefore, the primary method for measuring ACA in clinical practice is indirect measurement on X-rays.

[0006] Existing methods for measuring the ACA on conventional X-rays suffer from three major drawbacks: cumbersome operation and poor accuracy. Since the 1970s, over a dozen methods for measuring the ACA on anteroposterior X-rays have been developed. However, these traditional methods are generally inconvenient and inaccurate in clinical applications due to three major drawbacks: 1. Measurement requires a dedicated table or scientific calculator; 2. The measurement point is obscured by the femoral head, relying on subjective guesswork; and 3. Complex geometric construction is required. These three drawbacks lead to large subjective errors and inconvenience in clinical ACA measurement. With the exception of patent number 201810038910.7, no other measurement method currently avoids these three drawbacks. This has limited the effectiveness of THA (Total Hip Arthroplasty) surgery in orthopedic and radiology departments. However, this patent (patent number 201810038910.7) suffers from numerous components and complex procedures. Summary of the Invention

[0007] In response to the three major shortcomings of measuring ACA on conventional X-rays in the existing technology, the present invention provides a measurement tool and method for measuring the anteversion angle of acetabular prosthesis, which can improve the convenience and accuracy of ACA measurement, thereby improving the imaging evaluation of THA surgery.

[0008] To achieve the above object, the present invention can be carried out using the following technical solutions:

[0009] In a first aspect, the present invention provides a measuring tool for measuring the anteversion angle of an acetabular prosthesis, comprising:

[0010] Base plate, which is imprinted with the acetabulum targeting pattern and intersecting edge curves;

[0011] The acetabulum aiming pattern includes a semicircle and an isosceles triangle, the isosceles triangle and the semicircle share a base, the two sides of the isosceles triangle and the arc of the semicircle are located on the same side of the base, and the intersection curve is located on the other side of the base;

[0012] When measuring the anteversion angle of the acetabular prosthesis on a hip joint AP radiograph, the bottom edge is aligned with the long axis of the acetabular ellipse, the intersection curve intersects with the unobstructed part of the acetabular ellipse at a point, and this point and the center of the semicircle are connected to form a straight line. The angle formed by the straight line and the bottom edge of the semicircle is the radiographic anteversion angle of the acetabular prosthesis.

[0013] As the measuring tool for measuring the anteversion angle of the acetabular prosthesis as described above, further, the intersection curve is defined by the major axis of the acetabular ellipse;

[0014] The acetabular ellipse is the projection of the opening edge of the acetabular prosthesis on the anteroposterior radiograph of the hip joint. The long axis of the acetabular ellipse is the X-axis, the perpendicular bisector of the long axis is the Y-axis, and the center O of the acetabular ellipse is the origin. A plane rectangular coordinate system is established. The acetabular ellipse is set as ellipse O, and the lengths of its long axis and short axis are 2a and 2b respectively. A ray with an angle of θ with the long axis is drawn from the center O of the acetabular ellipse to intersect the acetabular ellipse at point A. The coordinates of point A are (x, y) and satisfy the following equations:

[0015]

[0016] According to the above equations, the equation of the intersection curve is obtained: 2 -x 2 -xy+a 2 =0.

[0017] As described above, the measuring tool for measuring the anteversion angle of the acetabular prosthesis, further, the intersection curve is engraved with an angle scale.

[0018] As for the above-mentioned measuring tool for measuring the anteversion angle of the acetabular prosthesis, further, the base plate is made of a transparent material.

[0019] In a second aspect, the present invention provides a method for measuring the anteversion angle of an acetabular prosthesis, using the above-mentioned measuring tool, which comprises the following steps:

[0020] An anteroposterior radiograph of the hip is obtained and opened electronically;

[0021] Place the base plate on the screen of the electronic device and adjust the size of the hip joint AP radiograph and the position of the base plate so that the bottom edge of the semicircle in the acetabular aiming pattern completely coincides with the long axis of the acetabular ellipse and the arc of the semicircle coincides with the top contour of the acetabular prosthesis.

[0022] Observe the intersection of the intersection curve and the unobstructed part of the acetabular ellipse, and read the angle scale at this intersection.

[0023] As with the above-mentioned method for measuring the anteversion angle of the acetabular component, further, when the base of the semicircle in the acetabular aiming pattern completely coincides with the major axis of the acetabular ellipse, but the arc of the semicircle does not coincide with the top contour of the acetabular component, then the symmetry of the two arc-shaped areas enclosed by the two sides of the isosceles triangle and the top of the acetabular component is observed;

[0024] If the two arc-shaped areas are symmetrical, the base of the semicircle will completely coincide with the major axis of the acetabulum ellipse;

[0025] If the two arcuate areas are asymmetrical, the base of the semicircle does not completely coincide with the major axis of the acetabular ellipse.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Compared with most traditional methods for measuring acetabular anteversion, the measurement method of the present invention has three major advantages: no need for estimation, no need for calculation, and no need for drawing on X-ray films;

[0028] 2. Compared with a few other acetabular anteversion and measurement methods that have the above three advantages, the measurement tool of the present invention has a simpler structure and simpler operating steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a schematic structural diagram of a measuring tool according to an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the intersection curve of an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the measurement method according to an embodiment of the present invention;

[0033] Figure 4 Schematic diagram of the measurement method according to an embodiment of the present invention;

[0034] Figure 5 Schematic diagram of the measurement method according to an embodiment of the present invention;

[0035] Figure 6 This is a step diagram of a measurement method according to an embodiment of the present invention;

[0036] Figure 7 This is an operation diagram of the measurement method according to an embodiment of the present invention;

[0037] Figure 8 This is an operation diagram of the measurement method according to an embodiment of the present invention;

[0038] Figure 9 This is an operation diagram of the measurement method according to an embodiment of the present invention;

[0039] Figure 10 This is an operation diagram of the measurement method according to an embodiment of the present invention;

[0040] Among them, 1. Base plate; 2. Semicircle; 3. Isosceles triangle; 4. Intersecting curve; 5. Angle scale. DETAILED DESCRIPTION

[0041] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] Example:

[0043] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0044] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0045] In the description of the present invention, "plurality" means at least two, such as two or three, unless otherwise specifically defined. Furthermore, unless otherwise specified or defined, the terms "mounted," "connected," and "connected" should be understood broadly, meaning, for example, fixed, removable, or integral; mechanical or electrical; direct or indirect through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention.

[0046] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0047] In a first aspect, the present invention provides a measurement tool for measuring the anteversion angle of an acetabular prosthesis, comprising a base plate 1, an acetabular aiming pattern on the base plate 1, and an intersection curve 4. The acetabular aiming pattern comprises a semicircle 2 and an isosceles triangle 3. The isosceles triangle 3 and the semicircle 2 share a base. The two sides of the isosceles triangle 3 and the arc of the semicircle 2 are located on the same side of the base. The intersection curve 4 is located on the other side of the base. When measuring the anteversion angle of the acetabular prosthesis on a hip joint anteroposterior radiograph, the base is aligned with the major axis of the acetabular ellipse. The intersection curve 4 intersects the unobstructed portion of the acetabular ellipse at a point. This point and the center of the semicircle 2 form a straight line. The angle formed by the straight line and the base of the semicircle 2 is the radiographic anteversion angle of the acetabular prosthesis.

[0048] Specifically, the existing method of measuring ACA on ordinary X-ray films has three major shortcomings, namely, the need for calculation, the need for drawing, and the need for estimation, which affect the accuracy and convenience of its clinical application. The present invention can overcome the above three shortcomings, see Figures 1 to 5 , a semicircle 2 and an isosceles triangle 3 with a common base are engraved on the bottom plate 1. According to the different conditions of the acetabular prosthesis, when using this measuring tool to measure the anteversion angle of the acetabular prosthesis on the anteroposterior radiograph of the hip joint, align the bases of the semicircle 2 and the isosceles triangle 3 with the major axis of the acetabular ellipse, and then observe the intersection of the intersection curve 4 on the bottom plate 1 and the unobstructed acetabular ellipse. This intersection is connected with the center of the semicircle 2 to form a straight line. With the help of the mathematical properties of the intersection curve 4, the angle formed by the straight line and the bottom of the semicircle is exactly equal to the radiographic anteversion angle of the acetabular prosthesis. Finally, use an angle meter to measure the degree of its anteversion angle. It should be noted that on the anteroposterior radiograph of the hip joint, the acetabular prosthesis with a perfect circular opening has an opening outline projection of an ellipse, which is called the acetabular ellipse. A part of the acetabular ellipse is blocked by the acetabular prosthesis and the femoral prosthesis and cannot be seen (see Figures 3 to 5 (red dashed line).

[0049] As an optional embodiment, in some embodiments, the intersection curve is defined by the major axis of the acetabulum ellipse;

[0050] The acetabular ellipse is the projection of the opening edge of the acetabular prosthesis on the anteroposterior radiograph of the hip joint. The long axis of the acetabular ellipse is the X-axis, the perpendicular bisector of the long axis is the Y-axis, and the center O of the acetabular ellipse is the origin. A plane rectangular coordinate system is established. The acetabular ellipse is set as ellipse O, and the lengths of its long axis and short axis are 2a and 2b respectively. A ray with an angle of θ with the long axis is drawn from the center O of the acetabular ellipse to intersect the acetabular ellipse at point A. The coordinates of point A are (x, y) and satisfy the following equations:

[0051]

[0052] According to the above equations, the equation of the intersection curve is obtained: 2 -x 2 -xy+a 2 =0.

[0053] Specifically, in the acetabulum aiming pattern, the center O of the semicircle is taken as the origin, the straight line where the bottom edge is located is the X-axis, and the perpendicular bisector of the bottom edge is the Y-axis to establish a plane rectangular coordinate system; assuming that the diameter of the semicircle is 2a, the equation of the intersection curve is: y 2 -x 2 -xy+a 2 = 0. Using this coordinate system and curve equation: y 2 -x 2 -xy+a 2 =0 determines the curve as the intersection curve.

[0054] As mentioned above, the intersection curve has a special mathematical property that allows the angle between the intersection of the unobstructed part of the acetabular ellipse and the line connecting the center of the acetabular ellipse and the major axis of the acetabular ellipse to be exactly equal to the radiographic anteversion angle of the acetabular prosthesis; this mathematical property of the intersection curve is the key to the technical principle of the present invention. The following derivation process proves that the angle between the intersection curve and the unobstructed part of the acetabular ellipse is exactly equal to the radiographic anteversion angle of the acetabular prosthesis. 2 -x 2 -xy+a 2 = 0, that is, the intersection curve, just has this special mathematical property.

[0055] In existing technologies, the McLaren method (McLaren method: radiographic anteversion angle of acetabular prosthesis = arcsin[b / a]) is usually used to accurately measure the anteversion angle of the acetabular prosthesis. However, since the dotted part of the ellipse O in the figure is blocked, the short axis b cannot be directly measured, and therefore the McLaren method cannot be used for accurate measurement.

[0056] See again Figure 2Therefore, on a anteroposterior radiograph of the hip joint, the opening edge of an acetabular prosthesis with a radiographic anteversion angle of θ is projected as an acetabular ellipse. A rectangular coordinate system is established with the major axis of the acetabular ellipse as the X-axis, the perpendicular bisector of the major axis as the Y-axis, and the center of the acetabular ellipse, O, as the origin. Let the acetabular ellipse be ellipse O, with its major and minor axis lengths being 2a and 2b, respectively. From point O, draw ray OA, such that the angle it makes with the major axis of ellipse O is exactly equal to θ; ray OA intersects the portion of acetabular ellipse O not obscured by the femoral prosthesis at point A. Let the coordinates of point A be (x, y), then x and y satisfy the following equations:

[0057]

[0058] Simplifying the above equations, we can get:

[0059] y 2 -x 2 -xy+a 2 =0

[0060] It can be seen from this that for an acetabular prosthesis with a fixed opening radius of a, that is, an acetabular ellipse with a fixed long axis length of 2a on the hip joint anteroposterior radiograph, when the anterior inclination angle θ takes infinite different values, the corresponding position of point A will form the curve y 2 -x 2 -xy+a 2 = 0. The curve y 2 -x 2 -xy+a 2 =0 is the equation of the intersection curve.

[0061] Similarly, for an acetabular prosthesis with a fixed opening radius of a, that is, an acetabular ellipse with a fixed long axis length of 2a on the anteroposterior view of the hip joint, when its anteversion angle is unknown, draw the intersection curve y 2 -x 2 -xy+a 2 =0, find the intersection A' of the curve and the acetabular ellipse O', and the angle between O'A' and the major axis of the ellipse (the intersection of the positive semi-axis of the x-axis) is the anteversion angle θ. This is the principle of measuring the anteversion angle using the intersection curve.

[0062] As an optional implementation, in some embodiments, an angle scale is engraved on the intersection curve 4. The angle scale represents the angle formed by the line connecting the intersection point and the center of the semicircle and the base of the semicircle. This allows the corresponding angle value to be read directly on the intersection curve 4, eliminating the need for a protractor and improving convenience.

[0063] As an optional implementation, in some embodiments, the base plate 1 is made of a transparent material. This facilitates placing the base plate 1 directly on the screen of an electronic device, thereby better aligning the bases of the semicircle 2 and the isosceles triangle 3 with the major axis of the acetabular ellipse, thereby improving accuracy.

[0064] In a second aspect, the present invention provides a method for measuring the anteversion angle of an acetabular prosthesis, using the above-mentioned measuring tool, which comprises the following steps:

[0065] Step 110: Obtain an AP radiograph of the hip joint and open it via an electronic device.

[0066] In this step, see Figure 7 The AP radiograph of the hip joint is a commonly used X-ray examination method for evaluating the structure and condition of the hip joint. After the radiograph is taken, it can be transferred to an electronic device such as a computer, tablet computer, or mobile phone and opened through software. In this embodiment, the AP radiograph of the hip joint is opened on a computer through a PACS system (full name: Picture Archiving and Communication System).

[0067] Step 120: Place the base plate on the screen of the electronic device, and adjust the size of the hip joint AP radiograph and the position of the base plate so that the bottom edge of the semicircle in the acetabulum aiming pattern completely coincides with the long axis of the acetabulum ellipse, and the arc of the semicircle coincides with the top contour of the acetabulum prosthesis.

[0068] In this step, see Figure 8 , place the transparent base plate on the computer screen, and then adjust the size of the hip joint AP film through the zoom function of the PACS system so that the bottom edge of the semicircle in the acetabulum aiming pattern can completely coincide with the long axis of the acetabulum ellipse. Among them, if the arc of the semicircle also coincides with the top contour of the acetabulum prosthesis, it can help the operator further confirm that the bottom edge of the semicircle has completely coincided with the long axis of the acetabulum ellipse.

[0069] Step 130: Observe the intersection of the intersection curve and the unobstructed portion of the acetabulum ellipse, and read the angle scale of the intersection.

[0070] In this step, observe the intersection of the edge curve and the unobstructed part of the acetabulum ellipse ( Figure 10 Since the angle scale corresponding to the intersection is the radiographic anteversion angle of the acetabular prosthesis, the anteversion angle of the acetabular prosthesis can be obtained by directly reading the scale value on the intersection curve, and the measurement is completed.

[0071] As an optional embodiment, in certain embodiments, when the bottom side of the semicircle in the acetabulum aiming pattern just completely coincides with the major axis of the acetabulum ellipse, but the arc of the semicircle cannot coincide with the top contour of the acetabulum prosthesis, then observe whether the two arc-shaped areas enclosed by the two sides of the isosceles triangle and the top of the acetabulum prosthesis are symmetrical; if the two arc-shaped areas are symmetrical, then the bottom side of the semicircle just completely coincides with the major axis of the acetabulum ellipse; if the two arc-shaped areas are asymmetrical, then the bottom side of the semicircle does not completely coincide with the major axis of the acetabulum ellipse.

[0072] Specifically, see Figure 9 If the bottom edge of the semicircle completely coincides with the major axis of the acetabular ellipse, but the arc of the semicircle cannot coincide with the top contour of the acetabular prosthesis, it means that the acetabular prosthesis is not hemispherical. At this time, we can observe whether the two sides of the isosceles triangle and the top of the acetabular prosthesis are symmetrical to further confirm whether the bottom edge of the semicircle completely coincides with the major axis of the acetabular ellipse, so as to improve the accuracy of subsequent measurements.

[0073] In some implementations, the top contour of the acetabular prosthesis may not be visible on the X-ray film, such as a bone cement prosthesis, or the top contour of the acetabular prosthesis may be an asymmetric shape on the X-ray film, such as a revision prosthesis with a reinforcement block. In this case, it is only necessary to observe whether the bottom edge of the semicircle completely coincides with the long axis of the acetabular ellipse, without using the arc of the semicircle and the two sides of the isosceles triangle for auxiliary judgment.

[0074] In summary, the main innovation of the present invention lies in finding an intersection curve, which has a characteristic that it intersects with the unobstructed acetabular ellipse at a point, and the intersection point and the center of the semicircle are connected to form a straight line. The angle formed by the straight line and the bottom edge of the semicircle is the radiographic anteversion angle of the acetabular prosthesis. The specific value can be directly read through the angle scale on the intersection curve. Therefore, it has the advantages of no need for estimation, no need for calculation, and no need for drawing on X-ray films, thereby improving the convenience and accuracy of ACA measurement, thereby improving the imaging evaluation of THA surgery.

[0075] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0076] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the essence of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A measuring tool for measuring the anteversion angle of an acetabular prosthesis, characterized in that: include: Base plate, which is imprinted with the acetabulum targeting pattern and intersecting edge curves; The acetabulum aiming pattern includes a semicircle and an isosceles triangle, the isosceles triangle and the semicircle share a base, the two sides of the isosceles triangle and the arc of the semicircle are located on the same side of the base, and the intersection curve is located on the other side of the base; When measuring the anteversion angle of the acetabular prosthesis on a hip joint AP radiograph, the bottom edge is aligned with the long axis of the acetabular ellipse, the intersection curve intersects with the unobstructed part of the acetabular ellipse at a point, and this point and the center of the semicircle are connected to form a straight line. The angle formed by the straight line and the bottom edge of the semicircle is the radiographic anteversion angle of the acetabular prosthesis.

2. The measuring tool for measuring the anteversion angle of the acetabular prosthesis according to claim 1, characterized in that: The intersection curve is defined by the major axis of the acetabulum ellipse; The acetabular ellipse is the projection of the opening edge of the acetabular prosthesis on the anteroposterior radiograph of the hip joint. The long axis of the acetabular ellipse is the X-axis, the perpendicular bisector of the long axis is the Y-axis, and the center O of the acetabular ellipse is the origin. A plane rectangular coordinate system is established. The acetabular ellipse is set as ellipse O, and the lengths of its long axis and short axis are 2a and 2b respectively. A ray with an angle of θ with the long axis is drawn from the center O of the acetabular ellipse to intersect the acetabular ellipse at point A. The coordinates of point A are (x, y) and satisfy the following equations: According to the above equations, the equation of the intersection curve is obtained: 2 -x 2 -xy+a 2 =0.

3. The measuring tool for measuring the anteversion angle of the acetabular prosthesis according to claim 1, characterized in that: Angle scales are engraved on the intersection curve.

4. The measuring tool for measuring the anteversion angle of the acetabular prosthesis according to claim 1, characterized in that: The bottom plate is made of transparent material.

5. A method for measuring the anteversion angle of an acetabular prosthesis, characterized in that: Using the measuring tool according to any one of claims 1 to 4, comprising the following steps: An anteroposterior radiograph of the hip is obtained and opened electronically; Place the base plate on the screen of the electronic device and adjust the size of the hip joint AP radiograph and the position of the base plate so that the bottom edge of the semicircle in the acetabular aiming pattern completely coincides with the long axis of the acetabular ellipse and the arc of the semicircle coincides with the top contour of the acetabular prosthesis. Observe the intersection of the intersection curve and the unobstructed part of the acetabular ellipse, and read the angle scale at this intersection.

6. The method for measuring the anteversion angle of the acetabular prosthesis according to claim 5, characterized in that: If the base of the semicircle in the acetabular aiming pattern completely coincides with the major axis of the acetabular ellipse, but the arc of the semicircle does not coincide with the top contour of the acetabular component, then check whether the two arc-shaped areas enclosed by the two sides of the isosceles triangle and the top of the acetabular component are symmetrical. If the two arc-shaped areas are symmetrical, the base of the semicircle will completely coincide with the major axis of the acetabulum ellipse; If the two arcuate areas are asymmetrical, the base of the semicircle does not completely coincide with the major axis of the acetabular ellipse.

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