Method for measuring static anterior-posterior displacement of the tibia in the knee

Abstract

The application discloses a kind of measurement methods of knee joint tibia static front and rear displacement, belong to medical image technology field, acquisition patient MRI image data: using MRI equipment to scan patient knee joint, obtain MRI image data;Patient takes supine position, and places a custom pillow below popliteal fossa, to support knee joint in relaxed state in the posture of extension, external rotation 15 °;MRI scanning obtains magnetic resonance image data, including sagittal position, coronal position and axial position sequence.The turning point of Blumensaat line to femoral condyle and the relative position of tibial platform are used in the application to evaluate tibial static front and rear displacement.In MRI sagittal plane, the turning point divides tibial platform into two segments.The ratio of the length of the front segment of tibial platform to the length of tibial platform is defined as BT index.Using this method can more simply and effectively characterize and quantify knee joint tibial static front and rear displacement, to provide a more accurate measuring means for clinical work and related research.

Description

Technical Field

[0001] This invention belongs to the field of medical imaging technology, and in particular relates to a method for measuring static anterior and posterior displacement of the tibia in the knee joint. Background Technology

[0002] Initially, measurements of static anteroposterior displacement of the tibia in the knee joint were based on lateral radiographs. However, the posterior borders of the medial and lateral femoral condyles are difficult to identify on radiographs, leading to significant measurement bias. Further research utilized sagittal or axial MRI to examine the static tibiofemoral relationship. To avoid the influence of tibial rotation, the mean horizontal displacement of the medial and lateral tibial condyles relative to the femur was used as a standard for measuring static anteroposterior displacement of the knee joint. However, regardless of whether based on sagittal or axial MRI, the fundamental principle of these methods is to measure the horizontal distance between the posterior borders of the tibial and femoral condyles. This means that the measured distance is affected by the morphology and size of the tibia and femur. Furthermore, these methods require separate measurements of the static displacement of the medial and lateral condyles, necessitating measurements on multiple MRI planes and requiring additional anatomical landmarks to determine the MRI planes used for measurement. Such measurement steps are numerous and complex, potentially leading to inaccurate results. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of traditional methods for measuring static anterior-posterior displacement of the tibia in the knee joint and to provide a new BT index. This index can simply and accurately quantify the static anterior-posterior relationship between the tibia and femur, and is non-invasive and intuitive. The invention of this index will be of great significance for accurately diagnosing anterior and posterior cruciate ligament injuries, studying complications of cruciate ligament rupture, guiding anterior and posterior cruciate ligament reconstruction surgery, and predicting prognosis. This invention provides a method for measuring static anterior-posterior displacement of the tibia in the knee joint.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for measuring static anterior-posterior displacement of the tibia in the knee joint, specifically including the following steps:

[0006] S1. Acquire patient MRI image data: Use MRI equipment to scan the patient's knee joint and acquire MRI image data;

[0007] S101. The patient lies supine with a custom-made pillow placed under the popliteal fossa to support the knee joint in a relaxed position with extension and external rotation of 15°.

[0008] S102. MRI scans yield magnetic resonance imaging data including sagittal, coronal, and axial sequences, each of which includes T1 and T2 proton-weighted images.

[0009] S2. Processing MRI images: All measurements are performed using software;

[0010] S201. Referring to previous research, obtain a standard image that fully displays the Blumensaat line, which is defined as a cross-section showing the complete anterior cruciate ligament or the remaining anterior cruciate ligament.

[0011] S202. The steps for measuring the BT index are as follows: First, draw the Blumensaat line along the cortical bone at the top of the intercondylar notch, and define the turning point of the Blumensaat line to the subchondral bone of the anterior femoral condyle as point O.

[0012] S203. Carefully draw the tangent of the tibial plateau, define the inflection point from the tibial plateau to the anterior tibial cortex as point A, and define the inflection point from the tibial plateau to the posterior tibial cortex as point C.

[0013] S204. Draw a vertical line through point O to the tibial plateau. The intersection of these two lines is defined as point B.

[0014] S205. Define the ratio between AB and AC as the BT exponent.

[0015] S206. Scan the knee joint of a normal human body, collect data and obtain MRI image data;

[0016] S207. After acquiring images using MRI scans, measurements are performed using software. By defining four points A, B, C, and O, the BT index, defined as the ratio between AB and AC in a normal human knee joint, is finally calculated.

[0017] S208. By collecting knee joint data from multiple normal individuals, calculating the BT index of multiple normal individuals, and storing the multiple BT indices for easy comparison with the BT index of patients in the future.

[0018] S209. After comparison, if the patient's BT index is higher than that of a normal person, it indicates that the static anterior displacement of the tibia is more severe; if the patient's BT index is lower than that of a normal person, it indicates that the static posterior displacement of the tibia is more severe.

[0019] As a further description of the above technical solution:

[0020] In S101, a 3.0-T magnetic resonance imaging device is used. By placing a customized pillow, the patient can lie supine without having to exert force to control the joint position. The pillow cushion allows the knee joint to be easily and stably maintained at a certain angle, which facilitates the scanning process and improves the accuracy of the scanning results.

[0021] As a further description of the above technical solution:

[0022] In step S201, the T2 fat images obtained from MRI scans are processed using the imaging software Radiant DICOM Viewer (Medixant, Poznan, Poland), and the image that fully displays the Blumensaat line is used as the standard working section.

[0023] As a further description of the above technical solution:

[0024] In step S202, the line drawing function of the software is used to draw the Blumensaat line on the MRI sagittal image along the bone cortex at the top of the intercondylar notch. The drawn Blumensaat line needs to be straight and close to the edge of the bone cortex.

[0025] As a further description of the above technical solution:

[0026] In S205, AB / AC is the final BT index, which is the ratio of the anterior tibial plateau length to the tibial plateau length. The larger the BT index, the more severe the anterior displacement of the tibia; the smaller the BT index, the more severe the posterior displacement of the tibia.

[0027] As a further description of the above technical solution:

[0028] Measurements were taken from 67 normal knee joints and 67 knee joints with complete anterior cruciate ligament rupture. The tibial plateau length of the anterior cruciate ligament group was 34.72±3.03 mm, the AB length was 22.11±3.44 mm, and the BT index was 0.64±0.08. The tibial plateau length of the normal knee joint was 35.48±3.14 mm, the AB length was 16.75±1.81 mm, and the BT index was 0.46±0.06.

[0029] As a further description of the above technical solution:

[0030] The ROC curve was used to assess the ability of the BT index to diagnose complete anterior cruciate ligament rupture. The results showed that the BT index has an extremely high ability to diagnose complete anterior cruciate ligament rupture, with an area under the curve (AUC value) as high as 0.989.

[0031] As a further description of the above technical solution:

[0032] The BT index has a cutoff value of 0.53 for diagnosing anterior cruciate ligament rupture, with a sensitivity of 95.5%, a specificity of 94%, and an accuracy of 94%.

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] This invention utilizes the relative position of the Blumensaat line's inflection point at the anterior femoral condyle and the tibial plateau to assess static anterior-posterior tibial displacement. On a sagittal MRI plane, this inflection point divides the tibial plateau into anterior and posterior segments. The ratio of the anterior plateau length to the tibial plateau length is defined as the BT index. A larger BT index indicates more severe anterior tibial displacement, while a smaller BT index indicates more severe posterior tibial displacement. This method uses this ratio to assess static anterior-posterior tibial displacement in the knee joint. Theoretically, this method avoids the influence of individual morphological differences in the tibial and femoral medial and lateral condyles, resulting in a more accurate assessment of static anterior-posterior tibial displacement. Furthermore, using the BT index to assess SATS (Stabilized Anterior-posterior Displacement) is more convenient and concise, as the measurement only requires working on a sagittal MRI plane that clearly displays the Blumensaat line. Therefore, this method provides a simpler and more effective way to characterize and quantify static anterior-posterior tibial displacement in the knee joint, offering a more accurate measurement tool for clinical work and related research. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the definition point O structure of a method for measuring static anterior-posterior displacement of the tibia in the knee joint proposed in this invention;

[0036] Figure 2 This is a schematic diagram of the definition points A, B, and C of the method for measuring static anterior-posterior displacement of the tibia in the knee joint proposed in this invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Please see Figure 1-2 This invention provides a technical solution: a method for measuring static anterior-posterior displacement of the tibia in the knee joint, specifically including the following steps:

[0039] S1. Acquire patient MRI image data: Use MRI equipment to scan the patient's knee joint and acquire MRI image data;

[0040] S101. The patient lies supine with a custom-made pillow placed under the popliteal fossa to support the knee joint in a relaxed position with extension and external rotation of 15°.

[0041] S102. MRI scans yield magnetic resonance imaging data including sagittal, coronal, and axial sequences, each of which includes T1 and T2 proton-weighted images.

[0042] S2. Processing MRI images: All measurements are performed using software;

[0043] S201. Referring to previous research, obtain a standard image that fully displays the Blumensaat line, which is defined as a cross-section showing the complete anterior cruciate ligament or the remaining anterior cruciate ligament.

[0044] S202. The steps for measuring the BT index are as follows: First, draw the Blumensaat line along the cortical bone at the top of the intercondylar notch, and define the turning point of the Blumensaat line to the subchondral bone of the anterior femoral condyle as point O.

[0045] S203. Carefully draw the tangent of the tibial plateau, define the inflection point from the tibial plateau to the anterior tibial cortex as point A, and define the inflection point from the tibial plateau to the posterior tibial cortex as point C.

[0046] S204. Draw a vertical line through point O to the tibial plateau. The intersection of these two lines is defined as point B.

[0047] S205. The ratio between AB and AC is defined as the BT index. The higher the BT index, the more severe the static anterior displacement of the tibia; the lower the BT index, the more severe the static posterior displacement of the tibia.

[0048] S206. Scan the knee joint of a normal human body, collect data and obtain MRI image data;

[0049] S207. After acquiring images using MRI scans, measurements are performed using software. By defining four points A, B, C, and O, the BT index, defined as the ratio between AB and AC in a normal human knee joint, is finally calculated.

[0050] S208. By collecting knee joint data from multiple normal individuals, calculating the BT index of multiple normal individuals, and storing the multiple BT indices for easy comparison with the BT index of patients in the future.

[0051] S209. After comparison, if the patient's BT index is higher than that of a normal person, it indicates that the static anterior displacement of the tibia is more severe; if the patient's BT index is lower than that of a normal person, it indicates that the static posterior displacement of the tibia is more severe.

[0052] Specifically, in S101, a 3.0-T magnetic resonance imaging device is used. By placing a customized pillow, the patient can lie supine without having to exert force to control the joint position. The pillow cushion allows the knee joint to be easily and stably maintained at a certain angle, which facilitates the scanning process and improves the accuracy of the scanning results.

[0053] Specifically, in S201, the T2 fat phase image obtained from the MRI scan is processed using the imaging software Radiant DICOM Viewer (Medixant, Poznan, Poland), and the image that fully displays the Blumensaat line is used as the standard working section.

[0054] Specifically, in step S202, the line drawing function of the software is used to draw the Blumensaat line on the MRI sagittal image along the bone cortex at the top of the intercondylar notch. The drawn Blumensaat line needs to be straight and close to the edge of the bone cortex.

[0055] Specifically, in S205, AB / AC is the final BT index, which is the ratio of the anterior segment length of the tibial plateau to the tibial plateau length. The larger the BT index, the more severe the anterior displacement of the tibia; the smaller the BT index, the more severe the posterior displacement of the tibia.

[0056] Specifically, measurements were taken from 67 normal knee joints and 67 knee joints with complete anterior cruciate ligament rupture. The tibial plateau length of the anterior cruciate ligament group was measured to be 34.72±3.03 mm, the AB length was 22.11±3.44 mm, and the BT index was 0.64±0.08. The tibial plateau length of the normal knee joint was measured to be 35.48±3.14 mm, the AB length was 16.75±1.81 mm, and the BT index was 0.46±0.06.

[0057] Specifically, the ability of the BT index to diagnose complete anterior cruciate ligament rupture was assessed using ROC curves. The results showed that the BT index has an extremely high ability to diagnose complete anterior cruciate ligament rupture, with an area under the curve (AUC value) as high as 0.989.

[0058] Specifically, the cutoff value for the BT index in diagnosing anterior cruciate ligament rupture is 0.53, with a sensitivity of 95.5%, a specificity of 94%, and an accuracy of 94%.

[0059] Working principle: In the first step, the patient lies supine with a custom-made pillow placed under the popliteal fossa to keep the knee joint relaxed and in a position of extension and 15° external rotation. The custom-made pillow allows the patient to maintain the knee joint easily and stably at a certain angle without exerting force to control its position, facilitating the scanning process and improving the accuracy of the scan results. A 3.0-T magnetic resonance imaging (MRI) device will be used, including sagittal, coronal, and axial sequences. Each sequence includes T1 and T2 proton-weighted densities. The second step utilizes the imaging software RadiAntDICOMViewer (Medixant). Poznan (Poland) processed T2 fat-phase images obtained from MRI scans, using an image fully displaying the Blumensaat line as the standard working section. This section shows the complete anterior cruciate ligament (ACL) or residual ACL. Using the software's drawing function, the Blumensaat line was drawn on the sagittal MRI image along the cortical bone at the top of the intercondylar notch. The turning point from the Blumensaat line to the subchondral bone of the anterior femoral condyle was marked as point O. The drawn Blumensaat line should be straight and close to the edge of the cortical bone. The third step involved carefully drawing the tibial plateau along its length. Tangents were drawn to the anterior and posterior cortical regions of the tibia. The intersection of the anterior tibial cortical tangent and the tibial plateau line was marked as point A, and the intersection of the posterior tibial clivus tangent and the tibial plateau line was marked as point C. A perpendicular line was drawn from point O to the tibial plateau line, and the intersection of this perpendicular line and the tibial plateau line was defined as point B. AB / AC is the final BT index, which is the ratio of the anterior tibial plateau length to the tibial plateau length. A larger BT index indicates more severe anterior tibial displacement, and a smaller BT index indicates more severe posterior tibial displacement. The measurement method of this invention was used to measure 67 normal knee joints and 67 knee joints with complete anterior cruciate ligament ruptures. The tibial plateau length of the anterior cruciate ligament group was measured as follows: The tibial plateau length of a normal knee joint was measured to be 34.72±3.03 mm, the AB length was 22.11±3.44 mm, and the BT index was 0.64±0.08. The tibial plateau length of a normal knee joint was measured to be 35.48±3.14 mm, the AB length was 16.75±1.81 mm, and the BT index was 0.46±0.06. The ability of the BT index to diagnose complete anterior cruciate ligament (ACL) rupture was evaluated using ROC curves. The results showed that the BT index has an extremely high ability to diagnose complete ACL rupture, with an area under the curve (AUC) as high as 0.989. The cutoff value for the BT index in diagnosing ACL rupture was 0.53, with a sensitivity of 95.5%, a specificity of 94%, and an accuracy of 94%.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for measuring static anterior-posterior displacement of the tibia in the knee joint, characterized in that, Specifically, the following steps are included: S1. Acquire patient MRI image data: Use MRI equipment to scan the patient's knee joint and acquire MRI image data; S101. The patient lies supine with a custom-made pillow placed under the popliteal fossa to support the knee joint in a relaxed position with extension and external rotation of 15°. S102. MRI scans yield magnetic resonance imaging data including sagittal, coronal, and axial sequences, each of which includes T1 and T2 proton-weighted images. S2. Processing MRI images obtained from MRI scans: All measurements are performed using software; S201. Obtain a standard image that fully displays the Blumensaat line, defined as a cross-section showing the complete anterior cruciate ligament or the remaining anterior cruciate ligament; S202. The steps for measuring the BT index are as follows: First, draw the Blumensaat line along the cortical bone at the top of the intercondylar notch, and define the turning point of the Blumensaat line to the subchondral bone of the anterior femoral condyle as point O. S203. Draw the tangent of the tibial plateau, define the inflection point from the tibial plateau to the anterior tibial cortex as point A, and define the inflection point from the tibial plateau to the posterior tibial cortex as point C. S204. Draw a vertical line through point O to the tibial plateau. The intersection of the tibial plateau tangent and the vertical line to the tibial plateau is defined as point B. S205. Define the ratio between AB and AC as the BT exponent. S206. Scan the knee joint of a normal human body, collect data and obtain MRI image data; S207. After acquiring images using MRI scans, measurements are performed using software. By defining four points A, B, C, and O, the BT index, defined as the ratio between AB and AC in a normal human knee joint, is finally calculated. S208. By collecting knee joint data from multiple normal individuals, calculating the BT index of multiple normal individuals, and storing the multiple BT indices for easy comparison with the BT index of patients in the future. S209. After comparison, if the patient's BT index is higher than that of a normal person, it indicates that the static anterior displacement of the tibia is more severe; if the patient's BT index is lower than that of a normal person, it indicates that the static posterior displacement of the tibia is more severe.

2. The method for measuring static anterior-posterior displacement of the tibia in the knee joint according to claim 1, characterized in that, In S101, a 3.0-T magnetic resonance imaging device is used, and a customized pillow is placed so that the patient does not need to exert force to control the joint position when lying supine.

3. The method for measuring static anterior-posterior displacement of the tibia in the knee joint according to claim 1, characterized in that, In step S201, the T2 fat images obtained from MRI scans are processed using the imaging software Radiant DICOM Viewer, and the image that fully displays the Blumensaat line is used as the standard working section.

4. The method for measuring static anterior-posterior displacement of the tibia in the knee joint according to claim 1, characterized in that, In step S202, the line drawing function of the software is used to draw the Blumensaat line on the MRI sagittal image along the bone cortex at the top of the intercondylar notch. The drawn Blumensaat line needs to be straight and close to the edge of the bone cortex.

5. The method for measuring static anterior-posterior displacement of the tibia in the knee joint according to claim 1, characterized in that, In S205, AB / AC is the final BT index, which is the ratio of the anterior tibial plateau length to the tibial plateau length. The larger the BT index, the more severe the anterior displacement of the tibia; the smaller the BT index, the more severe the posterior displacement of the tibia.

6. A method for measuring static anterior-posterior displacement of the tibia in the knee joint according to any one of claims 1-5, characterized in that, Measurements were taken from 67 normal knee joints and 67 knee joints with complete anterior cruciate ligament rupture. The tibial plateau length of the anterior cruciate ligament group was 34.72±3.03 mm, the AB length was 22.11±3.44 mm, and the BT index was 0.64±0.

08. The tibial plateau length of the normal knee joint was 35.48±3.14 mm, the AB length was 16.75±1.81 mm, and the BT index was 0.46±0.

06.

7. The method for measuring static anterior-posterior displacement of the tibia in the knee joint according to claim 6, characterized in that, The ability of the BT index to diagnose complete anterior cruciate ligament rupture was evaluated using ROC curves. The results showed that the BT index has an extremely high ability to diagnose complete anterior cruciate ligament rupture, with an area under the curve (AUC) value as high as 0.

989.

8. The method for measuring static anterior-posterior displacement of the tibia in the knee joint according to claim 7, characterized in that, The BT index has a cutoff value of 0.53 for diagnosing anterior cruciate ligament rupture, with a sensitivity of 95.5%, a specificity of 94%, and an accuracy of 94%.

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