Method for evaluating soft tissue laxity in total knee arthroplasty

Abstract

This invention relates to a method for assessing soft tissue laxity during total knee arthroplasty, comprising: establishing a total knee joint model using a prosthetic bone model with artificial ligaments and muscles; applying progressively increasing tension to the medial and lateral sides of the knee joint using a TKA soft tissue balance solver to obtain a lattice coordinate diagram of the medial and lateral joint gap; selecting a pad of thickness I based on the medial and lateral knee joint gap, and plotting two straight lines y = I and x = I on the lattice coordinate diagram, recording the number of points above y = I (called the lateral laxity redundancy parameter A), and recording the number of points to the right of x = I (called the medial laxity redundancy parameter B); simultaneously calculating the sum of the distances from each point above y = I to the line y = I (called the lateral laxity redundancy parameter C), and calculating the sum of the distances from each point to the right of x = I to the line x = I (called the medial laxity redundancy parameter D); and assessing the degree of soft tissue laxity redundancy.

Description

Technical Field

[0001] This invention relates to a method for assessing soft tissue laxity during total knee arthroplasty, belonging to the field of medical device technology. Background Technology

[0002] Total knee arthroplasty (TKA) includes various procedures such as single-compartment replacement, double-compartment replacement, and total knee replacement. However, the success of all procedures depends on the appropriate prosthesis-bone-soft tissue relationship to establish a good knee joint kinematic-dynamic pattern and achieve normal postoperative knee function. Up to 20% of TKA patients are dissatisfied with the postoperative outcome, possibly due to the prosthesis implantation method and target values ​​(appropriate medial and lateral soft tissue laxity and balance). However, the exact definition of appropriate medial and lateral laxity after total knee arthroplasty and the impact of these target parameters on postoperative outcomes remain unclear. Traditional evaluation and adjustment of soft tissue laxity in total knee arthroplasty rely on the surgeon's personal experience, or use simple mechanical devices to measure gaps, or measure the force under the thickness of the fixation pad. These methods cannot evaluate the force-gap relationship or simultaneously measure both soft tissue elasticity and laxity. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for assessing soft tissue laxity during total knee arthroplasty (TKA). This method is a novel approach for comprehensively and quantitatively assessing the degree of soft tissue laxity during TKA, providing a reference for determining the appropriate target range for intraoperative soft tissue laxity redundancy in TKA surgery. It changes the clinical practice of TKA surgery and improves postoperative efficacy, possessing significant research and application value.

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

[0005] A method for assessing soft tissue laxity during total knee arthroplasty, comprising:

[0006] An artificial total knee joint model was established using a prosthetic bone model with artificial ligaments and muscles.

[0007] When the knee joint is flexed at a certain angle, the TKA soft tissue balance solver is used to apply gradually increasing tension to the inner and outer sides of the knee joint to obtain a lattice coordinate map of the inter-articular space of the knee joint.

[0008] Based on the medial and lateral knee joint gaps, a pad with a thickness of I is selected. On the dot matrix coordinate diagram, two straight lines y = I and x = I are drawn respectively. The number of dots above y = I is called the lateral relaxation redundancy parameter A, and the number of dots to the right of x = I is called the medial relaxation redundancy parameter B. At the same time, the sum of the distances between each dot matrix above y = I and the straight line y = I is calculated, which is called the lateral relaxation redundancy parameter C. The sum of the distances between each dot matrix to the right of x = I and the straight line x = I is calculated, which is called the medial relaxation redundancy parameter D.

[0009] Calculate the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, and medial relaxation redundancy parameter D when the knee joint is flexed at a certain angle.

[0010] The degree of soft tissue relaxation redundancy is assessed by combining the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, and medial relaxation redundancy parameter D.

[0011] A second aspect of the present invention provides another method for assessing soft tissue laxity during total knee arthroplasty, comprising:

[0012] An artificial total knee joint model was established using a prosthetic bone model with artificial ligaments and muscles.

[0013] When the knee joint is flexed at a certain angle, the TKA soft tissue balance solver is used to apply gradually increasing tension to the inner and outer sides of the knee joint to obtain a lattice coordinate map of the inter-articular space of the knee joint.

[0014] Based on the medial and lateral knee joint gaps, a pad with a thickness of I is selected. On the dot matrix coordinate diagram, two straight lines y = I and x = I are drawn respectively. The number of dots above y = I is called the lateral relaxation redundancy parameter A, and the number of dots to the right of x = I is called the medial relaxation redundancy parameter B. At the same time, the sum of the distances between each dot matrix above y = I and the straight line y = I is calculated, which is called the lateral relaxation redundancy parameter C. The sum of the distances between each dot matrix to the right of x = I and the straight line x = I is calculated, which is called the medial relaxation redundancy parameter D.

[0015] Calculate the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, and medial relaxation redundancy parameter D when the knee joint is flexed at a certain angle.

[0016] When the knee joint is continuously flexed and changes angle, two fixed inversion and valgus stresses are applied respectively to obtain the medial and lateral gap curve balance diagram of the knee joint within the range of continuous angle change.

[0017] Select a pad of appropriate thickness, calculate the area between the medial and lateral gap curves and the pad thickness line, and obtain the medial relaxation redundancy parameter E and the lateral relaxation redundancy parameter F within the range of continuous angular movement of the knee joint under the pad thickness.

[0018] The degree of soft tissue relaxation redundancy is assessed by combining the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, medial relaxation redundancy parameter D, medial relaxation redundancy parameter E, and lateral relaxation redundancy parameter F.

[0019] The assessment method preferably involves applying gradually increasing tension ranging from 30N to 90N to the inner and outer sides of the knee joint, with tension applied at 5N intervals.

[0020] In the aforementioned assessment method, preferably, the knee joint flexion angle is continuously varying from 0° to 90°, and the two fixed inversion and valgus stresses are 80N and 120N.

[0021] The present invention has the following advantages due to the adoption of the above technical solutions:

[0022] 1. This invention abandons the previous approach of assessing the relationship between knee joint laxity and postoperative efficacy under static discontinuous and single tension (stress) conditions. It innovatively proposes the concept of quantifying soft tissue laxity across the entire range of motion of the knee joint under dynamic, continuous, and different tension conditions. This helps to study the dose-response relationship between laxity and postoperative efficacy and helps joint surgeons determine the optimal intraoperative soft tissue laxity target value (laxity redundancy). This is an important theoretical innovation.

[0023] 2. In order to quantify soft tissue relaxation under dynamic, continuous, and varying tensions, this invention innovatively employs a TKA soft tissue balance solver and robot-assisted knee replacement surgery to record the gaps between the medial and lateral soft tissues of the knee joint under different tensions. Simultaneously, it records the medial and lateral gap curve balance diagrams under different varus and valgus stresses within the 0°-90° range of knee joint motion. By calculating the number of solver lattice points above or above a certain pad thickness, and the sum of the distances between the lattice points and the line corresponding to the pad thickness, the area between the medial and lateral gap curves and the pad thickness line is calculated. After comprehensive evaluation, the medial and lateral relaxation redundancy of the knee joint under a certain pad thickness is obtained, representing a novel method for quantifying soft tissue relaxation redundancy.

[0024] 3. This invention dynamically and continuously assesses the soft tissue laxity redundancy during knee replacement surgery under different knee joint tensions and different flexion angles, and determines the appropriate target range of intraoperative soft tissue laxity values. It is expected to profoundly change the clinical practice of knee replacement surgery and improve the postoperative efficacy of knee replacement surgery, and has important research and application value. Attached Figure Description

[0025] Figure 1 This is a dot matrix coordinate diagram of the medial and lateral interarticular space of the knee joint provided in an embodiment of the present invention;

[0026] Figure 2 The second embodiment of the present invention provides a balance curve diagram of the medial and lateral gaps of the knee joint within the range of motion of 0°-90°. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," "third," "fourth," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0029] Currently, the assessment of soft tissue laxity in total knee arthroplasty (TKA) is static and discontinuous, which has limitations. Although some studies have objectively described the medial and lateral laxity or anterior and posterior laxity of the knee joint by applying fixed varus / valgus stress or anterior / posterior drawer stress at different knee flexion angles and analyzed the relationship between knee laxity and postoperative efficacy, the conclusions of different studies are controversial. This may be because the laxity assessment in these studies is still static, conducted at one or a few knee flexion angles under a single varus / valgus or anterior / posterior drawer stress, rather than dynamically and continuously studying knee laxity throughout the entire range of flexion and extension under different stresses. This cannot comprehensively depict and quantify the soft tissue laxity of the knee joint. Furthermore, traditional TKA aims for equal flexion-extension gaps at 0° extension and 90° flexion; however, studies have shown that 36% of patients with equal flexion-extension gaps have moderate knee laxity in the flexion position. This may be because traditional TKA only considers the flexion-extension balance at 0° and 90°, without considering the soft tissue balance throughout the entire range of knee flexion and extension. Traditional mechanical measuring tools struggle to quantitatively assess knee joint gaps and soft tissue balance across the entire range of knee flexion and extension. While the development of navigation-assisted and robot-assisted knee replacement surgery has made dynamic, real-time measurement of the medial and lateral soft tissue gaps a reality in recent years, most navigation and robotic systems only provide gap values ​​at 0° and 90° flexion, omitting assessments at moderate flexion. Therefore, quantifying and balancing soft tissues across the entire range of knee flexion and extension may help improve postoperative function and patient satisfaction.

[0030] On the other hand, the laxity of the human knee joint differs between the medial and lateral sides and varies with the flexion and extension angles. A certain degree of laxity exists in a normal human knee joint, termed physiological laxity, but its specific definition is not universally agreed upon. Furthermore, the medial and lateral gaps of a naturally normal knee joint are not symmetrical, leading some doctors to question whether TKA surgery needs to pursue the traditional balance between 0° and 90° flexion. Studies have confirmed that the medial soft tissues of a natural knee joint are consistently tighter than the lateral soft tissues during flexion and extension, and the laxity of a natural knee joint increases from extension to moderate flexion, but remains essentially unchanged or slightly increases upon further flexion to 90°.

[0031] Postoperative soft tissue laxity after total knee arthroplasty (TKA) affects the kinematic and dynamic parameters of the knee joint and its clinical function. Previous studies have shown that laxity of the medial collateral ligament (MCL) can easily lead to abnormal anterior femoral displacement during high flexion. However, lateral soft tissue laxity does not appear to affect clinical efficacy. Moderate lateral soft tissue laxity may help the artificial knee achieve medial axial displacement similar to that of a natural knee and may help increase postoperative knee range of motion. One possible reason is that a certain degree of lateral laxity already exists in normal knee joints. Nakamura et al. found that medial laxity of the knee joint leads to abnormal knee kinematic patterns, while lateral laxity has a smaller impact. Computer simulation studies have also shown that if a neutral lower limb alignment is achieved after TKA, even excessive lateral laxity will not result in femoral condyle lift-off. Studies by Mizu-Uchi et al. found a positive correlation between moderate medial laxity under valgus stress (tibiofemoral joint line angle within 0°-10° range), axial rotation of the tibiofemoral joint (1°-10°), and postoperative KSS scores after total knee arthroplasty (TKA). Patients who achieved medial pivot movement postoperatively had better function and satisfaction. Onsem et al. found that patients with lower self-reported functional scores after TKA exhibited greater anterior displacement of the medial tibiofemoral joint surface during the standing-sitting-squatting (closed-chain movement) phase at 0°-30° flexion, and instability at 30°-60° flexion (more posterior roll of the femoral condyle). In contrast, patients with higher scores showed virtually no posterior roll at moderate flexion and stability at moderate flexion. At 60°-90° flexion, the lateral femoral condyle showed less posterior roll than high-scoring patients. High-scoring patients exhibited a movement similar to natural knee roll. The authors suggest that further research is needed to explore the relationship between preoperative knee laxity at different flexion angles and postoperative knee kinematics. Lutzner et al. also found abnormal knee kinematics in patients whose function did not improve after TKA. However, Warth et al. did not find better clinical function in patients who achieved intraoperative medial pivot movement. In summary, no studies have yet confirmed the required degree of soft tissue relaxation and tibiofemoral joint kinematic pattern during total knee arthroplasty.

[0032] To address the shortcomings of traditional methods for evaluating and adjusting soft tissue laxity in total knee arthroplasty (TKA), which rely on the surgeon's personal experience, simple mechanical clearance measurements, or force measurements under the thickness of the fixation pad, failing to assess the force-clearance relationship and simultaneously measure both soft tissue elasticity and laxity, this invention provides a method for assessing soft tissue laxity during TKA. This method provides a reference for determining an appropriate target range for intraoperative soft tissue laxity redundancy in TKA surgery, thereby changing clinical practice and improving postoperative efficacy. It has significant research and application value.

[0033] The technical solution of the present invention will be explained in detail below with reference to specific embodiments.

[0034] Example 1

[0035] Step a: Establish an artificial total knee joint model using femoral, tibial, and patellar prosthesis models with artificial ligaments and muscles; simulate total knee replacement surgery by performing femoral and tibial osteotomies respectively, and insert a femoral prosthesis trial model after the osteotomies are completed;

[0036] Step b: With the knee joint flexed at 0°, 10°, and 90°, use the TKA soft tissue balance solver to apply dispersive tension to the medial and lateral sides of the knee joint, with a tension range of 30N-90N, applied at 5N intervals, to obtain a lattice coordinate map of the medial and lateral knee joint space (e.g., Figure 1 As shown, the horizontal axis represents the inner gap, and the vertical axis represents the outer gap (unit: mm).

[0037] Step c: Based on the medial and lateral knee joint gaps, select a pad of appropriate thickness (record the thickness as 1 mm), and draw two straight lines y = 1 and x = 1 respectively. Record the number of points above y = 1, which is called the lateral relaxation redundancy parameter A. Record the number of points to the right of x = 1, which is called the medial relaxation redundancy parameter B. At the same time, calculate the sum of the distances between each point above y = 1 and the straight line y = 1, which is called the lateral relaxation redundancy parameter C. Similarly, calculate the sum of the distances between each point to the right of x = 1 and the straight line x = 1, which is called the medial relaxation redundancy parameter D.

[0038] Step d: Calculate the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, and medial relaxation redundancy parameter D at three knee flexion positions: 0°, 10°, and 90°.

[0039] Step e: Combine the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, and medial relaxation redundancy parameter D to assess the degree of soft tissue relaxation redundancy.

[0040] Figure 1The diagram shows the dot matrix coordinates of the medial and lateral gaps after applying different dispersing tensions (30N-90N in 5N intervals) to the medial and lateral sides with the knee flexed at 0°, 10°, and 90° using the TKA soft tissue balance solver. Each point represents the gap on the medial side and the gap on the lateral side under a certain tension. Using the horizontal line (dashed line) of y=16mm as the boundary, the number of triangular dots above the y=16mm horizontal line represents the lateral relaxation redundancy at 90° flexion with a 16mm pad thickness. Using the vertical line (dotted line) of x=16mm as the boundary, the number of triangular dots to the right of the vertical line (dotted line) of x=16mm represents the medial relaxation redundancy at 90° flexion with a 16mm pad thickness. Similarly, the relaxation redundancy at 0° and 10° flexion can also be calculated. If all dots are below the y=16mm horizontal line, the lateral relaxation redundancy is considered to be 0, meaning the lateral soft tissue is too tight. If all the dots are to the left of the vertical line x = 16 mm, the relaxation redundancy on the medial side is considered to be 0, meaning that the medial soft tissue is too tight. The relaxation redundancy takes into account the medial and lateral gaps under different spreading tensions. Compared with the previous static and discontinuous single tension assessment method for soft tissue relaxation, the relaxation redundancy assessment method proposed in this invention can achieve dynamic and continuous quantification of the relaxation of the medial and lateral soft tissues of the knee joint.

[0041] Example 2

[0042] Step a: Establish an artificial total knee joint model using femoral, tibial, and patellar prosthesis models with artificial ligaments and muscles; simulate total knee replacement surgery by performing femoral and tibial osteotomies respectively, and insert a femoral prosthesis trial model after the osteotomies are completed;

[0043] Step b: Select a pad of appropriate thickness (thickness recorded as a constant T), and apply varus stress of 80N and 120N respectively to the knee joint within its full range of motion from 0° to 90° flexion; then apply valgus stress of 80N and 120N respectively. The robot's camera automatically obtains a balance curve diagram of the medial and lateral joint space of the knee joint within its full range of motion from 0° to 90° flexion by monitoring positioning points on the femur and tibia. Figure 2 The outer gap curve is on the left side of the Y-axis, the inner gap curve is on the right side of the Y-axis, and the gap in the middle is the average value of the inner and outer gap curves.

[0044] Calculate the area enclosed by the line X = -T and the outer gap curve to its left, and record it as the outer relaxation redundancy parameter F. The area enclosed by the line X = -T and the outer gap curve to its right is not included in this calculation. Similarly, calculate the area enclosed by the line X = T and the inner gap curve to its right, and record it as the inner relaxation redundancy parameter E. The area enclosed by the line X = T and the inner gap curve to its left is not included in this calculation.

[0045] c: Combine the medial relaxation redundancy parameter E and the lateral relaxation redundancy parameter F to assess the degree of soft tissue relaxation redundancy.

[0046] Figure 2 The diagram shows the balance graph of the maximum medial and lateral gaps measured using a TKA surgical robot with continuous knee flexion from 0° to 90° under varus and valgus stresses. The vertical axis represents the knee flexion angle. The negative values ​​on the left side of the horizontal axis represent the lateral gap (Lat), and the vertical curve on the left (extending along the y-axis) represents the change of the lateral gap with the knee flexion and extension angles. The positive values ​​on the right side of the horizontal axis represent the medial gap, and the dashed curve on the right side represents the change of the medial gap with the knee flexion and extension angles. The area enclosed by the vertical line on the right (x = 11 mm pad thickness) and the curved portion to its right is defined as the medial laxity redundancy within a 90° range of knee flexion and extension. The area enclosed by the vertical line on the left (x = -11 mm pad thickness) and the vertical curve to its left is defined as the lateral laxity redundancy within a 90° range of knee flexion and extension. If all vertical curves are to the right of the vertical line (x = -11 mm pad thickness), the lateral laxity redundancy is considered to be 0, meaning the lateral soft tissue is too tight. If all the curves on the right are to the left of the vertical line on the right, then the relaxation redundancy on the inner side is considered to be 0, which means that the inner soft tissue is too tight.

[0047] Example 3

[0048] Step a: Establish an artificial total knee joint model using a prosthetic bone model with artificial ligaments and muscles;

[0049] Step b: With the knee joint flexed at 0°, 10°, and 90°, use the TKA soft tissue balance solver to apply dispersive tension to the medial and lateral sides of the knee joint, with a tension range of 30N-90N, applied at 5N intervals, to obtain a lattice coordinate map of the medial and lateral knee joint space (e.g., Figure 1 As shown, the horizontal axis represents the inner gap, and the vertical axis represents the outer gap.

[0050] Step c: Based on the medial and lateral knee joint gaps, select a pad of appropriate thickness (record the thickness as I), and draw two straight lines y = I and x = I respectively. Record the number of points above y = I, which is called the lateral relaxation redundancy parameter A. Record the number of points to the right of x = I, which is called the medial relaxation redundancy parameter B. At the same time, calculate the sum of the distances between each point above y = I and the straight line y = I, which is called the lateral relaxation redundancy parameter C. Similarly, calculate the sum of the distances between each point to the right of x = I and the straight line x = I, which is called the medial relaxation redundancy parameter D.

[0051] Step d: Calculate the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, and medial relaxation redundancy parameter D at three knee flexion positions: 0°, 10°, and 90°.

[0052] Step e: With the knee joint continuously flexed from 0° to 90°, apply varus and valgus stresses of 80N and 120N respectively to obtain a balance curve diagram of the medial and lateral joint space within the 0°-90° range of motion (e.g., Figure 2 (as shown);

[0053] Step f: Select a pad of appropriate thickness, calculate the area between the medial and lateral gap curves and the pad thickness line (the specific calculation method is shown below), and obtain the medial relaxation redundancy parameter E and the lateral relaxation redundancy parameter F within the 0°-90° range of motion of the knee joint under a certain pad thickness.

[0054] Step g: Combine the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, medial relaxation redundancy parameter D, medial relaxation redundancy parameter E, and lateral relaxation redundancy parameter F to assess the degree of soft tissue relaxation redundancy.

[0055] Of course, the present invention can also combine the ratios of the above six parameters A / B, C / D, and E / F to evaluate the degree of soft tissue relaxation redundancy.

[0056] To quantify soft tissue relaxation under dynamic, continuous, and varying tensions, this invention innovatively employs a TKA soft tissue balance solver and robot-assisted knee replacement surgery. It records the gaps between the medial and lateral soft tissues of the knee joint under different tensions, and simultaneously records the medial and lateral gap diagrams under different varus and valgus stresses within the knee joint's 0°-90° range of motion. By calculating the sum of the number of solver lattice points above or above a certain pad thickness and the distance between the lattice points and the line representing the pad thickness, the area between the medial and lateral gap curve balance diagram and the pad thickness line is calculated. This yields the medial and lateral relaxation redundancy of the knee joint at a given pad thickness, representing a methodological innovation for quantifying soft tissue relaxation redundancy.

[0057] This invention dynamically and continuously assesses soft tissue laxity during knee replacement surgery under different knee joint tensions and flexion / extension angles throughout the entire procedure, and determines the appropriate target range for intraoperative soft tissue laxity. This is expected to profoundly change the clinical practice of knee replacement surgery and improve postoperative efficacy, and has significant research and application value.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of evaluating soft tissue laxity in total knee arthroplasty, characterized by, include: An artificial total knee joint model was established using a prosthetic bone model with artificial ligaments and muscles. When the knee joint is flexed at a certain angle, the TKA soft tissue balance solver is used to apply gradually increasing tension to the inner and outer sides of the knee joint to obtain a lattice coordinate map of the inter-articular space of the knee joint. Based on the medial and lateral knee joint gaps, a pad with a thickness of I is selected. On the dot matrix coordinate diagram, two straight lines y=I and x=I are drawn respectively. The number of dots above y=I is called the lateral relaxation redundancy parameter A, and the number of dots to the right of x=I is called the medial relaxation redundancy parameter B. At the same time, the sum of the distances between each dot matrix above y=I and the straight line y=I is calculated, which is called the lateral relaxation redundancy parameter C. The sum of the distances between each dot matrix to the right of x=I and the straight line x=I is calculated, which is called the medial relaxation redundancy parameter D. Calculate the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, and medial relaxation redundancy parameter D when the knee joint is flexed at a certain angle. When the knee joint is continuously flexed and the angle changes, two fixed inversion and valgus stresses are applied respectively to obtain the medial and lateral gap curve balance diagram of the knee joint within the continuously changing angle range of motion. The vertical axis of the medial and lateral gap curve balance diagram is the knee flexion angle. The part with negative values ​​on the left horizontal axis represents the lateral gap, and the vertical curve on the left side of the coordinate axis represents the change of the lateral gap with the knee flexion and extension angle. The part with positive values ​​on the right horizontal axis represents the medial gap, and the dashed curve on the right side represents the change of the medial gap with the knee flexion and extension angle. Select a pad of appropriate thickness, and record the thickness as a constant T. Calculate the area between the medial and lateral gap curves and the pad thickness line within the full range of motion of the knee joint from 0° to 90° flexion. Obtain the medial relaxation redundancy parameter E and the lateral relaxation redundancy parameter F within the continuously changing angle range of the knee joint under this pad thickness. Calculate the area enclosed by the line X = -T and the lateral gap curve to its left, and record it as the lateral relaxation redundancy parameter F. Calculate the area enclosed by the line X = T and the medial gap curve to its right, and record it as the medial relaxation redundancy parameter E. The degree of soft tissue relaxation redundancy is assessed by combining the lateral relaxation redundancy parameter A, lateral relaxation redundancy parameter C, medial relaxation redundancy parameter B, medial relaxation redundancy parameter D, medial relaxation redundancy parameter E, and lateral relaxation redundancy parameter F.

2. The evaluation method according to claim 1, characterized in that Apply gradually increasing tension of 30N-90N to the inner and outer sides of the knee joint, with tension applied at 5N intervals.

3. The evaluation method according to claim 2, characterized in that The knee joint flexion angle is continuously variable from 0° to 90°, and the two fixed inversion and valgus stresses are 80N and 120N.

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