Tibial spacer and total knee prosthesis

Abstract

This invention provides a tibial liner and a total knee prosthesis. The tibial liner includes a medial liner and a lateral liner. The medial liner is used to engage with the medial condyle, and the lateral liner is used to engage with the lateral condyle. The cross-sectional line formed by the intersection of the articular surface of the medial liner and the sagittal plane includes a first arc segment and a second arc segment, with the second arc segment located posterior to the first arc segment. The sagittal radius of the first arc segment is smaller than that of the second arc segment. The first arc segment includes a functional area that is used to contact the medial condyle during translation and rolling of the femoral prosthesis. The tibial liner provided by this invention effectively reduces the posterior height of the medial liner, allowing the knee prosthesis to rotate stably around the medial side. It also reduces wear on the knee prosthesis and prevents the posterior side of the medial liner from affecting further posterior rolling of the medial condyle during high flexion movements, thus improving the high flexion performance of the knee prosthesis.

Description

Technical Field

[0001] This invention relates to the field of orthopedic implants, specifically to a tibial liner and a total knee joint prosthesis. Background Technology

[0002] Knee replacement surgery uses an artificial knee joint prosthesis to replace the diseased articular cartilage and meniscus while preserving the normal joint ligaments and other tissues. As a result, it has the advantages of minimal trauma, rapid recovery, reduced pain, and a more natural range of motion. Therefore, knee replacement surgery is widely used in the treatment of knee joint problems.

[0003] In a normal person, during knee flexion from -5° (extended position) to 120° (bent position), the medial femoral condyle 1 undergoes approximately 1.5 mm of anterior-posterior translation (e.g., ...). Figure 1 As shown in the diagram, the lateral femoral condyle 2 undergoes approximately 18 mm of anterior-posterior translation. This movement causes the femur to externally rotate relative to the tibia around the medial condyle during knee flexion from extension to 120° flexion.

[0004] In previous bionic total knee joint designs, the medial tibial pad was usually designed as a single-radius ball-and-socket or near-ball-and-socket shape. The advantage is that it can provide medial stability under all movements and ensure that the knee joint rotates with the medial side as the center. However, under high flexion (such as squatting) movements, this single-radius design will cause the medial femoral condyle prosthesis to be restricted by the higher posterior side of the medial tibial pad, so that the femoral prosthesis cannot roll further backward, thus affecting the high flexion performance of the prosthesis. Summary of the Invention

[0005] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0006] The inventors discovered that activities that cause significant wear and tear on the knee joint during daily activities include gait, climbing stairs, going down stairs, standing up from a chair, and turning. During these activities, the external rotation of the knee joint generates a torque of up to 10-30 Nm, while the internal rotation generates only 5-6 Nm. Due to the larger external rotation torque, the contact point between the lateral femoral condyle and the lateral articular surface of the tibia (i.e., the surface of the lateral tibial pad that mates with the lateral femoral condyle) often rolls backward to the posterior side of the lateral tibial pad. However, due to the smaller internal rotation torque of the knee joint, the contact point between the medial femoral condyle and the medial articular surface (i.e., the surface of the medial tibial pad that mates with the lateral femoral condyle) often fails to reach the posterior side of the medial tibial pad. Therefore, in the design of the bionic total knee joint, the height of the posterior side of the medial pad is appropriately reduced to better simulate normal human movement. This ensures the stability of movements that account for a large proportion of daily life, such as gait, going up and down stairs, standing up from a chair, and turning, while also satisfying the characteristic that the femoral prosthesis can roll further backward during a few deep squatting movements.

[0007] The present invention aims to at least partially solve one of the technical problems in the related art. To this end, embodiments of the present invention provide a tibial liner, and embodiments of the present invention also provide a total knee joint prosthesis with high flexion performance.

[0008] The tibial pad of this invention, used in knee replacement surgery to engage with the medial and lateral condyles of the femoral prosthesis, includes: a medial pad and a lateral pad, wherein the medial pad engages with the medial condyle, and the lateral pad engages with the lateral condyle; the articular surface of the medial pad intersects with a sagittal plane passing through the lowest point of the medial pad to form a cross-section line comprising a first arc segment and a second arc segment, the second arc segment being located posterior to the first arc segment, the sagittal radius of the first arc segment being smaller than the sagittal radius of the second arc segment, and the first arc segment including a functional area for contacting the medial condyle during translation and rolling of the femoral prosthesis.

[0009] The tibial liner provided in this embodiment of the invention has a single-radius design for the medial articular surface functional area, and the sagittal radius of the posterior non-functional area is greater than that of the anterior functional area. This effectively reduces the height of the posterior side of the medial liner, thereby ensuring that the medial condyle of the femoral prosthesis and the medial articular surface have a high degree of fit in the key functional area, allowing the knee prosthesis to rotate stably with the medial side as the center. It also reduces the wear of the knee prosthesis and prevents the posterior side of the medial liner from affecting the further posterior roll of the medial condyle under high flexion movements, thus improving the high flexion performance of the knee prosthesis.

[0010] In some embodiments, the ratio of the sagittal radius of the first arc segment to the sagittal radius of the second arc segment is greater than or equal to 1:5.

[0011] In some embodiments, the ratio of the sagittal radius of the first arc segment to the sagittal radius of the second arc segment is 1:5 to 1:2.

[0012] In some embodiments, the ratio of the length of the first arc segment in the front-rear direction to the length of the articular surface of the inner liner in the front-rear direction is 0.75:1-0.95:1.

[0013] In some embodiments, the vertical distance between the front end point of the first arc segment and the lowest point of the cross-section line is 5.3mm-9.5mm.

[0014] In some embodiments, the vertical distance between the rear end point of the second arc segment and the lowest point of the cross-sectional line is 1.5mm-3.5mm.

[0015] Another embodiment of the present invention provides a total knee joint prosthesis, comprising: a femoral prosthesis, the tibial prosthesis including a medial condyle and a lateral condyle; and a tibial pad, the tibial pad being the tibial pad described in any of the above embodiments.

[0016] In some embodiments, the ratio of the sagittal radius of the first arc segment to the sagittal radius of the distal end of the medial condyle is 1.1:1 to 1.65:1.

[0017] In some embodiments, the knee replacement prosthesis is a posterior stabilizing knee prosthesis or a posterior cruciate ligament replacement prosthesis. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating the knee flexion process.

[0019] Figure 2 This is a schematic diagram of the structure of the posteriorly stabilized knee joint prosthesis in an embodiment of the present invention.

[0020] Figure 3 This is a front view of the posteriorly stabilized knee joint prosthesis in an embodiment of the present invention.

[0021] Figure 4 yes Figure 3 AA section diagram.

[0022] Figure 5 yes Figure 3 A cross-sectional view of the tibial liner in the embodiment.

[0023] Figure 6 This is a schematic diagram of the posterior cruciate ligament replacement prosthesis in an embodiment of the present invention.

[0024] Figure 7 This is a front view of the posterior cruciate ligament replacement prosthesis in an embodiment of the present invention.

[0025] Figure 8 yes Figure 7 AA section diagram.

[0026] Figure label:

[0027] 100. Tibial pad; 110. Medial pad; 111. Medial articular surface; 120. Lateral pad; 131. First arc segment; 132. Second arc segment;

[0028] 200. Femoral prosthesis; 210. Medial condyle; 220. Lateral condyle; 300. Tibial support. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] To better explain and illustrate the technical solutions of the present invention, the directions and other aspects involved in the present invention will be explained and described in conjunction with the conventional descriptive methods in the art.

[0031] In the fields of anatomy and medical devices, directions and planes such as internal, external, anterior, posterior, distal, proximal, sagittal, coronal, and cross-section have specific meanings and are well known to those skilled in the art. Unless otherwise specified, these terms refer to the meanings generally accepted by those skilled in the art. The following is a brief explanation of the terms involved in this application to better understand the technical solution.

[0032] When describing the human body, joints, or prostheses, the sagittal plane refers to a longitudinal section that divides the body or joint into left and right parts from the front-to-back direction. The sagittal plane passing through the center of the body is called the median sagittal plane, which divides the body into two equal parts. It's understood that the sagittal plane refers to the section when a person is standing upright normally, with the knee flexion angle at 0°. The section can change when the knee joint or knee prosthesis flexes or extends, or when the body's posture is adjusted. The coronal plane is a section that divides the body or joint into front and back parts, and this section is perpendicular to the sagittal plane.

[0033] Typically, when describing the human body, joints, or prostheses, three different directions are involved: distal, medial, and posterior. The distal end refers to the end of the body or joint relatively far from the head. The proximal end refers to the end of the body or joint relatively close to the head. The medial side refers to the side relatively close to the midsagittal plane of the body. The lateral side refers to the side relatively far from the midsagittal plane of the body. The anterior side refers to the side relatively close to the chest in the sagittal plane. The posterior side refers to the side relatively close to the back in the sagittal plane.

[0034] Specifically, embodiments of this application provide a tibial pad 100, which is used in knee replacement surgery to replace the lateral meniscus of the tibia and cooperates with the medial condyle 210 and lateral condyle 220 of the femoral prosthesis 200. It is understood that the tibial pad 100 includes a left-leg tibial pad for the left leg and a right-leg tibial pad for the right leg, wherein the left-leg and right-leg tibial pads are radially symmetrical about the midsagittal plane of the human body.

[0035] The following is based on Figures 2-8 The structure of the tibial liner 100 provided in an embodiment of the present invention is described.

[0036] like Figure 2As shown, the tibial liner 100 includes a medial liner 110 and a lateral liner 120. The medial liner 110 is located medial to the lateral liner 120, meaning the medial liner 110 is closer to the midsagittal plane of the human body than the lateral liner 120. The proximal surface of the medial liner 110 is the medial articular surface 111, and the proximal surface of the lateral liner 120 is the lateral articular surface. The medial articular surface 111 engages with the medial condyle 210, and the lateral articular surface engages with the lateral condyle 220. During knee joint movement, the femoral prosthesis 200 rotates about the medial condyle 210 as an axis. The medial condyle 210 internally rotates along the movement trajectory on the medial articular surface 111, and the lateral condyle 220 externally rotates along the movement trajectory on the lateral articular surface.

[0037] The cross-sectional line formed by the intersection of the articular surface (medial articular surface 111) of the medial liner 110 and the sagittal plane includes a connected first arc 131 and a second arc 132, with the second arc 132 located posterior to the first arc 131. The sagittal radius of the first arc 131 is smaller than that of the second arc 132. The sagittal radius can also be referred to as the radius of curvature of an arc. The first arc 131 includes a functional area that is used to contact the medial condyle 210 during translation and rolling of the femoral prosthesis.

[0038] The sagittal plane is Figure 3 Section AA in the diagram corresponds to the range of the contact path during the interaction between the medial articular surface 111 and the medial condyle 210. The functional area is the movement path of the medial condyle 210 during internal rotation. The movement path of the medial condyle 210 refers to the set of points where the medial condyle 210 contacts the medial articular surface 111 during flexion, i.e., the trajectory of the medial condyle 210 moving on the medial articular surface 111 during knee joint prosthesis flexion. Furthermore, the points on the functional area are also the lowest points of the medial articular surface 111 in the coronal plane. The sagittal radius of the first arc 131 is consistent, therefore the sagittal radius of the functional area is consistent, ensuring that the main functional area of ​​the medial articular surface 111 (the contact area with the medial condyle 210) forms a single-radius ball-and-socket shape, improving the rotational stability of the knee prosthesis including the tibial pad 100 of this embodiment.

[0039] The second arc 132 is a non-functional area. By making the sagittal radius of the second arc 132 greater than that of the first arc 131, the relative height of the last side of the medial articular surface, i.e., the height of the posterior lip of the medial liner, can be appropriately reduced. This allows the knee prosthesis using the tibial liner 100 provided in this embodiment of the invention to achieve a higher degree of flexion by further posterior rolling of the medial condyle 210 during high flexion movements.

[0040] The tibial liner provided in this embodiment of the invention has a single-radius design for the medial articular surface functional area, and the sagittal radius of the posterior non-functional area is greater than that of the anterior functional area. This effectively reduces the height of the posterior side of the medial liner, thereby ensuring that the medial condyle of the femoral prosthesis and the medial articular surface have a high degree of fit in the key functional area, allowing the knee prosthesis to rotate stably with the medial side as the center. It also reduces the wear of the knee prosthesis and prevents the posterior side of the medial liner from affecting the further posterior roll of the medial condyle under high flexion movements, thus improving the high flexion performance of the knee prosthesis.

[0041] Specifically, the first arc 131 includes an anterior lip region and a functional region, with the functional region located behind the anterior lip region, and the second arc 132 is the posterior lip region.

[0042] Optionally, the ratio of the sagittal radius RT1 of the first arc 131 to the sagittal radius RT2 of the second arc 132 is greater than or equal to 1:5. The inventors of this application discovered through experimental research that when the ratio of the sagittal radius RT1 of the first arc 131 to the sagittal radius RT2 of the second arc 132 is less than 1:5, the stability of the medial condyle 210 during rotation may be affected. Therefore, when the sagittal radius RT1 of the first arc 131 and the sagittal radius RT2 of the second arc 132 meet the above conditions, the rearmost height of the medial pad 110 can be effectively reduced, allowing the medial condyle 210 of the knee prosthesis to roll further posteriorly in a high flexion state, improving the high flexion performance of the knee prosthesis, enhancing its usability, and effectively ensuring the rotational stability of the knee prosthesis, thus preventing dislocation of the femoral prosthesis 200.

[0043] Further optionally, the ratio of the sagittal radius RT1 of the first arc 131 to the sagittal radius RT2 of the second arc 132 is between 1:5 and 1:2, which can further effectively reduce the rearmost height of the medial liner 110, allowing the medial condyle 210 of the knee joint prosthesis to roll backward to a greater extent in a high flexion state.

[0044] For example, the ratio of the sagittal radius RT1 of the first arc 131 to the sagittal radius RT2 of the second arc 132 can be 1:2, 1:3, 1:4, or 1:5. The inventors of this application have found through experimental research that when RT1 / RT2 meets the above range, the height of the last side of the medial pad 110 can be effectively reduced, so that the medial condyle 210 of the knee joint prosthesis can roll backward to a greater extent in a high flexion state.

[0045] Furthermore, such as Figure 5 As shown, the length of the first arc 131 in the anterior-posterior direction is L1, and the length of the medial articular surface 111 in the anterior-posterior direction is LAP. Optionally, 0.75≤L1 / LAP≤0.95.

[0046] Table 1: Ratio range of the distance between the front end of the least worn area of ​​the inner pad and the frontmost part of the inner pad in the front-back direction to the total length of the inner pad under various motions.

[0047]

[0048] The inventors of this application discovered through experimental research that, after total knee replacement, the main wear location of the medial liner 110 exhibits distinct regional characteristics. Under various movements, the main wear location is consistently in the middle and posterior regions, with a significant reduction in wear in a certain area on the rearmost side. Furthermore, under various movements, the proportion of the less worn area on the rearmost side of the medial liner 110 relative to its total anterior-posterior length varies. The findings indicate that the ratio of the distance between the front end of the less worn area on the rearmost side of the medial liner 110 and the frontmost point of the medial liner 110 in the anterior-posterior direction to the total length of the medial liner 110 ranges from approximately 75% to 95%, as detailed in Table 1. When designing the tibial liner 100 of the present invention, the cross-sectional line formed by the less worn non-functional area of ​​the medial articular surface 111 of the medial liner 110 in the sagittal plane can be designed as the second arc 132, and the cross-sectional line formed between the front end of the less worn non-functional area of ​​the medial articular surface 111 in the sagittal plane and the front end of the medial articular surface 111 can be designed as the first arc 131.

[0049] Therefore, the ratio of the length L1 of the first arc 131 in the anterior-posterior direction to the length LAP of the medial articular surface 111 in the anterior-posterior direction is designed to be 0.75≤L1 / LAP≤0.95. This is the result of experimental verification by the inventors of this application. When the length L1 of the first arc 131 in the anterior-posterior direction and the length LAP of the medial articular surface 111 in the anterior-posterior direction meet the above conditions, it ensures that the main functional area of ​​the medial articular surface 111 is a single radius, and can effectively reduce the height of the rear side of the medial pad 110, so that the medial condyle 210 of the knee joint prosthesis can roll further backward in a high flexion state, thereby improving the high flexion performance of the knee joint prosthesis and improving the use effect.

[0050] For example, L1 / LAP can be 0.75, 0.85, 0.90, or 0.95. The inventors of this application have found through experimental research that when L1 / LAP is at the above values, the structure of the inner pad 110 is more reasonable and the performance is better.

[0051] like Figure 5 As shown, the front endpoint of the first arc 131 is the highest point of the first arc 131, and the rear endpoint of the second arc 132 is the highest point of the second arc 132. The front endpoint of the first arc 131 is higher than the highest point of the second arc 132.

[0052] Optionally, the vertical distance between the anterior end point of the first arc 131 and the lowest point of the cross-sectional line formed by the intersection of the medial articular surface 111 and the sagittal plane is H1, where 5.3mm≤H1≤9.5mm, that is, the anterior lip height of the medial liner 110 is greater than or equal to 5.3mm and less than or equal to 9.5mm.

[0053] In addition, the vertical distance between the rear end point of the second arc 132 and the lowest point of the cross-section line is H2, where 1.5mm≤H2≤3.5mm, that is, the height of the rear lip of the inner pad 110 is greater than or equal to 1.5mm and less than or equal to 3.5mm.

[0054] Another embodiment of the present invention provides a total knee arthroplasty, comprising a femoral prosthesis 200 and a tibial pad 100. The tibial prosthesis 200 includes a medial condyle 210 and a lateral condyle 220. The tibial pad 100 can be the tibial pad 100 described in any of the above embodiments. The total knee arthroplasty also includes, Figure 2 The tibial support 300 is connected to the side of the tibial pad 100 away from the femoral prosthesis 200.

[0055] Furthermore, such as Figure 4 As shown, the inner condyle 210 is a sphere with a single radius, and its distal surface is a sphere with a single radius. Optionally, the ratio of the sagittal radius RT1 of the first arc 131 to the sagittal radius RF of the distal end of the inner condyle 210 is 1.1:1-1.65:1.

[0056] The inventors of this application discovered through experimental research that when the sagittal radius RT1 of the first arc 131 and the sagittal radius RF of the distal end of the medial condyle 210 satisfy the above conditions, the medial condyle 210 and the medial articular surface 111 can form a suitable fit. This fit ensures that the knee prosthesis rotates medially, preventing abnormal anterior displacement of the medial condyle 210 in a high flexion state. Simultaneously, this fit provides a larger medial contact area between the medial condyle 210 and the medial articular surface 111, ensuring uniform force distribution on the tibial pad 100. This reduces wear on the knee prosthesis and extends its service life.

[0057] For example, the ratio of the sagittal radius RT1 of the first arc 131 to the sagittal radius RF of the distal end of the medial condyle 210 can be 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1 or 1.65:1, so that the medial condyle 210 and the medial articular surface 111 form a more suitable fit.

[0058] It should be noted that knee replacement prostheses can be... Figure 2 The posterior stabilized knee prosthesis shown or such Figure 6 The posterior cruciate ligament replacement prosthesis shown is not limited to this application.

[0059] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0061] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0062] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0063] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A tibial spacer for cooperating with a medial condyle and a lateral condyle of a femoral prosthesis in a knee replacement surgery, characterized in that, Comprising: a medial liner for cooperating with the medial condyle and a lateral liner for cooperating with the lateral condyle; a cross-section line formed by the articular surface of the medial liner and a sagittal plane passing through the lowest point of the medial liner comprises a first segment of an arc and a second segment of an arc connected to each other, the second segment of the arc is located at the posterior side of the first segment of the arc, the sagittal radius of the first segment of the arc is smaller than the sagittal radius of the second segment of the arc, the first segment of the arc comprises a functional zone for contacting the medial condyle during translation and rolling of the femoral prosthesis, the ratio of the sagittal radius of the first segment of the arc to the sagittal radius of the second segment of the arc is greater than or equal to 1:

5.

2. The tibial bushing of claim 1, wherein, The ratio of the sagittal radius of the first segment of the arc to the sagittal radius of the second segment of the arc is 1:5-1:

2.

3. The tibial bushing of claim 1, wherein, The ratio of the length of the first segment of the arc in the anteroposterior direction to the length of the articular surface of the medial liner in the anteroposterior direction is 0.75:1-0.95:

1.

4. The tibial bushing of claim 1, wherein, The vertical distance between the anterior end point of the first segment of the arc and the lowest point of the cross-section line is 5.3mm-9.5mm.

5. The tibial spacer of any of claims 1-4, wherein, The vertical distance between the posterior end point of the second segment of the arc and the lowest point of the cross-section line is 1.5mm-3.5mm.

6. A total knee prosthesis, characterized in that Comprising: a femoral prosthesis comprising a medial condyle and a lateral condyle; a tibial liner according to any one of claims 1-5.

7. The total knee prosthesis of claim 6, wherein, The ratio of the sagittal radius of the first segment of the arc to the sagittal radius of the distal end of the medial condyle is 1.1:1-1.65:

1.

8. The total knee prosthesis of claim 6 or 7, wherein, The total knee prosthesis is a posterior stabilized knee prosthesis or a posterior cruciate ligament substituting prosthesis.

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