Tibial spacer and total knee prosthesis

Abstract

This invention proposes a tibial liner and a total knee joint prosthesis. The tibial liner includes a medial liner and a lateral liner. The medial liner has a medial articular surface. The cross-sectional line formed by the intersection of the medial articular surface and the sagittal plane includes an anterior lip segment, a functional segment, and a posterior lip segment connected in sequence. The sagittal radius of the anterior lip segment is larger than that of the functional segment, which effectively reduces the height of the anterior side of the medial liner and avoids interference between the femoral prosthesis and the anterior side of the medial liner during posterior tilt assembly of the knee joint prosthesis, thus preventing interference with the normal contact of the articular surface.

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, this single-radius design will result in a higher anterior height of the medial tibial pad. Under posterior tilting assembly, interference will occur between the femoral prosthesis and the tibial pad, affecting the normal contact of the articular surfaces. Summary of the Invention

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

[0006] Activities that cause significant wear and tear on the knee joint during daily activities include gait, climbing stairs, descending stairs, standing up from a chair, and turning. During these activities, external rotation of the knee joint generates a torque of up to 10-30 Nm, while internal rotation generates only 5-6 Nm. Due to the relatively low internal rotation torque, the contact point between the medial femoral condyle and the medial articular surface (i.e., the surface where the medial tibial pad mates with the lateral femoral condyle) often fails to reach the anterior side of the medial tibial pad. Therefore, in the design of a biomimetic total knee joint, appropriately lowering the height of the anterior side of the medial pad better simulates normal human movement. This ensures stability during common daily activities such as gait, climbing stairs, descending stairs, standing up from a chair, and turning, while also effectively preventing interference between the tibial pad and the femoral prosthesis during posterior tilt assembly.

[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.

[0008] The tibial liner of this invention, used in knee replacement surgery to cooperate with a femoral prosthesis, includes: a medial liner and a lateral liner. The medial liner has a medial articular surface, and the lateral liner has a lateral articular surface. The medial articular surface is used to cooperate with the medial condyle of the femoral prosthesis, and the lateral articular surface is used to cooperate with the lateral condyle of the femoral prosthesis. The cross-sectional line formed by the intersection of the medial articular surface and the sagittal plane passing through the lowest point of the medial articular surface includes an anterior lip segment, a functional segment, and a posterior lip segment connected in sequence. The functional segment is used to contact the medial condyle during translation and rolling of the femoral prosthesis, and the sagittal radius of the anterior lip segment is larger than the sagittal radius of the functional segment.

[0009] The tibial liner provided in this embodiment of the invention has a single-radius structure for the medial articular surface of the tibial liner, and the sagittal radius of the anterior lip segment is greater than that of the functional segment. This effectively reduces the height of the anterior 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 avoids interference between the femoral prosthesis and the anterior side of the medial liner during posterior tilt assembly, which would affect the normal contact of the articular surface.

[0010] In some embodiments, the ratio of the sagittal radius of the anterior lip segment to the sagittal radius of the functional segment is less than or equal to 2.5:1.

[0011] In some embodiments, the ratio of the distance between the posterior end point of the anterior lip segment and the foremost point of the inner liner in the anteroposterior direction to the total length of the inner liner in the anteroposterior direction is between 0.38:1 and 0.63:1.

[0012] In some embodiments, the sagittal radius of the posterior lip segment is greater than the sagittal radius of the functional segment.

[0013] In some embodiments, the ratio of the sagittal radius of the posterior lip segment to the sagittal radius of the functional segment is less than or equal to 5:1.

[0014] In some embodiments, the ratio of the distance between the rear end point of the functional segment and the foremost point of the inner pad in the front-back direction to the total length of the inner pad in the front-back direction is 0.75:1-0.95:1.

[0015] In some embodiments, the vertical distance between the anterior end point of the anterior lip segment and the lowest point of the cross-sectional line is 4.0 mm to 8.9 mm.

[0016] In some embodiments, the vertical distance between the rear end point of the rear lip segment and the lowest point of the cross-sectional line is 1.5mm-3.5mm.

[0017] Another embodiment of the present invention provides a total knee joint prosthesis, comprising: a femoral prosthesis including a medial condyle and a lateral condyle; and a tibial pad, wherein the tibial pad is the tibial pad described in any of the above embodiments.

[0018] 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. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the knee flexion process.

[0020] Figure 2 This is a schematic diagram of the structure of the posteriorly stabilized knee joint prosthesis in an embodiment of the present invention.

[0021] Figure 3 This is a front view of the posteriorly stabilized knee joint prosthesis in an embodiment of the present invention.

[0022] Figure 4 yes Figure 3 AA section diagram.

[0023] Figure 5 yes Figure 3 A cross-sectional view of the tibial liner in the embodiment.

[0024] Figure 6 This is a schematic diagram of the posterior cruciate ligament replacement prosthesis in an embodiment of the present invention.

[0025] Figure label:

[0026] 100. Tibial pad; 110. Medial pad; 111. Medial articular surface; 120. Lateral pad; 121. Lateral articular surface; 131. Anterior lip segment; 132. Functional segment; 133. Posterior lip segment;

[0027] 200. Femoral prosthesis; 210. Medial condyle; 220. Lateral condyle; 300. Tibial support. Detailed Implementation

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The following is based on Figures 2-6 The structure of the tibial liner 100 provided in an embodiment of the present invention is described.

[0035] 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 121. 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.

[0036] The cross-sectional line formed by the intersection of the medial articular surface 111 and the sagittal plane includes the sequentially connected anterior lip segment 131, functional segment 132, and posterior lip segment 133. That is, the anterior lip segment 131, functional segment 132, and posterior lip segment 133 are connected sequentially from front to back. It should be noted that the anterior lip segment 131, functional segment 132, and posterior lip segment 133 are all circular arcs. The functional segment 132 is used to contact the medial condyle 210 during the translation and rolling of the femoral prosthesis 200. It should be noted that the anterior lip segment 131 and posterior lip segment 133 are both non-functional segments. The sagittal radius of the anterior lip segment 131 is larger than the sagittal radius of the functional segment 132. The sagittal radius can also be referred to as the radius of curvature of the circular arc.

[0037] Specifically, the sagittal plane is Figure 3 Section AA in the figure corresponds to the range of the contact path during the engagement of the medial articular surface 111 and the medial condyle 210. Functional segment 132 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, that is, the trajectory of the medial condyle 210 moving on the medial articular surface 111 during knee joint prosthesis flexion. Furthermore, the points on functional segment 132 are also the lowest points of the medial articular surface 111 in the coronal plane. The sagittal radius of functional segment 132 is consistent, ensuring that the main functional segment 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.

[0038] By making the sagittal radius of the anterior lip segment 131 larger than that of the functional segment 132, the relative height of the anterior side of the medial articular surface 111, i.e. the anterior lip height of the medial liner 110, can be appropriately reduced. This allows the femoral prosthesis 200 to more smoothly engage with the tibial liner 100 during posterior tilt assembly of the knee joint prosthesis using the tibial liner 100 provided in this embodiment of the invention.

[0039] The tibial liner provided in this embodiment of the invention has a single-radius structure for the medial articular surface of the tibial liner, and the sagittal radius of the anterior lip segment is greater than that of the functional segment. This effectively reduces the height of the anterior 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 avoids interference between the femoral prosthesis and the anterior side of the medial liner during posterior tilt assembly, which would affect the normal contact of the articular surface.

[0040] Optionally, the ratio of the sagittal radius RT1 of the anterior lip segment 131 to the sagittal radius RT2 of the functional segment 132 is less than or equal to 2.5:1. Through experimental research, the inventors of this application discovered that when the ratio of the sagittal radius RT1 of the anterior lip segment 1311 to the sagittal radius RT2 of the second segment 131 is greater than 2.5:1, the stability of the medial condyle 210 during rotation may be affected. Therefore, when the sagittal radius RT1 of the anterior lip segment 131 and the sagittal radius RT2 of the functional segment 132 meet the above conditions, the anterior height of the medial liner 110 can be effectively reduced, effectively avoiding interference between the femur and tibia on the anterior side under posterior tilt assembly, and also effectively ensuring the rotational stability of the knee joint prosthesis, preventing dislocation of the femoral prosthesis 200.

[0041] For example, the ratio of the sagittal radius RT1 of the anterior lip segment 131 to the sagittal radius RT2 of the functional segment 132 can be 1.5:1, 2.0:1, or 2.5:1. The inventors of this application have found through experimental research that when RT1 / RT2 meets the above values, the height of the foremost side of the inner pad 110 can be effectively reduced, making the structure of the inner pad 110 more reasonable.

[0042] Furthermore, such as Figure 5 As shown, the distance between the rear end point of the front lip segment 131 and the front end of the inner liner 110 in the front-back direction is L1, and the total length of the inner liner 110 in the front-back direction is LAP. Optionally, 0.38≤L1 / LAP≤0.63.

[0043] Table 1 shows the range of the ratio of the least worn area on the foremost side of the inner liner to the total length of the inner liner under various motion conditions.

[0044]

[0045] Specifically, the inventors of this application discovered through experimental research that after total knee arthroplasty, the main wear location of the medial liner 110 exhibits distinct regional characteristics. Under various gait patterns, the main wear location is consistently in the middle and posterior regions, with a significant reduction in wear in a certain area at the foremost end. Furthermore, under various gait patterns, the proportion of the less worn area at the foremost end of the medial liner 110 to the total anterior-posterior length of the medial liner 110 varies. It was found that the ratio of the distance between the posterior end of the less worn area at the foremost end of the medial liner 110 (i.e., the posterior endpoint of the anterior lip segment 131) and the foremost end of the medial liner 110 in the anterior-posterior direction to the total length of the medial liner 110 ranges from approximately 38% to 63%, as detailed in Table 1. When designing the tibial liner 100 of this embodiment, the cross-sectional line formed by the less worn non-functional area at the foremost end of the medial articular surface 111 in the sagittal plane can be designed as the anterior lip segment 131.

[0046] Therefore, the result of the inventors of this application verifying that 0.38≤L1 / LAP≤0.63 is the result of their experiments. When L1 and LAP meet the above conditions, it ensures that the main functional area of ​​the medial articular surface 111 is a single radius, and can also effectively reduce the height of the foremost side of the medial liner 110, thus avoiding interference between the femur and tibia on the anterior side under the rearward tilt assembly.

[0047] For example, L1 / LAP can be 0.38, 0.45, 0.55, or 0.63. 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 can be more reasonable and the performance can be better.

[0048] Furthermore, the inventors discovered that the single-radius design of the medial condyle in related technologies can lead to the medial condyle being restricted by the higher posterior side of the medial condyle during high flexion movements (such as squats), preventing the femoral prosthesis from rolling further backward and thus affecting its high flexion performance. In everyday movements, the contact point between the medial condyle and the medial articular surface often cannot reach the posterior side of the medial condyle. Therefore, in the design of a biomimetic total knee joint, the posterior height of the medial condyle can be appropriately reduced to better simulate normal human movement, ensuring stability during everyday activities while still allowing the femoral prosthesis to roll further backward during certain deep squat movements.

[0049] Specifically, such as Figure 5As shown, the sagittal radius RT3 of the posterior lip segment 133 is greater than the sagittal radius RT2 of the functional segment 132. Making the sagittal radius RT3 of the posterior lip segment 133 greater than the sagittal radius RT2 of the functional segment 132 can appropriately reduce the relative height of the posterior side of the medial articular surface 111, i.e., the height of the posterior lip of the medial liner 110. This allows the knee prosthesis using the tibial liner 100 provided in this embodiment of the invention to achieve a higher degree of flexion during high flexion movements, effectively preventing the posterior side of the medial liner 110 from affecting the further posterior roll of the medial condyle 210 during high flexion movements, thus improving the high flexion performance of the knee prosthesis.

[0050] Optionally, the ratio of the sagittal radius RT3 of the posterior lip segment 133 to the sagittal radius RT2 of the functional segment 132 is less than or equal to 5:1. The inventors of this application discovered through experimental research that when RT3 / RT2 is greater than 5:1, the stability of the medial condyle 210 during rotation may be affected. Therefore, making RT3 / RT2 less than or equal to 5:1 can effectively reduce the posterior height of the medial liner 110, 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.

[0051] Further optionally, 2:1≤RT3 / RT2≤5:1, so that RT3 and RT2 meet the above conditions, can further effectively reduce the rearmost height of the medial liner 110, so that the medial condyle 210 of the knee prosthesis can roll backward to a greater extent in a high flexion state.

[0052] For example, RT3 / RT2 can be 1:2, 1:3, 1:4, or 1:5. The inventors of this application have found through experimental research that when RT3 / RT2 meets the above values, the height of the last side of the medial pad 110 can be effectively reduced, allowing the medial condyle 210 of the knee joint prosthesis to roll backward to a greater extent in a high flexion state.

[0053] like Figure 5 As shown, the distance between the rear end point of functional segment 132 and the front end of inner liner 110 in the front-rear direction is L2. Optionally, 0.75≤L2 / LAP≤0.95.

[0054] Table 2: 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-rear direction to the total length of the inner pad under various motions.

[0055]

[0056] The inventors of this application discovered through experimental research that the wear degree in a certain area on the posterior side of the medial liner 110 is significantly reduced. It was found that the ratio of the distance between the front end of the less worn area on the posterior side of the medial liner 110 and the frontmost point of the medial liner 110 in the anteroposterior direction to the total length of the medial liner 110 ranges from approximately 75% to 95%, as shown in Table 2. When designing the tibial liner 100 of this embodiment, the cross-sectional line formed by the less worn non-functional area on the posterior side of the medial articular surface 111 of the medial liner 110 in the sagittal plane can be designed as the posterior lip segment 133.

[0057] Therefore, the result of the inventors of this application, which is to achieve 0.75≤L2 / LAP≤0.95, is the result of experimental verification. When L2 and LAP meet the above conditions, it can ensure that the main functional area of ​​the medial articular surface 111 is a single radius, and can also 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.

[0058] For example, L2 / LAP can be 0.75, 0.85, 0.90, or 0.95. The inventors of this application have found through experimental research that when L2 / LAP is at the above values, the structure of the inner pad 110 can be more reasonable and the performance can be better.

[0059] like Figure 5 As shown, the anterior end point of the anterior lip segment 131 is the highest point of the anterior lip segment 131, and the posterior end point of the posterior lip segment 133 is the highest point of the posterior lip segment 133. The anterior end point of the anterior lip segment 131 is higher than the posterior end point of the posterior lip segment 133.

[0060] Optionally, the vertical distance between the anterior end point of the anterior lip segment 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 4.0mm≤H1≤8.9mm, that is, the anterior lip height of the medial liner 110 is greater than or equal to 4.0mm and less than or equal to 8.9mm.

[0061] In addition, the vertical distance between the rear end point of the rear lip segment 133 and the lowest point of the cross-section line is H2, where 1.5mm≤H2≤3.5mm (to be supplemented). That is to say, 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.

[0062] Another embodiment of the present invention provides a total knee arthroplasty, comprising a femoral prosthesis 200 and a tibial pad 100. The femoral 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 2The tibial support 300 is connected to the side of the tibial pad 100 away from the femoral prosthesis 200.

[0063] Furthermore, such as Figure 4 As shown, the medial 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 RT2 of the functional segment 132 to the sagittal radius RF of the distal end of the medial condyle 210 is 1.1:1-1.65:1.

[0064] The inventors of this application discovered through experimental research that when the sagittal radius RT2 of the functional segment 132 and the sagittal radius RF of the distal end of the medial condyle 210 meet the above conditions, the medial condyle 210 and the medial articular surface 111 can form a suitable fit. This fit can ensure that the knee prosthesis rotates with the medial side as the center, preventing the medial condyle 210 from abnormally moving forward in a high flexion state. At the same time, this fit also provides a larger medial contact area between the medial condyle 210 and the medial articular surface 111, so that the tibial pad 100 is evenly stressed, thereby reducing the wear of the knee prosthesis and extending the service life of the knee prosthesis.

[0065] For example, the ratio of the sagittal radius RT2 of the functional segment 132 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 femoral prosthesis in a knee replacement surgery, characterized in that, Comprising: a medial liner having a medial articular surface for cooperating with a medial condyle of the femoral prosthesis, and a lateral liner having a lateral articular surface for cooperating with a lateral condyle of the femoral prosthesis; the medial articular surface intersects with a sagittal plane passing through a lowest point of the medial articular surface to form a cross-sectional line comprising, in order, an anterior lip segment, a functional segment, and a posterior lip segment, the functional segment for contacting the medial condyle during translation and roll of the femoral prosthesis, a sagittal radius of the anterior lip segment being greater than a sagittal radius of the functional segment, a ratio of the sagittal radius of the anterior lip segment to the sagittal radius of the functional segment being less than or equal to 2.5:

1.

2. The tibial bushing of claim 1, wherein, a ratio of a distance in an anterior-posterior direction between a posterior end point of the anterior lip segment and an anterior-most end of the medial liner to a total length of the medial liner in the anterior-posterior direction is between 0.38:1 and 0.63:

1.

3. The tibial bushing of claim 1, wherein, a sagittal radius of the posterior lip segment is greater than a sagittal radius of the functional segment.

4. The tibial bushing of claim 3, wherein, a ratio of the sagittal radius of the posterior lip segment to the sagittal radius of the functional segment is less than or equal to 5:

1.

5. The tibial spacer of claim 3 or 4, wherein, a ratio of a distance in an anterior-posterior direction between a posterior end point of the functional segment and an anterior-most end of the medial liner to a total length of the medial liner in the anterior-posterior direction is between 0.75:1 and 0.95:

1.

6. The tibial bushing of claim 1, wherein, a vertical distance between an anterior end point of the anterior lip segment and the lowest point of the cross-sectional line is between 4.0 mm and 8.9 mm.

7. The tibial bushing of claim 3, wherein, a vertical distance between a posterior end point of the posterior lip segment and the lowest point of the cross-sectional line is between 1.5 mm and 3.5 mm.

8. 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 1-7.

9. The total knee prosthesis of claim 8, wherein, a ratio of a sagittal radius of the functional segment to a sagittal radius of a distal end of the medial condyle is between 1.1:1 and 1.65:1.

Images