Design method of personalized knee joint unicompartmental prosthesis with balanced total flexion path

Abstract

The invention belongs to the technical field of medicine, and discloses a design method of a personalized knee joint unicompartmental prosthesis with a balanced total flexion path. Based on personalized femoral condyle equal-height points and tibia plane information of a patient, a personalized femoral condyle equivalent equal-height circle is established, and then a personalized equal-height single-condyle prosthesis is designed. The invention provides a brand-new unicompartmental prosthesis design for individual patients, and aims to maintain the height of the femoral condyle of the knee joint along the flexion path after operation, so as to maintain the natural balance of the soft tissue of the knee joint along the flexion path after operation.

Description

Technical Field

[0001] This invention belongs to the field of medical technology, and in particular relates to a personalized unicompartmental knee prosthesis design method with full flexion path balance. Background Technology

[0002] Unicompartmental knee replacement (UKA) is a partial knee replacement surgery designed to relieve pain caused by arthritis in the medial or lateral region of the knee joint. In recent years, with the advancement of surgical techniques and the popularization of minimally invasive surgery, the number of patients undergoing unicompartmental knee replacement has increased rapidly. However, the efficacy of this surgery is highly dependent on the surgeon's experience, and there are various unsatisfactory clinical outcomes. These factors include: (1) a higher revision rate than total knee replacement (TKA) due to the spread of arthritis to other areas, ligament instability, and loosening or failure of implant components; (2) high technical requirements for lower limb mechanical alignment or implant component placement, and uncertainties in the force lines at other flexion angles; and (3) a shorter lifespan for implants compared to total knee replacement. Recent clinical articles indicate that current unicompartmental knee replacement surgery cannot restore normal tibial axial rotation function of the knee joint.

[0003] There are two main types of unicompartmental knee arthroplasty systems: multi-radius fixed-platform and single-radius mobile-platform unicompartmental knee arthroplasty. Lower limb mechanical alignment is a widely adopted guiding principle in arthroplasty to achieve soft tissue balance on the medial and lateral sides of the knee joint. However, mechanical alignment only applies to knee balance in the anterior, fully extended position. Because unicompartmental knee arthroplasty alters the articular surfaces of the tibiofemoral joint, and each patient's situation is different, current unicompartmental surgery cannot control knee balance at other flexion angles or along the entire flexion path, thus affecting the biomechanical function of soft tissues, such as the medial and lateral collateral ligaments, at other flexion angles. Intraoperative soft tissue imbalance is considered one of the main factors leading to postoperative complications (such as moderate flexion instability and high flexion limitation), affecting patient functional outcomes and the lifespan of the replacement component. Currently, no new unicompartmental knee arthroplasty prosthesis has been developed that can restore native knee balance across the entire flexion path.

[0004] Existing literature 1: Rao Zhitao, Zhou Chaochao, Zhang Qidong, Kernkamp WA, Wang Jianping, Cheng Liming, Foster TE, Bedair HS, Li Guoan. "There are constant iso-points of femoral condyle height along the knee flexion path." Journal of Knee Surgery, Sports Traumatology and Arthroscopy. February 2021; 29(2): 600-607. doi: 10.1007 / s00167-020-05990-x.

[0005] Existing reference 2: Zhou Chaochao, Zhang Zhenming, Rao Zhitao, Foster T, Bedair H, Li Guoan. "Physiological arthrokinetics of the tibiofemoral joint and morphological translation of the femoral condyle." Journal of Biomechanics. June 23, 2021; 123:110536. doi: 10.1016 / j.jbiomech.2021.110536.

[0006] Existing reference 3: Zhang Zhenming, Zhou Chaochao, Rao Zhitao, Foster T, Bedair H, Li Guoan. “A study on the changes in femoral condyle height during knee flexion: implications for the balance of the surgical gap in TKA.” Archives of Orthopedic Trauma Surgery. October 2022; 142(10): 2849-2855. doi: 10.1007 / s00402-021-04155-w.

[0007] Existing reference 4: Yu Jia, Xia Yulian, Zhou Chaochao, Cai Zongyuan, Li Jingsheng, Foster T, Bedair H, Li Guoan. "Study on characteristic movement patterns of the knee joint during weight-bearing flexion." Chinese Journal of Biomedical Engineering. June 1, 2023, pp. 2237–2244, doi: 10.1007 / s10439-023-03259-1.

[0008] This invention has discovered that, in existing technical documents 1-4, during full weight-bearing flexion of the knee joint, there exists a point on the sagittal plane of the medial and lateral femoral condyles, the height of which remains approximately constant on the tibial plane. Figure 2 , Figure 3 (A), Figure 6 (B) This point is called the "contour point." This finding suggests that if the contour point is used as a reference point to measure changes in femoral condyle height, the medial or lateral femoral condyle can maintain an approximately constant height relative to the tibial plane during flexion. This constant height represents the equivalent circle radius of the femoral condyle structure relative to the planar representation of the tibial surface. Each person's femoral condyle has a specific contour point location, determined based on the individual's knee joint morphology. Using the individual femoral condyle contour point as a reference, a circular femoral prosthesis connected to the tibial surface can be constructed. Figure 7 This prosthesis maintains isohyetal motion of the knee joint along the flexion path, thereby preserving the natural balance of the knee joint along the flexion path (and consequently maintaining the natural balance of the medial or lateral soft tissues at different flexion angles). Based on this principle, this invention provides a novel unicompartmental knee replacement prosthesis tailored to individual patients (based on each patient's specific femoral condyle isohyetal position), aiming to maintain the height of the femoral condyle along the flexion path postoperatively, thereby maintaining the natural balance of the knee joint soft tissues along the flexion path and enhancing the biomechanical function of the knee joint after unicompartmental knee replacement. Summary of the Invention

[0009] To overcome the technical problems existing in current unicompartmental knee arthroplasty (such as the inability of current unicompartmental surgery to control the balance of the knee joint at other flexion angles or along the entire flexion path; difficulty in soft tissue balance during surgery; joint instability in the middle flexion stage and limitation of high flexion), this invention discloses a personalized unicompartmental knee prosthesis design method with full flexion path balance.

[0010] The technical solution is as follows: a personalized unicompartmental knee prosthesis with full flexion path balance, characterized in that the prosthesis design includes: 1. Based on the patient's personalized femoral condyle contour points and tibial plane information, a personalized femoral condyle structure equivalent contour circle is established, and then a personalized contour unicompartmental prosthesis is designed; the designed unicompartmental prosthesis can be completed using 3D printing / additive manufacturing with metal or non-metal materials; and preoperative planning and visualization can be performed.

[0011] For each patient's knee joint, a three-dimensional CT or MRI model is required. The geometric features of the femoral condyle must first be determined, including: (1) The position of the geometric circle fitted in the sagittal plane of the medial and lateral femoral condyles, including the position of the center point of the geometric circle and the radius of the circle, and the distance between the center points of the geometric circles of the medial and lateral condyles; Specifically, such as Figure 3 As shown, using a three-dimensional knee joint model, the position of the femoral condyles is adjusted. Utilizing the posterior geometry of the medial and lateral femoral condyles, a concentric fitted cylinder of the medial and lateral condyles is constructed in the sagittal plane of the joint. Two sagittal vertical cross-sections of the cylinder are determined at the maximum radius of the two posterior femoral condyles of the knee joint. The centers of the two circular cross-sections are defined as the geometric centers of the medial and lateral femoral condyles, and the line connecting the two geometric centers is defined as the geometric central axis GCA (Geometry Center of the Knee Joint). Figure 6 ); (2) The location of the condylar points of the medial and lateral condyles is the location of the most lateral points on the left and right sides of the femoral condyles. Figure 4 (A), Figure 6 ); like Figure 4 As shown in Figure (A), the geometric feature points of the femoral condyles are defined; the line connecting the most prominent points of the medial and lateral femoral condyles is the TEA axis, and the midpoint of the axis is defined as the center of the knee joint. Figure 6 The left-right dimensions of the condyles of the medial and lateral femoral condyles are defined as the left-right width of the femoral ankle; the left-right distance of the geometric circles of the sagittal plane of the medial and lateral femoral condyles is defined as the left-right width of the sagittal plane of the femoral ankle. (3) The anteroposterior dimensions of the medial and lateral femoral condyles in the sagittal plane ( Figure 4 (B)); like Figure 4As shown in Figure (B), it is defined as the distance between the anterior and posterior points of the medial and lateral condyles in the sagittal plane; (4) Use a three-dimensional knee joint model to establish the tibial plane.

[0012] Specifically, such as Figure 5 As shown, first establish the long axis of the tibia, which is along the axial direction of the tibial shaft and parallel to the posterior wall of the tibial shaft. Then, establish a plane perpendicular to the long axis of the tibia at the proximal end of the tibia. The angle between the tibial surface and the plane perpendicular to the long axis of the tibia in the sagittal plane is defined as the posterior tilt angle of the tibial plane. Then, according to the posterior tilt angle of the tibial plane, rotate the plane perpendicular to the long axis of the tibia to obtain a tibial plane parallel to the tibial surface. (5) Determine the position of the isotope of the medial and lateral femoral condyles on the sagittal plane of the posterior femoral condyles (the isotope of the medial and lateral femoral condyles refers to the point in the femoral condyle that maintains a constant height relative to the tibial plane during knee flexion).

[0013] Specifically, for each patient's knee joint, the present invention first measures the geometric parameters in (1) to (4) above, and then uses the correlation database of the contour points of normal knee joints and the geometric parameters of knee joints to determine the position of the contour points of the patient's knee joint on the sagittal plane of the femoral condyle by interpolation. Figure 2 , Figure 3 (A)). This database is based on the inventor's research (References 1-4), including three-dimensional geometric parameters of the knee joint, three-dimensional motion data of the knee joint from extension to full flexion, and the position of the femoral condyle isotopes for people of different ages, heights, weights, and sexes. Figure 3 (A) refers to the horizontal and vertical positions. Among these, the anteroposterior dimension of the femoral condyle in the sagittal plane is linearly related to the position of its contour points in the sagittal plane. Therefore, the position of the medial femoral condyle's contour points in the sagittal plane can be determined by two interpolation equations (e.g., ...). Figure 3 (A) shows): Horizontal position = 0.275 × femoral condyle length + 4.71; Vertical position = 0.289 × femoral condyle length + 3.43. The horizontal position of the femoral condyle at its contour point in the sagittal plane is calculated from the posterior wall of the femoral condyle, and the horizontal position is calculated from the base of the femoral condyle.

[0014] 2. In the personalized unicompartmental prosthesis design of this invention, using the calculated position of the patient's femoral condyle contour point as the center, a personalized femoral condyle equivalent contour circle is established. Based on this, a personalized contour unicompartmental prosthesis is designed, and the overall design is as follows: Figure 7 As shown, it includes: (1) Based on the position of the contour point of the knee joint of an individual patient on the sagittal plane of the femoral condyle, a tibial surface simulating the posterior inclination of the tibia is constructed at the selected tibiofemoral joint line. The distance between the contour point and the tibial plane determines the radius of the femoral condyle equivalent circle, also known as the contour circle. (2) The contour circle represents the equivalent structure of the femoral condyle in the sagittal plane relative to the tibial plane. The femoral unicompartment prosthesis model is constructed using the equivalent femoral structure. From the standing position to the high flexion position, the contour circle of the femoral condyle constitutes the main articular surface contour of the medial or lateral unicompartment in the sagittal plane. (3) At low flexion and hyperextension angles, the articular surface contour uses a curve extending forward from the lowest point of the contour circle to simulate the natural anatomical contour of the patient's femoral condyle and its contact with the tibial plane at low flexion and hyperextension angles, thereby increasing joint stability; the curve of this anterior contour of the femoral condyle prosthesis consists of a single-radius curve or a multi-radius curve. (4) When the high flexion angle is >90°, the femoral condyle is a curved surface with a radius smaller than that of the iso-circle to increase the contact area with the tibiofemoral component, thereby increasing the stability of the joint at high flexion.

[0015] 3. After determining the geometric parameters of the knee joint based on the individual patient's condition according to the above steps, including the position of the interpolated contour points on the sagittal plane of the femoral condyle ( Figure 7 (Figure A) shows a tibial surface constructed at the selected tibiofemoral joint line to simulate a patient-specific tibial posterior tilt. Figure 7 (Figure B) shows that the distance between the contour point and the tibial plane determines the radius "R1" of the femoral condyle equivalent circle, also known as the contour circle. Figure 7 (C) diagram in the image, typically between 10mm and 50mm). On the sagittal plane of the femoral condyle, draw a circle with the contour points as centers and the radius of the contour circle. Figure 7 Figure (D) represents the equivalent circle of the femoral condyle. This equivalent circle represents the equivalent structure of the femoral condyle in the sagittal plane relative to a specific tibial plane. Therefore, in this invention, the femoral assembly uses the femoral equivalent structure (equivalent circle profile) to construct its primary structure. From the standing position to the high flexion position, the femoral condyle equivalent (high) circle constitutes the primary articular surface profile of the medial or lateral unicompartmental prosthesis in the sagittal plane. Figure 7 (Figure (E)) can help maintain a stable height of the femoral condyle and other high points during joint flexion and extension.

[0016] At low flexion and hyperextension angles, the contour of the unicompartmental prosthesis articular surface formed by the contour circle differs too much from the femoral morphology, requiring extension to the anterior femur. Figure 7in (Figure F), to closely maintain the anatomical structure of the knee joint. Therefore, the articular surface contour of the unicompartmental prosthesis needs to use a curve to extend forward from the lowest point of the equicircular contour to simulate the natural anatomical contour of the femoral condyle of a specific patient and the contact with the tibial plane at low flexion and hyperextension angles.

[0017] At high flexion angles (>90°), in order to increase the posterior stability of the tibiofemoral component, the equicircular femoral condyle component can be replaced with a curved surface with a radius smaller than the radius of the equicircular contour ( Figure 7 in (Figure G)), which is similar to the natural anatomical structure of the knee joint.配合胫骨平面的后唇设计,以保持股骨髁的高度和增加股骨髁的后方稳定性。(It is) designed in cooperation with the posterior lip of the tibial plane to maintain the height of the femoral condyle and increase the posterior stability of the femoral condyle.

[0018] Correspondingly, the design of the tibial plate surface is adjusted accordingly. The tibial surface is designed along the natural tibial slope (usually between 0° and 10°). At low flexion and hyperextension angles, a front lip of the tibial surface is constructed ( Figure 7 in (Figure H)); at high flexion angles, a posterior lip is constructed on the rear part of the tibial plate surface ( Figure 7 in (Figure H)).

[0019] Figure 8 A simplified contour diagram is designed for the femoral prosthesis. At low flexion and hyperextension angles, the articular surface contour uses a curve to extend forward from the lowest point of the equicircular contour to simulate the natural anatomical contour of the femoral condyle of a specific patient and the contact with the tibial plane at low flexion and hyperextension angles, thereby increasing the stability of the joint; the curve of the anterior contour of this femoral condyle prosthesis is composed of a single-radius curve (the size of the radius R₂ is determined according to the anatomical morphology analysis of the femoral condyle of a normal human knee joint, usually between 20 mm and 80 mm, R₂ > R₁) in ( Figure 8 Figure A) or a multi-radius (the sizes of the radii R₂ and R₄ are determined according to the anatomical morphology analysis of the femoral condyle of a normal human knee joint, usually between 20 mm and 80 mm, R₂ > R₁, R₂ > R₄) curve in ( Figure 8 Figure B); At high flexion angles >90°, the equicircular femoral condyle component is replaced with a curved surface "R₃" with a radius smaller than the radius of the equicircular contour (the size of the radius R₃ is determined according to the anatomical morphology analysis of the femoral condyle of a normal human knee joint, usually between 5 - 30 mm, R₃ < R₁) to increase the contact surface with the tibiofemoral component ( Figure 8 ), thereby increasing the stability of the joint at high flexion.

[0020] In step 3, the tibial surface is designed with a single-radius contour in the sagittal plane; or a double-radius contour design, where the radius of the front lip is different from the radius of the rear lip, and the front and rear lips intersect at the lowest point, and the lowest point of the tibial surface is designed in the middle section in the anteroposterior direction of the tibial plane; or a triple-radius contour design, including the radius of the front lip, the radius of the rear lip, and the middle radius, and the lowest point of the tibial surface is located on the middle contour.

[0021] Specifically, such as Figure 9 As shown, the tibial surface is designed along the natural tibial slope. Figure 9 The tibial surface can be designed with a single-radius profile in the sagittal plane. Figure 9 (Figure A) (The radius R is determined based on the anatomical analysis of the tibia in the knee joint of a normal person, and is usually between 100mm and 1000mm); or a double-radius contour design ( Figure 9 (Figure B) shows that the radius of the anterior lip, "R1" (the size of R1 is determined based on the anatomical analysis of the tibia in the knee joint of a normal person, usually between 50mm and 1000mm), is different from the radius of the posterior lip, "R2" (the size of R2 is determined based on the anatomical analysis of the tibia in the knee joint of a normal person, usually between 50mm and 1000mm). The anterior and posterior lips intersect at their lowest point. The lowest point of the tibia surface can be designed in the middle section of the anterior-posterior direction of the tibia; or a three-radius contour design ( Figure 9 (See Figure (C)). The radius of the anterior lip is "R3", the radius of the posterior lip is "R5", and the radius of the midsection is "R4" (the sizes of R3, R4, and R5 are determined based on the anatomical morphology of the tibia in a normal knee joint, usually between 50-1000 mm, where R4>R3, R4>R5). The lowest point of the tibia is located in the midsection contour "R4". In all designs, based on the biomechanics of tibiofemoral contact in a normal knee joint, the lowest point can be designed (but is not limited to) in the midsection of the anteroposterior direction of the tibia. The anterior lip helps maintain anterior stability of the knee joint in full extension and low flexion angles, while the posterior lip helps maintain posterior stability of the knee joint during high flexion. The smaller radius of the posterior lip than the anterior lip is beneficial for the posterior rolling motion of the femur during flexion.

[0022] The femoral and tibial components need to be designed in a coordinated manner, such as... Figure 10 As shown, the anterior lip of the tibia is constructed to correspond to the anterior part of the femur for low flexion and hyperextension angles; for high flexion angles, the posterior lip of the tibia is constructed to correspond to the posterior top of the femur for the posterior part of the tibial plate.

[0023] In combination with all the above-mentioned technical points, the beneficial effects of this invention are as follows: First, based on the latest findings in biomechanical research, this invention reveals that during full weight-bearing flexion of the knee joint, there exists a point on the sagittal plane of both the medial and lateral femoral condyles. During knee flexion, the height of this point on the tibial plane remains approximately constant. Figure 2(A) and (B) are schematic diagrams of contour points. The diagrams show that the femoral condyle height measured at the contour points remains stable along the flexion path; the posterior condyle TEA point and the geometric center show different heights at different flexion angles; therefore, the contour points can measure the knee joint balance with a single height value throughout the flexion range, and thus can be used as physiological reference points for measuring the natural balance of the knee joint along the flexion path. This point is referred to in the literature as the "contour point" (e.g., Figure 2 As shown in (B), the femoral condyle height along the knee flexion path is measured using contour points and the posterior condyle geometric center. The contour point height remains stable along the flexion path. The posterior condyle TEA center and geometric center show different heights at different flexion angles. These data indicate that the contour points are physiological reference points for maintaining knee joint balance throughout the flexion range. The location of the femoral condyle contour points varies from person to person and can be determined in practice based on an individual's 3D CT or MRI model of the knee joint. Figure 3 (A) Therefore, if contour points are used as reference points for measurement, the femoral condyle can maintain an approximately constant height relative to the tibial plane during flexion. Figure 2 (B)). Through this discovery, the present invention demonstrates that, relative to the planar representation of the tibial surface, this constant height represents the equivalent circular radius of the femoral condyle structure, embodying the organic interaction between the femoral condyle and the tibial plateau. Based on this innovative theory, the present invention proposes constructing a circular femoral prosthesis of equal height connected to the tibial surface, using the individual knee joint isotope as a reference. Figure 7 This prosthesis maintains the natural isohyetal motion of the individual knee joint, thereby preserving the natural balance of the knee joint in the flexion path (maintaining medial or lateral soft tissue balance). This is a novel, individualized unicompartmental prosthesis designed to maintain the natural height of the femoral condyle of the knee joint in full flexion. Figure 2 (B) ), thereby maintaining the natural physiological balance of the knee joint.

[0024] Secondly, the personalized unicompartmental prosthesis disclosed in this invention is developed based on the latest research results in knee joint biomechanics and is the first personalized joint prosthesis that considers the balance design of the entire flexion path. Its characteristic of natural balance of the entire flexion path overcomes the limitation of traditional unicompartmental replacement prosthesis design, which relies only on the balance of the force line in the standing position and cannot control the balance of other flexion angles. Figure 6 (B) shows the changes in the isotope along the flexion path of a typical knee joint after replacement with different unicompartmental prostheses. The figure shows that conventional prostheses alter the isotope characteristics of the natural isotope of the knee joint, while the prosthesis designed in this invention better reflects the isotope characteristics, thus better maintaining the physiological soft tissue balance of the joint along the flexion path and restoring the biomechanical function of the joint.

[0025] Third, current unicompartmental knee arthroplasty primarily relies on knee joint alignment in extension to determine prosthesis placement. However, extension does not represent knee joint balance at other flexion angles. Various methods of balancing along the flexion path in practical applications are based on corresponding assumptions and lack support from fundamental biomechanical research. The full flexion path balancing method proposed in this invention fills this gap, fully utilizing the biomechanical characteristics of the knee joint being at the same height along the flexion path, encompassing joint balance at various angles, simplifying the challenge of interarticular balancing during surgery, and making it possible to accurately restore natural joint balance along the flexion path postoperatively. This allows for the wider clinical application of unicompartmental knee arthroplasty in treating knee joint diseases (medial or lateral).

[0026] Fourth, the personalized unicompartmental prosthesis replacement method provided by this invention makes full use of advanced medical imaging and three-dimensional computer simulation technology, realizing a full-chain treatment design including precise individual patient analysis, unicompartmental prosthesis design, preoperative surgical planning, and preoperative surgical simulation. It can promote the application of intelligent digital orthopedic technologies, such as computer-aided personalized surgical instruments, intraoperative navigation technology, and robotic surgery technology in clinical practice. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure; Figure 1 A flowchart illustrating the design process of a personalized unicompartmental knee prosthesis with full flexion path balance provided in this invention embodiment; Figure 2 The following is a schematic diagram of contour points provided in an embodiment of the present invention; wherein, (A) is a schematic diagram of the change in femoral condyle height along the knee flexion path measured using the femoral condyle contour point, the posterior condyle TEA point and the geometric center point; (B) is a schematic diagram of the change in the height of the femoral condyle along the flexion path of the knee joint measured by the TEA point, the geometric center point (GCA) and the contour points. Figure 3 The diagram shows the structure of the medial and lateral femoral condyles in the sagittal plane according to an embodiment of the present invention; wherein, (A) is the construction of the medial and lateral femoral condyles in the sagittal plane of the knee joint, and (B) is a three-dimensional schematic diagram including the medial and lateral femoral condyles in the sagittal plane, the geometric center point and the geometric circle; Figure 4 This is a schematic diagram of the femoral ankle structure provided in an embodiment of the present invention; wherein, (A) the maximum width of the femoral condyle in the coronal plane is determined by the distance between the medial and lateral condylar points, and the width of the femoral condyle in the sagittal plane in the coronal plane is determined by the distance between the medial and lateral sagittal planes; (B) the anteroposterior dimensions of the medial and lateral femoral condyles in the sagittal plane are determined by the anteroposterior distance between the medial and lateral condyles in the sagittal plane. Figure 5The diagram showing the construction of the tibial plane of the knee joint provided in the embodiment of the present invention includes the tibial axis, the tibial plane, and the posterior tilt angle of the tibial plane; wherein, (A) is the front of the tibia, and (B) is the sagittal plane of the tibia; Figure 6 A schematic diagram of the knee joint provided in an embodiment of the present invention; wherein, (A) is a three-dimensional view of the construction of the sagittal plane of the femoral condyles on the medial and lateral sides of the knee joint and the tibial plane, and (B) is a typical diagram of the variation of the contour points of the knee joint along the flexion path; Figure 7 To design a unicompartment prosthesis using the geometric parameters of the femoral condyle, (A) is to determine the contour points of the medial and lateral sides of the femoral condyle, (B) is to determine the tibial plane, (C) is to determine the radius of the contour circle (R1, 10-50mm), (D) is to construct the contour circle, (E) is to design a patient-specific unicompartment prosthesis system based on the contour circle, (F) is to design the anterior part of the patient-specific unicompartment component based on the joint shape, (G) is to design the posterior part of the patient-specific unicompartment component based on the joint shape, and (H) is to design the anterior and posterior lips of the surface of the patient-specific unicompartment tibia. Figure 8 A simplified design diagram of a femoral condyle prosthesis provided in an embodiment of the present invention; wherein, (A) is a design diagram with a single radius (the size of R2 is determined based on the anatomical morphology analysis of the femoral condyle of a normal person's knee joint), and (B) is a design diagram with curves of different radii (the sizes of R2 and R4 are determined based on the anatomical morphology analysis of the femoral condyle of a normal person's knee joint); Figure 9 The following is a design drawing of the tibial surface along the natural tibial slope provided in the embodiments of the present invention; wherein, (A) is a design drawing of the tibial surface with a single radius (the size of R is determined according to the anatomical morphology of the tibial plane of the knee joint of a normal person, and is between 100-1000mm), (B) is a design drawing of the tibial surface with a double radius, and (C) is a design drawing of the tibial surface with a triple radius. Figure 10 The diagram shows the combination of the femoral condyle and tibial components of the unicompartment prosthesis provided in the embodiment of the present invention; wherein, (A) is a schematic diagram of the interaction between the femoral component and the tibial component of the unicompartment prosthesis system in extension and hyperextension, and (B) is a schematic diagram of the interaction between the femoral component and the tibial component in bending and high bending. Figure 11 The following is a schematic diagram of the femoral component implanted and installed on the femoral condyle according to an embodiment of the present invention; wherein, (A) is an installation diagram of the unicompartment prosthesis with the prosthesis contour point and the knee joint contour point as the target; (B) is a contour diagram of the unicompartment prosthesis system in the extension path; and (C) is a contour diagram of the unicompartment prosthesis system in the high bending path. Figure 12 The overall application and implementation process of personalized unicompartmental prosthesis surgery; Figure 13 Personalized 3D knee joint model rendering based on a CT scan of the knee joint; Figure 14A geometric analysis rendering of a 3D knee joint model; Figure 15 A diagram illustrating the effects of personalized knee joint alignment adjustments; Figure 16 To design a personalized, contour-equal-height monotube component rendering; Figure 17 Three-dimensional models of the femoral and tibial components of a personalized unicompartmental prosthesis; where (A) is the frame model and (B) is the solid model; Figure 18 A three-dimensional model of a personalized unicompartmental prosthesis and an assembly diagram of the knee joint; wherein, (A) is the femur and tibia before assembly, and (B) is the femur and tibia after assembly. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] The innovation of this invention lies in its determination of the equivalent height circle of the femoral condyle based on the specific tibiofemoral joint geometry parameters of unicompartmental patients. Therefore, the unicompartmental prosthesis designed in this invention can maintain the natural balance of the femoral condyle along the flexion path, thereby greatly simplifying the intraoperative gap balancing problem, saving surgical time, and better restoring joint function.

[0030] Example 1, as Figure 1 As shown in the embodiment of the present invention, a personalized unicompartmental knee arthroplasty system with full flexion path balance is provided. The system includes: The unicompartment prosthesis design module establishes a personalized femoral condyle equivalent contour circle based on the patient's personalized femoral condyle contour point and tibial plane information, and then designs a personalized contour unicompartment prosthesis model. Based on the designed personalized unicompartmental prosthesis model, the computer simulation of the installation of the personalized unicompartmental prosthesis model is used with personalized knee joint contour points to simulate the completion of the unicompartmental prosthesis replacement with full flexion path balance, and to carry out preoperative planning and visualization.

[0031] Example 2: A personalized unicompartmental knee prosthesis design with full flexion path balance. Starting with a patient-specific 3D CT or MRI model of the knee joint, since the femoral condyle contour is not a simple circle and the tibial surface is not a simple plane, a holistic system design for the femoral condyle and tibial surface is required. Figure 7As shown, this is so that the height of the medial or lateral condyle, measured at isotopes, remains constant when the knee is flexed. Figure 6 (B) thus maintaining the natural balance of the knee joint in the flexion path. In traditional joint design, the femoral component is usually designed based on the geometry of the femoral condyle. Due to technical difficulties, parameters such as tibial and joint movement are difficult to incorporate into the main factors to be considered in femoral condyle design, making it difficult to maintain the natural balance of the knee joint at other flexion angles. Figure 6 (B)).

[0032] This invention innovatively proposes a personalized unicompartmental knee prosthesis design with full flexion path balance. In this novel design concept, the isotope maintains a stable height along the flexion path. The posterior condyle TEA center and geometric center exhibit different heights at different flexion angles. Figure 2 (B) Therefore, the isotopes are physiological reference points for maintaining knee joint balance throughout the entire range of flexion.

[0033] like Figure 3 The sagittal plane of the femoral condyle and the 3D view of the geometric center circle of the femoral condyle in the sagittal plane are shown in the diagram. Using a 3D knee joint model, the position of the femoral condyle is adjusted. Concentric fitted cylinders of the medial and lateral femoral condyles are established in the sagittal plane of the joint, utilizing the posterior geometry of the medial and lateral femoral condyles. Two sagittal vertical cross-sections of the cylinder are determined at the maximum radius of the two posterior femoral condyles of the knee joint. The centers of the two circular cross-sections are defined as the geometric center of the medial and lateral femoral condyles, and the line connecting the two geometric center centers is defined as the geometric central axis GCA. The positions of the contour points are calculated by geometric parameter interpolation. For each patient's 3D CT or MRI model of the knee joint, the geometric features of the femoral condyle are first determined, including: (1) The position of the geometric circle fitted in the sagittal plane of the medial and lateral femoral condyles (including the position of the center point of the geometric circle and the radius of the circle), and the distance between the center points of the geometric circles of the medial and lateral condyles. In actual operation, the present invention adjusts the position of the femoral condyles and uses the posterior geometry of the medial and lateral femoral condyles to establish concentric fitted cylinders of the medial and lateral condyles in the sagittal plane. Figure 3 (Figure A) shows the two sagittal vertical cross-sections of the cylinder located at the maximum radius of the two posterior femoral condyles of the knee joint. Figure 3 (See Figure (B)). The centers of the two circular cross-sections are defined as the geometric centers of the medial and lateral femoral condyles, and the line connecting the two geometric centers is defined as the geometric center axis (GCA).

[0034] (2) The location of the condylar points of the medial and lateral condyles is defined as the location of the most lateral points on the left and right sides of the femoral condyles. Figure 4As shown in Figure (A), these are the geometric feature points of the medial and lateral femoral condyles of the knee joint. The line connecting the most prominent points of the medial and lateral femoral condyles is called the TEA axis, and the midpoint of the axis is defined as the center of the knee joint. The lateral distance between the most prominent points of the medial and lateral condyles is defined as the maximum lateral width of the femoral condyles; the lateral distance in the sagittal plane between the medial and lateral femoral condyles is defined as the lateral dimension of the geometric center point of the medial and lateral condyles. (3) The anterior-posterior dimension of the medial and lateral femoral condyles in the sagittal plane is defined as the distance between the anterior and posterior points of the medial and lateral condyles in the sagittal plane. Figure 4 (Figure B shows the anteroposterior dimensions of the medial and lateral femoral condyles) (4) On the sagittal plane of the posterior femoral condyles on the medial and lateral sides of the joint, the position of the isotopes of the medial and lateral femoral condyles is determined by interpolation using the above femoral condyle geometric parameters (the isotopes of the medial and lateral femoral condyles refer to the points in the femoral condyles that maintain a constant height relative to the tibial plane during knee flexion); the line connecting the isotopes of the medial and lateral femoral condyles is the isotope axis.

[0035] (5) Establish the tibial plane. First, the long axis of the tibia needs to be established ( Figure 5 The long axis of the tibia runs along the axial direction of the tibial shaft and is parallel to the posterior wall of the tibial shaft. For example... Figure 5 As shown, a plane perpendicular to the long axis of the tibia is then established at the proximal end of the tibia. The angle between the tibial surface and the plane perpendicular to the long axis of the tibia in the sagittal plane is defined as the posterior tilt angle of the tibial plane. Figure 5 Then, based on the posterior tilt angle of the tibial plane, rotate the plane that was constructed perpendicular to the long axis of the tibia to obtain a tibial plane parallel to the tibial surface.

[0036] (6) The height of the femoral condyle is determined by the vertical distance from the isotope of the femoral condyle to the tibial plane. Figure 6 (A)). The geometric features of the femoral condyles include the sagittal geometric center of the medial and lateral femoral condyles, the medial and lateral condylar points, contour points, the center of the knee joint, and the tibial plane; therefore, in practical applications, for each specific knee joint, such as Figure 17 , Figure 18 As shown, the present invention can use its three-dimensional model to measure the above geometric parameters, such as the geometric center point of the sagittal plane of the medial and lateral femoral condyles, the contour points of the medial and lateral condyles, the medial and lateral condylar processes, the tibial plane, etc. This greatly simplifies the design process of personalized unicompartmental prostheses.

[0037] For example, unicompartmental prosthesis design utilizes personalized contour points and the tibial plane to design a personalized unicompartmental prosthesis, that is, establishing a personalized femoral condyle equivalent contour circle and designing a personalized contour-equivalent unicompartmental prosthesis model, including: (1) Based on the position of the contour point of the knee joint of an individual patient on the sagittal plane of the femoral condyle, a tibial surface simulating the posterior inclination of the tibia is constructed at the selected tibiofemoral joint line. The distance between the contour point and the tibial plane determines the radius of the femoral condyle equivalent circle or the contour circle. (2) The contour circle represents the equivalent structure of the femoral condyle in the sagittal plane relative to the tibial plane. The femoral unicompartment prosthesis model is constructed using the equivalent femoral structure. From the standing position to the high flexion position, the contour circle of the femoral condyle constitutes the main articular surface contour of the medial or lateral unicompartment in the sagittal plane. (3) At low flexion and hyperextension angles, the articular surface contour uses a curve extending forward from the lowest point of the contour circle to simulate the natural anatomical contour of the patient's femoral condyle and its contact with the tibial plane at low flexion and hyperextension angles, thereby increasing joint stability; the curve of this anterior contour of the femoral condyle prosthesis consists of a single-radius curve or a multi-radius curve. (4) When the high flexion angle is >90°, the femoral condyle is a curved surface with a radius smaller than that of the iso-circle to increase the contact area with the tibiofemoral component, thereby increasing the stability of the joint at high flexion.

[0038] After determining the position of the patient's knee joint contour points on the sagittal plane of the femoral condyle using the steps described above ( Figure 7 Figure (A) shows the contour points for calculating the medial and lateral sides of the femoral condyles. Following the steps described above, a tibial surface simulating the patient's specific posterior tibial tilt needs to be constructed at the selected tibiofemoral joint line. Figure 7 (Figure B) defines the tibial plane; the vertical distance between the contour points and the tibial plane is defined as the radius of the femoral condyle contour circle or equivalent circle. Figure 7 The radius of the contour circle is determined in Figure (C), with R1 approximately 10mm-50mm. Therefore, the radius of the equivalent circle of the femoral condyle is also affected by the height of the tibial plane. Increasing the position of the tibial plane can lead to a decrease in the radius of the equivalent circle, while decreasing the position of the tibial plane can lead to an increase in the radius of the equivalent circle. Changing the slope of the plane will also cause changes in the corresponding contour point position and the radius of the equivalent circle. The method of this invention can conveniently handle these design variables.

[0039] On the sagittal plane of the femoral condyle, draw a circle with the contour points as centers and the radius of the contour circle; this circle represents the equivalent circle of the femoral condyle. Figure 7 (D) The iso-circle is constructed. This equivalent circle represents the equivalent structure of the femoral condyle in the sagittal plane relative to a specific tibial plane. Therefore, in this invention, the femoral assembly uses the femoral equivalent structure (equivalent circle profile) to construct its profile. From the standing position to the high flexion position, the femoral condyle iso-circle forms the main articular surface profile of the medial or lateral unicompartmental prosthesis in the sagittal plane ( Figure 7 Figure (E) shows a patient-specific unicompartmental prosthesis system designed based on contour circles, which allows the femoral condyle contour points to maintain a stable height relative to the tibial plane during joint flexion and extension. Figure 11 Figure (A) shows the placement of a unicompartmental prosthesis with the prosthesis and knee joint at the same height as the target. The unicompartmental prosthesis system in extension ( Figure 11 (Figure B) and high curvature ( Figure 11 (Figure C) is a contour diagram of the path, which is related to the natural knee joint height along the flexion path. Figure 6 (B) is consistent with the change of the contour point along the flexion path after replacement with different unicompartmental prostheses. The figure shows that the height of the contour point changes non-linearly after replacement with a traditional prosthesis, while the height of the contour point changes approximately linearly after replacement with the prosthesis of the present invention. The prosthesis designed by the present invention can better reflect the natural contour characteristics of the knee joint.

[0040] At low flexion and hyperextension angles, the contour of the unicompartmental prosthesis articular surface formed by the contour circle does not match the femoral morphology and needs to be extended to the anterior part of the femur to closely maintain the anatomical structure of the knee joint. Figure 7 (Figure F). Therefore, the articular surface profile of the unicompartmental prosthesis needs to use a curve extending forward from the lowest point of the isocircle to simulate the natural anatomical profile of the femoral condyle in a specific patient and its contact with the tibial plane at low flexion and hyperextension angles. At high flexion angles (>90°), to increase posterior stability of the femoral condyle, the isocircle component of the femoral condyle can be replaced with a surface with a radius smaller than that of the isocircle. Figure 7 The diagram (G) in the figure closely resembles the natural anatomy of the knee joint. This helps maintain the height of the femoral condyle and increase its posterior stability.

[0041] Accordingly, the design of the tibial plate surface is adjusted accordingly, with the tibial surface designed along the natural tibial inclination, constructing the anterior lip of the tibial surface at low flexion and hyperextension angles. Figure 7 (Figure H); at high flexion angles, construct the posterior lip on the posterior surface of the tibial plate ( Figure 7 (H) diagram in the middle.

[0042] Figure 8 A simplified diagram illustrating the design of a femoral prosthesis. At low flexion and hyperextension angles, the articular surface profile uses a curve extending anteriorly from the lowest point of the iso-circle to mimic the natural anatomical profile of the femoral condyle in a specific patient and its contact with the tibial plane at low flexion and hyperextension angles, thereby increasing joint stability; the curved profile of this anterior femoral condyle prosthesis can be derived from (…). Figure 8 (Figure A) The size of the single-radius curve (R2) is determined based on the anatomical analysis of the femoral condyle of the knee joint in normal individuals, and is between 20mm and 80mm; R2>R1) or ( Figure 8It consists of a multi-radius curve ((B) in the figure), where the sizes of R2 and R4 are determined based on the anatomical morphology analysis of the femoral condyles of normal people, and R4 < R2, intersecting with the contour circle of the femoral articular surface at its lowest point; the femoral component is designed using a part of the contour circle (R1, 10 - 30 mm). The front part is designed with a single radius (R2) that matches the contour of the natural femoral condyle, or a different radius curve (R2 and R4). The front femoral component intersects with the femoral component at its lowest point. The posterior top of the femoral condyle prosthesis can reduce the contour radius (R3) to achieve the effect of enhancing the stability of the highly flexed joint.

[0043] At high flexion angles (>90°), in order to increase the posterior stability of the femoral condyle, the contour circle component of the femoral condyle can be replaced with a curved surface (R3) with a radius smaller than the radius of the contour circle ( Figure 8 ), which is similar to the natural anatomical structure of the knee joint. The posterior top of the femoral condyle prosthesis can reduce the contour radius (the size of R3 is determined based on the anatomical morphology analysis of the femoral condyles of normal people, between 5 - 30 mm, and R3 < R1), in配合 with the design of the posterior lip of the tibial plane to maintain the height of the femoral condyle and increase the posterior stability of the femoral condyle.

[0044] Correspondingly, the design of the tibial plate surface needs to be adjusted accordingly to match the design of the femoral condyle. The overall tibial surface is designed along the natural tibial slope, constructing the anterior lip of the tibial surface ( Figure 7 in (H) of the figure, Figure 9 , Figure 10 ), to match the change in the anterior shape of the femoral condyle, which helps to maintain the anterior stability of the knee joint at low flexion and hyperextension angles ( Figure 10 in (A) of the figure); constructing the posterior lip of the tibial surface ( Figure 7 in (H) of the figure, Figure 9 , Figure 10 ), to match the change in the posterior top shape of the femoral condyle ( Figure 10 in (B) of the figure), which helps to maintain the posterior stability of the knee joint and keep the height of the femoral condyle at high flexion angles.

[0045] Specifically, the tibial surface is designed along the natural tibial slope ( Figure 9 ), and the tibial surface can be designed with a single radius contour in the sagittal plane ( Figure 9 in (A) of the figure), (the size of R is determined based on the anatomical morphology analysis of the tibial plane of normal people, between 100 - 1000 mm); or a double radius contour design ( Figure 9(Figure B) shows that the radius R1 of the anterior lip (between 50-1000 mm) differs from the radius R2 of the posterior lip (between 50-1000 mm). (The sizes of R1 and R2 are determined based on the anatomical morphology of the tibia in the knee joint of normal individuals, with R2 > R1). The anterior and posterior lips intersect at their lowest point. The lowest point of the tibia surface can be designed in the middle section of the anterior-posterior direction of the tibia; or a three-radius contour design can be used. Figure 9 (See Figure (C)). The radius of the anterior lip is R3, the radius of the posterior lip is R5, and the radius of the midsection is R4 (the sizes of R3, R4, and R5 are determined based on the anatomical morphology of the tibia in the knee joint of a normal person, with R4>R3 and R4>R5. The value of R3 ranges from 50 to 1000 mm; the value of R4 ranges from 100 to 5000 mm; and the value of R5 ranges from 50 to 1000 mm). The lowest point on the tibial surface is located at the midsection contour R4. In all designs, based on the biomechanics of tibiofemoral contact in a normal knee joint, the lowest point can be designed (but is not limited to) in the midsection of the anteroposterior direction of the tibia. The anterior lip helps maintain anterior stability of the knee joint in full extension and low flexion angles, while the posterior lip helps maintain posterior stability of the knee joint during high flexion. The radius of the posterior lip is smaller than that of the anterior lip, which is beneficial for the posterior rolling motion of the femur during flexion.

[0046] Description of the unicompartmental prosthesis system Figure 10 The unicompartmental prosthesis is installed on the femoral condyle with the contour point as a reference point to achieve precise digital unicompartmental prosthesis replacement. Figure 10 Illustration of a unicompartmental prosthesis system in knee extension and hyperextension positions. Figure 10 (Figure A) and the unicompartmental prosthesis system in the high flexion position of the knee joint ( Figure 10 The interaction between the femoral and tibial components in (B) diagram.

[0047] For example, in the unicompartmental prosthesis design module, the tibial surface is designed with a single-radius profile in the sagittal plane; or a double-radius profile design, where the radius of the anterior lip is different from that of the posterior lip, the anterior and posterior lips intersect at the lowest point, and the lowest point of the tibial surface is designed in the middle section of the anterior-posterior direction of the tibial plane; or a triple-radius profile design, including the radius of the anterior lip, the radius of the posterior lip, and the mid-section radius, with the lowest point of the tibial surface located in the mid-section profile.

[0048] The invention employs a personalized, contour-aligned unicompartmental prosthesis installation method, utilizing individualized contour points for precise placement. Unlike traditional unicompartmental prosthesis surgery, the femoral component designed in this invention uses the patient's specific contour point location as an implantation guide for placement on the femoral condyle. Figure 11 (Figure (A) in the diagram) means that during the procedure, the installation of the prosthesis components aims to align the contour points of the prosthesis with those of the femoral condyle. Figure 11(See Figure (A)). This installation design can fully utilize the patient's individual characteristics, such as joint geometry and femoral condyle contour, thus allowing for the full application of advanced personalized preoperative planning, personalized surgical instruments, surgical navigation technology, or robot-assisted surgery, etc. Such a design enables the entire surgery to be standardized, quantified, and intelligent, achieving precise digital unicompartmental prosthesis installation (e.g., Figure 17 , Figure 18 (As shown).

[0049] This equivalent (equipotential) component structure allows the knee joint's isotope to maintain a constant height relative to the tibial plane during flexion. Figure 6 Figure (B) in the middle, Figure 11 Figure (B) in the middle, Figure 11 (Figure C) of the present invention. Therefore, the unicompartmental prosthesis designed in this invention can reproduce the iso-height characteristics of the natural femoral condyle during knee flexion and maintain the dynamic natural balance of the knee joint along the flexion path. Figure 6 Figure (B) in the middle, Figure 11 Figure (B) in the middle, Figure 11 Figure (C) in the figure shows how to maintain a stable height at different knee angles. A unicompartmental prosthesis designed and installed in this way can maintain a stable height of the joint along the flexion path, which is consistent with the natural knee height along the flexion path.

[0050] The simulation of unicompartmental knee arthroplasty with contour points utilizes personalized contour points of the knee joint to precisely install a personalized unicompartmental knee arthroplasty with contour points, completing a simulated unicompartmental knee arthroplasty with contour points balancing the entire flexion path. This includes: the installation of the prosthesis components with the goal of aligning the contour points of the prosthesis with those of the femoral condyles; the application of individualized joint geometry parameters and the contour characteristics of the femoral condyles; and the use of preoperative planning, personalized surgical instruments, navigation technology, or robot-assisted technology to simulate the completion of a unicompartmental knee arthroplasty with contour points balancing the entire flexion path.

[0051] Application example: The clinical application of the personalized unicompartmental knee replacement of this invention incorporates a series of modern digital medical technologies ( Figure 12 This illustrates the overall application and implementation process of personalized unicompartmental surgery. After clinical diagnosis confirms the need for unicompartmental surgery, the first step is preoperative planning, which includes a 3D CT or MRI scan of the patient's knee joint and reconstruction of a 3D knee joint model; the 3D morphological parameters of the patient's knee joint are analyzed and measured (…). Figure 3 , Figure 4 , Figure 5 , Figure 6 ), determine the position of the contour points of the femoral condyle relative to the tibial plane ( Figure 3 Then, the design of personalized monocular components is carried out. Figure 7 , Figure 8 , Figure 9(and 10), and simulated the installation of the high unicompartment component during surgery ( Figure 11 For the manufacturing of unicompartments, personalized unicompartments can be rapidly manufactured using modern industrial manufacturing methods or 3D printing, using metallic or non-metallic materials. Figure 17 , Figure 18 The next step is to choose the surgical method. This unicompartmental replacement can be performed with computer-guided assistance, personalized instrument assistance (such as a personalized cutting guide), or robot assistance. Finally, a personalized unicompartmental replacement with full buckling path balance will be achieved.

[0052] The personalized unicompartmental knee replacement design proposed in this invention aims to maintain the natural height of the femoral condyle along the flexion path of the knee joint, thereby maintaining the overall natural balance of the knee joint during flexion. Figure 2 , Figure 6 , Figure 11 Figure (B) in the middle, Figure 11 (See Figure (C)). This personalized unicompartmental knee prosthesis integrates the holistic design principles of the femoral condyle and tibial plateau surfaces, and utilizes a novel concept of physiological equal height for the knee joint. By maintaining the physiological height of the femoral condyle, the natural tension of surrounding soft tissues (such as the medial and lateral collateral ligaments) can be preserved. Due to the truly equivalent (equal height circle) femoral condyle prosthesis design, the moderate flexion instability caused by abrupt changes in the prosthesis condyle radius, common in traditional knee replacement designs, is avoided. Furthermore, it prevents tightness in the knee joint at high flexion positions, thereby enhancing knee flexion capacity.

[0053] The personalized unicompartmental knee replacement design and clinical application of this invention differ conceptually from traditional knee prosthesis designs. Traditional knee prosthesis designs rarely consider the specific circumstances of individual patients, and the design of the tibial surface is often relatively "independent" of the femoral condyle design. The unicompartmental knee prosthesis design proposed in this invention is based on a personalized femoral condyle contour concept, using the patient's unique femoral condyle contour point as a reference, combined with the individual patient's knee anatomy and kinematic characteristics. Through a personalized integrated design of the tibial and femoral condyle surfaces, and prosthesis installation using the contour point as a reference, this design allows the prosthesis to maintain the natural physiological height of the femoral condyle and the balance of surrounding soft tissues during knee flexion, achieving the surgical design goals of restoring joint function and improving patient proprioception.

[0054] To further illustrate the effects of the embodiments of the present invention, the following experiment was conducted: The experiment was run on a computer, with preoperative planning, S1, CT or MRI scan of the patient's knee joint, and S2, a personalized 3D knee joint model, such as... Figure 13 As shown; S3, knee joint geometric parameter analysis, as follows Figure 14 As shown; S4, determine the personalized knee joint femoral ankle contour points, such as... Figure 15As shown; S5, design personalized high-profile single-panel components, such as Figure 16 As shown; S6, visualization of the single ankle prosthesis installation simulation.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A personalized unicompartmental knee prosthesis design method with full flexion path balance, characterized in that, The method includes: Based on the patient's personalized femoral condyle contour points and tibial plane information, a personalized femoral condyle equivalent contour circle is established, and then a personalized contour unicompartment prosthesis is designed. And conduct preoperative planning and visualization.

2. The personalized unicompartmental knee prosthesis design method with full flexion path balance according to claim 1, characterized in that, For each knee joint, a 3D CT or MRI model is used to determine the geometric features of the femoral condyle, including: (1) The position of the geometric circle fitted in the sagittal plane of the medial and lateral femoral posterior condyles, including the position of the center point of the geometric circle and the radius of the circle, and the distance between the center points of the geometric circles of the medial and lateral condyles; (2) The location of the condylar points of the medial and lateral femoral condyles is the location of the most prominent points on the left and right sides of the femoral condyles, and is defined as the geometric feature point of the femoral condyle; the line connecting the most prominent points of the medial and lateral femoral condyles is the TEA axis, the midpoint of the axis is defined as the center of the knee joint, the distance between the condylar points of the medial and lateral femoral condyles in the left and right directions is defined as the left and right width of the femoral ankle; the dimensions of the geometric circles of the medial and lateral femoral condyles in the sagittal plane in the left and right directions are defined as the left and right width of the femoral ankle in the sagittal plane. (3) The anteroposterior dimensions of the medial and lateral femoral condyles in the sagittal plane are defined as the distance between the anterior and posterior points of the medial and lateral femoral condyles in the sagittal plane; (4) The position of the isotopes of the medial and lateral femoral condyles on the sagittal plane of the medial and lateral femoral condyles; the line connecting the isotopes of the medial and lateral femoral condyles is the isotope axis; (5) Use computer simulation to create a three-dimensional knee joint model and establish the tibial plane.

3. The personalized unicompartmental knee prosthesis design method with full flexion path balance according to claim 2, characterized in that, In step (1), a three-dimensional knee joint model is simulated using a computer to adjust the position of the femoral condyles. Using the posterior geometry of the medial and lateral femoral condyles, a concentric fitting cylinder of the medial and lateral condyles is established in the sagittal plane of the knee joint. Two sagittal vertical cross sections of the cylinder are determined at the maximum radius of the two posterior femoral condyles of the knee joint. The center of the two circular cross sections is defined as the geometric center of the medial and lateral femoral condyles, and the line connecting the two geometric centers is defined as the geometric center axis GCA.

4. The personalized unicompartmental knee prosthesis design method with full flexion path balance according to claim 2, characterized in that, In step (5), firstly, the long axis of the tibia is established, which is along the axial direction of the tibial shaft and parallel to the posterior wall of the tibial shaft; then, a plane perpendicular to the long axis of the tibia is established at the proximal end of the tibia. The angle between the tibial surface and the plane perpendicular to the long axis of the tibia in the sagittal plane is defined as the posterior tilt angle of the tibial plane; according to the posterior tilt angle of the tibial plane, the plane perpendicular to the long axis of the tibia is rotated to obtain a tibial plane parallel to the tibial surface.

5. The personalized unicompartmental knee prosthesis design method with full flexion path balance according to claim 1, characterized in that, Establish a personalized femoral condyle structure equivalent height circle, and design a personalized height-equivalent unicompartmental prosthesis, including: (1) Based on the position of the contour point of the knee joint of an individual patient on the sagittal plane of the femoral condyle, a tibial surface simulating the posterior inclination of the tibia is constructed at the selected tibiofemoral joint line. The distance between the contour point and the tibial plane determines the radius of the equivalent contour circle of the femoral condyle. (2) The contour circle represents the equivalent structure of the femoral condyle in the sagittal plane relative to the tibial plane. The femoral unicompartment prosthesis is constructed using the equivalent femoral structure. From the standing position to the high flexion position, the contour circle of the femoral condyle forms the main articular surface contour of the medial or lateral unicompartment in the sagittal plane. (3) At low flexion and hyperextension angles, the articular surface contour uses a curve extending forward from the lowest point of the iso-circle to simulate the natural anatomical contour of the patient's femoral condyle and its contact with the tibial plane at low flexion and hyperextension angles; the curve of this anterior contour of the femoral condyle prosthesis consists of a single-radius curve or a multi-radius curve. (4) When the high flexion angle is >90°, the femoral condyle is a curved surface with a radius smaller than that of the iso-circle to increase the contact area with the tibiofemoral component, thereby increasing the stability of the joint at high flexion.

6. The personalized unicompartmental knee prosthesis design method with full flexion path balance according to claim 5, characterized in that, The tibial surface is designed with a single-radius profile in the sagittal plane; or a double-radius profile, with the radius of the anterior lip different from that of the posterior lip, the anterior and posterior lips intersecting at the lowest point, and the lowest point of the tibial surface designed in the middle section of the anteroposterior direction of the tibial plane; or a triple-radius profile, including the radius of the anterior lip, the radius of the posterior lip, and the mid-section radius, with the lowest point of the tibial surface located in the mid-section profile.

7. The personalized unicompartmental knee prosthesis design method with full flexion path balance according to claim 5, characterized in that, The femoral and tibial components need to be designed in coordination. For low flexion and hyperextension angles, the anterior lip of the tibial surface is constructed to correspond to the anterior part of the femur; for high flexion angles, the posterior lip of the tibial surface is constructed to correspond to the posterior top of the femur.

8. The personalized unicompartmental knee prosthesis design method with full flexion path balance according to claim 1, characterized in that, Computer simulation can be used to install a personalized unicompartmental knee joint prosthesis. Utilizing customized contour points of the knee joint, a personalized unicompartmental knee joint prosthesis model is precisely installed, simulating a full flexion path balanced unicompartmental knee joint prosthesis replacement surgery. This simulation includes: The installation of the prosthesis components aims to make the contour points of the prosthesis coincide with the contour points of the femoral condyles. By utilizing individualized joint geometry parameters and the contour characteristics of the femoral condyles, and applying preoperative planning, personalized surgical instruments, navigation technology or robot-assisted technology, a visual simulation of a contour unicompartmental prosthesis replacement surgery with full flexion path balance is performed.

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