Design method of sheep knee joint inner side bionic meniscus prosthesis

Abstract

The invention provides a design method of a bionic meniscus prosthesis on the inner side of a sheep knee joint. Compared with the prior art, the knee joint inner side bionic meniscus prosthesis designed and prepared through the method serves as a synthetic and non-absorbable full meniscus substitute, is implanted into a sheep knee joint in a free and non-fixed mode, and can treat severe meniscus injuries which cannot be repaired through meniscus resection or meniscus suture; and the defects related to the use of a meniscus allograft can be overcome, and the knee joint meniscus prosthesis can completely or partially replace the function of the original meniscus after implantation so as to recover the functional level of the knee joint.

Description

Technical Field

[0001] The invention belongs to the technical field of medical devices, and in particular relates to a design method for a bionic meniscus prosthesis of a sheep knee joint medial side. Background Art

[0002] The meniscus is a fibrous cartilage "C"-shaped structure in the lateral and medial compartments of the knee joint. Its functions include sharing intra-articular pressure and transmitting load, increasing the joint contact area, reducing contact pressure and stabilizing joint movement, secreting synovial fluid, lubricating the joint and nourishing cartilage, and providing proprioception.

[0003] Meniscus injury is one of the common injuries of the knee joint, and the meniscus has almost no ability to regenerate tissue. Partial or complete meniscus resection and meniscus suturing are common methods for treating meniscus tears and knee pain, but from the perspective of long-term prognosis, their treatment effects often have certain limitations and treatment complications. Subsequent studies have reported that meniscus resection will lead to changes in the load inside the knee joint, secondary knee degenerative lesions, and finally related diseases such as knee osteoarthritis. Meniscus suturing is only effective in the red zone of the meniscus. In the avascular area on the inner side of the meniscus, suturing is almost impossible due to insufficient blood supply.

[0004] Another solution for treating meniscus injuries is to use allogeneic grafts, but they will atrophy and undergo collagen remodeling after being transplanted into the patient's body, eventually leading to allograft breakage, joint instability and degenerative lesions. Grafts may also have other problems, such as limited donors, mismatching, rejection and infection risks.

[0005] With the development of biopolymer materials, biopolymer scaffolds have good development prospects in the repair of various tissue injuries. For example, collagen meniscus implants made of type I collagen fibers from bovine Achilles tendon have been used clinically. They act as templates for tissue repair and regeneration, interact with surrounding cells, and provide structural support for newly formed tissues. Collagen meniscus implants can produce good and stable clinical results, especially in terms of knee function and pain, with low incidence of complications and reoperations. However, there are many types of biopolymer scaffolds, and most of them are still in the experimental stage. We still lack a systematic understanding of their research. Therefore, it is crucial to find a safe and effective alternative therapy.

[0006] A free meniscus in the joint cavity is a design concept in the current development of artificial meniscus prostheses, which refers to a meniscus prosthesis that allows a certain degree of free movement, rather than strictly fixing the implant to the tibia surface. The design of this prosthesis simulates part of the natural movement function of the meniscus in the human knee joint, and is mainly used to reduce stress concentration between the prosthesis and the knee joint bone and maintain the flexibility of the joint function. The advantage of a free meniscus artificial prosthesis is that it is closer to the function of a natural knee joint and is suitable for patients who require flexible movement. However, the design of this prosthesis is also accompanied by the risk of prosthesis instability and excessive movement, which requires full evaluation and optimization during research and development and clinical use.

[0007] In addition, the structure of sheep's knee joints is highly similar to that of humans, especially in terms of the anatomical morphology and biomechanical function of the meniscus. The weight of sheep and the load on the knee joint are close to those of humans, which can simulate the load conditions of the human knee joint during activities such as walking and running, making it easier to study the injury and repair process of the knee meniscus. The sheep model is easy to design and operate experiments, and a meniscus injury or degeneration model can be created using precise methods to test the effects of new meniscus prostheses, tissue engineering scaffolds, or regenerative medicine technologies. This allows researchers to better simulate the function of the human meniscus, evaluate the effectiveness of various treatments or prostheses, and help improve the reproducibility and comparability of research. Summary of the invention

[0008] In view of this, the technical problem to be solved by the present invention is to provide a method for designing a bionic medial meniscus prosthesis of a sheep knee joint. The bionic medial meniscus prosthesis of the knee joint designed by this method can fully or partially replace the function of the original meniscus after implantation to restore the functional level of the knee joint.

[0009] The present invention provides a design method for a sheep knee joint medial bionic meniscus prosthesis, comprising the following steps:

[0010] S1) Establishment of a three-dimensional model of the knee joint: obtaining image data of the knee joint of an animal and importing the image data into a three-dimensional reconstruction software to obtain a three-dimensional model of the knee joint;

[0011] S2) Design of medial knee bionic meniscus prosthesis: Based on the three-dimensional morphology of the medial knee joint compartment of the animal body without cartilage and meniscus, the bionic meniscus prosthesis is designed by software to obtain the structural parameters of the medial bionic meniscus prosthesis;

[0012] S3) Preparation of medial bionic meniscus prosthesis of knee joint: According to the structural parameters of the medial bionic meniscus prosthesis, the medial bionic meniscus prosthesis of knee joint is prepared by using polymer materials.

[0013] Preferably, in step S1), the knee joint image data of the animal is obtained by CT scanning.

[0014] Preferably, after the image is imported into the three-dimensional reconstruction software in step S1), the image is threshold segmented, and the part to be further edited is manually selected, and redundant pixels are deleted. Then, the range of the rectangular frame in the image is adjusted in the coronal view, sagittal view and axial view to wrap all layers of the knee joint image, so as to obtain a three-dimensional model of the knee joint.

[0015] Preferably, the threshold segmentation range is 150-1500.

[0016] Preferably, the three-dimensional reconstruction software is Mimics medical imaging three-dimensional reconstruction software;

[0017] In the step S2), the bionic meniscus prosthesis is designed by using Mimics software.

[0018] Preferably, the step S2) is specifically as follows: based on the three-dimensional morphology of the medial knee joint compartment of the animal body that does not contain cartilage and meniscus, a bionic meniscus prosthesis is designed in Mimics software with reference to the geometric contour of the medial knee joint compartment to obtain the structural parameters of the medial bionic meniscus prosthesis.

[0019] Preferably, the step S2) further comprises: selecting a plurality of animals with similar weights to repeat the steps S1) and S2), averaging the structural parameters of the obtained medial bionic meniscus prosthesis, and obtaining the structural parameters of the medial bionic meniscus prosthesis of the knee joint to be prepared.

[0020] Preferably, the polymer material is selected from ultra-high molecular weight polyethylene.

[0021] Preferably, the method for preparing the medial knee joint bionic meniscus prosthesis in step S3) is specifically as follows:

[0022] A1) cutting the ultra-high molecular weight polyethylene;

[0023] A2) processing and shaping the surface of the cut ultra-high molecular weight polyethylene;

[0024] A3) finely carving the processed ultra-high molecular weight polyethylene;

[0025] A4) Cleaning and sterilizing the ultra-high molecular weight polyethylene after fine carving to obtain a medial knee joint bionic meniscus prosthesis.

[0026] Preferably, the method for preparing the medial bionic meniscus prosthesis of the knee joint in step S3) is 3D printing.

[0027] The present invention provides a method for designing a bionic meniscus prosthesis of a sheep's knee joint medial side, comprising the following steps: S1) establishing a three-dimensional model of the knee joint: acquiring knee joint image data of an animal body, and importing the data into three-dimensional reconstruction software to obtain a three-dimensional model of the knee joint; S2) designing a bionic meniscus prosthesis of the knee joint medial side: based on the three-dimensional morphology of the animal body's medial knee joint compartment that does not contain cartilage and meniscus, designing a bionic meniscus prosthesis through software to obtain structural parameters of the bionic meniscus prosthesis of the knee joint medial side; S3) preparing a bionic meniscus prosthesis of the knee joint medial side: preparing a bionic meniscus prosthesis of the knee joint medial side by using a polymer material according to the structural parameters of the bionic meniscus prosthesis of the knee joint medial side. Compared with the prior art, the medial knee joint bionic meniscus prosthesis designed and prepared by the present invention serves as a synthetic, non-absorbable total meniscus substitute, and is implanted in the sheep knee joint in a free, non-fixed manner. It can treat severe meniscus injuries that cannot be repaired by meniscectomy or meniscus suture, and can overcome the shortcomings associated with the use of meniscus allografts. After implantation, the knee joint meniscus prosthesis can fully or partially replace the function of the original meniscus to restore the functional level of the knee joint. Moreover, the present invention can also be combined with 3D bioprinting technology to produce 3D living tissue equivalents with the desired shape and structure to reproduce the complexity of human tissue. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a range diagram of the threshold segmentation in Embodiment 1 of the present invention;

[0029] Figure 2 is a range diagram of the threshold segmentation in Embodiment 1 of the present invention;

[0030] Figure 3 This is a detailed information diagram of the high molecular weight polyethylene used in Example 1 of the present invention;

[0031] Figure 4 This is a detailed information diagram of the high molecular weight polyethylene used in Example 1 of the present invention;

[0032] Figure 5 This is a schematic diagram of the technical process for preparing the bionic polymer polyethylene meniscus prosthesis for the medial side of the sheep knee joint in Example 1 of the present invention;

[0033] Figure 6 This is a photo of the sheep medial knee compartment bionic meniscus prosthesis in Example 1 of the present invention;

[0034] Figure 7 This is a photo of the complete removal of the medial meniscus in Example 1 of the present invention;

[0035] Figure 8 This is a photo of the sheep medial meniscus removed in Example 1 of the present invention;

[0036] Fig. 9 This is a photo of the scraper removing the femoral condyle and tibial plateau cartilage in the medial compartment in Example 1 of the present invention;

[0037] Fig.10 The three-dimensional model and medial compartment diagram of the sheep knee joint in Example 1 of the present invention;

[0038] Fig.11 This is a model diagram of the sheep bionic meniscus prosthesis initially designed in Example 1 of the present invention;

[0039] Fig.12 This is a model diagram of the improved sheep bionic meniscus prosthesis in Example 1 of the present invention;

[0040] Fig.13 This is a model diagram of a good position of the sheep bionic medial meniscus prosthesis in the knee joint in Example 1 of the present invention;

[0041] Fig.14 The design diagram and structural parameter diagram of the bionic meniscus prosthesis in Example 1 of the present invention;

[0042] Fig.15 This is a photograph of the prosthesis position under 30° flexion of the knee joint in Example 1 of the present invention;

[0043] Fig.16 This is a photograph of the prosthesis position at 60° flexion of the knee joint in Example 1 of the present invention;

[0044] Fig.17 This is a photograph of the prosthesis position under 90° flexion of the knee joint in Example 1 of the present invention;

[0045] Fig.18 This is a scanned image of the prosthesis position when the knee joint is flexed 120° in Example 1 of the present invention;

[0046] Fig.19 This is a scan of the position of the meniscus prosthesis at 30° flexion of the knee joint in Example 1 of the present invention;

[0047] Fig. 20 This is a scanned image of the position of the meniscus prosthesis at 60° flexion of the knee joint in Example 1 of the present invention;

[0048] Fig.21 This is a scanned image of the position of the meniscus prosthesis at 90° flexion of the knee joint in Example 1 of the present invention;

[0049] Fig. 22 This is a scan of the position of the meniscus prosthesis at 120° flexion of the knee joint in Example 1 of the present invention;

[0050] Fig.23 This is a graph showing the activity test results of sheep in each group one week after modeling in Example 1 of the present invention;

[0051] Fig.24 This is a graph showing the activity test results of sheep in each group 4 weeks after modeling in Example 1 of the present invention;

[0052] Fig.25 This is a graph showing the activity test results of sheep in each group 20 weeks after modeling in Example 1 of the present invention;

[0053] Fig.26 This is a graph showing the activity test results of each group of sheep before prosthesis implantation in Example 1 of the present invention;

[0054] Fig. 27 This is a representative image of the passive range of motion of the knee joint of the sheep in the prosthesis implantation group 12 weeks after implantation in Example 1 of the present invention;

[0055] Fig.28 Representative anteroposterior and lateral X-ray images of the knee joints of sheep in the prosthesis group in Example 1 of the present invention;

[0056] Fig.29 Representative anteroposterior and lateral X-ray images of the knee joints of sheep in the OA group in Example 1 of the present invention;

[0057] Fig.30 The representative anteroposterior and lateral X-ray images of the knee joints of the sheep in the blank control group in Example 1 of the present invention;

[0058] Fig.31 This is a representative MRI image of the knee joint of the sheep in the prosthesis group in Example 1 of the present invention;

[0059] Fig.32 This is a representative MRI image of the knee joint of sheep in the OA group in Example 1 of the present invention;

[0060] Fig.33 This is a representative nuclear magnetic resonance image of the knee joint of sheep in the blank control group in Example 1 of the present invention;

[0061] Fig.34 This is a macroscopic image of the medial femoral condyle and medial meniscus of a sheep in the prosthesis group in Example 1 of the present invention (the arrow indicates the location of cartilage wear);

[0062] Fig.35 This is a macroscopic image of the medial femoral condyle and medial meniscus of sheep in the OA group in Example 1 of the present invention (the arrow indicates the location of cartilage wear);

[0063] Fig.36 The macroscopic image of the medial femoral condyle and medial meniscus of sheep in the blank control group in Example 1 of the present invention;

[0064] Fig.37 This is a front view of the meniscus prosthesis in Example 1 of the present invention after 12 weeks of implantation;

[0065] Fig.38 This is a back view of the meniscus prosthesis in Example 1 of the present invention after being implanted for 12 weeks. DETAILED DESCRIPTION

[0066] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0067] The present invention provides a method for designing a bionic meniscus prosthesis of a sheep's knee joint medial side, comprising the following steps: S1) establishing a three-dimensional model of the knee joint: acquiring knee joint image data of an animal body, and importing the data into three-dimensional reconstruction software to obtain a three-dimensional model of the knee joint; S2) designing a bionic meniscus prosthesis of the knee joint medial side: based on the three-dimensional morphology of the animal body's medial knee joint compartment that does not contain cartilage and meniscus, designing a bionic meniscus prosthesis through software to obtain structural parameters of the bionic meniscus prosthesis of the knee joint medial side; S3) preparing a bionic meniscus prosthesis of the knee joint medial side: preparing a bionic meniscus prosthesis of the knee joint medial side by using a polymer material according to the structural parameters of the bionic meniscus prosthesis of the knee joint medial side.

[0068] The present invention has no particular limitation on the sources of all raw materials, and any commercially available raw materials may be used.

[0069] First, the image data of the knee joint of an animal is obtained and imported into a three-dimensional reconstruction software to obtain a three-dimensional model of the knee joint. The animal body can be any animal body familiar to those skilled in the art without any special limitation. In the embodiments provided in the present invention, sheep are specifically used as an example. The knee joint structure of sheep is closer to that of humans, and the joint compartment is more obvious. Using sheep as the experimental animal model can meet the high standard experimental requirements of the project for the anatomical structure of the knee joint; the knee joint image data of the animal body can be obtained according to the method well known to those skilled in the art, without special restrictions. In the present invention, the knee joint image data of the animal body is preferably obtained by CT scanning; the knee joint image data of the animal body obtained is preferably stored in DICOM format and imported into the three-dimensional reconstruction software; the three-dimensional reconstruction software is preferably Mimics medical imaging three-dimensional reconstruction software, and more preferably Mimics 17.0 medical imaging three-dimensional reconstruction software; further specifically, in the process of importing the three-dimensional reconstruction software, the correct orientation of up and down, front and back, and left and right is marked as required to ensure that the reconstructed three-dimensional orientation is consistent with the coordinate axis of the animal body, and the import is completed; further specifically, after importing into the three-dimensional reconstruction software, the image is threshold segmented, and the further edited part is manually selected, the redundant pixels are deleted, and then the range of the rectangular frame in the image is adjusted in the coronal image, the sagittal image, and the axial image. After all layers of the knee joint image are wrapped, a three-dimensional model of the knee joint is obtained. Threshold segmentation is to define the target object by selecting a gray value within a certain range, and the image area of ​​the gray value in this range will be extracted. Therefore, setting an accurate threshold is the key to tissue extraction. In the project, because it is necessary to establish a three-dimensional model of the knee joint with higher accuracy, the threshold analysis is changed during the image segmentation process to make the threshold setting more accurate, thereby ensuring the accuracy of the model. In the present invention, the range of the threshold segmentation is preferably 150 to 1500; more specifically, after all layers of the knee joint image are wrapped by adjusting the range of the rectangular frame in the image in the coronal, sagittal and axial views, the three-dimensional reconstruction software will calculate and generate a three-dimensional simulation model of the knee joint based on the templates of the femur and tibia, but the initially established model is relatively rough, so it is preferred to smooth the established three-dimensional model to obtain a smooth three-dimensional model of the knee joint.

[0070] Based on the three-dimensional morphology of the medial knee joint compartment of an animal body that does not contain cartilage and meniscus, a bionic meniscus prosthesis is designed through software to obtain the structural parameters of the medial bionic meniscus prosthesis; specifically, based on the three-dimensional morphology of the medial knee joint compartment of an animal body that does not contain cartilage and meniscus, a bionic meniscus prosthesis is designed in Mimics software with reference to the geometric contour of the medial knee joint compartment to obtain the structural parameters of the medial bionic meniscus prosthesis; in the present invention, the structural parameters of the medial bionic meniscus prosthesis are preferably saved in ".stl" format.

[0071] In order to improve the accuracy of the structural parameters of the obtained medial bionic meniscus prosthesis, it is preferred to further include selecting multiple animal bodies with similar weights to repeat steps S1) and S2), taking the average value of the structural parameters of the obtained medial bionic meniscus prosthesis, and obtaining the structural parameters of the medial bionic meniscus prosthesis of the knee joint to be prepared; the number of the multiple animal bodies with similar weights is preferably 2 to 4.

[0072] A medial bionic meniscus prosthesis of the knee joint is prepared by using polymer materials according to the structural parameters of the medial bionic meniscus prosthesis; the polymer material is preferably ultra-high molecular weight polyethylene, and its molecular weight is preferably above one million; the method for preparing the medial bionic meniscus prosthesis of the knee joint is preferably 3D printing or mechanical processing; the mechanical processing method is preferably specifically as follows: A1) cutting the ultra-high molecular weight polyethylene; A2) processing and shaping the surface of the cut ultra-high molecular weight polyethylene; A3) finely carving the processed and shaped ultra-high molecular weight polyethylene; A4) cleaning and sterilizing the finely carved ultra-high molecular weight polyethylene to obtain the medial bionic meniscus prosthesis of the knee joint. In the present invention, in the step A1), the cutting is preferably carried out by a sawing machine, and more preferably by a circular sawing machine; in the step A2), the surface of the cut ultra-high molecular weight polyethylene is preferably heated and formed by a milling machine; in the step A3), the ultra-high molecular weight polyethylene after processing and forming is preferably finely engraved by a fine engraving machine; quality inspection is preferably performed after fine engraving; laser engraving is preferably performed after quality inspection; in the step A4), the ultra-high molecular weight polyethylene after fine engraving is preferably cleaned by an ultrasonic cleaning machine; the sterilization treatment is preferably sterilized by γ-ray irradiation; final inspection is preferably performed after sterilization treatment; the specific steps of the final inspection are: the quality inspector inspects the appearance and packaging of the product.

[0073] The medial bionic meniscus prosthesis of the knee joint designed and prepared by the present invention serves as a synthetic, non-absorbable total meniscus substitute and is implanted in a sheep knee joint in a free, non-fixed manner, and can treat severe meniscus injuries that cannot be repaired by meniscectomy or meniscus suture, and can overcome the shortcomings associated with the use of meniscus allografts. After implantation, the knee joint meniscus prosthesis can fully or partially replace the function of the original meniscus to restore the functional level of the knee joint. Moreover, the present invention can also be combined with 3D bioprinting technology to produce 3D living tissue equivalents with the desired shape and structure to reproduce the complexity of human tissue.

[0074] In order to further illustrate the present invention, a design method of a bionic meniscus prosthesis of a sheep knee joint provided by the present invention is described in detail below in conjunction with an embodiment.

[0075] The reagents used in the following examples are all commercially available.

[0076] Example 1

[0077] 1.1 Experimental methods

[0078] 1.1.1 Establishment of the three-dimensional model of sheep knee joint

[0079] The hind limbs of healthy and intact 12-month-old sheep were selected for precise CT scanning, and the CT images stored in DICOM format were imported into Mimics 17.0 medical imaging 3D reconstruction software. During the import process, the correct orientation of up and down, front and back, and left and right was marked as required to ensure that the reconstructed 3D orientation was consistent with the sheep's coordinate axis, and then the import was completed.

[0080] Threshold segmentation is to define the target object by selecting a grayscale value within a certain range. The image area with grayscale values ​​in this range will be extracted. Therefore, setting an accurate threshold is the key to tissue extraction. In the project, because it is necessary to establish a three-dimensional model of the knee joint with high accuracy, the threshold analysis is modified during the image segmentation process to make the threshold setting more accurate, thereby ensuring the accuracy of the model. The present invention selects the range of threshold segmentation to be 150 to 1500. In this range, the complete bone grayscale value can be selected and the interference of other tissue grayscale values ​​can be excluded. Figure 1 and Figure 2 shown.

[0081] After threshold segmentation, manually select the part you want to edit further and delete its redundant pixels. Adjust the range of the rectangular frame in the image in the coronal, sagittal and axial views. After all layers of the knee CT are wrapped, Mimics will calculate and generate a 3D simulation model of the knee based on the templates of the femur and tibia. However, the initially established model is relatively rough, so the established 3D model is selected for smoothing to obtain a smooth 3D model of the knee.

[0082] 1.1.2 Design of the bionic meniscus prosthesis of the sheep knee joint

[0083] Based on the three-dimensional morphology of the medial knee compartment of the left lower limb of sheep without cartilage and meniscus, the bionic meniscus prosthesis was designed using Mimics software. The meniscus prosthesis model was designed in Mimics with reference to the geometric contour of the medial compartment, and finally the models of each part were saved in ".stl" format.

[0084] 1.1.3 Structural parameters of the medial bionic meniscus prosthesis

[0085] Three 12-month-old sheep hind limbs of similar weight were selected for precise CT scanning. After the knee joint was established using Mimics software, the same design method of the medial bionic meniscus prosthesis was adopted to obtain the structural parameters of the medial bionic meniscus prosthesis and take the average value.

[0086] 1.1.4 Preparation of medial bionic meniscus prosthesis

[0087] Select high molecular weight polyethylene (Purchasing manufacturer: Suzhou Aoshike Medical Equipment Co., Ltd., domestic standard: GB / T19701.2-2016, specific information such as Figure 3 and Figure 4 As shown in Figure 2, the raw materials for the prosthesis were selected and Beijing Chunli Zhengda Medical Instrument Co., Ltd. was commissioned to prepare the sheep medial knee compartment bionic meniscus prosthesis. The technical process of prosthesis preparation is as follows: Figure 5 The designed sheep medial knee compartment bionic meniscus prosthesis is shown in Figure 6 shown.

[0088] 1.1.5 Stability analysis of the medial bionic meniscus prosthesis

[0089] A 12-month-old sheep knee specimen was selected. The joint capsule was opened through the anteromedial approach, the medial meniscus was removed, and the excess cartilage was scraped off with a spatula to simulate the pathological anatomical structure of medial compartment OA. After the medial collateral ligament was severed, a meniscus prosthesis was implanted. After the bionic meniscus was implanted, high-resolution MRI plain scans were performed at 30°, 60°, 90°, and 120° knee flexion.

[0090] 1.1.6 Establishment of sheep medial meniscus injury and osteoarthritis model

[0091] This study used the classic medial meniscectomy-induced sheep osteoarthritis model. The sheep were randomly divided into three groups, namely the prosthesis implantation group, the meniscectomy group and the sham operation group, with 3 sheep in each group. Figures 7 to 9 As shown: The sheep were weighed and anesthetized intravenously with antacid. The left knee joint was prepared and disinfected with iodine. The skin was incised along the medial patellar approach to expose the joint capsule. The medial meniscus was completely removed, and part of the cartilage was scraped off with a spatula, and then the incision was sutured layer by layer. The sheep in the sham operation group only exposed the joint capsule and then sutured. Within one week after surgery, penicillin (30,000 units / kg body weight) was injected intramuscularly every day to prevent incision infection. The activity of the sheep was tested at the first week after surgery, the fourth week after surgery, and the 20th week after surgery (before prosthesis implantation). Briefly, the sheep were introduced into an open area and waited for 30 minutes to fully adapt to the venue. The sheep were then driven to quickly pass through a 200-meter straight and narrow passage, and the time it took for the sheep to pass was accurately recorded. Each sheep was tested three times, with a 10-minute interval between each test, and the average of the three tests was taken as its final running speed.

[0092] 1.1.7 Implantation of sheep medial compartment meniscus prosthesis and evaluation of the progression of osteoarthritis after surgery

[0093] The sheep were weighed and anesthetized intravenously with antacid. The hair around the left knee joint of the sheep was completely shaved. After disinfection with iodine, the skin was incised along the medial approach of the patella to expose the joint capsule. Subsequently, the joint capsule was incised and the medial collateral ligament was transected to fully expose the medial compartment of the knee joint. The medial compartment of the sheep in the prosthesis implantation group was fully cleaned, the knee joint was everted and the meniscus prosthesis was implanted. After the knee joint was fully flexed and extended to ensure the stability of the prosthesis, the medial collateral ligament was repaired with ligament sutures and the incision was sutured layer by layer. The sham operation group and the meniscectomy group were the same except for the steps related to the meniscus prosthesis implantation. Within one week after surgery, penicillin (30,000 units / kg body weight) was injected intramuscularly every day to prevent incision infection. After 12 weeks of prosthesis implantation, the activity of the sheep in each group was tested as described above, and the passive flexion and extension range of motion of the knee joint of the sheep was recorded. Finally, the sheep were euthanized by intravenous injection of sodium pentobarbital (90 mg / kg). The sheep's stifle joints were scanned using a DR direct digital X-ray camera system and a magnetic resonance imaging (MRI) within 3 hours after sacrifice.

[0094] 1.2 Experimental Results

[0095] 1.2.1 Three-dimensional model of sheep knee joint

[0096] like Fig.10 As shown in the figure, unlike small mammals such as SD rats and Japanese white rabbits, the sheep's knee joint structure is closer to that of humans, and the joint compartments are more obvious. Using sheep as an experimental animal model can meet the high standard experimental requirements of the project for the anatomical structure of the knee joint.

[0097] 1.2.2 Sheep medial meniscus prosthesis

[0098] The lower edge of the anterior horn of the medial bionic meniscus prosthesis in the initial design extended too far forward, which limited the knee joint movement to a certain extent, and the upper edge of the anterior horn was retained too much, invading the trochlear groove and limiting the patellar movement. Fig.11 Therefore, the meniscus prosthesis was further improved to meet the flexion conditions of the sheep knee joint when walking and jumping.

[0099] The improved medial bionic meniscus prosthesis is of moderate size, with the redundant anterior and posterior angles removed and the edges smooth and neat, in order to meet the normal flexion conditions of the knee joint, such as Fig.12 shown.

[0100] The three-dimensional reconstruction showed that the medial bionic meniscus prosthesis remained in the appropriate position in the anteroposterior, posterior, left and right positions of the knee joint, such as Fig.13 shown.

[0101] 1.2.3 Structural parameters of the medial bionic meniscus prosthesis

[0102] The average length of the medial bionic meniscus prosthesis was 21.0 mm, the average width was 17.4 mm, the average maximum height was 11.0 mm, and the minimum thickness at the center of the prosthesis was 1.8 mm. Fig.14 shown.

[0103] 1.2.4 Stability analysis of the medial bionic meniscus prosthesis based on sheep knee joint specimens

[0104] After the sheep medial knee compartment bionic meniscus prosthesis made of high molecular weight polyethylene material was implanted into the sheep cadaver joint specimen, it was found to be well positioned. In addition, in the absence of medial collateral ligament protection, the meniscus prosthesis free in the medial compartment of the knee joint had good stability when the knee was flexed at 30°, 60°, 90° and 120°. Figures 15 to 18 shown.

[0105] When the knee joint was kept in 30°, 60°, 90° and 120° flexion, the high-resolution MRI scan showed that the bionic meniscus maintained good stability at all angles, and no deformation or dislocation of the meniscus prosthesis was observed. Figures 19 to 22 .

[0106] 1.2.5 Evaluation of osteoarthritis progression after ovine medial meniscus prosthesis implantation

[0107] like Figures 23-26 As shown in the figure, an osteoarthritis model was successfully established by medial meniscus resection and cartilage scraping. At various times before meniscus prosthesis implantation, the running ability of sheep in the sham operation group was better than that of the other two groups that had undergone meniscus resection and cartilage scraping. At 12 weeks after prosthesis implantation, the running ability of sheep in the prosthesis implantation group was improved and reached a level similar to that of the sham operation group. In addition, the passive motion ability of the knee joint of sheep after prosthesis implantation was also tested. Fig. 27 The status of the sheep knee joint at different flexion angles was demonstrated, and no signs of knee jamming, clicking, or meniscus prosthesis dislocation were observed or touched.

[0108] like Figures 28-30 As shown in the figure, compared with the meniscectomy group (OA group), the prosthesis group maintained a good knee joint space and restored the mechanical alignment well.

[0109] In addition, if Figures 31-33 As shown, in the midsagittal and coronal planes, MRI showed that the consistency between the implant angle and the tibiofemoral cartilage was similar to that observed in the native meniscus of the sham group. The contact between the cartilage and the meniscus prosthesis was good, and the overall shape of the prosthesis was well maintained. The meniscus prosthesis did not shift significantly compared to the initial placement. Unfortunately, due to individual differences in sheep, the size match of the implanted meniscus prosthesis to the femoral condyle seems to be less than ideal.

[0110] After incision of the joint capsule, the consistency and color of the synovial fluid in all knee joints were normal.

[0111] There was no significant difference in the macroscopic appearance of the synovium in the prosthesis implantation group compared with the sham surgery group. Figures 34-36 As shown, in both the implant and meniscectomy groups, fibrous tissue developed along the entire circumference of the medial tibial plateau, whereas fibrous tissue formation in the sham group was limited to the area around the repaired medial collateral ligament. The fibrous tissue ingrowth from the joint capsule resulted in circumferential fixation of the meniscal prosthesis, which stabilized the meniscal prosthesis to the tibial plateau. In addition, compared with the meniscectomy group, the cartilage wear on the sheep femoral condyle was regenerated to a certain extent after implantation.

[0112] There is a concern that for high molecular weight polyethylene implants, the polyethylene debris from wear may cause abnormal biological responses, leading to serious complications such as osteolysis. Figures 37-38 As shown in the figure, the front and back of the meniscus prosthesis remained smooth after 12 weeks of implantation, and no obvious surface wear was observed. At the same time, no femoral and tibial osteolysis caused by polyethylene wear particles was found in the MRI imaging data.

[0113] It can be seen that the medial bionic meniscus prosthesis of the knee joint designed by the present invention not only has a low incidence of complications and reoperations in terms of knee joint function and pain, but can also treat severe meniscus injuries that cannot be repaired by meniscectomy or meniscus suture, and can overcome the shortcomings associated with the use of meniscus allografts.

[0114] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A design method for a sheep knee joint medial bionic meniscus prosthesis, characterized in that: The following steps are involved: S1) Establishment of a three-dimensional model of the knee joint: obtaining image data of the knee joint of an animal and importing the image data into a three-dimensional reconstruction software to obtain a three-dimensional model of the knee joint; S2) Design of medial knee joint bionic meniscus prosthesis: Based on the three-dimensional morphology of the medial knee joint compartment of the animal body without cartilage and meniscus, the bionic meniscus prosthesis is designed by software to obtain the structural parameters of the medial bionic meniscus prosthesis; S3) Preparation of medial bionic meniscus prosthesis of knee joint: According to the structural parameters of the medial bionic meniscus prosthesis, the medial bionic meniscus prosthesis of knee joint is prepared by using polymer materials.

2. The design method according to claim 1, characterized in that: In the step S1), the knee joint image data of the animal is obtained by CT scanning.

3. The design method according to claim 1, characterized in that: After the image is imported into the three-dimensional reconstruction software in step S1), the image is threshold segmented, and the part to be further edited is manually selected, and redundant pixels are deleted. Then, the range of the rectangular frame in the image is adjusted in the coronal view, sagittal view and axial view to wrap all layers of the knee joint image, so as to obtain a three-dimensional model of the knee joint.

4. The design method according to claim 3, characterized in that: The range of the threshold segmentation is 150-1500.

5. The design method according to claim 1, characterized in that: The three-dimensional reconstruction software is Mimics medical imaging three-dimensional reconstruction software; In the step S2), the bionic meniscus prosthesis is designed by using Mimics software.

6. The design method according to claim 1, characterized in that: The step S2) is specifically as follows: based on the three-dimensional morphology of the medial knee joint compartment of the animal body that does not contain cartilage and meniscus, a bionic meniscus prosthesis is designed in Mimics software with reference to the geometric contour of the medial knee joint compartment to obtain the structural parameters of the medial bionic meniscus prosthesis.

7. The design method according to claim 1, characterized in that: The step S2) also includes: selecting multiple animals with similar weights to repeat the steps S1) and S2), taking the average value of the structural parameters of the obtained medial bionic meniscus prosthesis, and obtaining the structural parameters of the medial bionic meniscus prosthesis of the knee joint to be prepared.

8. The design method according to claim 1, characterized in that: The polymer material is selected from ultra-high molecular weight polyethylene.

9. The design method according to claim 8, characterized in that: The method for preparing the medial bionic meniscus prosthesis of the knee joint in step S3) is specifically as follows: A1) cutting the ultra-high molecular weight polyethylene; A2) processing and shaping the surface of the cut ultra-high molecular weight polyethylene; A3) finely carving the processed ultra-high molecular weight polyethylene; A4) Cleaning and sterilizing the ultra-high molecular weight polyethylene after fine carving to obtain a medial knee joint bionic meniscus prosthesis.

10. The design method according to claim 1, characterized in that: The method for preparing the medial bionic meniscus prosthesis of the knee joint in step S3) is 3D printing.

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