MicroPort Orthopedics Launches China's First Domestically Developed Medial-Stabilized Total Knee Arthroplasty System

Recently, MicroPort Orthopedics, a subsidiary of Shanghai MicroPort Medical (Group) Co., Ltd. (hereinafter referred to as “MicroPort”), successively obtained registration certificates from the National Medical Products Administration for its Aspiration and SoSuperior internally stabilized total knee arthroplasty prostheses. This marks the first domestically produced, independently intellectual property-owned internally stabilized total knee replacement system approved for market launch in China. This product portfolio further enriches MicroPort Orthopedics’ domestic product line, providing more comprehensive total knee arthroplasty solutions for the vast number of Chinese patients suffering from degenerative knee diseases and other conditions. It addresses the long-standing challenge in knee arthroplasty of achieving both “stability” and “flexibility,” which have traditionally been mutually exclusive, while offering physicians a broader range of product options.

Degenerative knee joint disease, also known as knee osteoarthritis, is one of the most common and highly disabling conditions among the elderly. The incidence rate increases significantly with age; furthermore, factors such as obesity and long-term excessive running can accelerate knee joint wear and tear, leading to the onset of the disease. In China, the incidence rate among individuals aged 40–60 years is 10%–17%, surging to 50% in those over 60 years old, and reaching as high as 70% in those over 70 years old. Over the 20-year period from 1990 to 2010, the incidence of knee osteoarthritis in China increased by 45%, with its disability rate ranking second globally at 21.3%. Total Knee Arthroplasty (TKA) is the primary treatment for moderate to severe degenerative knee joint disease. Data indicates that the number of TKA procedures performed in China will reach 400,000 cases by 2020.

Improving patient satisfaction, accelerating postoperative recovery, and enabling patients to return to normal life as soon as possible are important challenges facing researchers in the field of artificial joints. For decades, researchers worldwide have continuously explored functional substitution for the anterior and posterior cruciate ligaments during surgery. The cruciate ligaments, comprising the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), are critical components of the knee joint. Frequent reports in sports news about athletes, particularly soccer players, requiring surgery or rest due to cruciate ligament injuries underscore their significant role in maintaining knee stability and motor function.The first generation of knee prostheses, known as "hinged knees," required resection of both the ACL and PCL, providing only flexion-extension movement and mechanical stability postoperatively, while failing to restore normal rotational function. Another design, the "posterior cruciate-retaining knee," emphasizes preserving PCL function; however, whether the PCL can be retained depends on individual patient conditions, leading to increased surgical difficulty and prolonged operative time. A study by Professor Bourne from the Department of Orthopedics at London Health Sciences Centre, Western University, Canada, indicated that nearly 20% of patients were dissatisfied with the outcomes of conventional total knee arthroplasty [1], primarily due to postoperative knee instability. Patients may experience a sensation of anterior subluxation and instability, especially when descending stairs, along with anterior knee pain and crepitus.Another type of prosthesis, termed the "posterior-stabilized knee," employs a cam-post mechanism to substitute for the PCL after resecting both cruciate ligaments. However, this approach requires more extensive bone resection, carries a relatively higher risk of prosthetic wear, and fails to resolve issues such as the sensation of subluxation when descending stairs, anterior knee pain, and crepitus. Currently, the latest "internally stabilized knee" prosthesis most closely mimics human physiological anatomy. After resecting both cruciate ligaments, it utilizes a specially designed insert to simultaneously replace the functions of the ACL and PCL. This design not only simplifies surgical procedures but also reconstructs the internal stability motion pattern of a normal knee joint.

The Aspiration and SoSuperior Cruciate-Retaining Total Knee Arthroplasty Systems, recently approved for market launch, feature MicroPort Orthopedics’ proprietary innovative highly biomimetic cruciate-retaining ball-and-socket articular surface design. The metallic components of the prosthesis (femoral condyles and tibial plateau) are made of cobalt-chromium-molybdenum alloy, while the highly biomimetic inserts are composed of ultra-high molecular weight polyethylene (UHMWPE). The safety of these materials has been validated through decades of clinical use, establishing them as mainstream choices in the knee prosthesis market. This cruciate-retaining total knee arthroplasty system not only provides greater range of motion and more reliable wear resistance but also restores normal kinematic mechanics of the knee joint and maintains stability during movement. As a result, postoperative kinematic characteristics and patient gait become more natural and flexible, allowing patients to virtually “forget” they have undergone knee replacement, thereby further enhancing patient satisfaction.

The Evolutionary History of Total Knee Arthroplasty Prostheses

The design philosophy of the “Internal Stability Knee” originates from MicroPort Orthopedics’ proprietary “Internal Axis Knee” (hereinafter referred to as the “Internal Axis Knee”) concept. Backed by over 20 years of successful clinical experience and extensive clinical follow-up data spanning 17 years, this design not only alleviates pain at the affected site but also significantly enhances postoperative patient satisfaction. This aligns with the directive in the “Opinions on Strengthening the Performance Appraisal of Tertiary Public Hospitals,” issued by the General Office of the State Council on January 30, 2019, which states that “patient satisfaction evaluation is one of the four indicators in the performance appraisal system for tertiary public hospitals.”

In 1998, the MicroPort Orthopedics medial pivot total knee arthroplasty system was launched in the United States. Clinical follow-up results over 17 years demonstrated an exceptionally high prosthetic survival rate (98.8%) and patient satisfaction rate (95%), with these findings published in the joint surgery journal *Knee*. George Macheras, Director of Orthopedics at KAT Hospital in Athens and the designer of this clinical follow-up study, is one of the earliest and most experienced experts globally in performing medial pivot knee surgeries. He stated that, as a form of "Fast Track Surgery," patients undergoing medial pivot knee arthroplasty could ambulate on the second postoperative day and be discharged within 3–4 days. Most followed-up patients regained the ability to engage in high-activity physical functions, such as mountain climbing and heavy manual labor. Notably, even obese patients weighing up to 100 kg reported high satisfaction with the surgical outcomes, which is quite remarkable. Another study published in the specialized journal *The Journal of Arthroplasty* indicated that, compared to traditional posterior-stabilized knee prostheses, patients receiving medial pivot knee prostheses achieved higher Forgotten Joint Score (FJS) ratings, making them more likely to "forget" that they had undergone total knee arthroplasty.

As one of the world’s most renowned knee prostheses, MicroPort Orthopedics’ medial pivot knee products have been implanted in over 600,000 cases globally in the more than 20 years since their market launch, dispelling the traditional belief that “patients cannot engage in high-intensity sports after undergoing knee replacement surgery.” In 2016, Mr. Terry Bradshaw, a prominent American athlete, four-time Super Bowl champion, and Pro Football Hall of Fame inductee, underwent total knee arthroplasty in the United States using MicroPort Orthopedics’ Evolution Medial Pivot Knee System. He expressed extreme satisfaction with the surgical outcomes as well as the postoperative stability and flexibility, voluntarily becoming a brand ambassador to personally demonstrate to patients the uniqueness and efficacy of the medial pivot knee system. In 2018, Houston Methodist Hospital in the United States performed total knee arthroplasties on two patients—Larry, a 77-year-old male, and Kelly, a 50-year-old female—using MicroPort Orthopedics’ medial pivot knee implants. Postoperatively, both patients were able to continue their passion for long-distance running and participated multiple times in local running competitions. Notably, 50-year-old Kelly has completed seven 5-kilometer races, one 10-kilometer race, and one mini-triathlon; while 77-year-old Larry participated in a 5-kilometer race just 13 months after surgery, securing second place in his age group.

Regarding the medial pivot kneeMedicineRegarding design and surgical key points, Professor Stephen Incavo of the Department of Orthopedic Surgery at the Academic Medical Institute of Weill Cornell Medicine in the United States stated: “The medial pivot knee demonstrates excellent clinical longevity. This may be attributed to its ability to maintain appropriate medial congruency, thereby providing anteroposterior stability of the knee joint, while allowing sufficient mobility on the lateral side, where greater knee motion occurs. This design prevents excessive sliding or restriction of the knee joint, enhancing range of motion while maintaining stability, thus leading to higher postoperative patient satisfaction. The bone-contact surface design of the medial pivot knee prosthesis also facilitates cement filling; its rough surface allows for effective penetration and bonding of bone cement, reducing the risk of loosening or detachment at the cement-prosthesis or cement-bone interfaces. The surgical technique for the medial pivot knee is simpler, lowering procedural difficulty and shortening operative time, enabling any surgeon proficient in total knee arthroplasty to master this procedure effectively.”

Professor Qu Tiebing, Director of the Joint Disease Diagnosis and Treatment Center at the China Rehabilitation Research Center and Beijing Bo'ai Hospital, Standing Committee Member of the Orthopaedic Branch of the Chinese Medical Association, Vice Chairman of the Knee Joint Professional Committee of the Orthopaedic Surgeons Branch of the Chinese Medical Doctor Association, and Deputy Leader of the Joint Surgery Group of the Orthopaedic Branch of the Chinese Medical Association, a renowned expert in joint surgery, stated: “Internal-stabilized knee prostheses combine stability with mobility, better meeting the physiological movement needs of the knee joint while providing enhanced stability. Historically, prosthetic stability and mobility have been contradictory; typically, greater stability compromises mobility, and vice versa. The internal-stabilized knee prosthesis excels in achieving an optimal balance between these two factors.”

Professor Wu Haishan, a renowned joint surgery expert who serves as a professor and chief physician at Shanghai Changzheng Hospital and Shanghai Ninth People’s Hospital affiliated with Shanghai Jiao Tong University, currently holds the positions of Head of the Chinese Knee Surgery Working Committee, Chairman of the Asia-Pacific Annual Conference on Joint Surgery, Standing Committee Member of the Orthopedic Surgeons Branch of the Chinese Medical Doctor Association, and Vice Chairman of the China Chapter of the Asia-Pacific Society for Artificial Joints. Professor Wu pointed out: “Compared with conventional knee prostheses, Medial-Stabilized (MS) knee prostheses feature more biomimetic designs that better align with the kinematics of knee movement. At last year’s COA conference, several major imported orthopedic companies successively launched related products. The ‘medial-pivot knee’ design originated from MicroPort, which has accumulated over 20 years of clinical experience. With the market launch of MicroPort’s domestically produced product, I believe it will bring greater benefits to patients across China.”

To match the domestically produced internal-stabilization total knee arthroplasty system recently approved for market launch, MicroPort Orthopedics’ China R&D team has designed a complete set of surgical instruments with fully independent intellectual property rights. These instruments incorporate technological innovations and design improvements tailored to clinical practice in China, better aligning with the surgical preferences of Chinese physicians, enhancing ease of use, and ensuring a smoother surgical procedure.

Weng Zixin, President of MicroPort Orthopedics (China), stated, “The approval of the first domestically produced total knee arthroplasty system signifies a further enhancement of MicroPort Orthopedics’ portfolio of Chinese-made joint products. We will continue to uphold MicroPort’s mission to ‘continuously innovate and provide physicians with genuine, superior, elegant, and affordable medical solutions that save and reshape patients’ lives or improve their quality of life.’ We remain committed to the research, development, and promotion of new orthopedic technologies, concepts, and products, ensuring that more patients in China have access to such genuine, superior, elegant, and affordable treatment solutions.”

Wang Gude, Chief Operating Officer of MicroPort, stated, “Stability and flexibility have always been a pair of contradictory elements in the development of knee prostheses, representing a goal that joint researchers worldwide have tirelessly pursued for years. At MicroPort Orthopedics, we are not content to merely remain at the level of ‘imitating Western products.’ As reflected in the name of one of the products in this system, ‘Aspiration’—which is one of our company’s eight core values—we strive to leverage our passion for self-improvement, knowledge-seeking, and courageous exploration. Our aim is to tailor more suitable treatment products and technologies for Eastern patients and physicians, conducting orthopedic innovation and R&D activities specifically localized for China. Following the approvals of Aspiration and SoSuperior, MicroPort Orthopedics will continue to introduce more locally innovative orthopedic products to benefit Chinese patients.”

References

[1] Bourne RB et al. “Patients satisfaction after total knee arthroplasty: who is satisfied and who is not?” ClinOrthopRelat Res, 2010.