There are two menisci on each side of the knee called the medial meniscus and the lateral meniscus. When viewed from above, the meniscus is a crescent-shaped structure with its edges attached to the joint capsule. Its longitudinal section is wedge-shaped, with thick edges and a thin center, which fits the shape of the articular surface of the femoral condyle and tibial plateau and serves to deepen the knee joint. The meniscus has a very important function for the knee joint, transferring the body weight to the tibia and distributing the load evenly over the tibial plateau, stabilizing the knee joint, especially in knees with anterior cruciate ligament deficiency – the meniscus is the secondary stabilizing structure of the knee joint. The meniscus also has a lubricating, cushioning effect, absorbs energy from impact, and provides some proprioception. The evolution of meniscal surgery In the 1950s, doctors agreed that for meniscal injuries, the meniscus should be completely removed; at the time, it was believed that if the removal was not complete, there would be remnants of the meniscus that would lead to regeneration of the meniscus, which would create new problems. Subsequently, the important role of the meniscus was gradually recognized, and it was also known that osteoarthritis of the knee would develop 10-15 years after complete meniscectomy. As a result, partial meniscectomy has been increasingly adopted and many techniques have been developed to repair the meniscus with sutures. However, not all meniscal injuries are repairable. For unrepairable meniscus, partial or total meniscectomy must be performed. However, how should a young patient who has to undergo a total meniscectomy and has early signs of osteoarthritis and knee pain after surgery be managed? This question is a challenge for the clinician. In 1970C1980, Carl Wirth performed the first meniscus transplant in Germany. This was certainly a great joy for many young patients with total meniscectomy. Statistics from 2002 show that since 1991, more than 4000 allogeneic meniscus transplants have been performed worldwide, with about 800 cases per year. Currently, meniscal transplantation is becoming a mainstream option for the treatment of early joint pain and osteoarthritis after total meniscectomy. When is a meniscus transplant needed? 1. The patient is under 45 years of age. 2.Patients who have undergone total or major meniscectomy and have pain in the corresponding compartment of the knee joint with meniscal defect, and who have failed to undergo non-surgical treatment, may be considered for meniscal transplantation treatment. 3. For these patients, the “ideal situation” is one in which the lower extremity has a normal line of force, the knee is stable, and the knee is beginning to show early degenerative joint changes. However, most patients with meniscal injuries have other injuries present. Only about 20% of meniscus grafts are performed alone, and most of these patients also show some degree of chondral pathology. The remaining 80% of concomitant lesions require surgical treatment. The most common of these are ligament injuries (most commonly ACL, but also PCL, PLC or composite ligament injuries), force line abnormalities (medial compartment in internal knee rotation or lateral compartment in external knee rotation), and chondral lesions (simple Outerbridge degree IV injury with subchondral bone exposure). In these cases, it is necessary to perform the appropriate force line improvement or ligament reconstruction surgery along with the meniscal transplantation. 4. In patients with ACL deficiency, after ACL reconstruction, meniscal transplantation can further improve knee stability due to meniscal deficiency. Some patients do not obtain satisfactory stability after ACL reconstruction alone, and if meniscus transplantation is performed, better stability and better knee function can be obtained. 5. There are no obvious signs of osteoarthritis of the knee. When is meniscus transplantation no longer suitable? 1.The knee joint has shown obvious osteoarthritic changes: femoral condyles become flattened, joint gap becomes narrow or even disappears, tibial plateau shows degenerative depression 2.Lower limb force line is abnormal, knee inversion or valgus – before performing meniscus transplantation, force line correction surgery must be performed 3.Knee joint is unstable -should be treated accordingly before or at the same time as meniscus transplantation, such as ligament reconstruction surgery 4, knee fibrosis, reflex sympathetic dystrophy or severe pain symptoms 5, previous history of knee infection 6, excessive obesity 7, severe muscle atrophy of the lower extremity Patients should, before choosing meniscus transplantation surgery Before choosing meniscus transplantation, patients should have some understanding of this surgery. The current follow-up for meniscus transplantation has been more than ten years, and the clinical results are relatively satisfactory, whether meniscus transplantation can significantly relieve the pain in the corresponding joint space caused by meniscectomy. However, the long-term results of meniscal transplantation and whether the articular cartilage is protected are still unproven, and therefore, physicians are not able to provide a guarantee of long-term surgical success. Patients who are potentially at risk, who may need a meniscus transplant have abnormal lower extremity forces, who have valgus or inversion of the knee, and who have lost the lateral or medial meniscus, who have had a total meniscectomy, who have early signs of cartilage degeneration in the knee, and who need early treatment with a meniscus transplant to prevent further articular cartilage degeneration and osteoarthritis, who have had a lateral meniscectomy In young patients with meniscectomy – osteoarthritis of the knee may develop after 2-5 years and should be considered for meniscal transplantation (whereas the appearance of osteoarthritis after medial meniscectomy may occur after 10-20 years) In young patients with meniscectomy who have ruptured the ACL and present with early articular It is necessary to perform a meniscal transplant For young patients with meniscectomy, if the posterior cruciate ligament is absent and early articular cartilage changes are present, it is necessary to perform a meniscal transplant For those who are potentially at risk, what tests should be performed? Examine the knee in a 45° standing posterior anterior x-ray and measure the joint space Check for friction sounds in the medial and lateral compartments of the knee Check for pain in the medial and lateral compartments of the knee after exercise These tests should be performed at least once a year Is it safe to use an allograft meniscus? Can the transplantation procedure cause disease transmission? The meniscus used in the procedure is sourced from a tissue bank and each donor is screened for appropriate serology, including HIV, hepatitis (B and C), and syphilis. The meniscus grafts obtained are subjected to deep freezing and some are also sterilized by gamma irradiation. Although there is no guarantee that meniscus grafts will not cause disease transmission, the incidence of disease transmission after meniscus transplantation is very low at 1 in 8,000,000, making the use of allograft meniscus grafts very safe. Can rejection occur after meniscus transplantation? The meniscus is considered “immune immune” because the cells of the meniscus are encased in a dense matrix. Therefore, meniscus transplantation does not require as strict a tissue match as traditional organ transplantation and does not require long-term immunosuppression after surgery. Currently, there have been no cases of rejection after allogeneic meniscus transplantation. The purpose of meniscus transplantation: Arthroscopically assisted small incision surgical technique, most operations are performed outside the patient’s body, minimizing surgical side effects Functional knee exercises can be performed in the early postoperative period (but later for strenuous activities) to provide a new meniscus in the meniscectomized knee, which can absorb impact forces during knee activities and protect the articular cartilage Reduces the likelihood of future joint replacement or delays joint replacement surgery Meniscal surgery: Arthroscopic intra-articular debridement, trimming of residual meniscal edges, creation of a suitable environment for meniscal implantation Preparation of the meniscal graft (medial meniscus using the anterior-posterior meniscal bone pin technique, lateral meniscus using the Key-hole technique) Implantation of the meniscal graft into the The meniscus graft is implanted into the knee joint, the meniscus is fixed using the inside-out suture technique, and a small incision is made inside or outside the posterior knee joint to fix the bone block of the transplanted meniscus (medial meniscus is fixed with the bone pins of the anterior and posterior meniscus corners, and lateral meniscus is fixed with the bone block of the Key-hole) The rehabilitation plan after the meniscus transplantation is for the patient to carry out post-operative functional rehabilitation exercises in full accordance with the arrangements made by the surgeon and the rehabilitator, especially The post-operative weight-bearing requirements for the patient must be strictly adhered to, and the patient should receive some exercise advice to protect their “investment”. A knee brace is worn postoperatively to protect the knee joint for 6 weeks. Exercises for quadriceps and N-flexor strength, mainly straight leg raising, are started on postoperative day 1. Within the first week postoperatively, you can start walking with a crutch, but you should wear a knee brace for protection and not put any weight on the affected limb; in the third week postoperatively, you can start putting weight on the affected limb to the extent that the patient can tolerate it; after 4-6 weeks of full weight-bearing (off the crutch), the affected knee should return to full flexion and extension by 2-3 months postoperatively. After 6 months, you can gradually start to perform sports activities until you resume normal activities (running, squatting, lateral gliding, cross-stepping, etc.) You can perform long sitting work 1 – 2 weeks after surgery, and you can start to perform normal work 3 months after surgery. In many cases, meniscus transplantation is combined with other surgeries, therefore, the specific rehabilitation program is subject to the surgeon’s guidance.