By Greer E. Noonburg, M.D.
The meniscus is a C-shaped fibrocartilage structure found within the knee. It functions as a shock-absorber, providing protection for the cartilage at the ends of the femur (thigh bone) and tibia (shin bone). A torn meniscus causes pain that can limit a person’s ability to participate in sports or even walking, depending on the extent of the damage. Meniscus tears are very common–over 750,000 patients undergo surgical treatment for their meniscal injuries annually. Orthopaedic surgeons commonly insert a small camera (arthroscope) into the knee joint to either repair or trim out the injured portion of the meniscus.
Unfortunately, loss of a significant portion of the meniscus will accelerate pressure on the articular cartilage at the ends of the femur and tibia. Over time, degenerative changes to the cartilage occur, causing pain (arthritis). The symptoms are commonly treated with non-steroidal pain medications, activity restrictions, and various types of injections with steroids or hyaluronate (called viscosupplementation). When the arthritis becomes severe, knee replacement may be the only option that will decrease the debilitating pain.
For active persons aged 55 years or younger, who have minimal meniscal tissue left due to arthroscopic removal, there is another possible treatment option: meniscus transplantation. Individuals who have pain after surgical removal of a substantial portion of their meniscus but have not yet developed significant arthritic changes in the cartilage, can benefit greatly from surgically transplanting a cadaver meniscus to alleviate their pain.
Meniscus transplant surgery is designed to restore the meniscal cushion that protects the knee cartilage. If the articular cartilage is already demonstrating osteoarthritic changes, it is probably too late for the procedure. Appropriately selected patients who undergo successful meniscus transplantation may participate in many physical activities with less discomfort due to restoration of the shock-absorbing meniscus. Despite its benefits, meniscal transplantation is an uncommon procedure due to the strict patient selection criteria, which include:
- Age 55 years or less
- Not obese
- Loss of 50 percent or more of the meniscus due to prior surgery or non-repairable meniscal damage
- Stable knee ligaments with minimal-to-no arthritis
- Activity-related pain
Before the surgery is performed, significant pre-operative planning is required. MRI (magnetic resonance imaging) of the knee will be required to assess the damaged meniscus, in addition to the rest of the knee’s structures to determine if there are other factors contributing to the patient’s knee pain. CT (computerized tomography) studies may be required to determine the correct meniscal graft size.
Meniscus allografts are obtained from young skeletally mature donors who match the recipient’s anatomy. It may take several weeks to find an appropriately sized meniscus for transplantation. The tissue is evaluated through a stringent process, which screens for bacteria, viruses, and contaminants. Orthopaedic bone, cartilage and soft tissue allografts are used on a daily basis in nearly every hospital in the country and have a very safe track record. The chances of acquiring an infection from allograft tissue are extremely rare. The meniscal allograft does not need to be a “tissue match” (like a liver or kidney transplant) because it does not contain live cells when it is placed in the recipient’s knee.
Meniscus transplantation is generally performed using an arthroscope, enabling the orthopaedic surgeon to see inside the knee through small incisions. The surgery is performed on an outpatient basis with the patient going home on the same day of the surgery, in most cases. Other knee problems, such as a torn ligament, may be corrected at the same surgery. The meniscus is inserted through a two to four inch incision and anchors to the tibia by one or two bone plugs attached to the meniscus allograft. The transplanted meniscus is then secured to the patient’s knee joint capsule using sutures inside the joint capsule.
After surgery, the patient is on crutches with a knee brace for four to six weeks to give the transplanted meniscus time to heal to the patient’s bone and joint capsule. Knee motion begins soon after surgery, but is limited to 0 – 90 degrees. Physical therapy is initiated within two weeks of the surgery. Most people can return to work in two to four weeks, however, jobs requiring active physical activity may take two to three months before returning. Sports participation should be addressed individually with your orthopaedic surgeon, but jumping activities and deep squatting should not begin before six months.
By six to twelve months after surgery, a complete release is given and the meniscus transplant recipient may resume their normal activities, including sports participation. A 75 to 85 percent success rate for meniscal transplant surgery has been described in clinical studies. Complications of meniscus transplantation are rare, but include knee stiffness, bleeding, infection, neurovascular injury, blood clots and incomplete meniscal allograft healing. Although meniscus transplantation has been performed for over a decade, the long-term benefits of meniscal transplantation in reducing cartilage wear are still being evaluated.
Meniscus transplantation may provide a significant improvement in pain and function in adults who have undergone surgical debridement of a large portion of their meniscal tissue but continue to have pain. The goal of mensicus transplant surgery is to restore the cushioning and stabilizing qualities of the meniscus to the knee.
Additional questions regarding meniscus transplantation may be answered by your orthopaedic surgeon or by contacting Dr. Noonburg at Chatham Orthopaedic Associates., 4425 Paulsen Street, Savannah, GA 31405, (912)355-6615