The meniscus is a disc-like chondral structure that is found between the femoral bone and the tibial bone and functions as a “shock absorber” in the continuous movements of the knee. Each knee has two menisci, a lateral and a medial. If meniscus damage is so severe that it cannot be repaired, it may need to be removed. However, without the presence of the meniscus as a “shock absorber” the risk of osteoarthritis in the knee increases.
For older patients with this condition, knee arthroplasty may be the appropriate solution. However, in the case of young and active patients under 55 years of age, another alternative treatment, such as meniscus transplant surgery, should be selected.
During meniscus transplant surgery, the already damaged and degenerated meniscus of the patient is replaced with donor cartilage tissue. Meniscus transplant surgery is not indicated for all patients. In the event of an advanced stage of knee arthritis, meniscus transplantation may not help. However, in a certain number of patients it can provide significant pain relief.
ANATOMY
The knee joint consists of three bones: the femur, the tibia and the patella. The last one lies in front of the knee joint providing, among other things, protection.
Between the femur and the tibia the menisci are found; two crescent-shaped cartilage structures that act as “shock absorbers”. In their shape and composition, the two menisci (medial and lateral) contribute to the smooth functioning of the knee by smoothing the joint surfaces and distributing loads more effectively.
DESCRIPTION
If the meniscus is severely injured or removed, the knee-protecting articular cartilage will begin to wear out more rapidly and the sliding between the femoral bone and the tibia will become painful. It is generally a pathological condition called degenerative osteoarthritis.
The purpose of meniscus transplantation is to replace the degenerated meniscus with donor cartilage, which relieves pain and delays osteoarthritis, although there are no long-term studies yet.
PREPARATION OF AN ALLOGRAFT
Healthy cadaveric tissue is obtained from a human donor and it gets frozen (allograft). After processing, it is thoroughly measured and stored. Proper measurement is one of the most important factors for the success of the transplantation. The exact size for the candidate will be selected during the transplant.
ALLOGRAFT SAFETY
Before selecting the donor, a screening procedure is performed. Once the donor is selected, the tissue undergoes several tests. Tissue safety is monitored by committees and official bodies and testing includes tests for viruses such as the West Nile virus, HIV / AIDS, hepatitis B and C as well as several micro-organisms.
SUITABILITY OF PATIENT
Although menisci have been transplanted for 20 years, it is still considered to be a relatively rare operation, partly due to the strict criteria that patients must meet for this procedure. Most people develop osteoarthritis of the knee after severe meniscus injuries. If the meniscus is worn too much, the meniscus transplant surgery is no longer useful.
The criteria for meniscus transplantation include:
- Patients under 55 years old and active
- Loss of half of the meniscus after injury or as a result of previous surgery.
- Severe and constant pain during activities
- Knee with stable ligaments
- No (or early) knee osteoarthritis
- Not obese
SURGICAL INTERVENTION
The meniscus transplant procedure is performed arthroscopically and the length of time the patient is hospitalized depends on the circumstances (from one to two days).
SURGERY
Knee arthroscopy is one of the most common surgeries. Through a very small incision a special micro-camera is inserted that provides a clear picture of the interior of the knee. Through some equally small incisions some special tools for surgery are introduced.
Typically, an allograft (cadaveric meniscus) is inserted through a 5 cm incision along with the very small incisions mentioned above and is stabilized by special sutures on the tibia.
SURGICAL COMPLICATIONS
The risk of complications in meniscal transplant surgery is very small. Stiffness, poor healing and integration are the most common complications. Other risks include bleeding, infection, as well as nerve and vessel injury.
The risk of donor tissue infection is very small, but real. There may be a double chance of someone being hit by a lightning bolt (1/800,000) rather than be infected by HIV/AIDS after a meniscus transplant (1/1,600,000).
RECOVERY
- The patient will need to wear a splint and use crutches during the first 4 to 6 weeks after surgery to allow the transplanted tissue to be integrated with the bone.
- Once pain and edema subsides, physiotherapy may begin. Special exercises restore the range of motion of the joint and its force.
- Part of the physiotherapy program focuses on the range of motion of the knee. Gentle stretching exercises improve flexibility of the joint and as the program progresses, strengthening exercises are added.
- Back to daily activities. Most patients are on sick leave for about 2 weeks. Depending on the type of work it may take 2 to 3 months for patients to return in manual work and long-hour standing. These are issues that are discussed with the treating physician. Freedom of movement (e.g. exercise) is usually permitted 6 to 12 months after surgery.
RESULTS
Many factors contribute to the success of a meniscus transplant and include:
- The condition of the knee prior to surgery
- The proper dimension of the allograft
- The allograft stitching technique
- Patient compliance and commitment to the rehabilitation program.
The results of studies on meniscus transplantation have not yielded excellent results. Overall, 21% to 55% of transplants fail within 10 years. Lateral meniscus transplants have higher success rates than medial meniscus transplants.
Synthetic menisci have also been tried out, but the results are controversial at the moment.
Meniscal transplantation is a useful treatment option, but not for all patients. Proper screening and adherence to treatment indications can offer significant help to young and active patients.
