A meniscal allograft is a real meniscus that has been obtained from a deceased donor. At this point in time, a real meniscus is still the best replacement for a missing meniscus (and better than any kind of artificial scaffold).
Meniscal allografts are obtained by specialist retrieval teams when the family of a patient, who has died from a non-infectious cause consents to them becoming a tissue donor. The donor is screened very carefully. If they are in a high risk category for potential infectious diseases or if there is any history of recent infection, the donor is excluded. The donor’s blood is also tested for all common bacteria, fungi and viruses (including HIV and Hepatitis). Positive results mean the donor tissue cannot be used. The donor tissue itself is then tested and, once again, if there are any positive results for any infectious organism, the tissue is not used. Tissue that successfully passes through the rigorous screening process is then sterilised and frozen.
Once processed, frozen and subsequently thawed for use, there are no living cells remaining within the meniscal allograft. The small amount of cellular material that is left is broken down and this sits within a dense matrix of collagen. Therefore, a meniscal allograft does not elicit an immune response, meaning that a person can receive a donor meniscus without the need for tissue typing, immunosuppressive medication or steroids. Furthermore, the donor tissue is not rejected, and it is referred to as ‘immunoprivileged’ tissue.
It is important is that the correct meniscus is implanted in the correct place (left vs right, medial vs lateral), and that the size of the donor meniscus correctly matches the size of the patient’s knee. Pre-operative X-rays with a size marker are obtained, and specific equations enable the
surgeon to calculate the dimensions of the donor meniscus that will be required. These dimensions are then compared to the measured dimensions of the available meniscal allografts that are stored at the tissue bank, to ensure the closest match possible is obtained.
The Human Tissue Authority (HTA) has strict quality and safety criteria, and the rules and regulations of the EU’s Tissue Act set extremely high standards for audit and quality control. All meniscal allograft tissue that is used in the UK (whether they are provided by a UK tissue bank such as NHS Blood Transfusion Tissue Services or from one of the various tissue banks in the U.S.A.) have to comply fully to these.