Matching the size of the donor knee to the size of the recipient knee is crucial for successful meniscus transplantation. Most surgeons accept that a mismatch of greater than 5-10% will lead to poor outcomes. Other variables associated with poor outcomes include axial malalignment, anterior cruciate ligament insufficiency, and the presence of significant arthritic changes such as femoral condylar flattening. Grade IV chondral lesions represent a relative contraindication, if not concurrently addressed with cartilage restoration techniques.
With meniscal allograft transplantation cell viability in the graft is not a major concern as the graft undergoes repopulation by the host, thus most grafts used today are fresh frozen, and this practice has not been found to affect outcomes.
Meniscal allograft processing, sterilization and storage procedures vary from center to center. Most American centers harvest the graft outside of a sterile operating room environment and then perform a sterilization wash. These grafts are then packaged and frozen at -80°C, until they are to be transplanted (fresh frozen sterilization technique). To decrease the risk of disease transmission, gamma irradiation the graft has been used in the past to enhance sterilization. However, it has been shown to degrade most collagen-based tissues and the meniscus is particularly susceptible. Tissue preservation techniques such as cryo-preservation and freeze-drying have shown little benefit and have generally been abandoned except by a few tissue banks.
Sekaran et al performed a cadaver study to look at whether nonanatomic meniscal transplant placement adversely affects the contact pressure distribution on the medial tibial plateau. They found placement in the nonanatomic posterior location caused a significant posterior shift in the centroid of contact area over all flexion angles.
Shaffer et al. designed a study to determine the accuracy of radiographic and magnetic resonance imaging techniques in preoperative sizing for allograft meniscus transplantation, as mismatch of less than a few millimeters is felt to be critical to success. They found plain radiographs and MRI to have similar reliability, with about 80% measuring within 5 mm of the actual value.
Answer 1: Axial malalignment leads to abnormal load sharing on the meniscus, and therefore must be addressed prior to or during transplantation.
Answer 2: ACL deficiency leads to instability that will lead to graft failure. ACL reconstuction must be performed prior to or at the time of meniscal transplantation.
Answer 4: Diffuse arthritic changes in the affected compartment is also considered a contraindication. Flattening of the femoral condyle on plain radiographs often indicates underlying osteoarthritis and also alters the loading of a meniscal graft and thus is generally a contraindication to transplantation.
Answer 5: Most authors have speculated that mismatch of greater than 5-10% has a negative effect.
Sekaran SV, Hull ML, Howell SM. Nonanatomic location of the posterior horn of a medial meniscal autograft implanted in a cadaveric knee adversely affects the pressure distribution on the tibial plateau. Am J Sports Med. 2002 Jan-Feb;30(1):74-82. PubMed PMID: 11799000.
PMID:11799000 (Link to Abstract)
Shaffer B, Kennedy S, Klimkiewicz J, Yao L. Preoperative sizing of meniscal allografts in meniscus transplantation. Am J Sports Med 2000;28:524-533
PMID:10921644 (Link to Abstract)