Meniscal Cartilage Damage
Meniscal cartilage is an integral structural component of the human knee, functioning to absorb shocks and providing load sharing, joint stability, congruity, proprioception, and lubrication and nutrition of the cartilage surfaces. Total and partial meniscectomy frequently result in degenerative osteoarthritis. The integrity of the menisci is particularly important in knees in which the anterior cruciate ligament has been damaged. In these situations, the menisci act as secondary stabilizers of anteroposterior and varus-valgus translation.
Meniscal allograft transplantation (MAT) is considered a salvage procedure, reserved for individuals with disabling knee pain following meniscectomy who are considered too young to undergo total knee arthroplasty or in individuals who require a total or near total meniscectomy for irreparable tears. As a result, the population intended to receive these transplants is relatively limited.
Issues under study include techniques for processing and storing the grafts, proper sizing of the grafts, and appropriate surgical techniques. The four primary ways of processing and storing allografts are fresh viable, fresh frozen, cryopreserved, and lyophilized. Fresh viable implants, harvested under sterile conditions, are less frequently used because the grafts must be used within a couple of days to maintain viability. Alternatively, the harvested meniscus can be fresh frozen for storage until needed. Cryopreservation freezes the graft in glycerol, which aids in preserving the cell membrane integrity and donor fibrochondrocyte viability. CryoLife is a commercial supplier of such grafts. Donor tissues may also be dehydrated (freeze-dried or lyophilized), permitting storage at room temperature. Several secondary sterilization techniques may be used, with gamma irradiation the most common. The dose of radiation considered effective has been shown to change the mechanical structure of the allograft; therefore, nonirradiated grafts from screened donors are most frequently used.
Meniscal allograft transplantation may be considered medically necessary in individuals who have had aprior meniscectomy and have symptoms related to the affected sidewhen all of the following criteria are met:
Meniscal allograft transplantation may be considered medically necessary when performed in combination, either concurrently or sequentially, with treatment of focal articular cartilage lesions using any of the following procedures:
Use of other meniscal implants incorporating materials such as collagen are considered investigational.
Practice Guidelines and Position Statements
International Meniscus Reconstruction Experts Forum
The International Meniscus Reconstruction Experts Forum (2015) published consensus statements on the practice of MAT (see Table 10). The Forum's statements included guidance on indications, graft procurement and preparation, surgical technique, and rehabilitation.
Table. Select Consensus Statements on the Practice of MAT
Indications for MAT:
MAT not recommended for asymptomatic meniscus deficient individual.
Potentially poorer outcomes expected in individuals with moderate to severe OA (Kellgren-Lawrence grade ≥3).
Non-irradiated fresh frozen or fresh viable grafts are recommended.
Mechanical axis alignment should be performed prior to MAT; if mechanical axis deviation present, consider realignment osteotomy.
Based on current evidence, the superiority of 1 surgical technique over another (all-suture vs bone) is not established.
Outcome scores should include:
MAT: meniscal allograft transplantation; OA: osteoarthritis.
National Institute for Health and Care Excellence
The guidance from the National Institute for Health and Care Excellence (2012) stated that the evidence on "partial replacement of the meniscus of the knee using a biodegradable scaffold raises no major safety concerns," but evidence for any advantage of the procedure over standard surgery was limited.
American Academy of Orthopaedic Surgeons
The American Academy of Orthopaedic Surgeons (2009) updated its position in 2014, still recommending MAT for active people younger than 55 years old, with the goal of replacing the meniscus cushion before the articular cartilage is damaged. The website also notes that "synthetic (artificial) meniscal tissue has been tried, but there is conflicting information at this time."