Knee Meniscus Replacement

Abstract

Meniscus has an important role in knee function as load bearing, shock absorption, joint stability, joint lubrication and proprioception, so we must preserve meniscus tissue as we can. Meniscus is composed of a network of collagen fibers (predominantly type 1 collagen) interposed with cells and extracellular matrix of proteoglycans and glycoproteins. Menisci are placed between medial and lateral femoral condyle and tibial plateau. Anatomical studies have shown that the degree of vascular penetration is 10% - 30% of the width of medial meniscus and 10%-25% of the width of lateral meniscus, so the majority of the meniscus is a vascular and must therefore derive nutrition from synovial fluid diffusion.

Once the meniscus has been torn and is removed from the joint, there are multiple complications after this removal as knee osteoarthritis, because meniscectomy cause a decrease of surface contact area, this leads to increase of contact pressure, leading to wear and gradual disappearance of cartilage and increase risk of early degeneration which end in osteoarthritis in long run.

So to overcome this complication we can replace removed meniscus with another graft (Meniscus Allograft Transplantation) or meniscal implant like Collagen Meniscus Implant and polyurethane scaffold.

Meniscal allograft transplantation is a viable option showing increasing evidence of clinical utility, although problems related to availability, size matching, cost and risk of disease transmission limit their use. Another optional treatment is that of biodegradable scaffolds collagen meniscus implant (CMI), which are based principally on tissue engineering concepts. The variability in body response to biodegradable implants and the quality of the tissue formed still pose a problem in this respect, under intense knee loading conditions.

Collagen meniscus implant (CMI) is resorbable natural polymer which composed of type I collagen. Collagen is a naturally occurring matrix polymer which is the predominant extra-cellular matrix component of most connective tissues, comprising one third of all protein found within tissues. Collagens are part of the extracellular matrix and mainly caries out a structural role in which density, and orientation results in varying mechanical properties. Purified type I collagen from bovine achilles tendon was used to fabricate a porous collagen meniscus, which was interspersed with glycosaminoglycan molecules.

In the future, stem cells may provide an alternative, potentially autogenous, source of meniscal tissue to regenerate the resected segment. Even with these advances, however, surgeons should continue to attempt meniscal repair whenever feasible and resect as little meniscal tissue as possible in tears that are deemed irreparable.

Stem cells are characterized by self-renewal capacity and multilineage differentiation potential to a variety of cell types of mesenchymal tissue like bone, cartilage or fat. Mesenchymal stem cells have the ability to differentiate into the repair cells themselves and to produce special growth factors for its repair.