Cartilage repair: Scaffolding

Regenerative scaffold-based procedures have emerged in the last years as a potential therapeutic option for the treatment of chondral and osteochondral lesions. The rationale of using a scaffold is to have a temporary 3D structure of biodegradable polymers for the growth of living cells. The ideal scaffold should reproduce biological and structural properties of the native tissue as close as possible, in order to allow cell infiltration, attachment, proliferation, and differentiation. Other important properties include biocompatibility and biodegradability at suitable time intervals, to support the initial tissue formation and then to be gradually replaced by the regenerating tissue. The use of scaffolds has been introduced into clinical practice to improve the results obtainable with the first-generation cell-based approach, autologous chondrocyte implantation (ACI), by overcoming its drawbacks and simplifying the procedure. ACI techniques were combined with scaffolds, developing matrix-assisted autologous chondrocyte transplantation (MACT). Cells were harvested and cultured in vitro and then seeded on the three-dimensional biomaterial, which favored the redifferentiation processes, better protection, more homogeneous distribution, and easier handling for surgical implantation. Many scaffolds have reached clinical practice, and studies are now being published with good mid- and long-term results, but showing also some limits. Whereas traumatic focal lesions of the femoral condyles were shown to have more chance of benefit from this treatment, other indications have more controversial results, with lower or even poor clinical outcome. Moreover, this approach suffers from a two-step operation, technical difficulties and regulatory restrictions for cell manipulation, and high costs. Thus, after a decade focused on expanding and improving MACT techniques, in more recent years, both researchers and clinicians have been looking for different solutions to regenerate the articular surface.