Synthetic meniscus replacement: a review

The number of meniscus-related operations continues to rise due to the ageing and more active population. Irreparable meniscal lesions generally require (partial) meniscectomy. Although a majority of the patients benefit from pain relief and functional improvement post-meniscectomy, some remain symptomatic. As an alternative to a meniscal allograft, which is only indicated for the severely damaged meniscus, most patients can nowadays be treated by implantation of a synthetic meniscal substitute. Currently three of these implants, two partial and one total replacement, are clinically available and several others are in the stage of preclinical testing. Grossly, two types of meniscal substitutes can be distinguished: porous, resorbable implants that stimulate tissue regeneration and solid, non-resorbable implants that permanently replace the whole meniscus. Although the implantation of a porous meniscus replacement generally seems promising and improves clinical outcome measures to some degree, their superiority to partial meniscectomy still needs to be proven. The evaluation of new prostheses being developed requires a wider focus than has been adopted so far. Upon selection of the appropriate materials, preclinical evaluation of such implants should comprise a combination of (in vitro) biomechanical and (in vivo) biological tests, while up to now the focus has mainly been on biological aspects. Obviously, well-defined randomised controlled trials are necessary to support clinical performance of new implants. Since the use of a meniscus replacement requires an additional costly implant and surgery compared to meniscectomy only, the clinical outcome of new products should be proven to surpass the results of the conventional therapies available.