The human knee meniscus: a review with special focus on the collagen meniscal implant.

Overview

The human knee meniscus is important for the protection of the knee joint from degeneration. Because it is so commonly injured, several methods have been developed to replace damaged meniscal tissue with either transplanted menisci or other synthetic implants. Here we review these different approaches, with a clinical and histological focus on the collagen meniscal implant (CMI or Menaflex), a tissue-engineered bovine collagen product. Clinical trials in patients receiving the CMI have demonstrated good clinical outcomes in follow-ups as long as 10 years. We review the findings of second-look biopsies of implanted CMI constructs; they demonstrate the fibrochondrocytic ingrowth of tissue mimicking a native meniscus. Integration of the CMI to host meniscus is also confirmed. The histologic inflammation occasionally observed around the graft appears to be of little clinical significance. We conclude that tissue-engineered menisci from bovine collagen are safe in the time period examined and that they hold promise for future repair of the meniscus in appropriate individuals.