The collagen meniscus implant.

Lesions in the meniscus occur particularly in young, active patients in the nonvascularized area which, consequently have a bad intrinsic healing capacity. This has a large impact on the mobility and function of the knee joint. Lesions, and partial lesions, lead to the progression of osteoarthritis over time in a large proportion of patients. The only clinical treatment for severe cases so far is an allograft donor meniscus, which is used mostly in patients with severe osteoarthritis with a completely destroyed meniscus. However, this technique still has to be considered as experimental and, thus, is not yet used on a routine basis. Various technical solutions have been advocated to repair meniscus lesions. One solution is to perform a partial meniscectomy and insert a collagen meniscus implant (CMI) at the site of the lesion. However, the initial mechanical properties of the collagen scaffold are inferior to the native meniscus. Therefore, it is only possible to perform a CMI implantation if the peripheral rim of the meniscus is still intact. Histology of preclinical and clinical biopsies of the implanted CMI demonstrated a repopulation of the scaffold by fibrous tissue and in time a remodeling of the fibrous tissue into fibrocartilaginous-like tissue. Based on histology, the ingrowth of new tissue into the CMI might occur by a process of synovial overgrowth, but other mechanisms of revitalization are also possible. Although some clinical studies demonstrated improvement in outcome scores, the number of patients was small in all studies and the positive effect on the prevention of progression of osteoarthritis was not compared with control groups