Introduction: Partial meniscectomy is the preferred treatment option for patients with irreparable meniscal tears. While generally accepted as producing favorable clinical results in the short run, it is widely accepted that meniscectomy induces articular cartilage degeneration in the long run. Thus, tissue regeneration post-meniscectomy is a desirable therapeutic approach in order to restore the function of the meniscus, thereby preventing long-term damage. A novel device, designed to act as a scaffold for blood vessel ingrowth and meniscal tissue regeneration in patients with irreparable meniscus tears and meniscal tissue loss, has recently been developed.
Methods: Fifty-two patients with an irreparable medial or lateral meniscal tear or partial meniscus loss, with intact rim, were treated with the meniscal scaffold in this prospective, non-randomised, single-arm, multi-centre clinical study. To date, biopsy samples 12 months post-implantation harvested from the center of the inner rim of the implanted scaffold meniscus using a standardized biopsy harvest protocol are available from 9 of the 52 patients. Histochemical staining was performed with haematoxylin and eosin, Masson’s trichrome, Sirius Red and combined Periodic Acid Schiff-Alcian Blue (PAS-AB). Immunohistochemistry was performed using the cartilage markers S100, the vessel markers CD31 and CD34, the smooth muscle marker SMA, and the histiocytic marker CD68.
Results: All biopsies showed fully vital material, with no signs of necrosis or cell death. In addition to a fibrous capsule, 3 distinct zones were identified based on the presence or absence of vessel structures, cellular morphology, and composition of extracellular matrix. Zone 1, a vascularized, fibrotic zone, mainly consisting of fibroblasts, was observed in 4/9 biopsies. Zone 2, an avascular and loose collagenized zone, consisting of a mixture of fibroblasts and chondrofibroblast-like cells, and Zone 3, an avascular and fibrin-rich zone, consisting of fibrochondroblast-like cells, were evident in all 9 biopsies.
Conclusions: All biopsies showed complete re-population, and thus can be regarded as vital structures, illustrating the biocompatibility of the meniscal scaffold. Moreover, zonal organisation, each with its own histological characteristics, suggests an ongoing process of regeneration, maturation and integration towards meniscus-like tissue. These data offer a first insight into the complex human healing potential after implantation of a polyurethane meniscus scaffold.
On behalf of the Actifit Study Group: R Verdonk, P Beaufils, J Bellemans, P Colombet, R Cugat, P Djian, H Laprell, P Neyret, H Paessler,
