Short-term evaluation of collagen meniscus implants by MRI and morphological analysis

Meniscectomy can lead to degenerative joint changes in the knee. Collagen meniscus implantation is a tissue engineering technique designed to stimulate regeneration of meniscal tissue in case of irreparable tears or previous meniscectomy. The implant is composed of type I collagen derived from bovine Achilles tendon and enriched with glycosaminoglycans. Previous clinical trials demonstrated satisfactory medium-term results in patients who received a collagen meniscus implant (CMI). In this study, CMI structure was analysed by light microscopy and scanning electronic microscopy (SEM). The same morphological studies were performed on two implant biopsies, obtained from two patients who underwent a second arthroscopic look six months after implantation. The evolution of the implant was also investigated by magnetic resonance imaging, 6 and 12 months postoperatively. CMI presented a multilamellar structure, with inner lacunae allowing tissue ingrowth. The lamellae were made of collagen fibrils, randomly oriented and preserving the typical 64-nm period. At second arthroscopic look, the implant appeared in continuity to the native residual meniscus and parameniscus, and showed good consistency and stability at probing. The biopsy specimens demonstrated invasion of the scaffold by connective tissue and blood vessels. The newly synthesised collagen fibrils were clearly distinguishable from the scaffold ones. No phagocytomacrophagic cells nor inflammatory reactions were observed inside the implant. MRI findings confirmed CMI biocompatibility and highlighted the evolution of the integration process with time. The data achieved in this study support the hypothesis that CMI stimulates regeneration of meniscal-like tissue, which could prevent the development of degenerative changes after meniscectomy.