The Human Knee Meniscus: A Review with Special Focus on the Collagen Meniscal Implant

Abstract

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.

Collagen scaffold meniscus implant integration in a canine model: A histological analysis

“…The implant acts as a temporary scaffold to enable the regeneration of a new tissue that resembles and performs similarly to native meniscal tissue. There have been several human clinical trials using this implant in both the United States and Europe with mainly positive clinical results …”

“…There have been several human clinical trials using this implant in both the United States and Europe with mainly positive clinical results. [13][14][15] Our study constitutes the detailed histologic examination of tissue from the canine model at both earlier and later time periods than a previous publication. 9 We describe the stepwise early histological changes and integration of this implant over the course of 17 months.…”

“…A more biological, tissue engineered approach has been attempted in animal models with biodegradable implants such as polycaprolacton polyurethanes, polyglycolic acid, hyaluronic acid, bovine collagen, and polyvinyl–alcohol hydrogels . Of these implants, the collagen and polyurethane scaffolds have properties that allow them to be sutured to an intact meniscus after partial meniscectomy, and have been used extensively in animal and clinical trials …”

“…10 Of these implants, the collagen and polyurethane scaffolds have properties that allow them to be sutured to an intact meniscus after partial meniscectomy, and have been used extensively in animal and clinical trials. 6,[11][12][13][14][15] In preclinical studies, a canine model is ideal for an investigation of such an approach because the meniscal biology of the animals is similar to humans and they, like humans, lack the intrinsic ability to fully regenerate cartilage defects. 16,17 The canine stifle joint is also highly sensitive to partial meniscectomy, more so than humans, developing early degenerative changes.…”

Current Concepts in Meniscus Tissue Engineering and Repair

“…Collagen meniscus implant (CMI®) is derived from bovine type I collagen and molded in the shape of meniscus that offers restoration of tissue function. This scaffold is porous and upon implantation, cell infiltration has been reported in clinical studies [90] . However, long-term follow-up studies have demonstrated significant shrinkage of the implant, possibly due to degradation, which would lead to decreased biomechanical function [91] .…”