Changes in articular cartilage after meniscectomy and meniscus replacement using a biodegradable porous polymer implant

Purpose: To evaluate the long-term effects of implantation of a biodegradable polymer meniscus implant on articular cartilage degeneration and compare this to articular cartilage degeneration after meniscectomy. Methods: Porous polymer polycaprolacton-based polyurethane meniscus implants were implanted for 6 or 24 months in the lateral compartment of Beagle dog knees. Contralateral knees were meniscectomized, or left intact and served as controls. Articular cartilage degeneration was evaluated in detail using India ink staining, routine histology, immunochemistry for denatured (Col2-¾M) and cleaved (Col2-¾Cshort) type II collagen, Mankin’s grading system, and cartilage thickness measurements. Results: Histologically, fibrillation and substantial immunohistochemical staining for both denatured and cleaved type II collagen were found in all three treatment groups. The cartilage of the three groups showed identical degradation patterns. In the 24 months implant group, degradation appeared to be more severe when compared to the 6 months implant group and meniscectomy group. Significantly more cartilage damage (India ink staining, Mankin’s grading system, and cartilage thickness measurements) was found in the 24 months implant group compared to the 6 months implant group and meniscectomy group. Conclusion: Degradation of the cartilage matrix was the result of both mechanical overloading as well as localized cell-mediated degradation. The degeneration patterns were highly variable between animals. Clinical application of a porous polymer implant for total meniscus replacement is not supported by this study.

Human meniscus: from biology to tissue engineering strategies

Once meniscus is damaged, a cascade of events occurs leading to degenerative joint changes of the knee. The morbidity of patients can significantly increase overtime and degeneration of the cartilage can progress, resulting in arthritis. Possibilities for treatment of meniscus lesions are primordially focused in repair and replacement (e.g., acellular scaffolds and meniscus allograft transplantation). Tissue Engineering and Regenerative Medicine have been providing new options in medical practice. However, these disciplines require deep understanding of the target tissue and physiopathology of the implicated disorder. In order to overcome the current limitations, fundamental studies have been made for developing reliable strategies aiming to obtain superior tissue healing. Herein, it is presented the most relevant insights and research directions on the fundamental biology and biomechanics of meniscus. The principles of tissue engineering (triad) and the significant in vitro and in vivo reports addressing meniscus regeneration are included, once these will provide the basements for future clinical directions