Swine Meniscus: Are Femoral-Tibial Surfaces Properly Tuned to Bear the Forces Exerted on the Tissue?

Menisci are subjected to different pathologies that affect the proper functions and biology of the knee. Over the years, different techniques were tried to repair meniscus injury and, when the reparation was not possible, to replace or regenerate it. These techniques still present a lack of controlled and independent clinical studies that do not allow identifying their effective failure rate. This rate could be due to a still incomplete knowledge about meniscal biology, its composition, and biomechanical properties. The purpose of this study was to analyze the relationship between the contact forces and the meniscal structures at the level of the femoral and tibial surfaces of the meniscus to improve the knowledge about this tissue, in view of the possible application in tissue engineering, for the production of meniscal scaffolds. Swine meniscal samples were studied for morphological (Safranin-O, Sirius Red, and collagen type I and II), biochemical (DNA, glycosaminoglycans [GAGs] and GAGs/DNA ratio), computed tomography scanning and biomechanical analyses (compression and traction tests) of femoral and tibial meniscal surfaces. Results revealed a biomechanical-dependent characterization of the meniscus. The femoral surface is characterized by a higher quantity of GAGs and a greater amount of cells (p < 0.01 for each analysis), with the interposition of radial and oblique fibers. These features are responsible of a higher resistance (p < 0.05) to compressive forces like that acted on by the femoral condyles. On the contrary, the tibial surface shows a circumferential arrangement of the fibers and a poorer GAGs presence and cellular spread (p < 0.01); these characteristics seem to allow a higher resistance (p < 0.05) of the tibial surface to traction forces. Results from this work provide useful information for the design and creation of meniscal substitute and suggest that the features of the meniscus are biomechanical-dependent, and that its composition and structure are dependent to the different forces that femur and tibia generate upon its surfaces.