Analysis of microvascular density and collagen structure of the medial meniscotibial ligament of the knee: Immunohistochemical study with CD31 and histology with Picrosirius red.

Background: The aim of the present study was to describe the structure of the collagen matrix and the microvascularization of the medial meniscotibial ligament (MMTL), in order to contribute to the refinement of the surgical technique for repairing these structures and consequently lead to a reduction in the risk of anterior cruciate ligament re-rupture.

Methods: Twelve MMTLs were obtained from deceased organ donors. The ligaments were initially analyzed macroscopically and evaluated histologically using hematoxylin and eosin staining. The evaluation of the collagen matrix was carried out using the Picrosirius red staining method under a polarized light microscope. Immunohistochemical study using monoclonal antibodies against CD31 was used to evaluate microvascularization.

Results: The MMTL was identified in 100% of the dissections. The hematoxylin and eosin-stained histological sections exhibited oriented and parallel collagen fibers, with low cellularity in its intrasubstance portion and increase in cellularity close to the meniscal insertion. Quantitative analysis of the collagen matrix showed a ratio of type I to type III collagen of 3.86 (±3.07). The average microvascular density in the intrasubstance portion was 33.71 ± 8.7 vessels/mm and in the meniscal insertion portion it was 74.14 ± 23.85 vessels/mm.

Conclusion: The MMTL is a structure with a predominance of Type I collagen in relation to Type III collagen and high microvascular density in the region of meniscal insertion. These findings suggest that the healing potential of MMTL, regarding ramp injuries, is high because these injuries occur in the meniscal insertion area.