Fig. 4
Identification of histomorphological differences between the upper and lower regions of both the AM and PL bundles of the ACL using immunohistochemical methods (VG (a), PC (b), Collagen (c); (A,B). Modified Verhoeff–Van Gieson staining (a) confirmed the characteristics of collagen and elastic fibers in magnified images. Collagen is indicated in red, and black dots represent elastic fibers. In Pentachrome staining (b), elastic fibers appear as brownish collagen clusters with black dots and were further analyzed using collagen immunohistochemical staining. The upper region of the AM bundle (A) displays a dense concentration of elastic fibers, whereas the lower region exhibits a sporadic, multiskewed pattern. Similarly, in the PL bundle (B), the upper region contains more elastic fibers than in the lower region. The collagen arrangement in the AM bundle (A-c) appears to be densely disorganized, while in the PL bundle (B-c), it exhibits an organized pattern with a lower collagen proportion. ACL-AM anterior cruciate ligament-anteromedial bundle, ACL-PL anterior cruciate ligament-posterolateral bundle.
