The Epiligament: Structure, Postnatal Development and Role in Ligament Healing

Abstract

While much is known about the ligament, the precise morphology and function of the thin layer of connective tissue lining its surface, termed the epiligament, have not been fully studied yet. Herein, we aimed at reviewing the recent findings on the structural and functional significance of the epiligament in both animal models and human tissue. The epiligament is made up of various connective tissue cells such as fibroblasts, fibrocytes, mast cells, and adipocytes and contains a number of neurovascular bundles. Arrangement of collagen fibers in the epiligament is rather chaotic, in multiple directions, which allows for greater mobility and resistance to stress. Differences in the collagen content and types of enzymes of the group of matrix metalloproteinases between the epiligament and the underlying ligament tissue have been reported and are reviewed herein. While the ligament tissue mainly contains collagen type I, the epiligament is also rich in collagen types III and V. As suggested by a number of studies, the epiligament plays a key role in ligament repair as a donor of cells and matrix metalloproteinases, particularly matrix metalloproteinase-2 and 9, which are essential for scar tissue remodeling. In conclusion, future studies will likely reveal additional functional aspects of the epiligament, which may allow scientists to devise more suitable treatment strategies for damaged ligaments in a world where injuries resulting from sports activities or daily routine have long merited their due attention.

Nerve Growth Factor and its association to osteoarthritis in the horse

“…Surrounding the ligament is the epiligament, a thin, vascularised layer that fuses with the periosteum. The cruciate ligament is sheathed within synovial membrane (Stamenov et al, 2019;Amiel et al, 1984).…”

Functional biomaterials for tendon/ligament repair and regeneration

“…The elastic fibers allow the ligaments to stretch and extend under load [ 21 ]. Ligaments can strengthen joints, increase their stability during movement and prevent them from dislocating and causing injury [ 12 ]. Most fibers are aligned almost parallel to each other, so their force characteristics are usually such that they are subjected to loads in only one direction [ 22 ].…”

“…Although technology has advanced in recent years, the issue of rehabilitation of tendon injuries has not met everyone’s expectations and remains a serious clinical challenge [ 11 ]. The conservative clinical approach uses fixed casts and restricted movement orthoses, which require a long ongoing rehabilitation program to achieve functional recovery [ 12 ]. Standard surgical options for clinicians include filling a partial T/L defect with a graft or, if the defect is large, filling the graft with bone or muscle to completely replace the T/L [ 13 ].…”

Injectable hydrogels for tendon and ligament tissue engineering

“…Collagen fibers that make up ligaments have a certain strength and stiffness. Elastic fibers give ligaments the ability to extend under load (Stamenov, Yordanova, Dimitrov, Telbiyska, & Stefanov, 2019). Ligaments connect bone to bone.…”