Correction

Abstract

Introduction Recent studies stressed the importance of the epiligament in ligament nutrition and healing. While ligaments of the knee joint have been the subject of extensive research, the epiligament of the medial collateral ligament has received only limited attention. The aim of our study was to present the ultrastructural morphological features of the epiligament of the medial collateral ligament in a rat knee joint. Materials and methods For the present study, we used eight eight-month-old male Wistar rats. A transmission electron microscopic study of the epiligament was conducted according to standard protocol. Results In the epiligament, we described the presence of fibroblasts with the typical features of proteinsynthesizing cells, as well as fibrocytes and adipocytes. We noted an abundance of blood vessels and nerve elements. Collagen fibers were organized in multidirectional bundles. Conclusions Our findings confirm that the cells and structures of the epiligament play an important role in the nutrition and healing of the medial collateral ligament.

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

“…Blood vessels in the EL are randomly dispersed, forming an extensively branching anastomotic network. They have thin walls and their intima consists of layers of endothelial cells surrounded by pericytes [15]. They are often accompanied by nerves, although they don’t always form neurovascular bundles [6,12,16-17].…”

“…They are often accompanied by nerves, although they don’t always form neurovascular bundles [6,12,16-17]. Nerve fibers are both myelinated and unmyelinated and form nerve trunks, whose external fibrous coat (epineurium) fills the space between the bundles of nerve fibers, each surrounded by perineurium [15]. Schwann cells have also been described [15].…”

The novel epiligament theory: differences in healing failure between the medial collateral and anterior cruciate ligaments

“…After extensive research on epiligament morphology of the MCL in rats and humans in both normal conditions and injury, as well as investigation of the same tissue in the ACL and comparison between these two commonly injured ligaments, a novel EL theory was proposed by Georgiev et al [6–8, 11, 12, 18–22].…”

“…In contrast to the ligament, the EL contains multiple cell types such as fibroblasts, fibrocytes, adipocytes, and blood vessels [6–8, 11, 12, 18–20, 33, 41]. Georgiev et al [21] presented the ultrastructural characteristics of these cells. Fibroblasts have been described as large and well formed; they display a very delicate chromatin structure with a prominent nucleolus.…”

“…Similar ultrastructural characteristics of fibroblasts and fibrocytes, as reported above, were confirmed by Georgiev et al [8] in humans. They finally concluded due to the ultrastructural characteristics that fibroblasts might be involved in differentiation, phagocytosis, and collagen synthesis; the authors also hypothesized that single collagen fibers or those grouped in bundles may respond to ligament tension in different directions [8, 21]. With the aim of obtaining more detailed knowledge of the MCL and ACL ELs and comparing it in rats, Iliev et al [32] found a statistically significant difference in the number of cells per mm 2 in the EL of the two ligaments, with a greater number in the MCL.…”