Microstructural characterization of the transition region between scar and normal tissues in a healing medial collateral ligament

The purpose of this study was to investigate the microstructure and collagen organization in the transition region between scar and normal tissues of the medial collateral ligament (MCL) in a rat model using scanning electron microscopy (SEM). Transition region microscopy consistently demonstrated continuity of collagen fibers and fibrils from the residual portions of the transected ligament through the scar region. Bifurcations/fusions, but no anastomosis, in fibers and fibrils were observed in both normal and scar tissues. In the scar region larger diameter fibers of the normal tissue bifurcated into smaller diameter fibrils in the scar region. This connection between larger diameter and smaller diameter tissues indicates that bifurcations/fusion are likely to be the dominant way in which force is transmitted in the healing ligament