Early Histologic and Ultrastructural Changes in Microvessels of Periosteal Callus

Abstract

New evidence showed that after fracture, periosteal microvessel endothelial cells and pericytes increased in population and transformed to mesenchymal cells. These changes, their subsequent extravasation as mesenchymal cells, and their development into chondroblasts were verified by basal lamina evidence. New evidence also suggested that continued extravasation of transformed microvessel cells rendered the fracture callus cartilage avascular.