[Callus formation and microvascular regeneration during the fracture healing process in the rat femur].

Correlation between the callus formation and its microvascular regeneration during the fracture healing process in the rat femur was examined under SEM and TEM utilizing the plastic injection method. Stabilization of bony fragments was provided by a miniature external fixator. Normal periosteal microvasculature consisted of 2 layers. In the outer layer, arterioles and venules formed the course network. In the inner layer, capillaries were situated in contact with the compact bone, forming polygonal meshes. In the medulla, the central longitudinal artery gave rise to numerous arterioles, which communicated with sinusoidal capillaries. The proliferation of the internal layer of the periosteal capillary network was observed in the periosteal callus. It is revealed that the trabecular structure of the periosteal and medullary calluses depended on their microvascular architecture. The anastomoses of newly-formed capillaries at the fracture site started first from the outer layer of the periosteum extended to the medulla then finally to the inner layer of the periosteum.