The Influence of Local Vascular Regeneration on Growth Plate Activity after Defined Growth Plate Lesions

Background:

The vascular anatomy of the growth plate is not yet fully understood with some reports on transphyseal vessels the role of which remains unclear. Further, the development of bone bridges and axial and longitudinal deformities cannot be completely explained with present knowledge.

Material and Methods: Under general anesthesia, a Salter-Harris-II-fracture was created at the medial aspect of the proximal tibia in 16 immature sheep and stabilized by an external fixateur. The perfusion study in ten sheep used Mercox^® and corrosion casts were obtained. The histological analysis of the remaining six sheep was made by conventional stains and immunohistochemistry against bromodeoxyuridine (BrdU) to evaluate the cell proliferation rate. The observation time was 0, 1, 2, 4, 6, and 12 weeks.

Results: The healing process of growth plate fractures followed a regular pattern. After posttraumatic depression of any proliferation up to 1 week, a rich neovascularization took place seen in the vascular casts and the histological sections. This phenomenon was dominant until the 6th week after injury. Then, the hypervascularity and the proliferation rate returned to normal. The temporary hypervascularity was closely associated with the increased proliferation rate demonstrated by immunohistochemistry.

Conclusions: Healing growth plate fractures is dominated by the vascular response to the injury. The temporary hypervascularity 1–6 weeks after the fracture leads to a higher proliferation rate of the chondrocytes in the proliferative zone. These results may be one explanation for the development of posttraumatic longitudinal and angular deformities as a result of temporary hypervascularity.