[Frontiers in Bioscience S3, 117-125, January 1, 2011]

Injury responses and repair mechanisms of the injured growth plate

Rosa Chung1, 2, 3, Bruce K Foster2, Cory J Xian1, 2, 3

1Discipline of Physiology, University of Adelaide, Adelaide, Australia, 2Department of Orthopaedic Surgery, Women's and Children's Hospital, North Adelaide, Australia, 3Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Mechanisms of bone growth and modelling
4. Growth plate injuries, injury responses and repair mechanisms
4.1. Growth plate injuries, their classification, and effects on bone growth
4.2. Injury responses after a growth plate fracture
4.2.1. Inflammatory phase
4.2.2. Fibrogenic phase
4.2.3. Osteogenic and maturation phases
4.3. Mechanisms of bony repair of injured growth plate cartilage
4.4. Effects of injuries and the adjacent non-injured growth plate tissue
5. Perspective & conclusions
6. Acknowledgements
7. References

1. ABSTRACT

The growth plate is responsible for longitudinal growth of children's long bones. However, being a cartilaginous tissue, the growth plate has a limited ability for regeneration and thus injured growth plate is often repaired by bony tissue resulting in bone growth defects of the involved limb. Understanding the pathophysiology of growth plate bony repair and developing preventative treatments remain a challenge. This review discusses previous and recent studies investigating growth plate injury responses and repair mechanisms in a rat tibial growth plate injury model. Following an injury, inflammatory, fibrogenic, osteogenic and bone-bridge maturation repair phases have been observed on days 1-3, 3-7, 7-14 and 10 onwards, respectively. Important roles of several growth factors and cytokines (such as PDGF-BB, FGF-2, TNF-alpha and IL-1beta) have been highlighted, regulating different phases of growth plate injury repair. Studies have also shown that while intramembranous ossification is the major mechanism responsible for the bony repair, endochondral ossification, to a lesser extent, also plays a role.  Further understanding of the growth plate injury responses and bony repair mechanisms is still required.