(A) Diagram of cell proliferation, migration, and differentiation (B) Diagram of different stages in the fracture healing process. Proliferation (circular arrow), differentiation (vertical arrow), production of growth factors (g_b: osteogenic growth factor, g_c: cartilage growth factor), and extracellular matrix (m_b: bone extracellular matrix, m_c: cartilage extracellular matrix, m: the total matrix).