Figure 1.

An illustration depicting the stages of fracture healing: 1) In the initial inflammatory phase (lasting up to 7 days after injury), the increased blood delivery to the affected site results in the formation of hematoma with a high content of cytokines; 2) cells attracted by cytokines and environmental factors (hypoxia, low pH, HIF1‐alpha, and VEGF) are responsible for the repair of damaged vessels and formation of provisional fibrous tissue called callus (7–10 days after injury); 3) at around two weeks after injury, MSCs undergo differentiation into osteoblasts and chondrocytes governed by Wnt and BMP signaling and provisional woven bone is generated; 4) in the final phase starting 3–4 weeks after injury and lasting up to several years, the woven bone is replaced by lamellar bone.