Our bones are the scaffold that allows us to cope with the strains of everyday life, but sadly, accidents happen. If our bones do break, they usually heal normally. But that’s not always the case. In fact, of the roughly 8 million fractures reported in the US each year, up to 10% won’t heal properly. If the bone doesn’t heal within the normal time frame, doctors call these non-union fractures… And they drastically reduce a person’s quality of life. To understand why non-union fractures occur, we first need to understand how normal healing works. First, ruptured vessels leak blood into the void caused by the fracture, and the blood forms a clotted mass, called a haematoma. At this stage, physicians try to ensure that the bone is properly aligned and fixed in place. During the next two weeks or so, the haematoma is transformed into a soft callus made of cartilage and connective tissue. Tiny blood vessels begin to work their way through this matrix, closely followed by bone making cells called osteoblasts which reinforce the callus. Eventually, the soft callus is transformed into hard bone and the fracture is healed but sometimes this normal healing process fails because the blood supply gets cut off, starving the fracture site of the specialised cells needed for healing. Regenerative medicine might give physicians a new way of reconnecting the blood supply to the fracture site. Scientists hope they can kick start the normal healing process by encouraging new blood vessels to grow into the gap. To do this, researchers harvest the population of the patient’s cells with a surface marker called CD34. Included in these cells are Endothelial Progenitor Cells or ‘EPCs’, which promote the growth of new blood vessels. Once isolated, these cells are infused into a gel, which helps to keep them in place at the fracture site. Then, a tiny bone graft is inserted into the fracture site along with the gel, providing a physical bridge between the two fragments that contains all the cell types needed for healing. The EPCs encourage new blood vessels to grow, and can also turn into the cells that form blood vessels. A large clinical trial is underway in Japan to test whether this cell therapy can boost the healing process for patients with non-union fractures, and whether this non-union can in fact, have a happy ending.