Dr. Matthew Wendt, Fellowship trained and Board Certified Orthopedic Surgeon, explains how broken bones heal: through surgical fix or casting.
There are two types of bone healing: Primary and Secondary.
Primary healing, also known as direct, is when the bone is surgically repaired or stabilized. This can be done with plates and screws, holding the bones together very tightly. Another type of primary healing is when osteoblasts bridge together from end to end. This is similar to a welder attaching two pieces of metal together at a seam.
The second form of healing, known as secondary bone healing, is when a fracture is repaired without surgery. This is done through a cast or sling. There is usually a slight gap at the site of the broken bone which allows for slight motion at that gap because the cast or sling does not keep the bones entirely still. Next, a hematoma forms between the gap. The cells within the hematoma and in the broken bone end send signals to the repair cells in our body to then send repair cells to the site of the break. Over time, the repair cells convert the collection of cells into flexible cartilage called callus. This callus is then converted into bone over a matter of weeks, bridging the gap between the bone ends. This is similar to gluing together a broken vase. The glue starts out soft but then hardens, bridging the break's gap. The final stage of bone healing: is Remodeling. This is where the body reshapes the callus to resemble the pre-injury form of the broken bone closely. After this process, the bone is as strong as if not stronger than it was before the break.
Learn more about primary and secondary bone healing from Dr. Wendt below!