It's easy to think of our bones as solid, lifeless matter where all of our living tissue just sits. But your skeleton is as much a living part of your being as your softer tissues and organs. The body stores minerals in the hard, compact bone. It produces red blood cells in the inner red marrow and stores fat in the yellow marrow.
It's important to remember that your bones are constantly changing. Cells called osteoclasts constantly break down old bone so that osteoblasts can replace it with new bone tissue -- a process called bone remodeling. Another type of cell called a chondroblast forms new cartilage. These are three of the primary cells responsible for bone growth -- and not just the bone growth you experience early in life. This constant bone remodeling gradually replaces old bone tissue with new tissue during the course of months.
Almost immediately after the break, the body begins to try and put itself back together again. Doctors often divide the overall process into four phases:
- When a bone breaks, the fissure also severs the blood vessels running down the length of the bone. Blood leaks out of these veins and quickly forms a clot called a fracture hematoma. This helps to stabilize the bone and keep both pieces lined up for mending. The clot also cuts off the flow of blood to the jagged bone edges. Without fresh blood, these bone cells quickly die. Swelling and inflammation follow due to the work of cells removing dead and damaged tissue. Tiny blood vessels grow into the fracture hematoma to fuel the healing process.
- After several days, the fracture hematoma develops tougher tissue, transforming it into a soft callus. Cells called fibroblasts begin producing fibers of collagen, the major protein in bone and connective tissue. Chondroblasts then begin to produce a type of cartilage called fibrocartilage. This transforms the callus into a tougher fibrocartilaginous callus, which bridges the gap between the two pieces of bone. This callus generally lasts for about three weeks.
- Next, osteoblasts move in and produce bone cells, transforming the callus into a bone callus. This hard shell lasts three to four months, and it provides necessary protection and stability for the bone to enter the final stage of healing.
- At this point, the body establishes the position of the bone within the flesh, begins reabsorbing bits of dead bone, and creates a hard callus to bridge the gap between the two pieces of bone. However, this bulge of tissue needs a lot of work before the bone can take any strain. Osteoclasts and osteoblasts spend months remodeling bone by replacing the bone callus with harder compact bone. These cells also decrease the callus bulge, gradually returning the bone to its original shape. The bone's blood circulation improves and the influx of bone-strengthening nutrients, such as calcium and phosphorus, strengthen the bone.
But even in the best of cases, fractures often require medical attention to heal as smoothly as possible. Did Humpty Dumpty just need the help of a talented orthopedist? Learn how doctors help broken bones heal properly on the next page.