10.14:
Fractures: Bone Repair
A fractured bone undergoes three stages of repair— reactive, reparative, and remodeling.
The initial reactive phase seals the damaged blood vessels forming a blood clot called fracture hematoma. It disrupts circulation, leading to the death of bone cells near the fracture.
The resulting cell debris causes swelling and inflammation, recruiting the phagocytes and osteoclasts to the injury site.
As the debris is cleared, new blood vessels extend into the hematoma, starting the reparative phase.
Fibroblasts and chondroblasts migrate from the undamaged regions of the bone into the fractured gap.
They form collagen fibers and fibrocartilage to bridge the broken ends, using a fibrocartilage repair tissue called soft callus.
As repair progresses, osteoprogenitor cells from the healthy regions of the bone differentiate into osteoblasts.
These osteoblasts begin forming spongy bone trabeculae at the fracture margins of the bone.
Gradually, the fibrocartilage around the external edges of the break is replaced with spongy bone or the hard callus.
During the final phase, osteoclasts and osteoblasts remodel and replace the peripheral spongy bone with compact bone, repairing the shaft wall.
10.14:
Fractures: Bone Repair
Treatment for a fracture is based on the type of break, the bone affected, and the patient's age.
Minor fractures with no bone displacement are treated by immobilizing the fractured bone using a cast or splint. However, in the case of fractures with displaced bones, the broken bones are repositioned before immobilization to ensure successful healing without deformation and loss of function. The realignment of fractured bone ends is performed through a process called reduction. If the procedure is done without surgery by manual positioning of the fractured bone, it is called closed or external reduction. On the contrary, in open or internal reduction, fractured bone ends are surgically aligned and secured using devices like screws, wires, rods, and plates. After reduction, the broken bones are immobilized using a cast, splint, sling, bandage, or external fixation devices for proper bone repair.
Some fractures require immediate or additional medical care to avoid serious complications. For example, an open fracture penetrating the skin needs to be treated urgently to prevent excessive bleeding and infection. Similarly, if an epiphyseal fracture is not treated properly, it can cause the growth plate to close prematurely, stopping bone growth. For instance, a tibial growth plate fracture in a child can lead to skeletal deformities, where the affected leg that suffers growth arrest may be shorter than the healthy leg as the child grows.