Final answer:
The repair of a bone fracture is a complex process that begins with the formation of a fracture hematoma and then progresses through stages of debris clearance by phagocytes, callus formation, and replacement of cartilage with trabecular bone, culminating in bone remodeling to restore the bone's original structure.
Step-by-step explanation:
Steps Involved in Fracture Repair
The healing process of a bone fracture consists of several critical stages:
- Fracture hematoma formation occurs when blood clots at the site of the fracture, typically within six to eight hours post-injury. The hematoma results due to blood flow disruption, which leads to the death of bone cells near the fracture.
- Capillaries grow into the hematoma, and phagocytic cells clear away dead cells. Within days, fibroblasts produce collagen fibers, and osteoblasts develop spongy bone, forming a fibrocartilaginous callus that bridges the fractured bones.
- Chondrocytes from the endosteum generate an internal callus, while periosteal chondrocytes and osteoblasts develop an external callus. This callus stabilizes the fracture within 48 hours after the break.
- Trabecular bone replaces the cartilage within the calli, forming a hard callus.
- Finally, bone remodeling takes place. Compact and spongy bone forms, and the bone structure is eventually restored to its pre-fracture state.
Sometimes, for effective bone healing, surgical intervention such as metal pins may be required to stabilize the broken pieces during repair.