Final answer:
The fourth step in the fracture healing process is remodeling, where excess bone material is removed and compact bone is added to restore the bone's original shape and strength.
Step-by-step explanation:
The healing of a bone fracture occurs in several steps. The fourth step in fracture healing is known as remodeling. During remodeling, osteoclasts and osteoblasts work together to reform the bone. Excess bone material is removed from the exterior of the bone and the medullary cavity, while compact bone is added to sculpt the bone close to its original shape. Although the bone remodeling phase can take many months, it ensures that the bone tissue resembles the original, unbroken bone in structure and strength.
The remodeling stage is critical because it allows bones to adapt to stresses by becoming thicker and stronger when subjected to stress. Without this stage, bones may not regain their previous capacity to handle the everyday loads and stresses they experience. This stage completes when the bone has achieved its natural form and function, although some irregularities may persist for years.