There are four main stages of healing for a fracture.
1) the formation of hematoma at the break (sometimes called a procallus)
In this stage the area of the break starts to pool blood and immune cells to start to clean up debris from the break and to deal with any foreign organisms that might have entered the area if the skin was damaged by the fracture.
2) the formation of a fibrocartilaginous callus
In this stage the the hematoma is replaced fibrocartilaginous tissue thanks to the contribution of fibroblasts that entered into the area with all the blood and other immune cells.
3) the formation of a bony callus
In this stage the fibrocartilage is replaced with spongy bone. The area is usually bigger than the original bone and is not a perfect fit with the surrounding bone.
4) remodeling and addition of compact bone
In this stage the bone remodeling occurs in which excess bone matrix is removed so that the bone is contnious with the surrounding bone.
Hope this helps with your question!