During which stage of bone healing is the callus formed?

The formation of a callus occurs during the third stage of bone healing, which is known as the callus formation stage. After a fracture, the body initiates a healing process that consists of several distinct stages. Initially, in the first stage, a hematoma forms at the fracture site, followed by inflammation which helps to set the stage for healing.

In the second stage, granulation tissue develops which provides a temporary scaffold for new tissue formation. The third stage is characterized by the conversion of this granulation tissue into a more stable structure known as a callus. This callus consists of both hard (bony) and soft (cartilaginous) tissue, supporting the fracture site and facilitating further stability as the bone starts to heal more robustly.

Finally, in the fourth stage, the callus is gradually remodeled and replaced by more organized bone tissue as the healing process continues, but the actual formation and presence of the callus itself defines the third stage of the healing process. This progression highlights the complexity of bone healing and the importance of each stage in restoring the integrity of the bone after a fracture.