Callus formation is seen between what duration of fracture healing

Stage of callus: This stage lasts for about 4-12 weeks. In this stage, the granulation tissue differentiates fuher and creates osteoblasts. These cells lay down an intercellular matrix which soon becomes impregnated with calcium salts. This results in the formulation of the callus also called woven bone. The callus is the first sign of union visible on X-rays, usually 3 weeks after the fracture. The formation of this bridge of woven bone impas good strength to the fracture. Callus formation is slower in adults than in children, and in coical bones than in cancellous bones. Ref: Maheswari; Essential Ohopaedics; 9th edition; Anatomy of Bone and Fracture Healing; Page no: 11