Comminuted midshaft humerus fracture with<unk>  formation. A<unk>  is a temporary formation of fibroblasts and chondroblasts which forms at the area of a bone fracture as the bone attempts to heal itself. The cells eventually dissipate and become dormant, lying in the resulting extracellular matrix that is the new bone. The<unk>  is the first sign of union visible on x-rays, usually 3 weeks after the fracture.<unk>  formation is slower in adults than in children, and in cortical bones than in cancellous bones.
Fibrocartilage callus
Granulation tissue
Prayer callus
Ossification center
Calculus 
Ossification
Demineralized bone matrix
Intramembranous ossification