A child is not a miniature of an adult, nor is he a little man. Children are like a “diamond” and their value and potential are sometimes immeasurable. Fracture is a common injury in children. Because children are growing and developing, there are great differences in tissue anatomy, physiology and biomechanics from adults. 1, the histological and anatomical characteristics of children’s bones Bones in the human body mainly undertake pillars, regulate mineral metabolism, have a unique growth function in children, or one of the hematopoietic organs. In adults, cortical bone is arranged in laminae and is dense and hard. This is not the case in children, especially in newborns, who are made up of intricately interwoven primitive tissues with no obvious lamellar structure and good toughness. With age, the primitive connective tissue is gradually replaced by lamellar structures. In children, the periosteum is thicker and rich in blood flow. The ends of the long bones of the limbs are made up of cartilage called epiphyses, while the metacarpals and phalanges of the hands and feet have epiphyses at only one end. An actively growing cartilaginous area called the epiphyseal plate is formed between the epiphysis and the metaphysis, showing a typical process of endochondral ossification. The epiphyseal plate is divided into four layers according to histological characteristics: the resting cell layer, the proliferating cell layer, the mast cell layer, and the temporary calcified layer, in which the interstices of the cells are filled with cartilage matrix and cellular matrix, enhancing the strength of the epiphyseal plate. The mast cell layer, however, is significantly reduced and is susceptible to epiphyseal separation from here. The blood supply to the epiphyseal plate is distributed to the resting cell layer by the epiphyseal artery on the epiphyseal side, while on the epiphyseal side the capillary collaterals are formed by the epiphyseal artery to nourish the temporary calcified layer. The mature epiphyseal plate forms a blood transport barrier between the epiphysis and the epiphysis. The composition of children’s bones is organic matter forming matrix, depositing inorganic salts, more water and less solid components. Therefore, children’s bones are more flexible than adult bones and more resistant to external forces of deformation. The fine pores within the bone cortex of children can limit the extension of the fracture line. Adult compressed bone cannot tolerate tension, but on the contrary, children’s bone with abundant fine pores is less likely to be compressed. The physiological characteristics of children’s bones In addition to hematopoiesis, inorganic salt metabolism and immune function, children’s bones also have the ability to grow. The endochondral ossification at the epiphysis makes it grow longitudinally, while the cell proliferation and ossification in the inner layer of the periosteum, i.e., endochondral ossification, makes it grow laterally. Because of the abundance of osteoblasts and osteoclasts and the high blood flow, their growth and shaping ability are stronger than those of adults, and once fractured, healing is rapid. The timing of epiphyseal ossification varies from site to site and can be an important indicator of bone growth and development in children. However, once the epiphyseal plate is damaged, it will cause delayed bone growth or bone and joint deformity. 3. Clinical characteristics of children’s fracture In addition to the main symptoms of fracture, children have early, extensive and often ecchymotic swelling after fracture due to loose soft tissues and elastic fascia. Among the systemic symptoms, the increase in body temperature after fracture is more obvious than that of adults, up to 38oC or more, especially in infants, and often lasts for 3-5 days, which is due to the absorption of hematoma and the entry of denatured protein into the blood circulation. X-ray examination after fracture is an indispensable diagnostic method, not only to determine the diagnosis, but also to clarify the type of fracture, displacement, and the presence of primary lesions such as bone cysts and osteogenesis imperfecta, etc. It is also an objective marker of fracture healing. The younger the epiphysis is, the more cartilaginous it is, so the epiphyseal plate should not be misdiagnosed as a fracture line and the small epiphysis as a fracture fragment, and CT and MRI examinations can improve the diagnosis. 4.Characteristics of fracture repair in children Children are growing and developing, with rich and active osteoblasts and osteoclasts, and strong blood circulation, fracture healing is rapid, and the younger the age, the faster the healing. Fractures of the epiphysis and the diaphysis can cause temporary growth acceleration of the affected limb due to the hyperplasia of the epiphyseal plate stimulated by blood filling, such as femoral diaphysis fracture can be overgrown by 8-20 mm, but the damage to the epiphyseal plate will lead to different degrees of growth and development disorders. In children, poor alignment and alignment after fracture, formation of shortening and angular deformity can be corrected to some extent with growth and development. The younger the child, the stronger the correction ability. However, inversion and valgus deformities and rotational deformities are not self-correcting.