Healthy adults have 206 bones in their bodies, which can be divided into three main parts, including the skull, trunk bones and limb bones, of which there are 29 bones in the skull, 51 bones in the trunk, and 126 bones in the limbs. However, in the period of children’s development, the number of bones is more than that of adults, usually 217 or 218, and the sacrum in children is five, which is fused into one in adults, and the coccyx can be four or five, which is also fused into one in adults. The coccyx may have 4 or 5 pieces that also fuse into 1 piece in adults to form the sacrum and coccyx, and the ilium, sciatica, and pubis each have two pieces in children that merge into two hip bones in adults, so there are 11-12 more bones in childhood than in adults. In addition, some people may have more or fewer bones than normal due to developmental abnormalities or hereditary reasons. If there are more bones than normal, it is considered that there are pathologic factors such as fracture or bone redundancy, and the condition needs to be clarified by means of imaging and other tests.