Empty bones may be caused by the following reasons: 1, due to infection, patients with acute septic osteomyelitis or tuberculosis of the bone lesions, may be due to the infection of the above parts of the bone destruction, defects; 2, due to bone necrosis, such as bone trauma, ischemia, or infections, inflammation, will cause gradual necrosis of the bone, necrotic bone may be rapidly absorbed and liquefied, resulting in bone defects; 3, due to bone-occupying lesions, such as bone tumors, especially malignant bone tumors, often have a large amount of bone destruction and then cause bone defects. The necrotic bone may be rapidly absorbed and liquefied, which will cause bone defects; 3, caused by bone occupying lesions, such as bone tumors, especially malignant bone tumors, which often have a large amount of bone destruction and then cause defects; 4, may be caused by bone cystic changes, bone cysts are often due to congenital hereditary factors or acquired local inflammation and injury within the bone, which will cause cystic necrosis, and at this time there will be local bone defects; 5, caused by bone necrosis. There are localized bone defects; 5, may also be caused by severe osteoporosis.