What is osteonecrosis? Osteonecrosis is a condition in which bone cells, osteoblasts, and medullary cells (blood vessels and nerves) become necrotic, resulting in multiple interruptions or severe deficiencies in the nutrition of bone tissues, causing metabolic disorders in bone and loss of nutrition in local bone tissues. In principle, osteonecrosis is divided into two main categories: one is osteonecrosis due to bacterial infection. For example, osteomyelitis, bone tuberculosis, septic arthritis, etc.; the other category is osteonecrosis caused by ischemia. For example, osteonecrosis caused by trauma, alcohol consumption, hormonal drugs, cold and dampness, liver and kidney deficiency, osteoporosis, flat hip, abnormal spinal cavernous disease, etc. Osteonecrosis can occur in any part of the body. The femoral head, humeral head, hand navicular, lunar bone, foot navicular, talus, ribs, patella and clavicle are the most common clinical cases. Especially the femoral head has the highest incidence. When osteonecrosis occurs in the femoral head, it is called osteonecrosis of the femoral head.