 while the average lifespan of human osteoclasts is about 2 to 6 weeks and the average lifespan of osteoblasts is approximately 3 months.In healthy bone these cells are constantly replaced by differentiation of bone marrow mesenchymal stem cells (MSC).However, in both non-traumatic osteonecrosis and alcohol-induced osteonecrosis of the femoral head, a decrease in the differentiation ability of mesenchymal stem into bone cells has been demonstrated, and altered osteoblastic function plays a role in ON of the femoral head.