Zhao et al. recruited 100 patients with early stage osteonecrosis of the femoral head, who were randomly assigned to bone marrow-derived mesenchymal stem cells treatment or core decompression treatment. Each bone marrow-derived mesenchymal stem cells-treated hip was implanted with 2×10(6) autologous ex vivo-expanded cells. Sixty months after operation, only 2 of the 53 bone marrow-derived mesenchymal stem cells-treated hips progressed, while 10 of 44 hips progressed in the core decompression group, bone marrow-derived mesenchymal stem cells treatment significantly improved the Harris hip score and decreased the volume of necrotic lesions of the femoral head.