Using autologous bone marrow mononuclear cells (BM-MNC) to treat patients with chronic limb ischemia has been proved safe and effective. However, processing bone marrow by Ficoll density gradient centrifugation is not only time consuming but also expensive. Manually processing of bone marrow also results in large variation in therapeutic cell quantity and quality which directly leads deviation of safety and efficacy of the cell therapy. This study is aiming to compare an automated bone marrow processing system with a conventional manual method in term of safety and efficacy.