Bone marrow contains cells which can induce and augment the growth of new, small arteries called collateral arteries. It has been shown in animals and in some case series that the transplantation of a concentrate of the patient's own bone marrow with stem cells into the ischemic limb can improve the blood circulation via the induction of collateral growth. However, it is not known if this bone-marrow stem cell induced collateral growth is sufficient to avoid otherwise necessary amputations.