Critical limb ischemia is a condition where the blood circulation in the limbs, in most cases the legs, is decreased so that pain and non healing wounds ensue. Mostly, this is a sequel of arteriosclerosis and/or diabetes. If surgical and other methods for the improvement of blood supply for the leg have failed or are not possible, most of these patients will proceed to amputation of the leg.

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.

Therefore, we conduct a study to compare the efficiency of concentrated bone marrow cells injected into the critically ischemic limb compared to a placebo procedure where only saline is injected. We think that the transplantation of autologous bone marrow will reduce the number of necessary leg amputations, reduce pain and induce wound healing. In this investigation, patients with limb threatening ischemia are randomly allocated either to the bone marrow group or to the placebo group. Patients in the bone marrow group will have their bone marrow harvested under sedation, and the bone marrow cells are concentrated. The cell concentrate will then be injected directly into the muscle of the diseased leg. Patients in the placebo group will undergo sedation as well but no bone marrow harvest is done, and saline is injected into the ischemic leg. The procedure will require about 1.5-2 hours, and the subjects will be admitted to a participating vascular Centre. Monthly examinations up to three months after the bone-marrow or placebo procedure are done. After the follow-up of three months, the rate of death and amputations and the wound healing process are compared between groups.

Adverse and serious adverse events will be recorded during this time period. Diagnostic studies will be obtained to measure blood flow in the treated leg during the follow up period and include skin oxygen measurements, pressure recordings in the leg and arteriography. Also, quality of life, pain and wound healing will be assessed.

After completion of the three months study participation, subjects who have been treated with placebo will be able to receive open-label bone marrow transplantation therapy.