This is a prospective, randomized, double-blind, placebo controlled, multicenter trial intended for subjects with critical limb ischemia (CLI) that are unsuitable for revascularization. The investigational treatment utilizes autologous concentrated bone marrow aspirate (cBMA) at the point of care. The bone marrow aspirate is obtained from the subject's hip, concentrated with a bone marrow concentration device, and delivered intramuscularly to the affected limb. Subjects meeting the inclusion/exclusion criteria will be randomized to receive either the investigational treatment (cBMA) or a placebo control (sham treatment).