Bone marrow is the soft, fatty network of connective tissue that fills the medulla, the internal cavity of the bone.
The marrow contains stem cells that produce the three cellular components of blood: platelets, leukocytes and red blood cells. The tissue also contains osteoprogenitor cells that help in the formation and growth of new bone.
Bone marrow can be combined with bone graft substitutes in lumbar spine fusion surgery with the goal of enhancing the probability of attaining a successful spinal fusion.