Stem cells are specialized cells found in different body tissues. They are undifferentiated, which means that they are not a specialized type of cell and can change to a more specialized form. When stem cells divide, they create progenitor cells, which can become more specialized cells. For example, human embryo stem cells eventually develop into more specialized cells that become organs, bones or blood cells. Cells from amniotic fluid (which surrounds an unborn baby while in the womb) and mesenchymal stem cells (which are harvested from adult tissues) are the kinds typically used in orthopaedic applications.
Stem cells can actually “replace and repair” body tissues and are thought to support healing. Stem cell treatment is routinely used in cancer of the blood (like leukemia and lymphoma), to replace diseased bone marrow, which makes the blood cells. Stem cells are also used to support the healing process in injured or diseased bone, skin or eye tissue. Bone marrow stromal cells are a type of mesenchymal stem cell that can develop into bones, ligaments, cartilage, and tendons. The cells are injected into the target area or may be implanted as a piece of tissue.
Bone marrow transplantation is the most well-known form of stem cell therapy and has been in use for over 30 years. The US Food and Drug Administration has approved several stem cell treatments for blood cancers. Theoretically, stem cell therapy could be used for many other conditions, especially those caused by cell degeneration. Stem cell therapy is currently being used in arthritis and degenerative joint disease. It is also used for treating fractures that won't heal, creating new joint cartilage and replacing the discs between the bones in the spine. Research is ongoing and new applications for stem cells are likely in the future.