Stem Cells and Orthopaedics

Stem cells may help tissues that are injured or damaged to renew and regenerate themselves. Depending on the treatment and medium, stem cells have the ability to become different types of cells such as bone, cartilage, and blood vessels. There are several conditions in which stem cells are used as treatment, including: avascular necrosis, arthritis, and nonunion.

When Avascular Necrosis of the femoral head occurs due to the diminished blood supply, there is a death of a segment of bone, which is considered necrotic. The surgeon can inject stem cells into this area to revive this area by drilling into the bone. When using stem cells to treat AVN, the surgeon will need to create a channel for new blood vessels to form into the area that lacks blood supply. After the channel is created, the stem cells are injected into the necrotic femoral head.

Stem cell treatments for joint pain and arthritis is not proven to be effective. However, there is some use in knee arthritis for cartilage regeneration.

 

The best use of stem cells in Orthopaedics is its treatment for nonunion fractures. A nonunion fracture is classified as a fracture that does not heal after a reasonable period of time or a fixation failure. Nonunion may also be due to motion of the bony ends and incomplete healing of the fracture; fractures of this nature will need a lot of assistance. Two elements are needed for treatment of nonunions: vascularity—which improve the local conditions to facilitate healing; and stability—in the form of fixation such as a rod or plate.

The most common causes of nonunion are smoking (5 times more common), diabetes, obesity, osteoporosis, unstable fixation, infection (most common), open fractures, and the severe displacement of the fracture.

 Options available for treatment:

1. Bone Morphogenetic Protein—very expensive
2. Bone Graft—donor site morbidity
3. Stem Cells

Stem cells must be extracted from the bone marrow and are aspirated and harvested from the anterior iliac crest. This procedure is performed with an outlet view under fluoroscopy. Once extracted, the bone marrow is prepared to be centrifuged. After centrifuging the bone marrow, a good sample is extracted for injection.

The surgeon will mark and localize the area for injection and the trocar is placed. The sample will then be injected into the fracture area—occasionally, two areas of nonunion are treated. Adult mesenchymal stem cells are special cells that can copy themselves, divide, and multiply. They can differentiate into bone cells that heal the nonunion and lay down new bone. This process can be monitored by alkaline phosphatase activity or by the genes of the stem cells. The whole cellular mechanism can help increase the vascularity of the nonunion.

It is important to note that adult mesenchymal stem cells are not embryonic stem cells. There is a large amount of information in regards to stem cells that is lacking or misleading. Cells should probably be combined with some type of matrix. Additionally, surgeons need a better delivery system and localization during the injection of the stem cells due to the fact that the dye kills the cells. It is beneficial to allow the cells to expand and grow in the culture prior to injection. Moreover, the effect of certain medications such as aspirin, Plavix, and Coumadin, should be studied further.