Bone Grafting Fundamentals
Bone grafting refers to a wide variety of surgical methods augmenting or stimulating the formation of new bone where it is needed.
There are four broad clinical situations in which bone grafting is performed:
- To stimulate healing of fractures -- either fresh fractures or fractures that have failed to heal after an initial treatment attempt.
- To stimulate healing between two bones across a diseased joint. This situation is called “arthrodesis” or “fusion”.
- To regenerate bone which is lost or missing as a result of trauma, infection, or disease. Settings requiring reconstruction or repair of missing bone can vary from filling small cavities to replacing large segments of bone up to 12 inches in length.
- To improve the bone healing response and regeneration of bone tissue around surgically implanted devices, such as artificial joints replacements (e.g. total hip replacement or total knee replacement) or plates and screws used to hold bone alignment.
What are my treatment options?
All methods of bone grafting involve adding some material to the specific site where bone is needed as a means of stimulating a new or more effective bone healing response. Now, minimally invasive bone grafting is available, meaning that the grafting can be performed with a needle, without a surgical incision. However, most methods require open implantation. This is necessary to insure that there is adequate space and proper positioning of the graft material. It is also necessary to remove scar tissues and dead or poorly vascularized tissues from the graft site, since this would interfere with the healing process. For more information about factors which may inhibit bone formation, see Fracture Non-Union.
Bone grafting falls into three general areas: Osteogenic Stimulation, Osteoconductive Stimulation, and Osteoinductive Stimulation.
Since only living cells can make new bone, the success of any bone grafting procedure is dependent on having enough bone forming “osteogenic” cells in the area. Areas of scarring, previous surgery or infection, bone gaps, and areas previously treated with radiation therapy are all likely to be deficient in bone forming cells.
Currently, bone-forming cells can be added to a graft site from two sources. Traditionally, healthy bone is removed from an area where it is unlikely to cause a disability and then transferred into the graft site. This is often from sites of the anterior or posterior pelvic iliac crests. It has recently become more accepted to transfer bone-forming cells using bone marrow, which can be obtained with a needle, without open, incisional surgery. Bone marrow can be injected into a graft site or mixed with other components as a composite graft. Both transplantation of a patient’s bone and transplantation of just the bone marrow are referred to as “autografts” or “autogenous bone grafts”.
Cleveland Clinic, and particularly Dr. George Muschler, has been a leader in the development of improved methods for using bone marrow as a bone graft. When bone marrow or other graft materials are delivered by injection, this method is defined as “minimally invasive bone grafting.”
“Osteo” means “bone”. Osteoconduction refers to the ability of some materials to serve as a scaffold on which bone cells can attach, migrate (meaning move or “crawl”), and grow and divide. Osteoconductive materials make it more likely for bone cells to fill the entire gap between two bone ends. They also serve as a spacer, which reduces the ability of fibrous tissue around the graft site from growing into the site.
Osteoconductive materials do not induce healing better than transfer of the patient’s own bone. However, when used appropriately, these materials can offer an effective alternative for many patients. This can save many patients from the additional surgical site and pain associated with that site in order to transplant their own bone.
Many materials are available as osteoconductive materials, and more are being developed.
Induction of bone formation refers to the capacity of a number of growth factors in the body to stimulate primitive bone cells to grow and mature, forming healthy bone tissue. Many of these growth factors are present in normal human bone. For this reason, methods have been developed to process human bone and prepare bone matrix which retains the normal growth factors, but limit, if not eliminate, the risk of transmitting diseases or viruses.
What are the risks of surgery?
Risks include nerve injury, infection, bleeding, and stiffness.