Bone grafting

Definition

Bone grafting is a surgical procedure by which new bone or a replacement material is placed into spaces between or around broken bone (fractures) or holes in bone (defects) to aid in healing.

Purpose

Bone grafting is used to repair bone fractures that are extremely complex, pose a significant risk to the patient, or fail to heal properly. Bone graft is also used to help fusion between vertebrae, correct deformities, or provide structural support for fractures of the spine. In addition to fracture repair, bone graft is used to repair defects in bone caused by birth defects, traumatic injury, or surgery for bone cancer.

Description

Bone is composed of a matrix, mainly made up of a protein called collagen. It is strengthened by deposits of calcium and phosphate salts, called hydroxyapatite. Within and around this matrix are located the cells of the bones, which are of four types. Osteoblasts produce the bone matrix. Osteocytes are mature osteoblasts and serve to maintain the bone. Osteoclasts break down and remove bone tissue. Bone lining cells cover bone surfaces. Together, these four types of cells are responsible for building the bone matrix, maintaining it, and remodeling the bone as needed.

There are three ways in which a bone graft can help repair a defect. The first is called osteogenesis, the formation of new bone by the cells contained within the graft. The second is osteoinduction, a chemical process in which molecules contained within the graft (bone morphogenetic proteins) convert the patient's cells into cells that are capable of forming bone. The third is osteoconduction, a physical effect by which the matrix of the graft forms a scaffold on which cells in the recipient are able to form new bone.

New bone for grafting can be obtained from other bones in the patient's own body (e.g., hip bones or ribs), called autograft, or from bone taken from other people that is frozen and stored in tissue banks, called allograft. A variety of natural and synthetic replacement materials are also used instead of bone, including collagen (the protein substance of the white fibers of the skin, bone, and connective tissues); polymers, such as silicone and some acrylics; hydroxyapatite; calcium sulfate; and ceramics. A new material, called resorbable polymeric grafts, is also being studied. These resorbable grafts provide a structure for new bone to grow on; the grafts then slowly dissolve, leaving only the new bone behind.

To place the graft, the surgeon makes an incision in the skin over the bone defect and shapes the bone graft or replacement material to fit into the defect. After the graft is placed into the defect, it is held in place with pins, plates, or screws. The incision is closed with stitches and a splint or cast is used to prevent movement of the bones while healing.

The costs associated with a bone graft vary. These costs include: the surgeon's fee (variable); anesthesiologist's fees (averaging $350 to $400 per hour); hospital charges (averaging $1,500 to $1,800 per day, more for intensive care or private rooms); medication charges ($200 to $400); and additional charges, including an assisting surgeon, treatment of complications, diagnostic procedures (e.g., blood work or x rays), medical supplies, and equipment use. The cost for the graft itself can range from $250 to $900.

This procedure is covered by many third-party insurers; insurance coverage should be explored for each individual case.

Aftercare

The time required for convalescence for fractures or spinal fusion may vary from one to 10 days, and vigorous exercise may be limited for up to three months.

Most bone grafts are successful in helping the bone defect to heal. The extent of recovery will depend on the size of the defect and the condition of the bone surrounding the graft at the time of surgery. Severe defects may take some time to heal and may require further attention after the initial graft. In one study of over 1,000 patients who received very large allografts after surgery for bone cancer, researchers found that approximately 85% of the patients were able to return to work or normal physical activities without using crutches. However, about 25% of these patients required a second operation, because the first did not heal properly. Less severe bone defects, though, should heal completely without serious complications.

Risks

The risks for any surgical procedure requiring anesthesia include reactions to the medications and breathing problems. The risks for any surgical procedure include bleeding and infection.

The drawbacks of autografts include: the additional surgical and anesthesia time (typically 30 minutes per procedure) to obtain, or harvest, the bone for grafting; added costs of the additional surgery; pain and infection that might occur at the site from which the graft is taken; and the relatively small amount of bone that is available for grafting.

The drawbacks of allografts include: variability between lots, since the bone is harvested from a variety of donors; the bone may take longer to incorporate with the host bone than an autograft would; the graft may be less effective than an autograft; and the possibility of transferring diseases to the patient. Other complications may result from the immune response mounted by the patient's immune system against the grafted bone tissue. With the use anti-rejection agents (drugs to combat rejection of grafted bone tissue) immune rejection is less of a problem.

Key Terms

Allograft

Tissue for transplantation that is taken from another person.

Autograft

Tissue for transplantation that is taken from the patient.

Hydroxyapatite

A calcium phosphate complex that is the primary mineral component of bone.

Osteoblasts

Bone cells that build new bone tissue.

Osteoclasts

Bone cells that break down and remove bone tissue.

Osteoconduction

Provision of a scaffold for the growth of new bone.

Osteocytes

Bone cells that maintain bone tissue.

Osteogenesis

Growth of new bone.

Osteoinduction

Acceleration of new bone formation by chemical means.

For Your Information

Periodicals

• Brown, Edwin H. "New Bones from the Sea: Tropical Coral." Medical Update 20 (Jan. 1997): 2.

• Cowley, Geoffrey. "Replacement Parts." Newsweek 129 (27 Jan. 1997): 66.

• DeLacure, Mark D. "Physiology and Healing of Bone Grafts." Otolaryngologic Clinics of North America 27, no. 5 (1994): 859.

• Farley, Dixie. "New Ways to Heal Broken Bones." FDA Consumer 30 (Apr. 1996): 14.

• Hayes, Ketra Marie, and Nancy L. Combs. "Perioperative Nursing Care of Patients with Craniofacial Injuries." ADRN Journal 64 (Sept. 1996): 383.

• Hotter, David S. "Band-Aids for Broken Bones." Machine Design 68 (4 Apr. 1996): 39.

• Kopp, Marleen. "Caring for the Adult Patient Undergoing Anterior/Posterior Spinal Fusion." Orthopedic Nursing 16, no. 2 (1997): 55.

• Larkin, Brenda G. "Understanding Bone Banking." Orthopedic Nursing 16, NO. 4, 1997: 49.

• Morgan, Peggy, and Toby Hanlon. "Power Medicine in 2000: Breakthrough Treatments for a New Millennium." Medical Update 20 (Jan. 1997): 2.

• "New Ways to Fix Bone Fractures." USA Today Magazine 124 (Feb. 1996): 4.

• Oseph, Lou. "The New World of Dental Care." Consumers Digest 35 (May 1996): 59.

• "Restoring Severely Disfigured Faces." USA Today Magazine, 125 (Oct. 1996): 8.

• Scaggs, David L., and George S. Bassett. "Adolescent Idiopathic Scoliosis: An Update." American Family Physician 53 (15 May 1996): 2327.

• Vangsness, C. Thomas, et al. "Soft Tissue for Allograft Reconstruction of the Human Knee: A Survey of the American Association of Tissue Banks." American Journal of Sports Medicine 24 (Mar. 1996): 230.

• American Association of Tissue Banks. 1350 Beverly Road, Suite 220-A, McLean, VA 22101. (703) 827-9582.

Source: Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group

The Essay Author is Lisa Christenson PhD.

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