| A bone graft is the placement of a piece of bone onto or into a damaged or defective bone to help it repair or to replace a missing portion. Eventually most of the graft dies and is replaced by new bone. In the meantime, the graft provides a scaffold on which new bone will grow.
Some bone grafts are needed for structural support. A hard bone (cortical bone), such as the tibia or a rib, is used for this purpose. This type of bone can bear weight and will last a long time, even years, before it is replaced by new bone growth.
Some bone grafts are needed in order to grow new bone (osteogenesis). This type of graft requires a spongy bone (cancellous bone), such as the iliac crest. Although not as strong as cortical bone, cancellous bone triggers new bone growth more quickly. It does this either by supplying living cells or by chemically triggering the growth of new cells by the host.
Sometimes bone is needed that already contains vessels (vascularized graft). This type of graft is needed in areas where blood supply is low or to repair large defects. Portions of the fibula (fibularis graft) and iliac crest are often used for vascularized bone grafts. These grafts remain and are not replaced by new bone growth.
Bone for the graft may be supplied from another site on the individual (autograft, or autogenic graft) or from another person or a cadaver (allograft, or allogenic graft). Bone grafts from other species (xenograft) have been attempted but are not recommended due to poor outcomes.
Autograft is the best way in which to transplant living bone cells that will grow into new bone. The bones most commonly used for autografts are the tibia (used for cortical graft), the fibula (used for cancellous or whole bone transplant), and the iliac crest (used for cancellous graft).
An allograft is the best choice when more bone is needed than can be physically or safely removed from the patient. Allografts typically provide more structural support and less osteogenesis. They do, however, trigger the growth of new bone in the host, even though they do not provide living cells. Sometimes, for a problem that requires both structural support and osteogenesis, a graft will contain both autogenic and allogenic material.
Ceramic materials can be used as cancellous bone substitutes. Hydroxyapatite and tricalcium phosphate create scaffolding on which new bone can grow. Their structure allows easy access for blood vessels and bone-forming cells (osteogenic cells). They are used in areas where bulk, rather than strength, is needed. A mixture of hydroxyapatite/tricalcium phosphate, ceramic beads, fibrillar collagen, and added autogenous bone marrow elements has also been used as a substitute for cancellous grafts. |
Source: Medical Disability Advisor
| Bone grafts are used to promote healing (union) of fresh fractures, and fill in areas left vacant after the removal of cysts, tumors, or bone that is necrotic due to trauma, infection, etc. They are also used to fuse joints (arthrodesis) such as in the spine (spinal fusion), and limit joint motion by placing a bone block (arthrorisis). |
Source: Medical Disability Advisor
| Bone grafts are performed in a hospital under general or regional anesthesia. In an autograft, the bone is removed and implanted during the same surgery. In an allograft, the surgery includes only placing the bone graft.
The damaged portions of the bone are cut away, and the graft is shaped to fit. The graft is either placed on top of the bone surface (overlay graft), as in a fracture repair, or inserted into an empty cavity within the bone (inlay graft), such as after a tumor or cyst has been removed.
Multiple cancellous chip grafts make use of pieces of cancellous bone. These pieces are packed into crevasses and holes created by the removal of a cyst or tumor. They are also packed around an artificial joint to stabilize it. A portion of an individual's own bone marrow (autologous bone marrow) is sometimes added to grafts to increase the potential of growing new bone.
Hemicylindrical graft is an extensive surgical procedure in which a large hemicylindrical cortical graft is removed from the affected bone. This graft, plus additional cancellous bone from the iliac, is placed across the defect. This procedure is used to prevent amputation following the removal of certain bone tumors.
Whole bone transplant, using primarily the fibula, replaces large pieces of bone in the arms that have typically been damaged by removal of a large tumor or where other major bone loss has occurred.
Removing and implanting a vascularized graft is a type of microvascular surgery. It is more complicated than a nonvascularized graft.
Bone used in an allograft is obtained from a bone bank and is usually processed. If used fresh, it would, like other transplanted tissue, soon trigger an inflammatory reaction. Processing (sterilization, followed by freezing or freeze-drying) reduces the graft's ability to trigger this reaction. Like any tissue donor, donors of bone grafts are screened for a number of conditions that would be hazardous to the recipient: bacterial, fungal, and viral (HIV, hepatitis B, and hepatitis C) infection; malignancy; collagen vascular disease; metabolic bone disease; and the presence of toxins.
Biochemical substances such as bone morphogenic protein (BMP), demineralized bone matrix (BMG), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) show promise in encouraging new bone growth (Laurencin). |
Source: Medical Disability Advisor
| The individual may have difficulty bearing weight for some time following the surgery. Although not all grafts generate the new bone growth or stability hoped for, both autogenic and allogenic bone grafts are typically successful. Dynamic exercise may be unsuitable for up to 3 months (Chen). Use of nicotine may delay incorporation of a graft and may delay wound/injury healing. |
Source: Medical Disability Advisor
| Individuals who undergo bone graft will most likely require physical therapy. The type and duration is related to the type and site of surgery (for example, hip replacement) and the site of autologous graft removal, if applicable. Individuals will learn range of motion and strengthening exercises for the muscles that surround the graft site and graft removal site (if applicable). Finally, individuals will learn mobility techniques for walking and transferring if the graft site is located on the low back or leg. |
Source: Medical Disability Advisor
| In an autograft, the individual faces complications of both bone removal and bone placement. The surgery is longer and more complicated, with a greater risk of sufficient blood loss to require transfusion. The normal limb or iliac crest from which the graft is taken is at risk of damage and instability. Adjacent nerves and muscles may also sustain damage. Both the donor and the recipient site take longer to heal. The donor site is at risk of injury, such as fracture. After removal of a portion of the iliac crest, there is risk of hernia, nerve, and arterial injury and cosmetic deformity. Donor sites may be reported as painful, based on similar criteria.
Despite screening, in an allograft there is the possibility of contracting a bloodborne disease from the donated tissue. And despite processing, the risk of an inflammatory reaction remains. This risk is slight, however; no antirejection drugs are given in an allograft.
As in all surgeries, postsurgical infections are a risk in both allograft and autograft procedures. Anesthesia always carries the risks of breathing problems and reaction to the anesthetics used. |
Source: Medical Disability Advisor
| The surgical site must be protected until the physician deems it strong. The site from which an autograft was removed may be protected by work restrictions from injury such as fracture for up to 12 months. The type and site of surgery will dictate specific restrictions. |
Source: Medical Disability Advisor
| Chen, Andrew L. "Bone Graft." MedlinePlus. National Library of Medicine. 23 Sep. 2004 <http://www.nlm.nih.gov/medlineplus/ency/article/002963.htm>.Laurencin, Cato T., and Yusuf Khan. "Bone Graft Substitute Materials." eMedicine. Eds. Jonathan Black, et al. 3 Mar. 2004. Medscape. 23 Sep. 2004 <http://emedicine.com/orthoped/topic611.htm>. |
Source: Medical Disability Advisor
| Feedback |
| Send us comments, suggestions, corrections, or anything you would like us to hear. If you are not logged in, you must
include your email address, in order for us to respond. We cannot, unfortunately, respond to every comment.
If you are seeking medical advice, please contact your physician. Thank you! |
Send this comment to:
Sales
Customer Support
Content Development
|
|
| |
|
|
|
|
|
This publication is designed to provide accurate and authoritative information in
regard to the subject matter covered. It is published with the understanding that
the author, editors, and publisher are not engaged in rendering medical, legal,
accounting or other professional service. If medical, legal, or other expert assistance
is required, the service of a competent professional should be sought. We are unable to respond to requests for advice.
Any Sales inquiries should include an email address or other means of
communication.
|