A graft is living tissue, bone, or synthetic material that is transplanted from one location to another to repair damage the body can’t fix on its own. In surgery, grafts are used to replace missing skin after burns, rebuild bone lost to injury or disease, and reroute blood flow around blocked arteries. The concept is one of the oldest in medicine, with records of skin grafting dating back more than 3,000 years to ancient India, and it remains one of the most common and versatile tools in modern surgery.
How Grafts Are Classified
Grafts are categorized by where the tissue comes from. An autograft uses tissue taken from your own body, moved from a healthy donor site to the area that needs repair. Because the tissue is yours, your immune system doesn’t reject it, and it integrates faster than any alternative. Autografts are considered the gold standard across nearly every surgical specialty.
An allograft comes from another human, often a cadaver donor. These are carefully processed and sterilized before use. A xenograft comes from an animal, typically a pig or cow, and is used when human tissue isn’t available or practical. Isografts, a less common category, come from a genetically identical donor like an identical twin. Each step further from your own tissue increases the risk that your immune system will treat the graft as a foreign invader.
Skin Grafts
Skin grafting is probably the most widely recognized type. Surgeons remove a layer of skin from one part of the body and apply it to a wound that’s too large or too deep to heal on its own. This is common after severe burns, traumatic injuries, or surgical removal of damaged tissue.
There are two main types. A split-thickness graft takes only the top layers of skin and is used for larger wounds. A full-thickness graft includes the entire depth of the skin and is reserved for smaller areas where cosmetic appearance matters more, such as the face or hands. In one study of lower-limb skin grafts, 94% looked successful at first inspection, though that number dropped to 67% by six weeks as some grafts partially failed. The biggest risk factors for failure were poor circulation in the legs, higher body weight, and use of medications that suppress the immune system.
During the first week to ten days, a new skin graft must attach to the wound bed and re-establish blood flow. The graft initially survives by absorbing fluid from the tissue beneath it, then gradually turns pink as new blood vessels grow into it, a process called vascularization.
Bone Grafts
Bone grafting repairs fractures that shatter or don’t heal correctly, fuses vertebrae in spinal surgery, and rebuilds jawbone before dental implants. The grafted material serves as a scaffold that your body’s own bone cells can grow into and eventually replace.
Autologous bone, harvested from your own hip or another site, heals fastest because it contains living bone-forming cells. The downside is that it requires a second surgical site, which means more pain and a limited supply of donor bone. For medium and smaller defects, surgeons often use allografts from human donors, animal-derived xenografts, or synthetic materials like ceramics and bioactive glass that the body can gradually absorb.
In dental applications, a bone graft needs at least three months to heal before an implant can be placed on top of it. Larger grafts can take nine to twelve months. Initial recovery from the procedure itself takes about a week.
Vascular Grafts
When arteries become too blocked or damaged to carry blood effectively, surgeons can bypass the problem section using a graft. This is the principle behind coronary artery bypass surgery and peripheral bypass procedures in the legs. The preferred material is a segment of your own saphenous vein, the long vein running along the inner leg, because natural vein grafts outperform synthetic alternatives. However, nearly a third of patients who need peripheral bypass surgery don’t have suitable veins available, either because of prior surgeries or vein disease. In those cases, surgeons use synthetic tubes made from polyester or a type of fluoropolymer. Studies comparing the two synthetic options have found no clear advantage of one over the other.
Graft-Versus-Host Disease
One of the most serious complications in grafting occurs not when the body rejects the graft, but when the graft attacks the body. This is called graft-versus-host disease (GVHD), and it happens almost exclusively after bone marrow or stem cell transplants. Immune cells from the donor recognize the recipient’s tissues as foreign and launch an attack, potentially damaging the skin, liver, and digestive tract.
The process unfolds in stages. Chemotherapy or radiation given before transplant damages the recipient’s tissues and triggers inflammation. Donor immune cells then encounter the recipient’s cells, identify them as different, and begin multiplying. In the final stage, those activated immune cells migrate to organs throughout the body, causing widespread tissue damage. GVHD that appears within the first 100 days after transplant is classified as acute. Chronic GVHD develops later and can produce different, longer-lasting symptoms including skin thickening, dry eyes, and joint stiffness.
Bioengineered Grafts
When natural tissue isn’t available, bioengineered skin substitutes offer an alternative. These products combine natural and synthetic components to mimic the structure of real skin. Some use animal collagen as a base layer with a silicone sheet acting as a temporary outer barrier. Others go further, seeding scaffolds with living human cells, typically fibroblasts from donated neonatal tissue, that produce growth factors to encourage healing. For chronic wounds like diabetic foot ulcers, products built on absorbable mesh scaffolds populated with living cells have become a standard option.
A newer approach cultures a patient’s own skin cells onto a carrier material, then applies the sheet to the wound. This combines the immune compatibility of an autograft with the convenience of a lab-grown product, avoiding the need for a painful donor site.
A Practice With Ancient Roots
Grafting has a remarkably long history. The Sushruta Samhita, an ancient Indian medical text from more than 3,000 years ago, describes using skin and fat from the buttock region as a free graft for nasal reconstruction. That technique was largely forgotten in Western medicine until the early 1800s, when a German surgeon successfully reconstructed a nose using a free skin autograft inspired by the Indian method. In 1869, Swiss surgeon Jaques-Louis Reverdin performed a landmark experiment, harvesting tiny bits of skin from a patient’s arm with the tip of a lancet and fixing them into the wound bed. His “pinch graft” technique proved that small pieces of transplanted skin could take hold and grow. By 1886, a German surgeon named Carl Thiersch refined the approach further, using a razor blade to cut ultra-thin strips of skin. His method, the forerunner of the modern split-thickness graft, became the standard for decades.