Ask Dr. Lund: What Is a Bone Graft?
Learn about how bone graft materials and procedures have changed with technology advances.
The body is remarkable in its ability to regrow bone. But in some medical situations—when broken bones fail to heal, for example—your body may need some help. That help often comes in the form of a bone graft. But what is a bone graft, exactly? Orthopedic trauma surgeon Dr. Erik Lund uses grafts regularly for fracture repair. He explains that advances in medicine have expanded the variety of bone grafts available. In addition, he describes each type of graft and explains how it is used to address missing bone or boost bone growth.
There are three categories of bone graft
“A graft replaces bone structure and promotes healing,” says Dr. Lund. “Although we have a natural ability to regrow bone, our regenerative healing capacities decline as we age. Grafts help further the body’s natural ability to make bone when a broken or damaged bone fails to heal. In some cases, I use grafts to repair an initial fracture that might not heal without a graft. In other cases, we use graft material to repair a fracture that did not heal well. Additionally, we use bone grafts to treat diseases of the bone, like tumors or cancer.” Dr. Lund explains that there are three sources of graft material.
- Autograft. This graft material is taken from the patient’s own bone. “Autograft provides the best biology to treat an unhealed fracture, also known as a nonunion,” explains Dr. Lund. “Autograft has osteogenic, osteoconductive and osteoinductive properties. That means that it contains cells, proteins, and bone structure.”
- Allograft. Allograft is bone graft material taken from a cadaver. “Cadaver material is really just osteoconductive,” says Dr. Lund. “That means it acts as a conduit for bone growth. It provides structure and some minerals, but not many bone cells. Although there is a theoretic danger of disease transmission via cadaver tissue, the risk is exceedingly low. That’s because cadaver tissue is sterilized in a highly monitored and regulated process to prevent transfer of any living cells. We estimate a one-in-a-million chance of infection via allograft. I tell my patients that they are more likely to be infected by a needle stick or another invasive procedure than by an allograft.”
- Bone substitutes. The third category includes commercial product alternatives to a bone graft. These products include demineralized bone matrix (DBM) and injectables like calcium phosphate or calcium sulfate. “Sometimes, I need a large volume of bone graft, but I can only take so much autograft from the patient,” explains Dr. Lund. “In these cases, I can use DBM to increase or expand the graft. I might use calcium phosphate or calcium sulfate injectables that harden into bone.”
How autograft is harvested
“An autograph can come from the femur, pelvis, tibia, fibula, or calcaneus bones,” says Dr. Lund. “We usually collect graft material with a special tool through a small incision. The tool reams the inside of the bone, irrigates the reamed bone to make a slurry, and aspirates the slurry into a collection dish. The aspirated bone has the consistency of slushy ice. This method provides an incredible amount of bone graft that is full of rich cell material. When I surgically fix the fracture, I pack the harvested autograft material around the bone, where the surrounding muscles hold the graft in place.”
Dr. Lund notes that many people imagine a bone graft as an actual piece of bone that is harvested from the patient and then placed at the site of injury. “Although we have used pieces of bone in the past, we don’t use that method as often today,” he says. “Usually, I use reamed aspirated bone because it offers more patient benefit. Using aspirated bone means less pain and morbidity, and lower surgical complication risks. Because we often collect the graft material from the bone that’s being repaired, there are also no additional incisions or surgery sites.”
Conditions that benefit from a bone graft
“Graft material can be used to treat a simple fracture nonunion or a nonunion related to infection,” explains Dr. Lund. “If I’m treating a nonhealing fracture, the focus is on providing biology to promote healing. By comparison, infection cases often involve loss of bone volume that must be replaced.”
- Promoting fracture healing. “If you have a broken bone that didn’t heal, you probably aren’t missing a lot of bone,” notes Dr. Lund. “You just need biology, because the bone itself does not want to heal. It may have lost its intrinsic drive to heal. That means the bone has become dormant, or quiescent. There may be scar tissue on the bone, which puts it into a static state of nonunion fiber. We use autograft to treat this type of nonunion. In order to reinvigorate healing, I surgically roughen the bone edges, remove the scar tissue from the middle of the bone, and then insert the bone graft into the nonunion site. Bone graft is a sort of magic ingredient that supports the body’s remarkable ability to make new bone.”
- Replacing bone structure.“Let’s say you have a bad infection and we have to resect or remove a quantity of bone to clear the infection,” says Dr. Lund. “The removed bone leaves a bone void or gap. We want to provide structure and biology to fill the gap and treat the injury. In this case, I might use some autograft, but expand it with allograft.”
Recovery following a bone graft
“It takes at least three months to know whether a graft has properly healed a fracture,” says Dr. Lund. “We monitor the repair through this period. It is rare, but possible, to weaken the bone during the bone graft harvest, causing a subsequent fracture. Other known but rare risks accompany any surgery, including infection, bleeding, blood clots, nerve damage, or complications with anesthesia. Although these complications are unlikely, we are here to follow your progress and ensure the best possible outcome.”
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