Spinal fusion is one of the most common surgeries done in the neck or back. The basic idea is to fuse together painful bones in the spine so that they heal into a single, solid bone. In order for bones to fuse or heal together, additional bone is needed. This additional bone is called a bone graft.
Many bone graft options are used today. They are often are combined together. The graft that is best for your problem will depend upon which section of your spine needs to be fused, your age, and your general health.
The standard technique used in fusion is to take extra bone from one part of the body (harvest) and move (graft) it to another part of the body, such as the spine. This type of bone graft is called an autograft.
A surgeon usually takes the bone from an area of the body where its removal will not cause a problem. In spine surgery the bone is typically harvested from the iliac crest, which is the rim of the pelvic bone. The surgeon uses sharp tools to "scoop" the bone out of the iliac crest.
Although taking bone from the iliac crest has been used with good results, there are, however, some disadvantages.
- In some cases, it hurts to remove the bone and this pain may last for some time after the surgery.
- There is a limited amount of bone in the iliac crest, especially as we get older and our bone thins and weakens.
- The iliac crest may fracture or break.
- An infection or bleeding may occur.
There are several other options for bone grafts. Your surgeon will discuss which graft alternative may be most appropriate for you.
Local Bone Autograft
In some spinal fusion procedures, parts of the spinal bones are removed to relieve pressure on the nerve roots. This removed bone is often saved during the surgery and used as the graft. The advantage with local bone is that it is the patient's own bone and is not rejected, plus there is no additional incision and pain at the hip. The disadvantage is that there is a limited amount of bone that can be harvested from the small spinal bones.
Cadaver or Allograft Bone
Many surgeons use bone that is harvested from a donor or cadaver. This type of graft is typically acquired through a bone bank. Like other organs, bone can be donated upon death.
These types of bone grafts have been used for a long time in spinal fusion surgery. Unlike grafts taken from the patient, allografts do not form new bone. Instead, the allograft works as a bridge that allows the natural bone of the body to grab onto and grow through. Over time, the natural bone replaces the donor bone.
Allograft bone comes in different shapes and sizes to fit into the area of the spine where it is needed. In most cases, allografts are good at getting bone to heal.
These grafts are made from calcium materials and are often called a ceramic. These materials are similar in shape and consistency to autograft bone. Ceramics also have the advantage of being made without cadaver bone and are available in large amounts.
Bone marrow is located in the centers of long bones, such as the bones in your arms, thighs, and legs. The marrow is the area where stem cells live. Stem cells are special cells in your body that can turn into other types of cells. They have some ability to make new bone.
Current research is finding new ways of harvesting stem cells. Today, the doctor draws the stem cells out of the bone marrow with a needle, much like the way blood is drawn from your arm for tests. The cells are then combined with another graft like local, allograft, or synthetic bone to speed the healing process.
Biologics or Proteins
There are proteins in all of our bodies that cause new bone to form. A very common type is called bone morphogenic protein (BMP). BMP has been used to promote solid spine fusions for some time and is a common graft option. BMP has very powerful bone forming capabilities, and care must be taken with its use. Some studies of the spine and BMP show that too much bone may be formed.
The American Academy of Orthopaedic Surgeons
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