Bone Grafts
Overview:
Bone grafts are commonly used in spinal surgery. An organizational approach to bone
grafts using the following outline is helpful. This will probably be more information than
most people desire. However, for the curious, this should include most of the
information necessary to arrive at a good understanding.
Autograft
Iliac crest
Anterior
Posterior
Cancellous bone harvest
Allograft
Fresh frozen or freeze-dried
Iliac Crest
Fibula
Femoral Ring
Other
Patella
Vertebral body
Other long bone
Science:
Bone grafts serve multiple purposes in spinal surgery. They bring necessary progenitor
cells to the proposed fusion site and their lattice like structure presents a scaffold for new
fusion bone to grow onto. The cells and chemicals that are necessary for fusion have
properties that spine surgeons call osteoinductive. The framework that is necessary for
new bone to grow along is called osteoconductive. In the fusion process the goal of the
surgeon is to have proper bone graft material that will bring both osteoinductive and
osteoconductive properties to the site for a successful fusion to occur.
Bone grafts also may be called upon to provide a structural support. In the case of a
lumbar fusion when the disc space is removed, a structural body is needed to maintain the
separation of the vertebral bodies (If this was not present the vertebral bodies would
collapse towards each other and narrow the space for nerves to go between them. Proper
alignment would not be maintained and pain may ensue) A femoral ring allograft is a
typical bone graft that has been used to place between the lumbar vertebrae.
A Surgeon’s Perspective:
A surgeon’s choice of bone graft will ideally be based upon the following factors:
What osteoinductive potential is necessary?
What osteoconductive potential is necessary?
How much structural support is necessary
Is harvest of local bone worth the risk in this case?
Is the supply of bone adequate?
Would other material (titanium cage, PEEK, carbon fiber) be useful?
A Patient’s Perspective:
Most patients will be explained the options of bone grafting when considering
their surgical procedure. The choices for graft are increasing on a daily basis. A
surgeon’s comfort level is obviously important in determining the ultimate bone graft to
be chosen. A patient, however, must carefully weigh the risks, benefits, and alternatives
in choosing the bone graft material to be placed in his/her body. The risk of infection
with a transmissible disease from the bone graft is very low. The complication rate of
bone graft harvest can be significant (10-25%). Furthermore the failure of successful
fusion from improper bone graft selection may require re-operation. All these issues
should be discussed prior to surgery.
New Developments:
Allograft bone has been sculpted into increasingly convenient forms for use in surgery.
Bone morphogenic proteins have revolutionized the methods of delivering osteoinductive
materials to the bone graft site. Coral material has been used to provide the scaffolding
for some types of grafts.