Bone Graft Harvest
An actual surgery done by Jeff Fischgrund, M.D.
Often times, spinal surgery involves a fusion of two adjacent spinal bones (vertebrae to vertebrae). A fusion occurs when bone grows between two of these vertebrae, thus stopping all motion between these two segments. In order to obtain a solid fusion, bone graft or other material which causes bone formation must be placed between various portions of the two spinal bones. This bone graft can be obtained from multiple places in the body, but is typically obtained from either the back of the waistline (posterior iliac crest) or front of the waistline (anterior iliac crest).
Typically, bone graft for fusions of the back of the neck (cervical spine) or the low back (lumbar spine) are obtained from the posterior iliac crest, while bone graft for fusions of the front of the cervical spine is obtained from the anterior iliac crest.
Posterior iliac crest bone graft is frequently obtained through incision over the back of the waistline, or can occasionally be obtained through the same incision as the incision for low back spine surgery. Strips of bone are removed from the outer portion of the iliac crest with sharp instruments called osteotomes and gouges. These bone strips are comprised of dense cortical bone and less dense cancellous bone. When bone graft is taken from the anterior iliac crest, a skin incision is made in the front of the waistline and the dense cortical bone is removed with the aid of a power saw. This dense cortical bone, which is removed from the anterior iliac crest, is often used for placement in the anterior cervical spine, following an anterior cervical discectomy.
A major complication of bone graft harvesting is pain associated with removal of the bone. Since this procedure involves removal of bone from the body with sharp objects, its pain intensity can be similar to that of fractures elsewhere in the body. Often times, patients may notice marked relief of their arm or leg pain following spine surgery, but are frustrated and disappointed by pain from the site of the bone graft harvest. This pain can often last several months. Besides the common complication of pain, the incisions from bone graft harvesting can lead to areas of numbness in either the back of the waistline, front of the waistline, or down the anterior thigh. The combination of pain and numbness following bone graft harvest can lead to an increased hospital stay following the surgical procedure, as well as a prolonged rehabilitation time from the procedure.
Recent advances in biotechnology has led to the induction of purified proteins called Bone Morphogenetic Proteins. Two proteins currently approved by the Food and Drug Administration (FDA) are Infuse (BMP-2) and OP-1 (BMP-7). These two proteins are normally found in humans, but can now be produced in large bioreactors. Once these purified proteins are placed in various sites throughout the body, it will begin a process which causes bone formation. When either Infuse or OP-1 is placed in between the spine bones, it can lead to a spinal fusion. The advantages of using these proteins is obvious; there is much less need for bone graft harvesting. Currently, Infuse is approved for use in the anterior lumbar spine, with the addition of a metal cage. OP-1 is approved for revision fusions in the posterior lumbar spine and for those patients who may have a difficult time healing their fusion.
Research continues on both of these proteins which should lead to their more widespread use in the near future.
In summary, bone graft harvesting and its use in the spine for spinal fusion has been the standard of care for several years and frequently leads to a solid fusion. A major disadvantage of bone graft harvest is the increased surgical time for this procedure, the pain and disability following the procedure, and the prolonged rehabilitation which is necessary. If you are scheduled to undergo a spinal fusion, you should ask your doctor if you are a candidate to receive these new bone morphogenic proteins, with the potential to decrease your postoperative pain and improve your outcome.