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Spinal Fusion and Bone Morphogenetic Protein

The Marriage of Science and Medical Technology

Peer Reviewed

Spinal Fusion has long been an accepted procedure for stabilizing the spine in cases of instability or discogenic back pain that has failed more conservative treatments. The surgery involves extensive muscle dissection often leading to permanent weakness and pain. A second surgical site is required for obtaining bone for grafting the fusion site. This creates an additional morbidity of harvesting bone graft from the patient’s pelvis. Patients often complain of pain from the graft harvest site that is more severe and lasts longer than the surgical site itself. The combined problems related to the surgical site and the bone graft harvesting have led researchers to design less invasive ways to achieve the same goal of spine stabilization.

Genetic Engineering
Using the combined disciplines of science and medicine, the solution is now within our grasp. Scientists have the technology to remove isolated strands of DNA (deoxyribonucleic acid), the building blocks of life, and place those strands inside the cells of other lower animal species where the cells can be grown in the lab creating unlimited amounts of the desired DNA. This process, called recombinant DNA or genetic engineering, has allowed scientists to mass-produce proteins that can be used by doctors to selectively drive certain functions in the human body including the formation of bone. The protein that has been identified for this function is called Bone Morphogenetic Protein. There are actually several types of BMP that have been identified. One of them, called rhBMP-2 has been extensively studied and shown to be effective as a substitute for bone graft that has been taken from the patient’s pelvis. Thus fusions performed with rhBMP-2 are as effective as bone graft without the need or problems associated with a second surgical site.

Laparoscopic Surgery
The second area of research involved creating less invasive ways to perform the spinal fusion, thus leading to less pain, shorter hospital stays, and more rapid return to a normal life. Much of the pain associated with surgery has to do with the detachment or cutting of muscle tissue. A technique has evolved called laparoscopic surgery, which allows access to the abdomen or in this case the spine itself through small incisions less than an inch in length. Small cameras and sophisticated instruments are inserted through these small incisions going between the muscles and into the abdominal cavity without cutting or tearing the muscle tissue.

Patient Outcomes
In December of 2001 Doctors at the New Hampshire Spine Institute reported on a series of 22 patients who had undergone spinal fusion using rhBMP-2 through a laparoscopic approach. The results were reported in the journal Spine 2001; 26:2751-2756. The research was done as part of a larger multicenter study sanctioned by the FDA. The average hospital stay was only 1 day, shorter than for any other reported fusion procedure. Of the 21 patients who completed the study; all of them reported improvement in back pain, leg pain, and function. They all achieved a solid fusion by 6 months and all of them were able to return back to work. This was the first study on spinal fusion that demonstrated a 100% success rate for both clinical and radiographic outcome.

Conclusion
This combination of scientific and medical technology represents the future of modern healthcare. As we unlock more of the mysteries of how the human body functions we will be able to manipulate those functions in a controlled manner using human proteins that are manufactured or grown in the laboratory but utilized in the living patient. We can then combine these “wonder-proteins” with minimally invasive surgical techniques to relieve back pain more quickly and efficiently. It is entirely likely that spinal fusions will soon be possible as an outpatient procedure.

rhBMP-2 has recently received clearance from the Food and Drug Administration (FDA) for specific uses. Consult your surgeon to learn if you are a candidate.

Updated on: 09/07/12
Jean-Jacques Abitbol, MD

The discovery of rhBMP-2 will have major implications in the way spine fusion surgery will evolve. The avoidance of bone graft morbidity is a major step in post-operative patient care and predictable fusion results should lead to improved patient outcomes.

Additionally, with the evaluation of minimal access surgery, this should further manage tissue trauma leading to earlier mobilization of the patient. Further application of gene therapy to spine surgery elsewhere is evolving.

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