Panel Recommends Approval of Bone Growth Protein as Alternative to
Bone Grafts in Spinal Fusion
rhBMP-2 Would Be Less Painful, With Speedier Recovery and Lower Cost,
Emory Researcher Says
panel of the U.S. Food and Drug Administration (FDA) has unanimously
recommended approval, with conditions, of a genetically engineered protein
that stimulates the growth of bone cells and could provide a viable
alternative to the painful bone grafts often used in spinal fusion surgery.
If approved, the protein, called rhBMP-2 (recombinant human bone morphogenetic
protein), would allow orthopaedic surgeons to use the body's own growth
system to generate new bone following traumatic injury or disease.
The rhBMP-2 protein is a
recombinant version of the naturally occurring BMP protein, which causes
new bone to grow in cells capable of developing into bone cells. Scott
D. Boden, M.D., an orthopaedic surgeon at Emory University School of
Medicine, has been studying rhBMP-2 since 1993 as a potential alternative
to spinal bone grafts. The Emory Spine Center has been a key contributor
to reaching this important milestone of the first bone growth factor
to be deemed approvable by an FDA panel.
The protein was developed
and discovered by its manufacturer, Wyeth-Ayerst Laboratories, and will
be distributed by Medtronic Sofamor Danek, a leader in spinal implants.
The FDA Orthopaedic and Rehabilitation Devices Panel's conditions for
approval include three post-approval studies.
When a person's lower back
is painfully injured, or when a patient suffers from chronic back pain
due to spinal deformity or instability caused by degeneration, cancer
or infection, surgeons can fuse two or more vertebrae in the spine to
relieve pressure. About half a million patients each year in the United
States undergo this operation. Spinal fusion surgery requires that the
surgeon take bone from the pelvis and apply it, or graft it, to the
compromised area of the skeleton. The harvesting procedure is painful,
and patients usually are immobilized for months while the graft fuses
with the host bone.
Emory has been the leader
of a pilot clinical trial of patients with degenerative disks and chronic
back pain conducted over the past five years at Emory, the University
of Wisconsin and UCLA. Dr. Boden and his colleagues found that 11/11
patients made solid bone with the rhBMP-2 protein.
Emory also has participated
in the pivotal randomized clinical trial involving 279 patients, which
has shown similar promising results. Approximately half the patients
received bone grafts and the other half were treated with rhBMP-2. All
the bone graft patients experienced pain at the donor graft site, whereas
the rhBMP-2 patients experienced no hip pain. Fusion rates for both
treatment groups were high, and patients in both groups were experiencing
similar relief from their low back pain at two years. The experimental
group experienced shorter operative times and less blood loss than did
the control group.
"Whereas in many instances
the body does not come through on its own, by using rhBMP-2 we can harness
the body's own power to generate bone, " says Dr. Boden. "The
exciting thing about rhBMP-2 is not only does it eliminate all the problems
associated with taking the patient's own bone, it also has the potential
to do it better."
When using the alternative
treatment, Dr. Boden and his colleagues fill a cylindrical cage of titanium
with a sponge soaked with BMP, then implant the cage in the spine where
new bone is needed. The BMP attracts bone to grow and eventually the
new bone surrounds the implanted titanium cage. If the FDA approves
the BMP-2 product, which could happen in the next few months, it will
be classified as a biological device.
The product's name will be
InFUSE Bone Graft, and it will be available in select centers, including
Emory, for very specific indication of anterior spine fusion with a
tapered titanium fusion cage.
"This new technology
will allow us to make bone safely and consistently," Dr. Boden
said. "This means the potential for faster recovery, better results,
less hospitalization and lower costs for eligible patients with low
Under the directorship of
Dr. Boden, the Emory Spine center is internationally recognized for
its award-winning research and excellence in clinical care and as one
of the largest university-based multidisciplinary spine centers in the