Doctors Studying Next Generation Surgery For Back Pain Sufferers

Northwestern Memorial Hospital is one of approximately 30 sites around the country testing the Maverick artificial disc made from cobalt-chrome alloy. Currently, three artificial discs are being investigated in the United States. The newest, the Maverick artificial disc, is different in that it has two rather than three components, which are both made of metal rather than using any plastics or polymers. Some studies have shown that plastics and polymers can eventually wear down, and the resulting debris and the subsequent tissue reaction to such debris is the primary factor limiting the longevity of joint replacements.

"Artificial joints in knees and hips have been around for decades, but progress in material engineering and refinement of surgical techniques finally mean we can attempt disc replacement in as critical a location as near the spinal cord," says Srdjan Mirkovic, M.D., a spine surgeon at Northwestern Memorial Hospital, assistant professor at Northwestern University's Feinberg School of Medicine, and principal investigator for the study at NMH.

At Northwestern Memorial, the study is being done collaboratively with surgeons in both orthopedics and neurosurgery.

The Maverick lumbar disc is made from a cobalt-chrome alloy, a metal frequently used for orthopedic implants. When assembled, it can move side to side or back to front. "The concept is borrowed from a concept used in replacing joints in other parts of the body," says John Liu, M.D., a neurosurgeon at Northwestern Memorial Hospital, assistant professor at the Feinberg School of Medicine and a co-investigator for the study. "The Maverick disc has no plastic parts and uses a simple design with only two moving parts. We expect this will decrease degradation of the disc and reduce problems with the mechanics of the disc."

Fusion, the current standard of care, is performed more than 200,000 times in the United States each year. "The reason we're looking for alternatives to fusion is that, while fusing two or more vertebrae in the spine together can eliminate pain, it does have drawbacks," explains Dr. Mirkovic. "The bone does not always heal or fuse correctly, and the recovery and rehabilitation periods are prolonged. The theory behind replacing the disc rather than using spinal fusion is that we may be able to preserve range of motion and decrease wear and tear at adjacent levels by distributing stress through the lower back."

As with fusion, the diseased disc is removed. Then, rather than fusing the surrounding vertebrae together, the Maverick artificial disc is inserted in its place. A calcium-rich substance anchors it in place. "The recovery may be quicker because we don't have to immobilize the lower back and wait for the bones to fully fuse as we do with fusion," explains co-investigator Matthew Hepler, M.D., an orthopedic surgeon at Northwestern Memorial and assistant professor at the Feinberg School of Medicine.

Discs are gel-like cushions between vertebrae that absorb shock and act like ball bearings when people bend and twist. Degenerative disc disease is part of the natural process of growing older. As people age, their intervertebral discs lose their flexibility, elasticity and shock absorbing characteristics. It is a common problem for athletes, but can affect anyone.

The Maverick artificial disc is an investigational device and is limited by federal law to investigational use. The research study will compare the outcomes of participants who receive an artificial disc with those of participants who have lumbar fusion. About two-thirds of study participants will receive the artificial disc and the rest will receive spinal fusion. Northwestern Memorial is enrolling participants who have failed conservative treatments such as medications and local injections for at least six months and who have pain originating from the disc itself. To learn more, please visit http://www.back.com/clinicaltrial or contact Northwestern Memorial's physician referral department at 312-926-8400 or 1-877-926-4NMH (4664).