International Physician Update

Artificial May Be Better: Trials Begin for New Disc

Neurosurgeons Gokaslan and Garonzik hope the new disc does the trick.

 This fall, neurosurgeon Ira Garonzik, M.D., and his mentor, Ziya Gokaslan, M.D., will quietly stepp outside the surgical status quo. They’re replacing a patient's degenerating disc with an artificial implant.

While artificial joints have become the standard stuff of orthopedic surgeries,
using artificial discs for chronic back pain is relatively unknown in this country.  But should a multicenter study now under way pan out—Hopkins is the only area center doing the cervical spine part of the trial—that approach could give surgeons a needed alternative to conventional disc surgery. It could spark the same sort of revolution that artificial hips and knees have brought to medicine.

Artificial discs have been used in Europe for almost 15 years. But U.S. applications have been slow to come, in part because no proper clinical trials have appeared.  More likely, Garonzik says, it’s also because the standard surgery—spinal fusion—has worked well enough.

In that procedure, surgeons remove the pain-causing, degenerating disc and in its place insert a bone graft that fuses to adjacent vertebrae, turning that segment into a solid block of bone. “Getting rid of the motion in that affected segment is the means of treating the pain,” explains Gokaslan, who directs Hopkins’ Neurosurgery Spine Service.

Still, despite more than 200,000 spinal fusions performed each year in this country, the procedure has drawbacks. The problem, he says, is that the spinal column is designed to move.  “After spinal fusion surgery, healthy discs above and below the fused area see much more stress than in the past. They degenerate much more quickly than they would with regular aging. That leads to another fusion surgery and another—each bringing progressive loss of motion
for the patient.”

Artificial disc surgery represents a dramatic shift in perspective from fusion, says Garonzik.  “Now we’re trying to get vertebrae not to fuse. We’re not trying to limit motion. Instead, we want to recreate as normal a movement as possible through the disc.”   The two-year trial employs a product called ProDisc, manufactured by a Swiss firm. With a top and bottom of durable metal alloy plates and a fitted convex polyethylene pad in between, the device can be tailored to each patient.

Of the several thousand who’ve received the disc in other countries, the 64 patients followed more than a decade remain largely pain-free and have restored range of motion. The disc becomes integrated into the spinal column. The Hopkins arm of the study involves the more challenging cervical spine area, but implanting the disc isn’t particularly difficult.  Because spinal fusion has a high success rate, both surgeons say, it surely won’t be replaced. “But we hope to improve upon it,” says Garonzik, “and this is a strong start.”