"Revision surgery to remove the implant ... will be potentially life-threatening in every case," he explained. "And at present, there is no consistently successful strategy to deal with a failed implant."

Thus, he said, the implants -- studied for just two years in the U.S. -- should be designed to last four decades. But Paul McAfee, a Johnson & Johnson consultant with a financial interest in the discs, indicated that he would be satisfied with far less.

"Well, I hope they will last 40 years," McAfee said during the hearing. But "honestly, to talk to the patients, 10 years is (a) pretty good outcome."

McAfee then went on to undermine one of the central arguments favoring implants over traditional -- and highly successful -- spinal fusions. Fans of the device say that it preserves motion and, in turn, reduces wear on nearby parts of the spine. But McAfee confessed that he "cannot find a single study on any motion-preserving device" that proves this theory.

Meanwhile, Andre van Ooij -- a Danish surgeon who has tracked hundreds of the operations in Europe -- later offered evidence about the implant's drawbacks. He noted "retrograde ejaculation and erectile dysfunction" in men. He also cited leg complications in others and pointed to joint degeneration as an especially big problem.

"All of these patients have really terrible leg and back pain," said van Ooij. And "revision is dangerous and sometimes impossible."

Van Ooij went on to cite a 17-year study showing that more than half of Charite recipients wound up with fair or poor results. Moreover, he said, spinal fusion -- which could have been employed in the first place -- rarely offers relief to failed patients down the road.

"There was a fusion done, and this is the only one of the re-operations (among those studied) that the patient is satisfied" with, he said. "So I really would stress that it is not a good solution for the problem" in the end.

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