Latest Findings of the Stanford Discography Group
Surgeons attending the International Society for the Study of the Lumbar Spine (ISSLS) got the surprise of the decade. A group of researchers from Stanford University led by Eugene Carragee presented the results of 10 years of study on discography. Discography is a diagnostic test used to determine which disc in the spine is causing problems. A dye is injected into the suspected disc(s). If the injection reproduces the patient's pain, the test is considered positive.
This test is used in a number of ways. First, it helps identify when and where a disc is the underlying cause of a patient's pain. That is very helpful when planning treatment that will specifically address the cause of the painful symptoms. On the flip side, it can rule out a disc problem. No one wants surgery to remove a disc only to find out there was nothing wrong with it. Anytime treatment is focused on the disc, the disc provocation test offers very useful information.
But the results of Dr. Carragee's work suggests that the puncture wounds left by discography eventually lead to disc degeneration. That puts the patient at an increased risk of disc herniation. In the study cited, two groups of adults without back pain were compared after 10 years' time. They all had baseline MRIs of the lumbar spine taken. One group had discography done at three lumbar levels (L345). The second (control) group did not have discography done. Follow-up MRIs were conducted whenever possible.
Three findings stand out from this study. 1) Patients with discs that had been punctured were at greater risk of disc degeneration compared with the control group. 2) The discography group had more than twice the number of new disc herniations compared to the control group. And those herniations were usually on the side of the puncture wound. 3) There were more reactive changes seen in the vertebral endplates in the discography group. The endplates are round discs of cartilage between the disc and the vertebral bone.
Based on the results of numerous studies (including this one) from Dr. Carragee's group, it's easy to jump to the conclusion that discography simply shouldn't be used anymore. If not from an evidence-based standpoint, then from a medical legal one. It would be one thing to show that the discography isn't a good (reliable, valid) diagnostic tool. It's something else to say it leaves people at risk of harmful side effects.
But Dr. Carragee pointed out that there are some other findings to consider. First, not all of the discs that were injected actually developed degenerative changes. Most of the degeneration was not accompanied by any symptoms. Without the MRIs, the patients wouldn’t even know they had a herniated disc. Looking at other areas of the lumbar spine, there was no evidence of accelerated disc degeneration. That helps prove that the changes observed weren't just part of the aging process and would have happened anyway even without discography.
What's the take-home message from all this? Well, first-of-all, the value of discography must be considered. Certainly, the results of the Stanford group must be carefully reviewed and repeated in other studies. Some members of the audience who sat in on the presentation of these findings asked if smaller needles or lower injection pressures would make a difference. Dr. Carragee noted that those two measures were already used in this study with the results as reported. In fact, they even used a nontoxic dye and avoided injecting the discs with antibiotics (using intravenous antibiotics instead).
It was also pointed out that if injection of the discs with discography causes disc degeneration, then other procedures that involve injecting the disc must be re-evaluated. That would include procedures such as intradiscal thermal therapies and disc replacement. It also complicates diagnostic testing before spinal fusion to identify the involved levels. Right now, there are no other tests that could do what discography does. An alternative way to test the disc must be found.
It's possible discography could be used effectively and safely with certain subgroups of patients but that hasn't been investigated or discovered as yet. For now, it's clear that the role of discography is being questioned and some further answers are needed. The Stanford Discography Project hopes to answer some of those questions in the not-too-distant future.
The BACK Letter. Will a New Study End the Use of Discography as a Diagnostic Test for Painful Disc Degeneration? In The BACK Letter. July 2009. Vol. 24. No. 7. Pp. 73,79-83.
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