Functional Analgesic Discography (FAD), what happened?

 Functional Analgesic Discography (FAD), a once promising successor of provocative discography (PD) in diagnosing discogenic low back pain. PD, the already bruised gold standard, has been beaten by Dr. Carragee to half dead and stays at the intensive care unit at this moment. For surgeons and radiologists alike, we almost lost a strong persuader to lure the patients into the operating or radiology rooms.

 FAD is a simpler test than PD that you inject anesthetic agent into the suspected disc, then ask the patients whether their chronic, daily agonizing low back pain has been decreased or gone. If so, lumbar interbody fusion surgery then may be indicated.
 Curiously, the FAD  clinical trial had been withdrawn prior to enrollment, dated Sept. 15, 2010.
 What happened?
 Here, if the news of withdrawn was true, I would like to do a mini-autopsy of this still-born yet important functional test, based on my personal experience of FAD in last 6 years:
 1. in relatively hydrated discs (young patients), the anesthetic agent may be contained inside the nucleus and cannot reach the annulus or bony endplates which have rich yet abnormal innervation (presumed to be the pain sources), hence no analgesic effect occurs;
 2. the amount of anesthetic agent injected may be another one of the important factors;
 3. leakage of the anesthetic agent into the spinal canal may result in false-positive outcomes;
 4. pain provocation does not occur in advanced dessicated discs, as opposed to their findings;
5.  a certain percentage of false-negative FAD proved otherwise by the later successful interbody fusions.

Anesthetic Discography in an 81 years old gentleman. Contrast inside the disc (red arrow).

FAD, like PD has certain limitations. It is a regret that they withdrew the clinical trial. There would have been an interesting and useful (with reservation) report.

P.S. the abbreviation: FAD is an unlucky one, according to urban dictionary: a thing that becomes very popular in a short amount of time, and then is forgotten at about the same speed.