Discography: an element of decision. Surgery versus chemonucleolysis.

It is a well known fact that both surgery and chemonucleolysis can cure a patient suffering from root pain due to a prolapsed intervertebral disc. However, the failure rate after intradiscal injection of chymopapain remains important. Analysis of the cases operated after unsuccessful chemonucleolysis show that about two thirds are due to a remaining discal fragment. Considering the possibility of a bad penetration of the enzyme in the herniated area, neither computed tomography (CT) scan nor myelography, but only discography, can demonstrate invasion of the prolapsed area. On a series of 165 patients injected with chymopapain in only one disc, discographic data were correlated with the result of the treatment on the root pain. Three items were analyzed: the size of the protruding area located at the back of the disc (closely related to operative findings, as shown on a previous study), the density of the contrast medium filling the protruding area, and the pain response during the injection. A large, well-filled protruding area characterizes a "good" image and correlated with 76% of good results. Likewise when the pain response is lateralized (in the buttock or the affected lower limb), it correlates with 42% of success and 13% of failures. In 24.8% of the cases a combination of good images and lateralized pain correlates with 97.5% of good results. Therefore discography should be an element of decision between surgery and chemonucleolysis, and should be considered as a preoperative examination.