Intradiscal pressure-volume response: a methodological contribution to chemonucleolysis. Preliminary results

A new method is presented to verify whether a lumbar disc is degenerated prior to chemonucleolysis. This consists in rapid injection of a 0.3-ml bolus of saline into the center of the disc (through the needle employed for chemonucleolysis), under continuous recording of the intradiscal pressure changes caused by this volume load. If the intradiscal pressure falls below 600 mm Hg within 2 minutes after the injection, there is a high probability (p less than 0.001) that the disc is degenerated. This method has many advantages: it obviates additional injection of contrast medium prior to chemonucleolysis, it prevents inhibition of chymopapain by the contrast medium, it saves time, and it reduces the total amount of fluid injected during chemonucleolysis.