Experimental study on chemonucleolysis. With special reference to the change of intradiscal pressure

The purpose of this study is to investigate mechanical change in the intervertebral disc after chemonucleolysis. Thirteen monkeys were used. After transperitoneal approach to the lumbar spine, 400 units of Discase was injected into each disc. The animals were killed 1 day; 1, 2, 3, 4, 6, and 12 weeks; and 1 year after chymopapain injection. Compression load was applied to the segment composed of a disc and adjacent vertebral bodies. Intradiscal pressure was measured simultaneously. A linear relationship was noticed between compression load and intradiscal pressure. In chymopapain-injected discs, the pre-existing pressure decreased or disappeared, and the increase of pressure for a given load was lower than that of the control. Our biomechanical study suggested that the decrease of intradiscal pressure as a possible mechanism of symptom relief in chemonucleolysis.