Chymopapain for herniated intervertebral disc. A methodologic analysis and an agenda for future research.

Chymopapain recently has won approval in the United States for use in chemonucleolysis of herniated intervertebral discs. New research findings will be emerging, but clinicians need criteria by which to assess new results, to evaluate the existing literature, and to strengthen future investigation. Twenty-six original articles on chemonucleolysis were reviewed according to nine criteria of validity and applicability. Common threats to validity were failure to use randomized controls, make blind outcome assessments, assure equal co-treatments, and to calculate statistical power when results were negative. Threats to applicability included wide variations and incomplete reporting of patient selection, procedure technique, and many relevant outcomes. Methods for improving these design features are suggested, and a basic study design is proposed for comparing chemonucleolysis with both surgical and conservative management techniques.