An experimental study comparing percutaneous discectomy with chemonucleolysis.

The aim of this study was to assess the macroscopic and microscopic reaction of the intervertebral disc to discectomy with the Automated Nucleotome (Surgical Dynamics, San Leandro, CA), and to compare this with simple trephining of the annulus and with chemonucleolysis. In eight adult sheep, two of four adjacent lumbar discs were randomly incised using the trephine of the Automated Nucleotome, while the remaining levels underwent nuclear excision with the Automated Nucleotome probe. Another four sheep underwent chemonucleolysis at three adjacent lumbar levels. All animals were killed at 6 weeks. The discs that had undergone trephining alone and those treated with the Automated Nucleotome probe had almost identical radiographic and macroscopic changes and showed similarities on microscopic examination. Macroscopically, these discs did not differ from control levels, whereas those treated with chymopapain showed marked changes with a reduction of both nuclear and annular volume. The results of this study suggest that any therapeutic effect of percutaneous discectomy with the Automated Nucleotome is likely to be attributable to the perforation of the annulus alone with the removal of small amounts of nuclear material contributing little, or nothing, to the claimed benefits of the procedure.