[Intradiscal injection of hypertonic saline, phenol-glycerin and osmic acid for the treatment of lumbar disc herniation: an experimental study].

Unlabelled: The present study was designed to investigate the possible clinical application of hypertonic saline (HS), phenol in glycerin (PHG) and osmic acid (OSA) for intradiscal therapy.

Materials & methods: HS in several concentrations, 10% PHG and 4% OSA were separately injected into the lumbar intervertebral discs of 60 Japanese white rabbits. Additionally, these substances were placed directly on the dura of the spinal cord of 48 guinea pigs. The animals were sacrificed periodically and were submitted to histological examination using light microscopy.

Results: HS caused localized necrosis of the nucleus pulposus cells in a concentration-related fashion. Some discs decreased their height. With time, all the discs generally regained their normal histology. Following administration of 10% PHG, the area of necrosis of the nucleus pulposus cells was more extensive than that by HS, but the regenerative or reparative reaction was not so brisk. Examination of the discs treated with 4% OSA demonstrated severe changes in the nucleus pulposus and the inner annulus fibrosus with resultant disc-space narrowing. The reparative tissue seen after injection of OSA was fibrocartilage in nature. No histological change was seen in the surrounding tissue including the neural tissue following administration of any of the substances.

Discussion: Chymopapain is the substance most frequently used for clinical chemonucleolysis. The major clinical complication with chymopapain has been anaphylaxis. The present substances have been used in other clinical applications without reports of anaphylaxis. In this report, HS was shown to hold the potential for reducing intradiscal pressure without induction of scar tissue or significant loss of disc function. PHG and OSA caused considerable but circumscribed histological damage to the disc tissue, but had no such effect on the neural tissues. These data suggested that HS, PHG and OSA may have clinical applications as agents in intradiscal therapy.