The effect of laser irradiation for nucleus pulposus: an experimental study

Background: The radicular pain caused by disc herniation can be explained by two mechanisms: the compression of the nerve root by the herniated disc or the irritation of the nerve root due to chemical factors. Percutaneous laser disc decompression (PLDD) was introduced for the treatment of lumbar disc hernias in the 1980s. Decompression of the nerve root is assumed to be an effective therapeutic mechanism for PLDD. However, laser irradiation might reduce the chemical factors that cause nerve root irritation by altering intra-disc proteins. We used nerve conduction velocities (NCV) and levels of two chemical factors to evaluate the differences between the two groups in this in vivo study. Methods: All rabbits had the nerve root in contact with the leakage from the nucleus pulposus. One group underwent laser irradiation for the leaking nucleus pulposus including the incision site of the disc and nucleus pulposus itself. The levels of two chemical factors, prostaglandin E2 and phospholipase E2, in the intervertebral disc were measured before and after laser irradiation. Results: NCV in the laser-irradiated group was significantly faster than in the non-laser-irradiated group. The levels of chemical factors were significantly reduced after laser irradiation. Conclusions: One of the mechanisms thought to be responsible for PLDD's effectiveness is a decrease in the chemical factors through protein alteration in the intervertebral disc by laser irradiation.