Treatment of Lumbar Intervertebral Disc Herniation Using C-Arm Fluoroscopy Guided Target Percutaneous Laser Disc Decompression

Introduction

P ercutaneous laser disc decompression (PLDD) is a viable alternative treatment for herniated lumbar disc disease. ¹ Choy initially used PLDD to treat extruded but nonsequestered lumbar disc herniations in 2001. ² In order to achieve optimal safety and efficacy they believed that the needle should be parallel to the disc axis, midway between the two end plates, and with the point just past the annulus fibrosus. However, in some patients, such needle orientation is often difficult to achieve by the routine dorsolateral approach (also called safe triangle approach) because the iliac crest is too high and/or the sacroiliac angle is too small. Therefore, the needle should be inserted into the disc with an extrathecal approach. In 1994 Choy ³ reported that this approach was safe and simple and did not cause radicular pain, postspinal tap headache, nor neurologic sequelae.

PLDD usess laser energy to vaporize a small volume of the nucleus pulposus, which reduces the pressure between the nucleus pulposus and the peridiscal tissue. This pressure loss induces retraction of the herniation away from the nerve root, thus reducing nerve root compression. However, in cases of extruded but nonsequestered lumbar intervertebral disc herniations, the continuity of the annulus fibrosus was damaged. It remains unknown whether an intradisc pressure decrease causes the extruded nucleus pulposus to significantly retract. Zhao et al ⁴ showed that in both the extrusion and lumbar canal stenosis groups, the excellent and good clinical outcome rate was 55.9% in patients treated with PLDD. The comparable group (contained lumbar intervertebral disc herniations) had an excellent and good rating of 82%. This demonstrates that intradiscal decompression has minimal effects on the extruded nucleus pulposus. In some patients, the height of the intervertebral space was significantly decreased (by ∼25–50%), suggesting that the height of the intervertebral space is not a reliable indication for intradiscal laser disc decompression. Furthermore, the failure rate (for technical reasons) is ∼1.5/1000. ⁵ Based on these findings, we hypothesize that insertion of the needle into the extruded part of the nucleus pulposus will decrease its volume and provide superior clinical effects compared to therapies that decrease the volume of the intradiscal nucleus pulposus. In this study, we modified the routine method of lumbar PLDD by inserting the needle into the extruded part of the disc rather than into the intervertebral space. We observed 25 patients with extruded but nonsequestered lumbar intervertebral disc herniation over a period of 1 year to investigate whether target PLDD (T-PLDD) is efficacious and safe.

Materials and Methods

This study was approved by the Shandong Provincial Hospital Ethics Committee. The Nd:YAG laser device was purchased from Dong Tai Ji Guang Technologic Ltd. Company, Beijing, China. It is a type of end firing optical fiber with light scatter in the end of the tip.

Results

Two patients complained of severe, unbearable radicular pain when the needle reached the epidural space, 6 patients complained moderate bearable pain, and 17 patients complained of slight pain. There were no neurologic sequelae.

The therapeutic efficacy (resolution of leg pain, back pain and self-reported disability) was assessed at 1, 3, 6, and 12 months, respectively, according to the modified MacNab criteria. ⁶ A satisfactory therapeutic outcome was obtained in this group of patients at 1, 3, 6, and 12 months. The successful (excellent and good outcome) rate was 80.0% (18 of 25), 88.0% (22 of 25), 92.0% (23 of 25) and 92.0% (23 of 25) at 1, 3, 6, and 12 months, respectively (Table 2).

Twenty-five patients underwent an MRI scan at 12 months after the minimal invasive operation. In these patients, we obtained 23 excellent and good clinical outcomes and 2 fair and poor clinical outcomes. Four of the patients with clinical excellent and good outcomes showed a reduction in the disc protrusion by >4 mm, and 17 of these patients showed a reduction in the disc protrusion by 3 mm. In 2 patients, the disc protrusion was reduced by ≤2 mm. The thecal cross-sectional area increased in all the clinically successful patients. The clinically fair and poor patients showed no appreciable change in the disc protrusion and the thecal cross-sectional area. No obvious intervertebral disc height loss and end plate damage were found in this group of patients.

Discussion

Surgery and minimally invasive techniques have been shown to improve the clinical outcomes of patients with herniated disc disease who had failed a 3-month course of adequate conservative therapy. ⁷ Because traditional open surgery, which has been in practice since 1934, would further weaken an already compromised posterior wall of the disc complex, such an approach may not be in the best interests of the patient with herniated disc disease. ⁸ Therefore, the minimally invasive therapies should be considered before resorting to traditional open surgery when patients do not respond to conservative therapies.

PLDD is one of the so-called “minimally invasive” treatment methods. It can vaporize the nucleus pulposus, and decrease its volume. It has been shown that a small reduction in the volume of the nucleus pulposus, which is composed of 60–80% water, is associated with a disproportionate fall in intradiscal pressure. ⁹ Therefore, PLDD is appropriate for the treatment of contained lumbar disc herniations. It has been shown that PLDD can improve the clinical outcomes of contained lumbar disc herniations. ¹ Schenk et al ¹⁰ reported success rates in larger studies varying from 75% (with a 95% CI of 69–81%) to 87% (with a 95% CI of 80–94%). The majority of the studies considered uncontained disc herniation (extrusion or sequestered) as exclusion criteria. Therefore, few studies have addressed the treatment of uncontained lumbar disc herniations by PLDD. Choy used PLDD to treat extruded but nonsequestered lumbar disc herniations in 2001, and achieved good pain relief in patients. In some instances, it even reversed neurologic deficits. ² Zhao et al. reported that in cases of extrusion and lumbar canal stenosis treated with PLDD, the excellent and good rates combined came to only 55.9%. ⁴

In this study, treatment of lumbar intervertebral disc herniation by T-PLDD was achieved by inserting the needle into the extruded part of the nucleus pulposus instead of into the intervertebral space. We obtained a combined excellent and good clinical outcome rate of 92.0%. A previous study showed that the symptoms of lumbar intervertebral disc herniation were caused by: mechanical pressure on the nerve root, aseptic inflammation of the nerve root arising from irritating products originating from the intervertebral disc, and annular neoneuralization. ¹¹ The T-PLDD technique can decrease the volume of the extruded part of the nucleus pulposus, therefore directly relieving the pressure on the nerve root. The photochemical effects of the laser can also decrease the volume of the extruded disc, thus alleviating the compression of the extruded disc and the nerve root. Furthermore, the photobiological effects of the laser can reduce nerve root edema. ¹² Taken together, T-PLDD can provide faster pain relief than can the traditional PLDD techniques for patients with extruded but nonsequestered disc herniations.

It would appear that using a posterior paramedian approach to inject the needle into the extruded portion of the nucleus pulposus, followed by laser-mediated vaporization, would result in neurologic sequelae. The nerve root, which is adjacent to the extruded portion of the nucleus pulposus, may become injured because of the high energy generated from the laser. However, no neurologic sequelae occurred in our patients who were treated using this approach. A key point of this technique is to use iohexol injection to verify that the needle is present in the extruded portion of the disc. To make sure that the tip of the laser fiber was inserted into the extruded part of the disc, not the intervertebral space, the tip of the laser that we used for T-PLDD technique was adjusted to protrude 0.4 cm from the needle. The shorter the distance between the laser tip and the needle, the more disc tissue can be vaporized and likely get more therapeutic effect. However, it has the higher risk that the fiber tip will “catch fire” and light up the entire proximal fibers and cause nerve damage. Furthermore, another important step in this treatment strategy is to apply a single pulse of 6.5 W each in a series of 1-sec duration when vaporizing the nucleus pulposus.

Because we needed to keep the involved nerve root “live”, we did not inject anesthetic into the epidural space. In cases of patients who complained of pain in the lower extremity when punctured (which is primarily caused by aseptic inflammation of the epidural), we always injected normal saline (∼5 mL) to dilute the inflammatory factors. Because the duration of pain is very short, neither sedatives nor analgesics were given to the patients during the whole procedure.

T-PLDD is an alternative method for extruded but nonsequestered lumbar disc herniation, when the intervertebral disc height is <75% of normal value or it is difficult to insert the needle into the intervertebral space through the traditional triangle approach. Target PLDD should not be used as a routine approach for contained lumbar intervertebral disc herniations or for patients with unstable neurological deficits, cauda equina syndrome, bony spinal canal stenosis, or calcification of the extruded disc. T-PLDD may be more effective for patients with extruded but nonsequestered lumbar disc herniations at the L5/S1 level than at other levels, because the thecal is much narrower and the interlaminal space is much wider in L5/S1.

This report is a preliminary study, and the defects of this article are that it is not a randomized controlled clinical trial, and the follow-up is short. We have submitted this report for publication because we found that treatment of lumbar intervertebral disc herniation with T-PLDD is safe and effective and generates good clinical outcomes. Future studies will include a randomized controlled clinical trial to test the efficacy and safety of using T-PLDD to treat lumbar intervertebral disc herniation, and using the Ho:YAG laser, which is better than the Nd:YAG laser in delivery of energy, which will make it will be safer to prevent the damage of adjacent neural structures. In the future, we will try to use the Ho:YAG laser for this target PLDD technique to treat lumbar intervertebral disc herniation.

Conclusion

Extruded but nonsequestered disc herniations can be treated with T-PLDD, a much simpler and less invasive procedure than traditional laminectomy and discectomy.