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Lumbar disc nucleoplasty using coblation technology: clinical outcome
  1. Alaa Azzazi,
  2. Sherif AlMekawi,
  3. Mostafa Zein
  1. Neurosurgery Department, Faculty of Medicine, Cairo University, Egypt
  1. Correspondence to Professor A Azzazi, 106 Gameat Eldowal St, 12th floor, Flat No 6, Mohandesseen, Cairo Egypt; alaaazzazi{at}yahoo.com

Abstract

Background and purpose Although the standard treatment for lumbar disc herniation is lumbar microdiscectomy, nucleoplasty offers a new technique with encouraging results in well selected cases. Nucleoplasty is a minimally invasive technique that manages intradiscal herniation through energy based removal of part of the nucleus pulposus. The purpose of this study was to assess the safety and clinical outcome of the nucleoplasty procedure in well selected cases.

Methods Coblation technology was used in 50 patients, who had radicular leg pain due to contained disc herniation or focal protrusion, from 2005 to 2008. Clinical outcome was assessed by the Visual Analog Scale and Oswestry Disability Index Questionnaire. Reduction in analgesic treatment was also recorded. The procedure was performed under local anesthesia.

Results The mean Visual Analog Scale score decreased from 8.2 to 1.3 at the 1 year evaluation (p=0.001). The Oswestry Disability Index Questionnaire decreased from 62.2 to 9.6 at the 1 year follow-up (p=0.001). Analgesic consumption was reduced or stopped in 90% of cases after 1 year. There was complete resolution of symptoms in 40 patients after 1 year. There were four patients who underwent conventional microdiscectomy. Five cases had postoperative discitis which cleared clinically and radiologically within 2 months without sequelae in four of them. One patient had to undergo operative instrumental fusion at the affected level.

Conclusion Nucleoplasty does not require general anesthesia, offers less morbidity and shortens recovery time. Contained herniated disc or focal protrusion are the most important inclusion criteria. Hence this technique is a promising tool in well selected cases.

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Introduction

The primary goal of surgical treatment for disc prolapse, protrusion or extrusion is the relief of nerve root compression by removing the herniated disc material. The primary modality of treatment has been lumbar microdiscectomy. However, herniated discs are of two basic types: contained and non-contained. Contained herniated discs have an intact outer annulus with displaced disc material being held within the outer annulus of the contained herniated disc. In contrast, non-contained herniated disc has localized displacement of disc material beyond the intervertebral disc space and a breach in the outer annulus.1

Recently, percutaneous disc decompression using nucleoplasty has emerged as an effective, minimally invasive, percutaneous technique for the treatment of low back pain and leg pain due to contained herniated discs. This procedure is attractive because it shortens surgery time, does not cause significant intraoperative or postoperative pain, is safe and allows for quick rehabilitation.2 3

The process takes place at temperatures ranging from 40 to 70° due to the effect of a layer of ‘ionized plasma’, engendered around the extremity of the spine wand. The ‘plasma’ has sufficient energy to break molecular bridges thereby disrupting molecules. Degradation products will spontaneously come out from the operative channel. This radiofrequency ablation, which utilizes low temperatures over a short time (2–3 min) without damaging surrounding tissues, allows reduction of the discal volume by about 10–20%.4 Nucleoplasty works by partial removal of the nucleus, decompressing herniated discs and relieving pressure on the nerve roots. In addition, it has been shown to reduce intradiscal pressure.5 Not all patients showing improvement had significant changes in the morphology of the herniated disc, which shows that improvement was through decreasing intradiscal pressure rather than changing disc morphology, leading to the disappearance of radicular symptoms.6

The purpose of this prospective study was to assess the safety and clinical outcome of the nucleoplasty procedure in well selected cases.

Materials and methods

This prospective study was conducted between 2005 and 2008. It included 50 patients (32 men and 18 women) who underwent percutaneous disc decompression using nucleoplasty. Prior to the procedure, informed consent was obtained from patients. Since the procedure is already established, and is not under trial, approval of the ethics board was not needed. Mean age was 41 years (range 25–61). Patients were clinically evaluated preoperatively and a neurological examination was performed. Patients' medical histories were reviewed, and pertinent data such as age, gender, smoking history, location of pain, functional status and medication intake were recorded. Lumbar disc herniation was present at one level in 32 cases (32 discs) and at two levels in 18 cases (36 discs). There were six cases with single level discs at L3–4, 16 cases at L4–5 and 10 cases at L5–S1. One case had two level affection at L3–4 and L4–5, and 17 cases had two level affection at L4–5 and L5–S1. The nucleoplasty procedure was performed for 68 discs (seven procedures at L3–4 level, 34 at L4–5 and 27 at L5–S1). Patient data are summarized in table 1.

Table 1

Patient data

Inclusion criteria

On MRI imaging, patients who had disc protrusion or contained herniated disc <6 mm, with a disc height >50%, were included in the study. Patients had to have radicular pain resistant to previous medical treatment and physiotherapy for a period of at least 3 months.

Exclusion criteria

Patients who had undergone previous lumbar surgery or had significant spinal stenosis, motor weakness, fracture, tumor or spondylolisthesis were excluded. Patients who had more than two symptomatic levels were also excluded.

Procedure

All patients were treated on an outpatient basis in the operating room after administration of prophylactic intravenous antibiotic. Nucleoplasty was performed on either one disc (in 32 patients) or two discs (in 18 patients). Total number of discs operated on was 68.

Percutaneous disc decompression using nucleoplasty was performed under local anesthesia or monitored anesthesia care in the usual sterile fashion. Under fluoroscopic guidance with the patient in the prone position, a 17 gauge, 6 inch Crawford needle was advanced via a left or right posterolateral discography approach to the junction of the annulus and nucleus. All patients underwent discography with 0.5 ml of contrast material to evaluate annular integrity just prior to nucleoplasty. Annular integrity was confirmed by observing that the contrast material did not pass into the epidural space. None of the patients had annular tears, as evidenced by discography. Some authors believe that a decrease in disc height of more than 50% is a contraindication as the wand is too close to the lumbar endplates.

The Spine wand (Arthrocare, Sunnyvale, California, USA) was inserted into the disc through the needle. The proximal and distal limits for intradiscal movement of the wand were identified, and disc decompression was started. At each level, six channels were made circumferentially at the 12, 2, 4, 6, 8, and 10 o'clock positions (figure 1).

Figure 1

Lumbar nucleoplasty procedure with the wand in the disc space.

Every channel was created by advancement of the wand in ablation mode and by its retraction in coagulation mode and the needle was removed. One treatment related problem that may occur is difficulty in threading the wand into the disc space once the needle is adequately positioned. Threading the wand may be difficult if the needle tip is positioned against the endplate or if the disc is extremely degenerated. Should this difficulty arise, it was extremely important not to force the wand into the disc space because it could be sheared off by the needle tip. Additionally, the wand and needle had to be removed as a single unit once the wand was extended past the needle tip.

All patients were discharged the same day with a prophylactic antibiotic and prescribed a non-steroidal anti-inflammatory drug to be taken for 1 week.

Outcome measures

Patients were examined after 2 weeks, 3 months, 6 months and 1 year. During examinations, radicular pain was evaluated using a Visual Analog Scale (VAS). In addition, pre and postoperative Oswestry Disability Index (ODI) Questionnaires were completed at all follow-up visits. Reduction in analgesic treatment was also recorded.

Results

Analysis of outcomes of percutaneous disc decompression using nucleoplasty was performed on 50 patients on a total of 68 discs. Patient gender distribution was 64% male, 36% female with a mean age of 41 years (range 25 to 61). Most patients (81.8%) had pain for more than 12 months' duration. Smoking was reported in 68% of patients. Mean procedure duration was 7.9 min per disc.

All data were analyzed using the χ2 test. Statistical analysis was conducted using SPSS for Windows statistical package. A p value <0.05 was considered statistically significant.

Table 2 summarizes the pre- and postoperative VAS scores, ODI and number of patients using analgesics at 2 weeks, 1 month, 3 months, 6 months and 1 year.

Table 2

Pre- and postoperative VAS score, ODI and number of patients using analgesics

The mean VAS score decreased from 8.2 to 1.1, 2.6, 1.7, 1.5 and 1.3 at the 2 week, 1 month, 3 month, 6 month and 1 year evaluations, respectively (p=0.001). ODI decreased from 62.2 preoperatively to 26.6, 13.6, 9.6 and 9.6 at the 1 month, 3 month, 6 month and 1 year follow-ups, respectively (p=0.001). Likewise, analgesic consumption was reduced or stopped in 64% of patients 2 weeks postoperatively and in 78%, 82%, 90% and 90% at 1 month, 3 months, 6 months and 1 year, respectively. There was complete resolution of symptoms in 38 patients at 6 months and in 40 after 1 year.

There were four patients who had persistent pain and underwent conventional microdiscectomy (p<0.01). There were no intraoperative complications. Five cases had postoperative discitis which cleared completely clinically and radiologically within 2 months without sequelae, and a good result was obtained at 6 months in four of them (p<0.01). One patient had to undergo operative instrumental fusion at the affected level.

MRI and/or CT were performed 6 months after the procedure. These investigations showed that bulging was eliminated in 34%, significantly reduced in 48% and unvaried in 18% of cases.

Discussion

Data provided by studies on the natural history of lumbar disc herniation and radiculopathy indicate that large and migrated herniations tend to decrease in volume to a greater extent than protrusions or small contained herniations which have less tendency to spontaneous regression. There are several treatment approaches for patients with nerve root compression due to a herniated disc.7 8

The success of open surgery for lumbosacral disc herniation is approximately 93–98% on short term evaluation but 5–7 years later it significantly decreases (75–80%). The so-called failed back surgery syndrome is caused by scar tissue or recurring hernia.9 10

Over the past decades, there has been increased interest in developing minimally invasive techniques for the treatment of disc herniations and chronic discogenic pain. This trend may be related to concerns relative to surgical trauma, potential complications of operative interventions and questionable efficacy in relieving discogenic pain.11–13 This has led to the emergence of different minimally invasive techniques such as percutaneous laser discectomy, intradiscal electrothermic therapy, percutaneous endoscopic discectomy and percutaneous nucleoplasty. Because nucleoplasty uses coblation technology with a non-heat driven ablation process, it produces minimal damage, minimal thermal penetration and localized effect. Chen et al have reported that there was no evidence of direct mechanical or thermal damage to the surrounding tissues in an experimental study using coblation of nucleus pulposus.4 5

The main goal of percutaneous procedures, other than effective treatment, is safety. While open surgery is effective, it has well known disadvantages, including epidural scarring, damage to bone, denervation of paraspinal muscles with consequent lumbar instability, long postoperative inactivity and the frequent ‘failed back surgery syndrome’.14

The concept of nucleoplasty is based on the principle that in an enclosed space a reduction in volume, even partial, confers a much greater reduction in pressure; this leads to decreased pressure on the nerve root and relief of sciatica, even without a radiographically evident reduction in total disc volume. After weeks or months, the partial vacuum causes the protruded portion of the nucleus pulposus (or other disc material) to move away from the nerve root back towards the centre of the disc, pushed by partially intact fibers and ligaments of the outer annulus; this process, along with regeneration of a more fibrous nucleus pulposus, favors restoration of the inner fibers of the annulus and decreases the tendency to further protrusion towards the spinal canal.15 16 The success of the procedure depends to a great extent on selecting lesions to treat: the protruding nucleus pulposus must be at least partially contained by the external fibers of the disc, without a large extrusion or migrated or sequestrated fragments. Such contained lesions are often circumferential bulges or protrusions which appear broad on axial MRI or CT.17 18 As MRI and CT do not usually enable distinction of a contained from an uncontained prolapse, in doubtful cases discography may help in assessing annular tears and extruded lesions. Discography may also show the size of the ‘neck’ connecting the protruded part of the disc with the central nucleus pulposus: the wider the connection, the more likely efficient transmission of pressure towards the centre of the disc.19 20

Nucleoplasty uses coblation (controlled ablation) technology with RF energy, providing controlled and highly localized ablation, resulting in rapid tissue removal with preservation of adjacent tissues. The proposed suggestion in this technique is that a small change in volume produces a large change in pressure; thus pain reduction may also arise from reduced intradiscal pressure. The only component of pain being treated is the leg pain caused by radicular compression.21 22

This technique has minimized the invasive nature of surgery and helped avoid or decrease complications such as fibrosis and infection linked to open surgery. The advantages of nucleoplasty are the percutaneous approach, outpatient procedure, local anesthesia or monitored anesthesia care and very short procedure time. Hence the patient can return to normal daily activities in just a few days.23–25

Our experience with nucleoplasty has been favorable, as reflected in our patients' VAS scores, analgesic consumption and ODI. The mean VAS score decreased from 8.2 to 1.1, 2.6, 1.7, 1.5 and 1.3 at the 2 week, 1 month, 3 month, 6 month and 1 year evaluations, respectively (p=0.001). ODI decreased from 62.2 preoperatively to 26.6, 13.6, 9.6 and 9.6 at the 1 month, 3 month, 6 month and 1 year follow-ups, respectively (p=0.001). Likewise, analgesic consumption was reduced or stopped in 64% of patients 2 weeks postoperatively and in 78%, 82%, 90% and 90% at 1 month, 3 months, 6 months and 1 year, respectively.

There were four patients who had persistent pain and underwent conventional microdiscectomy. There were no intraoperative complications. Five cases had postoperative discitis which cleared completely clinically and radiologically within 2 months without sequelae, and a good result at 6 months in four of them. One patient had to undergo operative instrumental fusion at the affected level.

From our experience, it was noted that the incidence of infection increases when the number of performed channels is more than six in a single level. It also increases when performing ablation near the endplates. The cases which developed discitis were among those done early in the study, denoting the significance of the surgeon's learning curve. Some authors believe that a decrease in disc height of more than 50% is a contraindication as the wand is too close to the endplates.20 26

Based on initial data, nucleoplasty appears to be a promising treatment for contained disc herniation with radiculopathy. Clinical studies using nucleoplasty have reported varying success, depending on the inclusion criteria. The results in these clinical reports are total resolution of leg pain in 70% of cases and patient satisfaction in approximately 80% after 6 months.3 11 27 28

Some authors have reported similar good results using the nucleoplasty technique in their patients. Sharps and Isaac treated 65 patients with low back and leg pain and reported that the procedure resulted in an overall 80% success rate.2 Singh et al reported on 67 patients with a similar etiology; the percentage of patients reporting improvement was 79% at 6 months.3 Our patients had improvement of, on average, 6.7 points at 6 months and 6.9 points at 1 year, in terms of VAS scores, with substantial reduction of analgesic consumption at the latest follow-up. Comparing the results of this study with previous studies, it is evident that strict inclusion criteria provided better results in all improvement parameters, not overall success rate. Despite technically successful procedures, four patients underwent microdiscectomy because of intractable pain. This failure rate is similar to those of other studies.

Cohen et al reported on seven patients who underwent nucleoplasty where only one patient reported >50% reduction in pain score. The authors mentioned that half of their patients had annular tears and that they had not formally measured the degree of herniation, and some of their patients had herniations extending more than 5 mm. They suggested that nucleoplasty should be done only in patients with small contained disc herniations and annular integrity.24 Indeed, our encouraging results are most probably due to strict patient selection criteria, including those mentioned by Cohen et al; patients with large or extruded disc herniations, with disc height <50% and with evident annular disintegration will not benefit from nucleoplasty and should not be treated with this technique.

This prospective study demonstrated a statistically significant improvement in VAS pain scores and functional status and a reduction in medication intake in a group of patients with radicular pain who failed conservative treatment. Moreover, we did not offer this procedure to patients with a history of open disc surgery at suspected levels, as these patients are considered poor surgical candidates and have historically been a challenging population to treat. The results of this study are similar to those reported by Alo et al in 2004. In his study, Alo used a Dekompressor 1.5 mm percutaneous discectomy probe to mechanically debulk the disc material, allowing for a reduction in intradiscal pressure. Although Alo et al used a different technology, they achieved the same goal as we did in our study using nucleoplasty.29 The mechanisms underlying the successes of both procedures are postulated to be related to disc remodeling, which results in volume reduction with a subsequent decrease in intradiscal pressure and a concomitant reduction in release of inflammatory mediators.30–32

Conclusion

Nucleoplasty in patients with lumbar disc herniation is a minimally invasive technique which provides rapid recovery in well selected cases. Following strict inclusion criteria maximizes the rate of success of the procedure. This procedure is indicated in patients with a disc protrusion or contained herniated disc <6 mm, with a disc height >50% and who failed to respond to conservative treatment for 3 months.

Key points

  • The standard treatment for lumbar disc herniation is lumbar microdiscectomy.

  • Nucleoplasty is a minimally invasive technique that manages intradiscal herniation through energy based removal of part of the nucleus pulposus.

  • 50 cases who had radicular leg pain due to contained disc herniation or focal protrusion underwent the procedure.

  • Clinical outcome was assessed through Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) Questionnaire.

  • Studying the outcome, this technique is a promising tool in well selected cases.

References

View Abstract

Footnotes

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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