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INTRODUCTION
Lumbar disc herniation is among the most common of the musculoskeletal diseases. Because majority of cases have a favorable prognosis, non-surgical treatment should be considered [1]. Minimally invasive procedures or lumbar disc surgery can be considered in cases that are non-responsive to conservative treatment [2].
The pathogenesis of pain in lumbar disc herniation involves both inflammatory and mechanical mechanisms [3]. If inflammation is the main cause of pain, anti-inflammatory treatment may be sufficient [4,5]. However, in the event of mechanical origin, decompression is required [6]. Surgical decompression can resolve the pain and dysfunction of disc herniation more rapidly than conservative treatment, but its benefit wanes over time [3,7]. In addition, many patients suffer from surgical complications, including failed back surgery syndrome [8-11]. Therefore, several minimally invasive procedures have been developed, which are designed to minimize tissue damage, including intradiscal electrothermal annuloplasty, nucleoplasty, automated percutaneous lumbar discectomy, percutaneous laser disc decompression, and percutaneous endoscopic lumbar discectomy [12].
The enSpire™ interventional discectomy system (SpineView, Inc., Fremont, CA, USA) is a nonthermal, needle-based tool designed to cut, grind, and aspirate disc tissue in lumbar discectomy procedures [13]. This device was approved by the Food and Drug Administration and released in the USA in 2009. However, there have been no reports to date on outcomes of treatment of lumbar disc herniation with enSpire™.
We designed this preliminary clinical observational study to evaluate the hypothesis that percutaneous mechanical lumbar disc decompression using enSpire™ improves the symptoms of lumbar disc herniation. The primary objective of the study was to evaluate changes in pain intensity at 3 months after percutaneous mechanical lumbar disc decompression. The secondary objective was to evaluate changes in the degree of disability after the procedure.
MATERIALS AND METHODS
This study was a preliminary clinical observational trial. The trial was conducted between January 1, 2014 and December 31, 2014 at the pain clinic of a university hospital, with a follow-up period of 3 months. The Institutional Review Board approved the study protocol; and all patients provided written informed consent to participate in the study.
Participants
Twelve participants were enrolled. The inclusion criteria were patients diagnosed with lumbar disc herniation based on symptoms (lower back pain and radiating leg pain), sign (< 70° in a straight-leg raise test), and magnetic resonance imaging (MRI); at least 20 years old; and non-responsive to conservative treatment for at least 3 months. The exclusion criteria were patients with a bulging or sequestrated disc; foraminal or extraforaminal disc herniation; signs of motor weakness or cauda equina syndrome; coagulopathy; infectious process; concomitant spinal disease such as spinal stenosis, facet syndrome, spondylolisthesis, compression fracture, tumor, or internal disc derangement; disc height ≤ 50% compared to a normal adjacent disc; multi-level lumbar disc herniation; and discordance between symptoms and MRI findings.
Variables
Before the procedure, several variables such as age, gender, symptom location, size of disc herniation, type of disc herniation on axial plane MRI, level of disc herniation, change of analgesic consumption (acetaminophen), duration of illness before percutaneous mechanical lumbar disc decompression, numeric rating scale (NRS) score for pain (0, no pain; 10, worst pain imaginable), and Oswestry Disability Index (ODI) score were assessed. NRS score and complications were assessed at the 1-month follow-up in our pain clinic. At the 3-month follow-up visit, NRS and ODI scores, change of analgesic consumption (acetaminophen), and any complications were assessed. Participants were divided into 2 groups depending on their response to treatment: Group 1, in which the NRS score improved by more than 50% at 3 months after procedure, and Group 2, in which the NRS score remained the same or improreved by less than 50%.
Intervention
All surgical procedures were carried out by a single expert in the operating room. A prophylactic antibiotic was injected 30 min before the procedure. Blood pressure, electrocardiogram, and pulse oximetry were monitored during the procedure. The patients were in the prone position with a pillow placed under the pelvis to reduce the lumbar lordotic curve. The disc level was confirmed with fluoroscopy before the procedure. After skin preparation, we inserted the introducer cannula through the Kambin’s triangle on the side ipsilateral to the symptoms under C-arm guidance (Fig. 1). For patients who had bilateral symptoms, we selected the appropriate side for the approach. To make a pilot hole and provide clearance for the device tip and device travel, the introducer cannula was carefully advanced into the intervertebral disc to 20 mm beyond the disc annulus. The cannula was pulled back to the junction between the nucleus and annulus on the side of entry, after which the enSpire™ device (Fig. 2) was inserted through the cannula. The depth of the device tip (5 or 10 mm) was selected by manipulating the locking ring. In the present study, a 10-mm depth was used in all cases; thus, the maximum distance between the cannula tip and device tip was 20 mm. The cannula was held parallel to and equidistant from the adjacent endplates on the fluoroscopic anterior-posterior and lateral views. With the device powered on, the cannula hub was slowly and repeatedly advanced and retracted for 90–120 s to remove sufficient tissue. This procedure was repeated 1–2 times, during which we removed 0.5–1 ml of disc material from each patient.
Statistical analyses
All data were presented as mean ± SD or as number of patients. Differences in age, ODI score, duration of illness, and change of analgesic consumption between Groups 1 and 2 were evaluated using an unpaired t-test or Mann–Whitney U test. Comparison of gender, symptom location, size of disc herniation, type of disc herniation, amounts of aspirated disc materials, and level of disc herniation between the groups was conducted using Fisher’s exact test. Differences in NRS scores between the initial and 1-month evaluations, and between the initial and 3-month evaluations, were analyzed using a paired t-test. P < 0.05 was considered statistically significant. All statistical analyses were performed using SPSS version 16.0.
RESULTS
Twelve individuals were recruited for this study and complete data were collected for all participants. Demographic and baseline data were presented in Table 1 and Fig. 3. Pain intensity and ODI scores were decreased after percutaneous mechanical lumbar disc decompression using the enSpire™ device; the pain reduction and improvement in disability were maintained for up to 3 months. In all individuals, the consumption of analgesics was decreased, with no difference between groups. Complications such as discitis, hematoma, or pain aggravation were absent in all patients.
Table 1
Demographic Data and Baseline Values for Patients
| Clinical characteristics | Values |
|---|---|
| Age (yr) | 44.5 ± 2.4 |
| Gender (M/F) | 7/5 |
| Symptom location (n) | |
| One side | 9 |
| Both side | 3 |
| Size of disc herniation (n) | |
| Protrusion | 8 |
| Extrusion | 4 |
| Type of disc herniation (n) | |
| Central | 6 |
| Subarticular | 6 |
| Duration of illness (months) | 30.4 ± 8.7 |
| Level of disc herniation (n) | |
| L4–L5 | 7 |
| L5–S1 | 5 |
| ODI score | |
| Before the procedure | 25.8 ± 4.6 |
| At 3 months | 18.2 ± 5.5* |
| NRS score | |
| Before the procedure | 6.9 ± 1.2 |
| At 1 month | 4.0 ± 2.7* |
| At 3 months | 2.8 ± 2.7* |
Fig. 3
Changes in the NRS over 3 months. Box plots shows the median (solid line), interquartile ranges (box), and values within 1.5 interquartile ranges from each side of the box (whiskers). *P < 0.05 compared with the initial NRS score.
Eight patients were placed in Group 1 and 4 in Group 2. There were no statistical differences between Groups 1 and 2, except that Group 2 had a longer mean duration of illness prior to the intervention (Table 2).
Table 2
Comparison between Group 1 and Group 2
DISCUSSION
We investigated outcomes of the enSpire™ interventional discectomy system in 12 patients with lumbar disc herniation for 3 months after treatment. After percutaneous mechanical lumbar disc decompression using the enSpire™ device, NRS and ODI scores were decreased. The success rate in reducing the NRS score more than 50% was 66.7%, similar to or better than other percutaneous disc decompression (PDD) procedures [14-19]. Moreover, there were no complications related to the enSpire™ discectomy procedure.
PDD is increasingly performed as an alternative to open discectomy [12,19]. Open discectomy has added risks related to general anesthesia, hospital stays of ≥ 2 days, high cost, potential complications related to broad tissue injury, and the possibility of persistent or recurrent pain [8]. On the other hand, percutaneous nuclear decompression procedures have advantages of no requirement for general anesthesia, discharge on the day of the procedure, relatively low cost, and less tissue injury.
The enSpire™ device appears similar to the Dekompressor® (Stryker Spine, Allendale, NJ, USA). Both are a high-rpm device for percutaneous mechanical disc decompression, but with different methods of removal of herniated nuclear material. The tip of the enSpire™ device is an expandable spiral cutting wire, whereas, the Dekompressor® has a screw-shaped tip [20]. In our experience, the enSpire™ has certain advantages over the Dekompressor®. First, the expandable spiral cutting wire of the enSpire™ device is wider than the tip of the Dekompressor®. When the spiral wire of the enSpire™ device is deployed, the maximum sweep diameter is 7 mm [13]. On the other hand, the Dekompressor® has 4 differently sized tips (13-, 15-, 17-, and 19-gauge) and 13 gauge (1.83 mm) is the maximum diameter. Second, the volume of aspirated disc material can be predetermined (0.5 or 1 ml) by manipulating the locking ring of the enSpire™ device. In the case of enSpire™, we anticipated better treatment results because of its wider cutting probe.
There is some debate over the efficacy of PDD. PDD, including nucleoplasty and use of the Dekompressor®, has only a weakly positive recommendation for treatment of lumbar radicular pain [21]. In other systematic literature reviews, the level of evidence for use of the Dekompressor® for chronic back pain and radicular leg pain is limited [2,18,22], particularly for long-term effects [23]. Despite negative results and recommendations against using PDD, few well-designed trials of PDD have been conducted, as compared to many trials of other treatment modalities such as open discectomy and epidural steroid injection [18].
Several limitations of this study should be considered when interpreting the results. First, the sample size was too small to evaluate correlations between clinical effectiveness and other variables or to identify possible rare complications related to the procedure; hence, the results may have little clinical significance. This was a preliminary study and participants were limited to improve the quality of the study. Second, the study period was limited and therefore, we were able to analyze only short-term outcomes of using enSpire™ (≤ 3 months). Therefore, further randomized controlled trials (enSpire™ vs. open discectomy or enSpire™ vs. other PDDs) and long-term follow-up studies are needed.
In conclusion, the enSpire™ interventional discectomy system is minimally invasive, easy to use, and effective and safe over the short term.
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