Abstract
Severe discogenic pain including axial or radicular pain is not easy to treat properly. Although mechanical correction was made possible to some extent, the high incidence of failed back surgery syndrome frustrates both patients and physicians. For discogenic pain, like other disorders, pain management is the discipline of intervention, principally with the application of certain techniques, such as intradiscal electrothermal therapy, nucleoplasty, Dekompressor and targeted disc decompression (TDD). These techniques are simple to use, have low complication rates and seem to be effective. The goals of interventional pain management include decrease the frequency and intensity of the pain, increase daily activities, quality of life, enhancement of coping skills and lowering narcotic use and/or other pain medications.
Keywords
intervertebral disc; pain; therapeutics: intradiscal;
1. Introduction
Various minimally invasive disc decompressions have been devised to avoid risk and complications from open surgery since the advent of chemical disc decompression using chymopapaine. Most techniques for disc decompression utilize coblation, laser, and physical aspiration, chemical or thermal methods. It is reported that these methods cause less complications compared with conventional surgery and could improve the discogenic pain of the patients.1, 2, 3 However, in terms of long-term outcome, effectiveness and cost are lacking well-designed studies to evaluate, resulting in a relatively low level of convincing evidence.
In this review, we wish to find out the minimally invasive procedures currently in application, such as intradiscal electrothermal therapy (IDET), nucleoplasty, Dekompressor and targeted disc decompression (TDD). Also, we discuss the level of the evidence, the recommendations based on the researchers' reports and the clinical usability of these procedures.
2. Intradiscal electrothermal therapy (IDET)
The rationale for heating intervertebral disc is strongly influenced by animal and clinical investigations on the ability of heat to stabilize joints by modifying the collagen. The IDET is the procedure which uses a navigable intradiscal catheter with a thermal-resistive coil as the tool. The procedure can be performed under conscious sedation. Using a standard posterolateral discogram technique a 30 cm catheter (SpineCATH Intradiscal Catheter or Decompression Catheter, Smith & Nephew Memphis, TN, USA) with a 5 cm or 1.5 cm active electrothermal tip is inserted through a 17-G introducer needle and advanced circuitously to the posterior annulus.
Electron microscopy of cadaver discs after standardized IDET has shown extensive collagen disorganization, decreased quantity of collagen, collagen fibril shrinkage, and chondrocyte damage when compared with a control.4 Despite numerous in vivo and in vitro studies using human and animal models, the precise pain relieving mechanism of intradiscal heating is unclear. Theoretic explanations of its mechanism of action are changes in disc biomechanics, annular contraction, thermally induced healing response, sealing of annular tears, annular denervation and decreased intradiscal pressure.5
The IDET is useful for managing the pain originated by annular tear or fissure because the IDET denature and shrink the collagen fibers and destruct the nociceptors. The inclusion criteria which are the most important variable of the outcome of treatment include persistent symptoms of axial low back pain and/or leg pain and impaired function at least over 6 months duration and nonresponsive to at least 6 weeks course of conservative medical management, concordant pain reproduced on discography, abnormal disc morphology and predominance of low back pain symptoms. Exclusion criteria include abnormal neurological findings and or compressive lesion, severe disc degeneration, segmental instability, other contraindicant medical conditions, and consideration of previous surgery.
Gerszten et al6 evaluated the clinical outcome of IDET for the treatment of chronic discogenic low back pain by prospective, nonrandomized clinical method. Twenty-seven patients, as determined by provocative discography and/or magnetic resonance imaging (MRI), being nonresponsive to conservative treatment for at least 6 months. Seventy-five percent of patients improved based upon the Oswestry Low Back Pain Disability Questionnaire while only 48% of patients were found to improve on the Short Form (SF)-36 Survey. The SF-36 Bodily Pain Subscale did improve relatively to other subscales in 52% of patients. There was no relationship found between outcome and duration of symptoms (p = 0.32), number of levels treated (p = 0.20), or worker's compensation (p = 0.38). There were no complications that resulted from the IDET treatment.
Appleby et al7 reported the meta-analysis with the visual analog scale (VAS) assessment of pain, the bodily pain, and physical functioning subscales of the SF-36 health survey, and the Oswestry disability index (ODI). The overall mean improvement in pain intensity was 2.9 points as measured by the VAS. The overall mean improvement in physical function was 21.1 points as measured by the SF-36. The overall mean improvement in bodily pain was 18.0 points as measured by the SF-36. The overall mean improvement in disability was 7.0 points as measured by the ODI. The overall incidence of complications was 0.8%. The complications include burning sensation one of legs, paresthesia and numbness in thighs, foot drop, increasing back and thigh pain, occurrence of headache, increasing radicular pain, decreased sphincter tone or fecal incontinence and discitis.
Ahn and Lee8 compared the clinical outcome of endoscopic discectomy with IDET. Clinical outcomes were assessed using the VAS, the ODI, and the modified MacNab criteria. The univariate and multivariate analyses were performed to evaluate the outcome predictors.
Park et al9 reported the efficacy of IDET for 25 patients with chronic lower back pain diagnosed as internal disc disruption (IDD) confirmed by MRI, preoperative discography. The follow-up duration was at least 1 year in all cases, and the visual analog scale, recovery rate, and satisfaction of each patient were evaluated. After IDET, 32% of the patients reported feeling more pain than before, 56% reported less pain, and 12% experienced no change. Forty-eight percent of the patients were satisfied with IDET, 44% were dissatisfied, and 8% were undecided about the treatment. About 1 year after IDET, nearly half of the study patients were dissatisfied with their treatment outcome. Consequently, 20% underwent fusion surgery 1 year after IDET.
According to Kallewaard et al,10 a positive RCT, a negative RCT, various positive prospective studies, and two negative studies have been published up to date. Notably, the fact that not more than two discs are degenerative is important. The outcomes in the cases with more extensive discus degeneration have been shown to be significantly worse. A serious limitation among the available IDET studies is that the selection criteria do not concur.
The following are described as complications: catheter breakage, nerve injury (cauda equina lesion), post-IDET spinal disc herniation, discitis, local infection and epidural abscess.10
3. Nucleoplasty
The decompression method, nucleoplasty, uses the coblation technology, in which a high-energy plasma field is generated. The procedure involves removing a part of the nucleus pulposus tissue by bipolar probe that creates radiofrequency energy, which excites the electrolytes in the nucleus. Two different mechanism actions exist according to the catheter direction. When the catheter enters forward, the coblation acts, by which the formed 120 μm, high-energy ionized plasma field around 1 mm breaks down the molecular bonds and dissolves the soft tissue material of the nucleus. When the catheter moves backward, the coagulation acts, by which relatively low temperatures (typically 50 °C to 70 °C) develop at the tip of the catheter causes the type 2 collagen fiber to degenerate and shrink. However, Kallewaard et al10 mentioned that the ionized plasma field could only arise in conductive surroundings in practice; this means that the treatment is not effective in a dehydrated disc. The advantages of this procedure are simplicity, relatively safety and low possibility of damaging the surrounding tissue thermally.
The performance of nucleoplasty in the selection of patients is most important. Inclusion criteria are as follows: radicular pain with or without axial neck/back pain, no improvement for at least 3 months of conservative therapies, disc herniation or protrusion confirmed by MRI, disc height more than 50% of normal disc height. Exclusion criteria are as follows: disc height less than 50% of normal disc height, severe spinal stenosis, disc extrusion or sequestration confirmed by MRI, cauda equine syndrome or newly developed signs of neurologic deficit, equivocal results of provocative discography and so on.
Zhu et al11 evaluated the efficacy of nucleoplasty in 42 patients with protrusion of lumbar intervertebral disc at a 2-year follow-up. The VAS score of back pain decreased from 7.7 ± 0.2 to 2.8 ± 0.3 at 1-week, 3.8 ± 0.3 at 1-year and 4.2 ± 0.3 at 2-year follow-up. The VAS score of leg pain decreased from 6.9 ± 0.1 to 2.2 ± 0.3 at 1-week, 3.0 ± 0.1 at 1-year and 3.4 ± 0.2 at 2-year follow-up. The VAS score of numbness decreased from 2.8 ± 0.2 to 0.4 ± 0.1 at 1-week, 0.6 ± 0.1 at 1-year and 0.9 ± 0.2 at 2-year follow-up. Before the operation, the mean value of ODI was 68.2 ± 10.9%. The value at 1 week follow-up was 28.6 ± 8.2%, at 1 year was 35.8 ± 6.5%, and at 2-year value was 39.4 ± 5.8%.
Manchikanti et al12 reported a systemic review of lumbar nucleoplasty. In spite of paucity reports in literature, the evidence of nucleoplasty is level II-3 (based on evidence developed by USPSTF) in the treatment of leg pain but no evidence in managing axial low back pain. The recommendation is 2B/weak recommendation in managing radicular pain due to herniated disc. No recommendation is available in managing axial low back pain.
Yan et al13 reported the comparison of cervical nucleoplasty with percutaneous cervical discectomy in the cervical disc herniation retrospectively. The number of enrolled patients was 176 [81 in the percutaneous cervical nucleoplasty (PCN) and 95 in the percutaneous cervical discectomy (PCD)]. The average follow-up time was 28.86 ± 4.52 months in PCN and 28.42 ± 3.21 months in PCD. The pain index improved from 7.12 ± 1.13 to 2.74 ± 0.89 in the PCN group and improved from 7.18 ± 1.09 to 2.71 ± 0.91 in the PCD group. The clinical results assessed by Macnab standard of PCN were good and excellent in 77.8% of PCN patients and 79.5% of PCD patients.
On the other hand, Cuellar et al14 mentioned that 32% of patients underwent nucleoplasty showed progressive degeneration in less than 1 year after nucleoplasty by MRI evaluation. But their sample size was relatively small and the indication criteria were somewhat uncertain. Postnucleoplasty MRI was carried out only when the patient complained of persistent symptoms after the procedures.
Several results of cervical nucleoplasty appear to be better than lumbar nucleoplasty.13, 15, 16 However, it is unclear why the cervical nucleoplasty is more effective than the lumbar nucleoplasty. One theoretical explanation is the anatomic differences. The cervical nerve root is confined to a relatively smaller space than its lumbar counterpart so the cervical nerve root responds more sensitively to even a minute reduction. For this reason, even if the pressure of the disc is reduced slightly, the decompression on the nerve root and reduction in clinical symptoms can be obvious. Another reason could be the topography of the lesion and direction from which it is approached for treatment. Since symptomatic herniation is directed posteriorly, cervical nucleoplasty can approach the lesion site effectively because it uses the anterior approach.15 Posterolateral approach is used commonly in lumbar nucleoplasty, but in cervical, the anterolateral approach is used and the probe can be positioned accurately in the lesion site posteriorly located.
The complication level appears to be acceptable.12, 17, 18 Potential complications include: infection, discitis, probe tip breakage or damage, bleeding, nerve damage, worsened pain, failure of technique, recurrence of herniation, paralysis, anaphylaxis and death.13, 19
Bonaldi et al20 reported the complication of cervical nucleoplasty included discitis, bradycardia, Horner's sign and hoarseness.
4. Dekompressor
Dekompressor, first introduced in 2002, is a device for sucking and removing the causative nucleus pulposus (approximately 0.5 – 2 mL) under fluoroscopic imaging using rotating probe with auger tip. The small diameter of the probe permits less damage to the intervertebral disc, in direct removal of the tissue of intervertebral disc, reading of decrease of the intradiscal pressure and taking a biopsy of the intervertebral disc.
According to Lierz,21 inclusion criteria include radicular pain associated with disc herniation less than or equal to 6 mm, clinical history and physical examination findings consistent with radiographic findings of a disc herniation <6 mm, duration of radicular pain longer than 6 months, failure of conservative therapy, good to excellent short-term (< 2 weeks) response to fluoroscopically guided transforaminal injection of local anesthetic and corticosteroid at symptomatic rampancy, confirmatory selective segmental spinal nerve block with 0.5 to 1.5 mL of anesthetic providing >80% relief of radicular pain lasting at least for the duration the local anesthetic could offer and preservation of disc height (less than 50% loss). Major exclusion criteria include progressive neurological deficit, more than two symptomatic levels, previous open surgery at proposed treatment level, spinal instability, spinal fracture or tumor, pain drawing inconsistent with clinical diagnosis and significant coexisting medical or psychological condition.21
Lierz et al21 published the results of a 1-year clinical follow-up of 64 patients treated by Dekompressor guided by computed tomography (CT) instead of fluoroscopy. The average reported pain level as measured by VAS was 7.3 before the procedure and 2.1 12 months after treatment. Before the procedure, 61 patients (95%) used opioid or nonopioid analgesics regularly. After 1 year, a reduction in analgesic use was in 51 patients (80%). Percutaneous discectomy was completed in 50 patients (62 levels) with an average reduction of 60.25% compared with preoperative VAS (p < 0.001).
Alo et al22 reported the findings on the results of herniated disc treated by Dekompressor. Clinical response in an initial cohort of 50 consecutive patients to chronic radicular pain was evaluated in a randomized prospective clinical trial. Data were collected for the 6-month outcome. They assessed the outcome using VAS score, analgesic usage, self-reported functional improvement and overall satisfaction. Seventy-four percent of patients reported reducing their analgesic intake, 90% of patients reported improvement in postdecompression functional status, and overall satisfaction with therapy was greater than 80%.
Lemcke and colleagues23 compared the difference between nucleoplasty and Dekompressor in the patients with MRI-proven disc protrusion suffering from low back pain and/or radiating pain in the lower extremities. The pain severity by VAS score, analgesic consumption, disability in daily life and ability to work were documented. They carried out the nucleoplasty or Dekompressor under fluoroscopic and CT-guidance. They followed up the patients after 6 and 12 months. A total of 69 patients were treated with lumbar Nucleoplasty and a total of 57 patients with Dekompressor. Comparing the therapy groups they found that a mean preoperative VAS score for back pain was 6.59 in the Nucleoplasty group and 6.42 in the Dekompressor group. The VAS scores for back pain immediately postoperative was 2.50 (Nucleoplasty) versus 1.39 (Dekompressor), 3.10 versus 1.12 6 months after surgery and 3.36 versus 1.23 1 year after surgery. The mean VAS scores for radicular pain were 5.68 (Nucleoplasty) versus 6.04 (Dekompressor) preoperatively, 1.40 versus 1.05 immediately postoperatively, 2.54 versus 1.28 after 6 months and 2.50 versus 1.05 after 1 year. In the between-group analysis, the VAS scores were significantly lower in the Dekompressor group for the low back pain as well as for the radiating pain, while there were no significant differences in the preoperative values between the two groups. They found a significantly lower analgesic consumption in the Dekompressor group 12 months after surgery, whereas there was no significant difference preoperatively. Concerning the inability to work and the disability in the tasks of daily activity no significant differences between the treatment groups could be obtained. In the Dekompressor group, they found a tendency to a better outcome concerning the low back pain in patients younger than 50 years compared with patients older than 50 years.
Singh et al24 reported the systemic review about previous reports on Dekompressor. Based on the United States Preventive Services Task Force (USPSTF) criteria the indicated level of evidence for Dekompressor is Level III for short- and long-term relief and the recommendation is 2C/very weak.
To conclude, in spite of lack of the evidence, the Dekompressor may be worth trying in the patients with leg pain and contained disc herniations prior to open discectomy because Dekompressor is easy to apply, relatively safe and less injurious to the disc.
5. Targeted disc decompression (TDD)
TDD comes from IDET technique for discogenic low back pain. When IDET procedure is performed, there is a shrinkage effect on collagen and intradiscal pressure changes. TDD uses this property. The catheter of TDD resembles that of IDET, but the active tip is 1.5 cm shorter than that of IDET. Kallewaard et al mentioned that because TDD is a thermocoagulation technique, the degree of hydration of the nucleus is, in principle, not important.10 Although there is a paucity of study and the evidence of this procedure is not known yet, TDD may be utilized increasingly and appears to provide good results.25
Recently, L'DISQ device (U&I Co., Uijeongbu, Korea) has been introduced as a new technique for percutaneous disc decompression. The device is designed to allow direct access to herniated disc material26 and vaporizes the herniated nucleus using bipolar radiofrequency current similar to Nucleoplasty. In contrast to the Nucleoplasty device, the Wand of L'DISQ can be curved and directed into a disc herniation.26 Lee et al reported the efficacy of L'DISQ in 27 patients with herniated nucleus pulposus related to radicular pain.26 At 24 weeks postprocedure the visual analog scale fell from 7.08 ± 1.22 to 1.84 ± 0.99, Oswestry disability index from 41.88 ± 10.61 to 16.66 ± 8.55%, Rolando-Morris questionnaire from 11.52 ± 3.91 to 2.68 ± 1.97 points and Bodily Pain Scale of SF-36 version 2 improved from 32.89 ± to 49.57 ± 4.96 scales. The passive straight leg raising test showed improvement from 60.20 ± 20.02 to 83.00 ± 14.29 degrees. In spite of the promising results of L'DISQ, more reports should be published to secure the evidence.
6. Summary
IDET, nucleoplasty, Dekompressor and TDD are all treatment modalities whose goal is to manage the pain originated from the intervertebral disc. Of course, the exact examinations of the discogenic pain including history taking, physical examination or provocative discography should be followed. In addition, it is important to apply strict criteria for the patients with discogenic pain in improving the outcome by minimally invasive intradiscal interventions mentioned above. In spite of contradictory opinions literature, the intradiscal procedures are simple to apply, have low rates of complications and seem to be effective. Finally, the following principle, “the treatment should not do harm”, should be considered when deciding which procedure to use.