Summary
Although establishing the diagnosis of lumbar disk herniation with associated leg pain is usually intuitive, diagnosis and treatment of lumbar discogenic pain remain difficult. It may account for one third of patients with lower back pain. The mechanism of this pain is still unclear, clinical presentation can vary, and imaging may be misleading. Provocative diskography remains the only diagnostic test that can relate changes observed on imaging tests and the patient’s pain, despite questioned validity of provocative diskography as an appropriate diagnostic test.
Percutaneous treatments for diskogenic lower back pain emerged in the early 2000s, and these therapeutic approaches seem to be more efficacious and less invasive alternatives to currently available surgical options. They are cost-effective, when compared to surgical approaches, and may cause fewer side effects. However, the true therapeutic value of these therapies has yet to be established. Proper patient selection may significantly improve successes of those minimally invasive treatments, so that fewer patients elect to undergo open spinal surgery.
Percutaneous disk decompression procedures when used as minimally invasive approaches to treat back and leg pain caused by contained disk herniation clinically had generally favorable clinical outcomes and complication rates were low. However, studies with higher level of evidence are lacking.
Introduction
Frequently cited causes of lower back pain include myofascial, discogenic, facetogenic origins, conditions originating from the sacroiliac joint, compression fractures, and lumbar stenosis. Low back pain is one of the most common causes of lost work time and is becoming a major economic burden. Discogenic pain remains one of the main causes of lower back pain.
This chapter highlights some interesting, novel, and minimally invasive therapeutic interventions, and those procedures should be used as a part of comprehensive, multidisciplinary treatment in order to produce the best results in a patient’s functional capacity and improvements in pain scores.
Intervertebral disk as a pain generator is difficult to evaluate using conventional and conservative methods. Patients frequently describe unrelenting low back discomfort and groin or occasionally leg pain that worsens with axial loading that improves with recumbency. Patients complain of increased pain in their lower back with Valsalva maneuver, prolonged sitting, or driving a car. The signs and symptoms provide a clue to the causative factors so that further steps can be taken to determine an accurate diagnosis. Imaging (e.g., magnetic resonance imaging [MRI]) correlates poorly with clinical findings, leaving open the question of pain causality. One approach to substantiate clinical findings and correlate the patient’s pain to the imaging study is to conduct a provocative or analgesic diagnostic diskography. Currently, this approach is the only diagnostic method to correlate anatomic abnormalities with clinically observed lower back pain. Despite wide clinical use, the diagnostic value of this test has been repeatedly questioned, mainly because of potentially high false-positive rates.
After a provisional diagnosis of discogenic pain has been established, an effective treatment is desired. Several commonly used minimally invasive intradiscal therapies involve careful denervation of the annulus fibrosus ( Fig. 66.1 ). So-called annuloplasty procedures have been clinically used, despite a lack of objective histologic findings of nociceptive fiber denervation or any changes in collagen fiber structure expected after intradiscal heat is used. The minimally invasive approach, low cost, and relative simplicity of these procedures, as well as a short recovery time, are major advantages of annuloplasty procedures when compared to surgical approaches such as lumbar fusion or disk replacement. Intradiscal electrothermal therapy (IDET; Smith and Nephews, London, United Kingdom), DiscTRODE (Valleylab, Boulder, Colorado), and Intradiscal Biacuplasty (Baylis Medical, Inc., Montreal, Canada) (see Fig. 66.1 ) have been historically used to treat discogenic pain.
The process of intervertebral disk degeneration includes induced dehydration of the intervertebral disk and a loss of nuclear material. Delamination and fissuring of the lamellar layers are physical changes, and the production of certain cytokines and other mediators is one of the biochemical and cellular changes occurring within the disk. Inside the intervertebral disk, the production of inflammatory cytokines including tumor necrosis factor-α (TNF-α), nitric oxide, and matrix metalloproteinases (MMPs) can be greatly altered. Nociceptors, normally limited to the outer third of the annulus, could be the substrate for discogenic pain when they are expanded over the larger annular area and penetrate further into the degenerated disk along the vasculature and fissures. Those C- and Aδ fibers are likely responsible for transmitting pain responses, and their elimination may, in theory, disrupt transmission of the pain signal.
Minimally invasive thermal procedures deliver heat inside the disk annulus via a resistive heating coil in, for example, IDET, bipolar biacuplasty (Kimberly Clark, Atlanta, Georgia), or unipolar, flexible (DiscTRODE; Valleylab, Boulder, Colorado) radiofrequency (RF) electrode to denervate nociceptive fibers and coagulate collagenous tissues.
During the application of RF, similar to any other tissue, alternating flow of electrical current causes ions in the tissue to alternate fast movements. This molecular vibration results in frictional heating and ablation. Ionic heating produces thermal injury of the cells when tissue temperature reaches > 42° C. The extent of cellular damage depends on multiple factors including the temperature, position, thickness of electrodes, and duration of heating. An increase in tissue temperature is a function of current density, which is greatest at the proximity of the electrode and decreases with increasing distance from the electrode. However, by increasing the power output, current density around the electrode is increased and lesion size is limited by the given current density.
Cooling the RF electrode internally can increase lesion size and is currently used during intradiscal biacuplasty procedures. Cooled RF probes have cooling sink lumens that extend to the tip of the electrode. The cooling fluid (water) circulates from the tip of the electrode to a synchronized water pump. As coolant removes heat from the tissue adjacent to the electrode, larger lesion volumes are produced by increasing power deposition and the duration of the current interval. An even larger lesion volume can be produced by using two internally cooled RF electrodes in a bipolar arrangement at significantly lower temperatures.
Introduction
Frequently cited causes of lower back pain include myofascial, discogenic, facetogenic origins, conditions originating from the sacroiliac joint, compression fractures, and lumbar stenosis. Low back pain is one of the most common causes of lost work time and is becoming a major economic burden. Discogenic pain remains one of the main causes of lower back pain.
This chapter highlights some interesting, novel, and minimally invasive therapeutic interventions, and those procedures should be used as a part of comprehensive, multidisciplinary treatment in order to produce the best results in a patient’s functional capacity and improvements in pain scores.
Intervertebral disk as a pain generator is difficult to evaluate using conventional and conservative methods. Patients frequently describe unrelenting low back discomfort and groin or occasionally leg pain that worsens with axial loading that improves with recumbency. Patients complain of increased pain in their lower back with Valsalva maneuver, prolonged sitting, or driving a car. The signs and symptoms provide a clue to the causative factors so that further steps can be taken to determine an accurate diagnosis. Imaging (e.g., magnetic resonance imaging [MRI]) correlates poorly with clinical findings, leaving open the question of pain causality. One approach to substantiate clinical findings and correlate the patient’s pain to the imaging study is to conduct a provocative or analgesic diagnostic diskography. Currently, this approach is the only diagnostic method to correlate anatomic abnormalities with clinically observed lower back pain. Despite wide clinical use, the diagnostic value of this test has been repeatedly questioned, mainly because of potentially high false-positive rates.
After a provisional diagnosis of discogenic pain has been established, an effective treatment is desired. Several commonly used minimally invasive intradiscal therapies involve careful denervation of the annulus fibrosus ( Fig. 66.1 ). So-called annuloplasty procedures have been clinically used, despite a lack of objective histologic findings of nociceptive fiber denervation or any changes in collagen fiber structure expected after intradiscal heat is used. The minimally invasive approach, low cost, and relative simplicity of these procedures, as well as a short recovery time, are major advantages of annuloplasty procedures when compared to surgical approaches such as lumbar fusion or disk replacement. Intradiscal electrothermal therapy (IDET; Smith and Nephews, London, United Kingdom), DiscTRODE (Valleylab, Boulder, Colorado), and Intradiscal Biacuplasty (Baylis Medical, Inc., Montreal, Canada) (see Fig. 66.1 ) have been historically used to treat discogenic pain.
The process of intervertebral disk degeneration includes induced dehydration of the intervertebral disk and a loss of nuclear material. Delamination and fissuring of the lamellar layers are physical changes, and the production of certain cytokines and other mediators is one of the biochemical and cellular changes occurring within the disk. Inside the intervertebral disk, the production of inflammatory cytokines including tumor necrosis factor-α (TNF-α), nitric oxide, and matrix metalloproteinases (MMPs) can be greatly altered. Nociceptors, normally limited to the outer third of the annulus, could be the substrate for discogenic pain when they are expanded over the larger annular area and penetrate further into the degenerated disk along the vasculature and fissures. Those C- and Aδ fibers are likely responsible for transmitting pain responses, and their elimination may, in theory, disrupt transmission of the pain signal.
Minimally invasive thermal procedures deliver heat inside the disk annulus via a resistive heating coil in, for example, IDET, bipolar biacuplasty (Kimberly Clark, Atlanta, Georgia), or unipolar, flexible (DiscTRODE; Valleylab, Boulder, Colorado) radiofrequency (RF) electrode to denervate nociceptive fibers and coagulate collagenous tissues.
During the application of RF, similar to any other tissue, alternating flow of electrical current causes ions in the tissue to alternate fast movements. This molecular vibration results in frictional heating and ablation. Ionic heating produces thermal injury of the cells when tissue temperature reaches > 42° C. The extent of cellular damage depends on multiple factors including the temperature, position, thickness of electrodes, and duration of heating. An increase in tissue temperature is a function of current density, which is greatest at the proximity of the electrode and decreases with increasing distance from the electrode. However, by increasing the power output, current density around the electrode is increased and lesion size is limited by the given current density.
Cooling the RF electrode internally can increase lesion size and is currently used during intradiscal biacuplasty procedures. Cooled RF probes have cooling sink lumens that extend to the tip of the electrode. The cooling fluid (water) circulates from the tip of the electrode to a synchronized water pump. As coolant removes heat from the tissue adjacent to the electrode, larger lesion volumes are produced by increasing power deposition and the duration of the current interval. An even larger lesion volume can be produced by using two internally cooled RF electrodes in a bipolar arrangement at significantly lower temperatures.
Intradiscal Electrothermal Therapy (IDET)
IDET technology, although limited in its use clinically, is still considered a valuable intradiscal procedure and will be briefly discussed (see Fig. 66.1 C ). It provides focal heat via an elongated resistive coil of very small diameter to the limited area of the posterior annulus. Possible mechanisms of pain relief were already discussed. The limited use results from the high temperatures attained just around the electrode itself and quick dissipation of the heat at 2- to 4-mm radius away from the coil. Positioning of the resistive coil within the posterior annulus of the disk can be prolonged, and multiple attempts may be required, or it may be necessary to pass another coil from the opposite side of the posterolateral disk to achieve optimal electrode placement within the interface between the annulus and the nucleus (see Fig. 66.1 C ). This may further damage the intervertebral disk, and sometimes placing the tip of the coil within the posterior annular fissure may extend too close to the neural canal. Indications for IDET include persistent discogenic low back pain despite prolonged and comprehensive conservative treatments including physical therapy and a directed home exercise program, similar to other annuloplasty procedures. Provocative or analgesic diskography should replicate or eliminate concordant pain at low disk pressurization (< 50 PSI). The clinical outcome studies on intradiscal electrothermal therapy (IDET) are listed with other annuloplasty studies in Table 66.1 .
| Study | Year | Type of Annuloplasty | Indications | Number of Patients | Type of Study | Outcomes | Complications | Conclusions |
|---|---|---|---|---|---|---|---|---|
| Kapural et al. ( ) | 2004 | IDET | Single-or two-level DDD and p.disco., > 50% disk height versus multilevel DDD | 34 | Prospective Matched study | 1,2-DDD > 50% improvement in VAS and PDI | None | IDET effective, but only in one-or two-level DDD |
| Assietti et al. ( ) | 2010 | IDET | Single-level DDD and p.disco., > 60% disk height | 50 | Prospective | VAS 68% decrease; ODI from 59.0+/−7.6% to 20.1+/−11% at 24 m | None | Effective/safe |
| Kapural et al., Kapural ( ) | 2008 | Biacuplasty | Single- or two-level DDD and p.disco., > 50% disk height | 15 | Prospective pilot | 7 of 13 > 50% VAS ODI to 17.5 and SF-36-PF from 51 to 67 @12 m | None | Effective/safe |
| Kvarstein et al. ( ) | 2009 | DiscTRODE | Chronic LBP, p.disco | 23 | Prospective randomized, double blind | No improvement study or sham at 12 m | None | Ineffective |
| Pauza et al. ( ) | 2004 | IDET | DDD and p.disco., > 80% disk height | 64 | Randomized sham-controlled prospective | 56% > 2 VAS change; 50% patients > 50% relief at 6 m | None | Effective/safe |
| Jawahar et al. ( ) | 2008 | IDET | DDD and positive discogram, > 80% disk height, WC patients | 53 | Prospective | VAS reduction 63%, ODI 70% | None | Useful in carefully selected WC patients |
| Karaman et al. ( ) | 2011 | Biacuplasty | Axial pain > 6 m; one or two levels DDD | 14 | Prospective observational | 78% of patients > 10 points Oswestry improvement | None | Effective/safe |
| Kapural et al. ( ) | 2012 | Biacuplasty | Single- or two-level DDD and p.disco., > 50% disk height | 64 | Randomized, sham-controlled prospective | 1 level DDD: VAS −2.78, SF-36-PF +18 2 level DDD:VAS −1.3, SF36-PF+10.5 ( Table 66.2 ) | None | Effective/safe |
∗ Patient selection varied, possibly resulting in the differences in clinical outcomes.
Multilevel disk degeneration seen on magnetic resonance imaging (MRI) appears to be an important negative predictor for the success of annuloplasty, especially when compared to a group of patients with one or two degenerated disks as shown on the MRI. There are few patients with a single disk disease compared to those with multilevel degeneration present on the MRI. Two other groups of patients who have much lower chance of successful functional capacity improvement after annuloplasty are overweight patients and patients receiving workers’ compensation benefits.
Another approach to annuloplasty utilizes a flexible radiofrequency electrode and is called DiscTRODE or percutaneous intradiscal radiofrequency thermocoagulation (PIRFT). Two studies, utilizing proper patient selection, showed minimal or no benefit from PIRFT. Kvarstein and coworkers reported minimal or no improvements in functional capacity, as did Kapural and associates. It appears that the design of the PIRFT electrode provided minimal heat dissipation, which, in turn, could not adequately denervate the posterior annulus.
Intradiscal Biacuplasty (IDB)
Intradiscal biacuplasty (IDB) is the latest, and seems to be the most promising, of the minimally invasive posterior annulus heating techniques (see Fig. 66.1 B ). This technology employs bipolar cooled RF electrodes named transdiscal electrodes (Kimberly Clark, Atlanta, Georgia). Initial data are encouraging. Internally cooling the electrodes provides more substantial and even heating over the wider area of the posterior annulus ( Fig. 66.2 ).
The procedure itself is fluoroscopy guided with the patient lying in the prone position. Electrodes are percutaneously inserted bilaterally in the posterior annulus of the intervertebral disk (see Fig. 66.1 A and Fig. 66.2 ). The generator delivers RF energy led by a temperature thermocouple near the tip of the electrode. The temperature increases gradually to 50° C, with an overall heat time of 15 minutes. During this time, the patient should be awake and conversant to decrease the probability of neurologic injury.
Initially, clinical biacuplasty data from two case series of 14 and 15 patients were completed. Both studies demonstrated significant pain relief following the disk biacuplasty procedure at 3, 6, and 12 months. The Turkish case series suggested > 50% improvement in pain scores at 6 months with good patient satisfaction. The U.S. pilot study involving 15 patients described reduction in the median visual analog scale (VAS) pain score from 7 to 3 cm at 6 and 12 months’ follow-up, respectively; an improvement in the Oswestry index from 23.3 to 16.5 points; and a significant increase in the SF-36 bodily pain scores.
The authors completed a sham, prospective randomized study on IDB ( Table 66.2 ). The aim of the study was to compare the efficacy of intradiscal biacuplasty with placebo using 1:1 randomization. Sixty-four patients were enrolled using the same selection criteria as in the pilot study (see the previous discussion and Table 66.2 ). Patients in the IDB group exhibited statistically significant improvements in physical function, decreased pain, and disability at 6 months’ follow-up as compared to patients who received the sham treatment (see Table 66.2 ).
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