The effect of radiofrequency current and heat on peripheral nerve action potential in the cat

Analyzing the Effect of Intraoperative Stimulation Voltage on Facial Numbness Following Radiofrequency Thermocoagulation in the Treatment of Idiopathic Trigeminal Neuralgia

INTRODUCTION

Radiofrequency thermocoagulation (RFT) effectively alleviates idiopathic trigeminal neuralgia (ITN); however, postoperative facial numbness poses a significant challenge. This issue arises due to the close proximity of high-temperature thermocoagulation, which not only ablates pain-related nociceptive fibers but also affects tactile fibers. Intraoperative sensory stimulation voltage (SV), which reflects the distance between the RFT cannula and the target nerve, potentially possesses the ability to prevent tactile fiber injury. This study aimed to investigate the influence of SV on postoperative facial numbness and provide valuable insights to mitigate its occurrence.

METHODS

A retrospective analysis was performed on 72 ITN patients with maxillary division (V2) pain who underwent RFT between 2020 and 2022. Among them, 13 patients with SV ≤ 0.2 V constituted the low SV group. Subsequently, a matched-cohort analysis was conducted on the remaining 59 patients. The patients paired with the low SV patients were subsequently enrolled in the high SV group, adhering to a 1:1 match ratio. The primary outcome was the facial numbness scale assessment at 3 days, 3 months and 6 months post-surgery. The pain intensity and medication burden served as the secondary outcomes.

RESULTS

We successfully matched a cohort consisting of 12 patients in the low SV group and 12 patients in the high SV group. Each patient experienced various degrees of facial numbness at 3 days post-RFT. Notably, the low SV group exhibited a higher incidence of moderate numbness (66.7% vs. 16.67%, P = 0.036), whereas the high SV group had more cases of mild numbness at the 6-month follow-up (25% vs. 83.3%, P = 0.012). Both groups demonstrated significant decreases in pain intensity and medication burden compared to before the operation.

CONCLUSIONS

SV proved to be a reliable parameter for mitigating the degree of postoperative facial numbness in RFT treatment for ITN. A relatively high sensory SV ranging from 0.3 to 0.6 V during the RFT procedure results in less facial numbness in the treatment of ITN.

Effectiveness and Safety of Radiofrequency Thermocoagulation Treatment Guided by Computed Tomography for Infraorbital Neuralgia Following Failed Conservative Treatment: A Retrospective Study

Purpose

To evaluate the effectiveness and safety of CT-guided radiofrequency thermocoagulation (RFT) for the treatment of infraorbital neuralgia following the failure of conservative management.

Patients and Methods

This was a single center, retrospective study which included 196 patients between the ages of 37 to 90 years, who suffered from infraorbital neuralgia, and had undergone CT-guided RFT treatment. The medical records of these patients were retrieved between January 7, 2015 and February 5, 2020, and the patients were followed up for 2 years. Follow-up outcomes included Numerical Rating Scale (NRS) scores, dosage of carbamazepine, time to take effect, status of recurrence and side effects. The effective rate was defined as the percentage of patients with postoperative NRS score reduction of >50%.

Results

The effective rates were 92.9%, 100%, 100%, 100%, 93.4% and 85.7% on the same day, week 1, month 1, month 6, year 1 and year 2 after RFT, respectively. After RFT, the postoperative NRS scores and dosage of carbamazepine were significantly reduced than those preoperatively (P < 0.05). The median time to take effect was zero day. Twenty-eight patients with recurrence underwent RFT again and achieved complete pain relief. All patients experienced numbness in the infraorbital nerve innervation area and the numbness scores gradually decreased over time.

Conclusion

CT-guided RFT treatment may be an effective and safe technique for pain relief in patients with infraorbital neuralgia following failed results from conservative treatment.

Radiofrequency Ablation of the Trochanteric Branches of the Femoral Nerve for the Treatment of Greater Trochanteric Syndrome

Background

Approximately 10–15% of the population over the age of 60 suffers from hip pain. Greater trochanteric pain syndrome (GTPS) is one of the most common diagnoses in patients with chronic hip pain, includes a number of disorders, and has a broad differential diagnosis. Conservative managements of GTPS, including pharmacologic interventions, physical therapy, chiropractic intervention, acupuncture, and more invasive techniques, such as intra-articular injections, commonly fail to provide patients with sufficient, long-term relief. While radiofrequency ablation (RFA) has been used to treat intra-articular hip pain in the past, there is little evidence for the feasibility of RFA for managing patients with GTPS. This case series builds on previous evidence that cooled radiofrequency ablation (CRF) of the trochanteric branch of the femoral nerve may offer patients with GTPS effective, safe, and lasting pain improvement.

Cases

A series of eight patients with GTPS underwent CRF of the nervus females to the trochanter. CRF procedures were either targeted at the left, right, or bilateral nerves.

Conclusion

This case series provides additional evidence for the safety and effectiveness of CRF of the nervus femoralis to the trochanter for offering long-term pain relief in patients with GTPS. All patients experienced at least two months of relief, with most patients experiencing ongoing relief from the procedure.

Effects of Pulsed Radiofrequency with Different Temperature on Model Rats of Chronic Constriction Injury

OBJECTIVES

The treatment for neuropathic pain is still a big challenge. Pulsed radiofrequency technique has been widely used to relieve neuropathic pain in recent years. The purpose of this study is to optimize the temperature for pulsed radiofrequency therapy.

DESIGN

Animal, experimental study.

METHODS

Seventy-five male SD rats were randomly divided into five groups: Sham operation group (Sham group), chronic constriction injury group (CCI group), PRF 42°C group (P42 group), PRF 50°C group (P50 group), and PRF 60°C group (P60 group). The hindpaw withdrawal threshold (HWT), paw thermal withdrawal latency (PTWL), sciatic nerve structure, and the concentration of spinal methionine enkephalin(M-ENK) were detected to identify which temperature is the best for PRF treatment.

RESULTS

PRF at 42°C, 50°C and 60°C significantly alleviated the pain in CCI rats. The therapeutic effects of 50°C and 60°C were similar, and both were better than 42°C. In addition, PRF using 42°C, 50°C, and 60°C mediated nerve injury to sciatic nerve were grade 1, 1, and 2, respectively. The concentration of M-ENK in spinal cord increased accompanying with the increasing of the temperature of PRF.

CONCLUSIONS

PRF using 50°C could induce less damage while achieving better improvement of mechanical and thermal pain threshold than 42°C and 60°C in CCI rats, which may be achieved by promoting the expression of M-ENK in spinal cord.

Masticatory Dysfunction After Computed Tomography-Guided Plasma Ablation vs. Radiofrequency Ablation on Gasserian Ganglion for Idiopathic Trigeminal Neuralgia: A Randomized Controlled Trial

OBJECTIVE

We aimed to evaluate masticatory dysfunction after two different types of ablation on the Gasserian ganglion for the treatment of idiopathic trigeminal neuralgia. We hypothesized that low-temperature plasma radiofrequency ablation (LTP-RFA) was noninferior to radiofrequency thermocoagulation (RFT) with respect to initial efficacy.

METHODS

In the randomized, single-blind, parallel-group, noninferiority trial, 204 participants with idiopathic trigeminal neuralgia were randomly allocated to receive plasma ablation in the LTP-RFA group and radiofrequency ablation in the RFT group in a 1:1 ratio, with random block sizes of four or six. Participants were examined at baseline (T0), on the day of discharge (T1), and at the 6-month follow-up (T2). The primary end point was the clinincal effective rate in the LTP-RFA group compared with that in the RFT group after intervention on the day of discharge. Noninferiority was prespecified at -10%.

RESULTS

The intention-to-treat analysis revealed that the initial efficacy rates were 91.2% in LTP-RFA group and 93.1% in RFT group (rate ratio [RR] = 0.979, 95% confidence interval [CI]: 0.904-1.061, P = 0.795). The difference between the two groups was 1.9% (95% CI: -5.6% to 9.4%), which showed that LTP-RFA demonstrated noninferiority compared with RFT in initial efficacy. Compared with the RFT group, the LTP-RFA group exhibited a significantly greater improvement in the maximum voltage of the masseter muscles with mean differences of 11.40 (95% CI: 10.52 to 12.27, P < 0.001) at T1 and 17.41 (95% CI: 14.68 to 20.13, P < 0.001) at T2, respectively. Similar results were observed for the asymmetry index of occlusion, the maximum voltage of the anterior temporalis, and the activity index of anterior temporalis / masseter muscles. No serious adverse events were observed in either group.

CONCLUSIONS

Compared with the RFT group, noninferior efficacy for pain relief and improvement of masticatory function was revealed in the LTP-RFA group.

Fluid Lubrication and Cooling Effects in Diamond Grinding of Human Iliac Bone

Background and Objectives: Although there have been research on bone cutting, there have been few research on bone grinding. This study reports the measurement results of the experimental system that simulated partial laminectomy in microscopic spine surgery. The purpose of this study was to examine the fluid lubrication and cooling in bone grinding, histological characteristics of workpieces, and differences in grinding between manual and milling machines. Materials and Methods: Thiel-fixed human iliac bones were used as workpieces. A neurosurgical microdrill was used as a drill system. The workpieces were fixed to a 4-component piezo-electric dynamometer and fixtures, which was used to measure the triaxial power during bone grinding. Grinding tasks were performed by manual activity and a small milling machine with or without water. Results: In bone grinding with 4-mm diameter diamond burs and water, reduction in the number of sudden increases in grinding resistance and cooling effect of over 100 °C were confirmed. Conclusion: Manual grinding may enable the control of the grinding speed and cutting depth while giving top priority to uniform torque on the work piece applied by tools. Observing the drill tip using a triaxial dynamometer in the quantification of surgery may provide useful data for the development of safety mechanisms to prevent a sudden deviation of the drill tip.

Efficacy and safety of pulsed radiofrequency as a method of dorsal root ganglia stimulation for treatment of non-neuropathic pain: a systematic review

BACKGROUND

We systematically reviewed the evidence on the efficacy and safety of dorsal root ganglion (DRG) targeted pulsed radiofrequency (PRF) versus any comparator for treatment of non-neuropathic pain.

METHODS

We searched MEDLINE, CINAHL, Embase, PsycINFO, clinicaltrials.gov and WHO clinical trial register until January 8, 2019. All study designs were eligible. Two authors independently conducted literature screening. Primary outcomes were pain intensity and serious adverse events (SAEs). Secondary outcomes were any other pain-related outcome and any other safety outcome that was reported. We assessed the risk of bias using the Cochrane tool and Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I). We conducted narrative evidence synthesis and assessed the conclusiveness of included studies regarding efficacy and safety.

RESULTS

We included 17 studies with 599 participants, which analyzed various pain syndromes. Two studies were randomized controlled trials; both included participants with low back pain (LBP). Non-randomized studies included patients with the following indications: LBP, postsurgical pain, pain associated with herpes zoster, cervicogenic headache, complex regional pain syndrome type 1, intractable vertebral metastatic pain, chronic scrotal and inguinal pain, occipital radiating pain in rheumatoid arthritis and chronic migraine. In these studies, the PRF was usually initiated after other treatments have failed. Eleven studies had positive conclusive statements (11/17) about efficacy; the remaining had positive inconclusive statements. Only three studies provided conclusiveness of evidence statements regarding safety - two indicated that the evidence was positive conclusive, and one positive inconclusive. The risk of bias was predominantly unclear in randomized and serious in non-randomized studies.

CONCLUSION

Poor quality and few participants characterize evidence about benefits and harms of DRG PRF in patients with non-neuropathic pain. Results from available studies should only be considered preliminary. Not all studies have reported data regarding the safety of the intervention, but those that did, indicate that the intervention is relatively safe. As the procedure is non-destructive and early results are promising, further comparative studies about PRF in non-neuropathic pain syndromes would be welcomed.

Identifying the Role of Block Length in Neural Heat Block to Reduce Temperatures During Infrared Neural Inhibition

BACKGROUND AND OBJECTIVES

The objective of this study is to assess the hypothesis that the length of axon heated, defined here as block length (BL), affects the temperature required for thermal inhibition of action potential propagation applied using laser heating. The presence of such a phenomenon has implications for how this technique, called infrared neural inhibition (INI), may be applied in a clinically safe manner since it suggests that temperatures required for therapy may be reduced through the proper spatial application of light. Here, we validate the presence of this phenomenon by assessing how the peak temperatures during INI are reduced when two different BLs are applied using irradiation from either one or two adjacent optical fibers.

STUDY DESIGN/MATERIALS AND METHODS

Assessment of the role of BL was carried out over two phases. First, a computational proof of concept was performed in the neural conduction simulation environment, NEURON, simulating the response of action potentials to increased temperatures applied at different full-width at half-maxima (FWHM) along axons. Second, ex vivo validation of these predictions was performed by measuring the radiant exposure, peak temperature rise, and FWHM of heat distributions associated with INI from one or two adjacent optical fibers. Electrophysiological assessment of radiant exposures at inhibition threshold were carried out in ex vivo Aplysia californica (sea slug) pleural abdominal nerves ( n = 6), an invertebrate with unmyelinated axons. Measurement of the maximum temperature rise required for induced heat block was performed in a water bath using a fine wire thermocouple. Finally, magnetic resonance thermometry (MRT) was performed on a nerve immersed in saline to assess the elevated temperature distribution at these radiant exposures.

RESULTS

Computational modeling in NEURON provided a theoretical proof of concept that the BL is an important factor contributing to the peak temperature required during neural heat block, predicting a 11.7% reduction in temperature rise when the FWHM along an axon is increased by 42.9%. Experimental validation showed that, when using two adjacent fibers instead of one, a 38.5 ± 2.2% (mean ± standard error of the mean) reduction in radiant exposure per pulse per fiber threshold at the fiber output (P = 7.3E-6) is measured, resulting in a reduction in peak temperature rise under each fiber of 23.5  ± 2.1% ( P = 9.3E-5) and 15.0 ± 2.4% ( P = 1.4E-3) and an increase in the FWHM of heating by 37.7 ± 6.4% ( P = 1E-3), 68.4 ± 5.2% ( P = 2.4E-5), and 51.9  ± 9.9% ( P = 1.7E-3) in three MRT slices.

CONCLUSIONS

This study provides the first experimental evidence for a phenomenon during the heat block in which the temperature for inhibition is dependent on the BL. While more work is needed to further reduce the temperature during INI, the results highlight that spatial application of the temperature rise during INI must be considered. Optimized implementation of INI may leverage this cellular response to provide optical modulation of neural signals with lower temperatures over greater time periods, which may increase the utility of the technique for laboratory and clinical use. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Safety and efficacy of microwave ablation for breast cancer thoracic metastases

Background

The objective of the study was to assess the safety and efficacy of microwave ablation (MWA) for breast cancer thoracic metastasis.

Materials and methods

Twelve patients in our institution with a single lesion of breast cancer thoracic metastases received MWA and invasive spine surgery from August 2014 to November 2016. MWA was executed using the MWA system (2,450 MHz) at 40 W or 50 W with thermometers to control the ablation end points. The pathology of thoracic metastases was confirmed through intraoperative biopsy before ablation. The postoperative complications were recorded. The patients were followed up at 1, 3 and 6 months with contrast-enhanced computed tomography and magnetic resonance imaging to monitor for tumor recurrence.

Results

The average duration of follow-up for breast cancer thoracic metastases patients (mean age 52.7±8.4 years) was 10.2 months. The rate of postoperative main complications was 8.3% (1/12). The recurrence rate was 16.6% (2/12) as confirmed by persistent enhancement.

Conclusion

MWA may be used as the adjuvant treatment for thoracic metastases of breast cancer. Results showed that few significant complications and less local recurrence occurred during the follow-up stage. Future research should aim at discovering more about the time controls for microwave-tissue interaction and treatment parameters before widespread use.

Clinical observation of CT-guided intra-articular conventional radiofrequency and pulsed radiofrequency in the treatment of chronic sacroiliac joint pain

Background

Sacroiliac joint pain (SIJP) is an important cause of low back pain and seriously affects the patients’ quality of life. Therefore, it is urgent to find effective treatment methods.

Objective

To observe the efficacy of intra-articular (IA) conventional radiofrequency (CRF) and pulsed radiofrequency (PRF) treatment of Sacroiliac joint syndrome (SIJS) under computed tomography (CT) guidance.

Study design

Retrospective comparative study.

Setting

Shengjing Hospital of China Medical University.

Patients and methods

Sixty-four patients with SIJS were enrolled in the Pain management. Patients were randomized into two groups: CRF (CRF group, n=32) and PRF (PRF group, n=32). At each observation time, the general condition, visual analog scale (VAS), the total efficiency rate, Oswestry disability index (ODI), and 36-item short-form health survey were followed up.

Results

Compared to the pretreatment value, the VAS and the ODI decreased in both groups after treatment (P<0.05). In the CRF group, the VAS and the ODI decreased significantly at 1 week after treatment (P<0.05); at 6 and 12 months after treatment, the VAS and the ODI were lower than that in the PRF group (P<0.05). The total efficiency rate in the CRF group and PRF group was 56.3% and 31.3%, respectively (P<0.05). After the relief of pain, both groups received different degrees of improvement in the quality of life. Compared to the pretreatment value, physical component summary (PCS) and the mental component summary (MCS) in both groups were increased after treatment (P<0.05); in the CRF group, PCS and MCS increased significantly at 1 week after treatment (P<0.05); and at 6 and 12 months after treatment, PCS and MCS were higher than those in the PRF group (P<0.05).

Conclusion

CT-guided IA PRF and CRF in the treatment of sacroiliac pain are safe and effective. CRF is superior to PRF in the early and late stage. It is recommended for the treatment of SIJP.

Thermal effect of percutaneous radiofrequency ablation with a clustered electrode for vertebral tumors: In vitro and vivo experiments and clinical application

Purpose

To investigate effects and heat distribution of radiofrequency ablation (RFA) on vertebral tumors in vitro and in vivo swine experiments and its clinical application.

Materials and methods

RFA was performed on the swine spine in vitro and in vivo for 20 min at 90 °C at the electrode tip, and the temperature at the electrode tip and surrounding tissues were recorded. Clinical application of ablation combined with vertebroplasty was subsequently performed in 4 patients with spinal tumors.

Results

In the in vitro study, the mean temperature at the front and ventral wall of the spinal canal was 50.8 °C and 43.6 °C, respectively, at 20 mm significantly greater than 37.7 °C and 33.7 ± 1.7 °C, respectively, at 10 mm ablation depth. The coagulative necrosis area was significantly (P < 0.0001) greater at 20 mm depth than at 10 mm depth (mean 17.0 × 20.7 mm² vs. 14.2 × 16.6 mm²). In the in vivo experiment, the local temperature increased significantly (P < 0.05) from around 36 °C before ablation to over 41 °C at 20 min after ablation, with the temperature at the electrode tip (90.4 °C) and within the vertebral body (67.0 °C) significantly (P < 0.05) greater than at the posterior (41.9 °C) and lateral wall (41.8 °C). From 2 to 5 weeks, bone remodeling began. Clinically, all four patients had successful RFA and vertebroplasty, with no neurological deficits. The pain scores were significanlty (P < 0.05) improved before (4.5–10, mean 8.0) compared with at four weeks (0–1.8, mean 1.8).

Conclusion

The clustered electrode can be efficiently and safely applied in the treatment of spinal tumors without damaging the spinal cord and adjacent nerves by heat distribution.

Lumbar Dorsal Root Ganglion Block as a Prognostic Tool Before Pulsed Radiofrequency: A Randomized, Prospective, and Comparative Study on Cost-Effectiveness

OBJECTIVES

In the study, we discuss the predictive value and cost-effectiveness of dorsal root ganglion (DRG) blocks before using dorsal root ganglion pulsed radiofrequency (DRG-PRF) in the treatment of low back pain.

METHODS

The study comprised 60 patients with low back pain who were randomly assigned into 2 groups. Patients in group 1 were screened using DRG block before DRG-PRF treatment for responders. Patients in group 2 underwent DRG-PRF treatment without DRG block. Successful outcome was defined as patient satisfaction, improvement in numerical rating scale, and medication use reduction.

RESULTS

In group 1 (n = 30), 24 patients demonstrated good response to DRG block, and 20 patients had successful outcome at 6 months after DRG-PRF therapy. In group 2 (n = 30), 25 of the patients had successful outcome at 6 months after DRG-PRF therapy. The mean medical costs were NT$ 19,245 and NT$ 16,375 for each successful case in groups 1 and 2, respectively.

CONCLUSIONS

In this comparative cost-effectiveness study, the application of diagnostic DRG blocks before DRG-PRF did not have a significant impact on patient satisfaction, pain index score, or pain medication reduction. Furthermore, the application of diagnostic DRG blocks resulted in overall greater medical costs. These findings suggest that DRG-PRF without screening by DRG block is more cost-effective and less invasive.

3D Image-Guided Percutaneous Radiofrequency Thermocoagulation of the Maxillary Branch of the Trigeminal Nerve Through Foramen Rotundum for the Treatment of Trigeminal Neuralgia

Percutaneous radiofrequency thermocoagulation of the trigeminal ganglion through the foramen ovale is a well-established procedure for the treatment of trigeminal neuralgia (TN). However, this approach can be tricky when individual trigeminal sub-branch nerve block is required. We report our initial experience of image-guided radiofrequency thermocoagulation of the maxillary branch through the use of foramen rotundum.From February 2012 to February 2015, we treated 25 patients with isolated TN of the maxillary branch. Radiofrequency thermocoagulation of the maxillary branch through the foramen rotundum was performed under fluoroscopy. TN pain was evaluated using the visual analogue scale both before and after the procedure.The mean preoperative visual analogue scale score was 8.6 ± 0.8. The pain completely disappeared after the initial procedure in 22 patients and after a second procedure in 2 patients. An additional patient had a postoperative visual analogue scale score of 2 and did not undergo further treatment. Facial numbness occurred in 23 patients but was tolerable. Patients were followed up for a mean of 14.74 months (range, 1-29 months). Recurrence was observed in 9 patients (36%) during the follow-up period. All recurrences were well managed with repeat procedures.Percutaneous radiofrequency thermocoagulation of the maxillary branch through the foramen rotundum under fluoroscopy is a safe and effective procedure for the treatment of isolated TN of the maxillary branch.

Use of sensory and motor action potentials to identify the position of trigeminal nerve divisions for radiofrequency thermocoagulation

OBJECT

The objective of this study was to develop an electrophysiological method for intraoperative localization of the trigeminal nerve branches during radiofrequency thermocoagulation (RFTC).

METHODS

Twenty-three patients who were scheduled to undergo RFTC were included. The trigeminal nerve root was stimulated through the foramen ovale using the radiofrequency cannula. Antidromic responses were recorded from the target division through supraorbital, infraorbital, and mental foramina electrodes, and an additional electrode at the masseter muscle. Sensory and motor action responses, as well as verbal and masseter contraction responses, were recorded and correlated.

RESULTS

The antidromic responses were easily recorded in the target division in all 23 patients, and they were invariably correlated with the patient's verbal responses. The potentials were recorded successively from V1 to V3. The amplitude in each division before and after RFTC showed little difference in response to electrical stimulation with the same current. The motor trigeminal nerve action potentials were recorded in 10 patients; 7 of these patients had postoperative masseter muscle weakness, while the remaining 3 had normal masseter muscle function. Potentials with low amplitudes were usually obtained from neighboring divisions, but no unexpected denervation of any branches was observed. All the patients experienced immediate pain relief after the procedure.

CONCLUSIONS

This technique is sensitive and easy to apply. The sensory and motor potentials matched the verbal responses and the complications. Although it cannot completely substitute for the patient's verbal response, this approach is helpful in uncooperative patients, and it predicts and reduces the incidence of masseter muscle weakness. The use of these complementary techniques could increase the chances of treatment success.

Percutaneous treatments for trigeminal neuralgia

Trigeminal neuralgia (TN) is a neurologic disorder, defined by paroxysmal electric shocklike painful attacks in 1 or more trigeminal nerve branches. Treatment of TN is diverse and includes minimally invasive percutaneous techniques, which consist of balloon compression, glycerol rhizotomy, and radiofrequency thermocoagulation. Although all 3 techniques are generally safe, efficient, and effective, a clear consensus has not been reached regarding their specific indications and degree of efficacy. The aim of this article is to describe the percutaneous treatments available for TN and outline their characteristics, technique, indications and efficacy.

Experience with conventional radiofrequency thermorhizotomy in patients with failed medical management for trigeminal neuralgia

Background

To evaluate the results of conventional radiofrequency thermorhizotomy (CRT) for trigeminal neuralgia (TN) in patients with failed medical management.

Methods

Patients with Trigeminal neuralgia who were referred to us for 'limited intervention' during the time frame July-2011 to Jan-2013 were enrolled for this study. CRT was administered by the Sweet technique. Pain relief was evaluated by the principle investigator.

Results

Eighteen patients were enrolled and completed a mean follow-up of 18.0 months. Pain relief was observed in 14 of 18 (77.8%) patients on the post-operative day, 14 of 18 (77.8%) at 1-month follow-up, 14 of 17 (82.4%) at 3-months follow-up, 12 of 15 (80%) at 6-months follow-up, 7 of 11 (63.6%) at 1-year follow-up and 2 of 6 (33.3%) 1.5 years of follow-up. Four patients required a repeat cycle of CRT; two at six months of follow-up and two at one year of follow-up. One patient was transferred for surgical intervention at six months of follow-up. Side-effects included facial hypoesthesia (n = 6); nausea/vomiting (n = 2), diminished corneal reflex (n = 13) and difficulty in chewing (n = 11). Severity of adverse effects gradually diminished and none of the patients who are beyond 6 months of follow-up have any functional limitation.

Conclusions

CRT is an effective method of pain relief for patients with Trigeminal neuralgia. Successful outcome (excellent or good) can be expected in 66.7% of patients after first cycle of CRF. The incidence and severity of adverse effects is less and the procedure is better tolerated by the patients.

Percutaneous bone lesion ablation

Benign tumors and metastatic bone lesions can be treated by ablation techniques performed either alone or in combination with other percutaneous techniques. Ablation techniques include ethanol or acetic acid injection and thermal ablation by means of energy deposition [including laser, radiofrequency, microwave, cryoablation, radiofrequency ionization and magnetic resonance (MR)-guided high-intensity focused ultrasound (HIFU)]. Goal definition of the therapy is crucial: ablation techniques can be proposed as curative treatments in benign bone tumors or oligometastatic disease (<3 lesions). Alternatively, these techniques can be proposed as palliative treatments aiming at reduction of pain, local control of the disease and tumor decompression. Depending on the lesion's location ablation can be combined with cementation with or without further metallic augmentation; local tumor control can be enhanced by combining ablation with transarterial bland embolization or chemoembolization. Thermal ablation of bone and soft tissues is characterized by high success and relatively low rates of potential complications, mainly iatrogenic thermal damage of surrounding sensitive structures. Successful thermal ablation requires a sufficient ablation volume and thermal protection of the surrounding vulnerable structures. This article will describe the general principles governing ablation and the mechanism of action for each technique and in addition will review the literature about safety and effectiveness of percutaneous imaging-guided ablation for benign and malignant (primary and metastatic) lesions.

Percutaneous pulsed radiofrequency treatment of the cervical dorsal root ganglion in the treatment of chronic cervical pain syndromes: a clinical audit

Cervicogenic headache and cervicobrachialgia are frequent diagnoses of chronic cervical pain. After failure of conservative treatment, an interventional approach may be indicated in the absence of any indication for causal surgical treatment. The pulsed radiofrequency (PRF) technique exposes the nerve to a high-frequency electric field while the temperature of the electrode tip does not exceed 42°C. This method is thought to be nondestructive and almost free of neurologic side effects and complications. Our extended pilot study was performed to confirm the perceived efficacy of PRF for short- and long-term relief of chronic cervical pain. We carried out a clinical audit of the first 18 patients treated with PRF at the cervical dorsal root ganglion. An independent evaluator reviewed the medical records. Patients with good clinical results at 8 weeks were evaluated for long-term effect (> 6 months), based on a 7-point Likert scale. Thirteen patients (72%) showed short-term clinical success (≥ 50% pain relief). Mean follow-up was 19.4 months (SD 8.9 months), maximum 2.5 years. The duration of satisfactory pain relief (6 or 7 on the Likert scale) varied between 2 and over 30 months, with a mean duration of 9.2 months (SD 11.2 months). Kaplan-Meier analysis illustrated that 50% of patients experienced success 3 months after treatment. We could not identify predictive variables for clinical outcome. None of the patients reported post-treatment neuritis or other adverse events. To our knowledge, this is the first documented series of chronic cervical pain syndromes treated with PRF. Satisfactory pain relief of at least 50% was achieved in 13 of 18 (72%) patients at 8 weeks. More than one year after treatment, six patients (33%) continue to rate treatment outcome as good or very good. No side effects were reported. j.

Success of initial and repeated medial branch neurotomy for zygapophysial joint pain: a systematic review

OBJECTIVES

To review the duration of pain relief after initial and repeated radiofrequency neurotomy (RFN) for cervical and lumbar zygapophysial joint pain.

METHODS

We searched PubMed to identify all articles that met review criteria for in-depth analysis, synthesis, and review.

RESULTS

Data from 16 articles are reported in this review, including 8 cervical studies, 7 lumbar studies, and 1 study of both cervical and lumbar treatment. Overall, methodology and design quality of cervical studies exceeded that of lumbar studies. For initial cervical RFN, average range duration of >50% pain relief was 7.3-8.6 months. Repeated cervical RFN was successful 67%-95% of the time when the first RFN procedure was successful. When the first RFN procedure was unsuccessful, repeated RFN was successful 0%-67% of the time. The average range duration of pain relief after successful repeated RFN was 6.0-12.7 months. For initial lumbar RFN, the average duration of >50% pain relief was 9.0 months. Repeated lumbar RFN was successful 33%-85% of the time when the first RFN procedure was successful. The average duration of pain relief after successful repeated lumbar RFN was 11.6 months.

CONCLUSIONS

The results of this review indicate that pain relief after initial RFN generally ends after 7-9 months and that repeating RFN is likely to provide additional pain relief if initial RFN was successful. Results are similar between cervical and lumbar spine studies.

Transcranial magnetic resonance–guided focused ultrasound surgery for trigeminal neuralgia: a cadaveric and laboratory feasibility study

Object

Transcranial MR-guided focused ultrasound surgery (MRgFUS) is evolving as a treatment modality in neurosurgery. Until now, the trigeminal nerve was believed to be beyond the treatment envelope of existing high-frequency transcranial MRgFUS systems. In this study, the authors explore the feasibility of targeting the trigeminal nerve in a cadaveric model with temperature assessments using computer simulations and an in vitro skull phantom model fitted with thermocouples.

Methods

Six trigeminal nerves from 4 unpreserved cadavers were targeted in the first experiment. Preprocedural CT scanning of the head was performed to allow for a skull correction algorithm. Three-Tesla, volumetric, FIESTA MRI sequences were performed to delineate the trigeminal nerve and any vascular structures of the cisternal segment. The cadaver was positioned in a focused ultrasound transducer (650-kHz system, ExAblate Neuro, InSightec) so that the focus of the transducer was centered at the proximal trigeminal nerve, allowing for targeting of the root entry zone (REZ) and the cisternal segment. Real-time, 2D thermometry was performed during the 10- to 30-second sonication procedures. Post hoc MR thermometry was performed on a computer workstation at the conclusion of the procedure to analyze temperature effects at neuroanatomical areas of interest. Finally, the region of the trigeminal nerve was targeted in a gel phantom encased within a human cranium, and temperature changes in regions of interest in the skull base were measured using thermocouples.

Results

The trigeminal nerves were clearly identified in all cadavers for accurate targeting. Sequential sonications of 25–1500 W for 10–30 seconds were successfully performed along the length of the trigeminal nerve starting at the REZ. Real-time MR thermometry confirmed the temperature increase as a narrow focus of heating by a mean of 10°C. Postprocedural thermometry calculations and thermocouple experiments in a phantom skull were performed and confirmed minimal heating of adjacent structures including the skull base, cranial nerves, and cerebral vessels. For targeting, inclusion of no-pass regions through the petrous bone decreased collateral heating in the internal acoustic canal from 16.7°C without blocking to 5.7°C with blocking. Temperature at the REZ target decreased by 3.7°C with blocking. Similarly, for midcisternal targeting, collateral heating at the internal acoustic canal was improved from a 16.3°C increase to a 4.9°C increase. Blocking decreased the target temperature increase by 4.4°C for the same power settings.

Conclusions

This study demonstrates focal heating of up to 18°C in a cadaveric trigeminal nerve at the REZ and along the cisternal segment with transcranial MRgFUS. Significant heating of the skull base and surrounding neural structures did not occur with implementation of no-pass regions. However, in vivo studies are necessary to confirm the safety and efficacy of this potentially new, noninvasive treatment.

Thermometry during coblation and radiofrequency ablation of vertebral metastases: a cadaver study

PURPOSE

To evaluate safety of coblation of simulated lytic metastases in human cadaveric vertebral bodies by measuring heat distribution during thermal tissue ablation and comparing it to radiofrequency ablation (RFA).

MATERIALS AND METHODS

Three devices were compared: a 10 mm single-needle RFA electrode, a 20 mm array RFA electrode and the coblation device. To simulate bone metastases, a spinal tumor model was used stuffing a created lytic cavity with muscle tissue. Measuring of heat distribution was performed during thermal therapy within the vertebral body, in the epidural space and at the ipsilateral neural foramen. Eight vertebral bodies were used for each device.

RESULTS

Temperatures at heat-sensitive neural structures during coblation were significantly lower than using RFA. Maximum temperatures measured at the end of the procedure at the neural foramen: 46.4 °C (± 2.51; RFA 10 mm), 52.2 °C (± 5.62; RFA 20 mm) and 42.5 °C (± 2.88; coblation). Maximum temperatures in the epidural space: 46.8 °C (± 4.7; RFA 10 mm), 49.5 °C (± 6.48; RFA 20 mm) and 42.1 °C (± 2.5; coblation). Maximum temperatures measured within the vertebral body: 50.6 °C (± 10.48; RFA 10 mm), 61.9 °C (± 15.39; RFA 20 mm) and 54.4 °C (± 15.77; coblation).

CONCLUSION

In addition to RFA, the application of coblation is a safe method to ablate vertebral lesions with regards to heat distribution at heat-sensitive neural spots. The measured temperatures did not harbor danger of thermal damage to the spinal cord or the spinal nerves.

Value of percutaneous radiofrequency ablation with or without percutaneous vertebroplasty for pain relief and functional recovery in painful bone metastases

OBJECTIVE

To evaluate the effectiveness of percutaneous radiofrequency (RF) ablation with or without percutaneous vertebroplasty (PV) on pain relief, functional recovery and local recurrence at 6 months' follow-up (FU), in patients with painful osseous metastases.

MATERIALS AND METHODS

Thirty RF ablations were performed in 24 patients (mean age: 61 years) with bone metastases. Half of the patients had an additional PV. The primary end point was pain relief evaluated by a visual analogue scale (VAS) before treatment, and at 1 and 6 months' FU. Functional outcome was assessed according to the evolution of their ability to walk at 6 months' FU. Imaging FU was available in 20 out of 24 patients with a mean delay of 4.7 months.

RESULTS

Reduction of pain was obtained at 6 months FU in 81% of cases (15 out of 18). Mean pretreatment VAS was 6.4 (±2.7). Mean VAS was 1.9 (±2.4) at 1 month FU, and 2.3 (±2.9) at 6 months' FU. Pain was significantly reduced at 6 months FU (mean VAS reduction = 4.1; P < 0.00001). Functional improvement was obtained in 74% of the cases. Major complications rate was 12.5 % (3 out of 24) with 2 skin burns, and 1 case of myelopathy. Local tumour recurrence or progression was recorded in 5 cases.

CONCLUSION

Radiofrequency ablation is an effective technique in terms of pain relief and functional recovery for the treatment of bone metastases, which provides a relatively low rate of local recurrence.

Management of bilateral trigeminal neuralgia with trigeminal radiofrequency rhizotomy: a treatment strategy for the life-long disease

BACKGROUND

The objective of this study was to evaluate the effectiveness of percutaneous controlled radiofrequency trigeminal rhizotomy (RF-TR) in patients with bilateral trigeminal neuralgia (BTN). Patients were analyzed after RF-TR in terms of outcome, safety and complications.

METHODS

Eighty-nine BTN patients underwent 186 RF-TR procedures. Eighty-seven patients had idiopathic trigeminal neuralgia (ITN) and two patients had multiple sclerosis (2.2%). Fifty-six (62.9%) were women and 33 (37.1%) were men. Ages ranged from 29 to 85 years. Anesthesia was administered at a determined optimal level, allowing patient cooperation for controlled and selective lesioning.

RESULTS

The mean follow-up period was 101.71 ± 77.7 months. Familial occurrence was seen in two (2.2%) patients. Synchronized pain was observed in 25 (28.2%) patients. Pain occurrence on the contralateral side was observed with an average duration of 124.7 ± 87.13 months. Fifty-four of the 89 patients underwent 146 RF-TR procedures for both sides and 35 underwent 40 RF-TR procedures for one side. Complete pain relief or partial satisfactory pain relief was achieved on the medically treated side in 35 patients. During follow-up, 36 patients required the second procedure and 7 required the third procedure. Acute pain relief was reported in 86 (96.6%) patients. Early (<6 months) pain recurrence was observed in 11 (12.3%) and late (>6 months) recurrence in 25 (28.0%) patients. Complications included diminished corneal reflex in four (2.1%) patients, keratitis in two (1.1%), masseter dysfunction in four (2.1%), dysesthesia in two (1.1%), and anesthesia dolorosa in one (0.5%).

CONCLUSIONS

RF-TR is an effective, selective, well-controlled, and effortlessly repeatable procedure for treating BTN, especially in the elderly, in terms of low morbidity and mortality rates and high rate of satisfactory pain relief.

Effects of pulsed versus conventional radiofrequency current on rabbit dorsal root ganglion morphology

Lesioning using radiofrequency (RF) current has been increasingly used in clinical practice for the treatment of pain syndromes. Although formation of heat causing "thermocoagulation" of the nervous tissues is thought to be responsible of the clinical outcome, a more recent modality of RF application named pulsed radiofrequency (PRF) delivers the RF current without producing destructive levels of heat. In our study, we compared the effects of conventional RF (CRF) and PRF on rabbit dorsal root ganglion (DRG) morphology, including also control and sham operated groups. The setting of the experiment and the RF parameters used were similar to those used in current clinical practice. The specimens were analyzed both with light microscopy and electron microscopy, two weeks after the procedure. At the light microscopic level, all groups had preserved the normal DRG morphology and no differences were observed between them. In the electron microscopic analysis there were no pathological findings in the control and sham operated groups. But the ganglion cells in the RF groups had enlarged endoplasmic reticulum cisterns and increased number of cytoplasmic vacuoles which were more evident in the CRF group. Some of the ganglion cells in the CRF group had mitochondrial degeneration, nuclear membrane disorders or loss of nuclear membrane and neurolemma integrity. The myelinated and unmyelinated nerve fibers were of normal morphology in all groups. Our results suggest that PRF application is less destructive of cellular morphology than CRF at clinically used "doses". Before making certain judgements, more experimental and clinical studies should be planned.

Water-cooled radiofrequency: a neuroablative or a neuromodulatory modality with broader applications?

We report the successful use of water-cooled radiofrequency where more traditional forms of neuroablation—conventional and pulsed radiofrequency—had failed to achieve adequate pain relief. We also discuss the mechanism of neural damage with water cooled radiofrequency and discuss why this technique may have a broader role in the management of a wide array of pain syndromes.

Percutaneous radiofrequency thermocoagulation under fluoroscopic image-guidance for idiopathic trigeminal neuralgia

OBJECTIVE

We retrospectively investigated the long-term results of percutaneous radiofrequency thermocoagulation (RFT) using fluoroscopic image-guidance for treatment of trigeminal neuralgia.

METHODS

A total of 38 patients diagnosed and treated with RFT as an idiopathic trigeminal neuralgia were investigated. To minimize the risks related to conventional technique based on cutaneous landmarks, and to eliminate the need to frequent reposition of cannula, we adopted a technique of image-guided fluoroscopic cannulation of the foramen ovale. To minimize sensory complication following thermal lesion, our target response was a generation of a lesion with mild to moderate hypalgesia rather than dense hypalgesia.

RESULTS

The immediate pain-relief was achieved in all patients underwent RFT. With mean duration of follow-up of 38.2 months (range,12-72), 11 (28.9%) experienced recurrence of pain. The mean timing of recurrence was 26.1 months (range,12-46). A 42.7% recurrence rate was estimated by Kaplan-Meier analysis for the 38 patients at 46 months; 20.2% within 2 years, 29.1% within 3 years. In the long-term, 27 patients (71%) and 6 patients (15.8%) showed Barrow Neurological Institute (BNI) score I and BNI score II responses. 3 (7.9%) patients was assessed as BNI score III, 2 patients (5.3%) showed BNI score IV response. As a complication, troublesome dysesthesia occurred in 3 of 38 patients (7.9%), however, there was no permanent cranial nerve palsy or morbidity.

CONCLUSION

These results indicates that RFT under fluoroscopic image-guided cannulation of foramen ovale is a safe, effective, and reliable means of treating trigeminal neuralgia.

The lumbar facet joint: a review of current knowledge: Part II: diagnosis and management

This article is the second article in a two-part review on lumbar facet joint pathology. In this review, we discuss the current concepts and controversies regarding the proper diagnosis and management of patients presenting with presumed facet-mediated lower back pain. All efforts were made to include the most relevant literature from the fields of radiology, orthopaedics, physiatry, and pain management. Our focus in this article is on presenting the evidence supporting or refuting the most commonly employed injection-based therapies for facet-mediated lower back pain.

Radiofrequency treatment in chronic pain

Chronic pain management physicians and patients are always looking for long-term solutions rather than short-lived interventions. There are three main nonsurgical modalities to ablate nervous system elements. These involve the use of extreme cold (cryoablation), high temperature radiofrequency and chemical neurolysis, such as alcohol or phenol. Radiofrequency ablation offers the advantage of being precise, reproducible and effective to a great extent. It also has the ability to stimulate before the ablation to avoid ablating the wrong nerve elements, which provides a considerable safety margin. In this article we will review the basis of radiofrequency ablation and some of the most common applications in the management of chronic pain.

Radiofrequência na dor crônica

Radiofrequência (RF) é uma técnica minimamente invasiva alvo-seletiva e tem sido usada durante muitos anos para o tratamento de diferentes doenças, como dor lombar crônica, neuralgia trigeminal e outros. Trata-se de uma corrente elétrica alternada com frequência oscilatória de 500.000 hz, que flui através de um eletrodo introduzido percutaneamente. O calor é formado ao redor do eletrodo porque o tecido age como um resistor. Essa técnica pode, portanto, ser usada para causar lesões em tecidos nervosos no tratamento de dor crônica. O objetivo desta revisão é abordar alguns aspectos importantes do mecanismo e evolução da radiofrequência na dor crônica. Serão abordados os aspectos básicos da Física e o mecanismo de ação da radiofrequência, método que tem sido usado para tratar dores crônicas de diferentes etiologias, além da evolução com o advento da radiofrequência pulsátil. O uso da radiofrequência no manejo da dor crônica é uma ferramenta útil em diferentes condições dolorosas e tem sido usada com sucesso por mais de 25 anos. Seu mecanismo de ação ainda não foi totalmente elucidado. A radiofrequência pulsátil é, em particular, uma técnica minimamente destrutiva e poderá ser uma alternativa à forma convencional de tratamento para a dor por radiofrequência.

Heat distribution in the spinal canal during radiofrequency ablation for vertebral lesions: study in swine

PURPOSE

To prospectively evaluate the safety of radiofrequency (RF) ablation for vertebral lesions by monitoring the temperature in swine vertebral models with and without a cortical bone defect.

MATERIALS AND METHODS

The institutional animal care and use committee approved the animal studies. In vivo and ex vivo studies were performed. In the in vivo study, 20 lumbar vertebrae from six swine were locally heated by using 1- or 2-cm active-tip internally cooled electrodes. In the ex vivo study, 12 fresh pig cadaver lumbar vertebrae were extracted from four swine, and spinal tumor models with or without cortical bone defect were created by stuffing a cavity with muscle tissue and locally heated by using a 1-cm active-tip internally cooled electrode. The temperature was monitored in the spinal canal and around the vertebral body during ablation. Mann-Whitney U test was used to indicate a significant difference between groups by using 1- and 2-cm active tip in the in vivo study and between groups with and without cortical defect in the ex vivo study.

RESULTS

In the in vivo study in which 1- and 2-cm active-tip needles were used, the temperature in the spinal canal rose to 38.2 degrees C +/- 2.7 (standard deviation) and 45.5 degrees C +/- 6.2, respectively. The latter was significantly higher than the former (P < .001). In the ex vivo study in which tumor models with or without a cortical bone defect were used, the temperature in the spinal canal rose to 48.4 degrees C +/- 6.2 and 31.3 degrees C +/- 3.4, respectively. The former was significantly higher than the latter (P < .001).

CONCLUSION

For in vivo cases with a 2-cm active tip and ex vivo cases with a vertebral posterior bone defect, the temperature rose to over 45 degrees C, potentially injuring the spinal cord and peripheral nerves.

Interventional techniques for back pain

Most Americans will be afflicted by some form of spine-related pain in their lifetime. In older patients, the most frequent source of back pain is lumbar spinal stenosis or vertebral compression fracture. Although most back pain is self-limited, some patients will require interventional techniques. This article reviews minimally invasive techniques for treating back pain, lumbosacral radicular pain, lumbar spinal stenosis, and compression fractures.

Pulsed radiofrequency: a critical review of its efficacy

Pulsed radiofrequency is a growingly popular pain treatment modality. However, its clinical efficacy remains controversial. In this review, the available literature on pulsed radiofrequency is critically analysed to determine its clinical efficacy. Our search of the literature for pulsed radiofrequency yielded 341 citations; after reviewing the abstracts we found 51 relevant articles. There were 4 review articles: 44 articles pertained to the application of pulsed radiofrequency by an electrode placed in the vicinity of a neural structure. Of these only two were randomised controlled trials. Of the remaining 42 articles, one was a non-randomised controlled trial, three were prospective uncontrolled trials: there were six retrospective studies, 11 case reports, eight laboratory studies, two position papers, five editorials and seven items of correspondence, while one publication reported two studies. Three articles pertained to transcutaneous application of pulsed radiofrequency. Of the two randomised controlled trials, one reported efficacy of the pulsed radiofrequency while the other reported it to be ineffective. The majority of the uncontrolled and observational studies reported clinical efficacy of pulsed radiofrequency, however many of these studies had limitations. Further randomised controlled clinical trials are recommended in order for the practising pain physician to clearly understand the role of pulsed radiofrequency in the treatment of various chronic pain syndromes.

Evidence-informed management of chronic low back pain with facet injections and radiofrequency neurotomy

The management of chronic low back pain (CLBP) has proven to be very challenging in North America, as evidenced by its mounting socioeconomic burden. Choosing amongst available nonsurgical therapies can be overwhelming for many stakeholders, including patients, health providers, policy makers, and third-party payers. Although all parties share a common goal and wish to use limited health-care resources to support interventions most likely to result in clinically meaningful improvements, there is often uncertainty about the most appropriate intervention for a particular patient. To help understand and evaluate the various commonly used nonsurgical approaches to CLBP, the North American Spine Society has sponsored this special focus issue of The Spine Journal, titled Evidence-Informed Management of Chronic Low Back Pain Without Surgery. Articles in this special focus issue were contributed by leading spine practitioners and researchers, who were invited to summarize the best available evidence for a particular intervention and encouraged to make this information accessible to nonexperts. Each of the articles contains five sections (description, theory, evidence of efficacy, harms, and summary) with common subheadings to facilitate comparison across the 24 different interventions profiled in this special focus issue, blending narrative and systematic review methodology as deemed appropriate by the authors. It is hoped that articles in this special focus issue will be informative and aid in decision making for the many stakeholders evaluating nonsurgical interventions for CLBP.

Application of radiofrequency treatment in practical pain management: state of the art

Many therapeutic interventions for chronic pain are available, and decisions about optimal management are not easy to make. Radiofrequency (RF) treatment is classified as a percutaneous minimal invasive procedure for patients who do not respond to appropriate medical and physical therapy. Although RF treatment is widely used differences in current practice exist due to ongoing controversies.

Osteoid Osteoma in an ex Vivo Animal Model: Temperature Changes in Surrounding Soft Tissue during CT-guided Radiofrequency Ablation

PURPOSE

To assess temperature changes in the soft tissue surrounding bone during radiofrequency (RF) ablation of osteoid osteoma in an ex vivo animal model.

MATERIALS AND METHODS

Intracortical cavities were created in fresh bovine long bone specimens obtained from a slaughterhouse as models for osteoid osteoma. Three groups of three specimens each were defined according to the thickness (1, 3, and 5 mm) of the cortical bone lamella separating the nidus from the periosteum. Three thermocouples were applied to the soft tissue surrounding the bone in defined distances (0, 5, and 10 mm) from the periosteum. Before RF ablation, the thickness of the cortical bone lamella was documented at computed tomography. Specimens were heated in a 37 degrees C basin. As soon as the measured temperature in the cavity of the specimen reached 35 degrees C, RF ablation was performed for 400 seconds, with a target temperature of 95 degrees C. During RF ablation, continuous measurements were performed simultaneously with digital thermometers. No simulation of vessel perfusion was used. The effect of the thickness of residual osseous lamella and the effect of the distance between the thermocouple and the periosteum were tested with an analysis of variance. Post hoc Bonferroni tests were performed.

RESULTS

Mean maximum temperatures of 69.1 degrees, 51.3 degrees, and 42.5 degrees C for 1-mm lamella; 59.2 degrees, 46.5 degrees, and 41.1 degrees C for 3-mm lamella; and 50.6 degrees, 44.8 degrees, and 40.0 degrees C for 5-mm lamella were measured 0, 5, and 10 mm, respectively, from the periosteum. Significant temperature differences were shown with analysis of variance and post hoc tests for the three groups of bone lamella thickness and distance (P < .001).

CONCLUSION

In the model of osteoid osteoma, the surrounding temperature (soft tissue) during RF ablation was shown to depend on the thickness of the cortical bone lamella and the distance from the periosteum.

A randomized, double-blind, controlled trial: intradiscal electrothermal therapy versus placebo for the treatment of chronic discogenic low back pain

STUDY DESIGN

A prospective, randomized, double-blind, placebo-controlled trial of intradiscal electrothermal therapy (IDET) for the treatment of chronic discogenic low back pain (CDLBP).

OBJECTIVES

To test the safety and efficacy of IDET compared with a sham treatment (placebo).

SUMMARY OF BACKGROUND DATA

In North America alone, more than 40,000 intradiscal catheters have been used to treat CDLBP. The evidence for efficacy of IDET is weak coming from retrospective and prospective cohort studies providing only Class II and Class III evidence. There is one study published with Class I evidence. This demonstrates statistically significant improvements following IDET; however, the clinical significance of these improvements is questionable.

METHODS

Patients with CDLBP who failed to improve following conservative therapy were considered for this study. Inclusion criteria included the presence of one- or two-level symptomatic disc degeneration with posterior or posterolateral anular tears as determined by provocative computed tomography (CT) discography. Patients were excluded if there was greater than 50% loss of disc height or previous spinal surgery. Fifty-seven patients were randomized with a 2:1 ratio: 38 to IDET and 19 to sham procedure (placebo). In all cases, the IDET catheter was positioned to cover at least 75% of the annular tear as defined by the CT discography. An independent technician connected the catheter to the generator and then either delivered electrothermal energy (active group) or did not (sham group). Surgeon, patient, and independent outcome assessor were all blinded to the treatment. All patients followed a standard postprocedural rehabilitation program. Independent statistical analysis was performed.

OUTCOME MEASURES

Low Back Outcome Score (LBOS), Oswestry Disability Index (ODI), Short Form 36 questionnaire (SF-36), Zung Depression Index (ZDI), and Modified Somatic Perceptions Questionnaire (MSPQ) were measured at baseline and 6 months. Successful outcome was defined as: no neurologic deficit, improvement in LBOS of greater then 7 points, and improvement in SF-36 subsets (physical function and bodily pain) of greater than 1 standard deviation.

RESULTS

Baseline demographic data, initial LBOS, ODI, SF-36, ZDI, and MSPQ were similar for both groups. No neurologic deficits occurred. No subject in either arm showed improvement of greater than 7 points in LBOS or greater than 1 standard deviation in the specified domains of the SF-36. Mean ODI was 41.42 at baseline and 39.77 at 6 months for the IDET group, compared with 40.74 at baseline and 41.58 at 6 months for the placebo group. There was no significant change in ZDI or MSPQ scores for either group.

CONCLUSIONS

The IDET procedure appeared safe with no permanent complications. No subject in either arm met criteria for successful outcome. Further detailed analyses showed no significant change in outcome measures in either group at 6 months. This study demonstrates no significant benefit from IDET over placebo.