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Clinical References, Evidence & Validation

Radiofrequency Ablation Using a Novel Multitined Expandable Electrode: Device Description and Research Study1

R.E. Wright, K.J. Allan, M. Kraft, & B.R. Holley. Minimally Invasive Surgery for Pain, Volume 2, Number 1, 41-54, Article published in MISP Journal, 2013

Abstract:

Durable pain remission using radiofrequency thermal neurotomy (RTN) requires thoughtful patient selection and a lesion of optimal size and position. Success necessitates complete ablation of approximately 8-10 mm of the targeted neural pathway. Technical failure may result if anatomic variations in the targeted pathway are not incorporated into the lesion and if the electrode is not positioned optimally relative to the target nerve. This paper presents an improvement in RF electrode design intended to improve RTN outcomes.  

Conclusions: 

This is the first description of a multitined, expandable electrode designed for use in spinal radiofrequency procedures. It is manufactured by Nimbus Concepts, LLC in Austin, Texas. This novel radiofrequency electrode was developed using dual deployable tines for electrical field diffusion and increased functional electrode surface area. The lesion it produces is geometrically predictable and thermally stable. ¶ The innovative design of the electrode and the resulting geometry and stability of the tissue lesion are uniquely suited to safe, technically efficient, and effective interruption of nociceptive pathways. Detailed anatomical research into afferent pain pathways provided the basis for the electrode design and supports the premise that this device will enable practitioners to consistently achieve appropriate tissue ablation with fewer heat cycles and less global tissue trauma compared to the various monopolar designs currently in use. ¶ The advent of a technologically advanced radio-frequency electrode that produces directional and optimally-sized lesions for neurotomy holds great promise for interventional pain management. The design simplifies technique and readily adapts to various RF ablation targets including the cervical, thoracic and lumbar zygapophyseal joints, the sacroiliac joint, and other targets along the spinal sympathetic chain. Furthermore, the multitinedconstruct has the potential to configure future devices that will shape lesions even more precisely for additional specific thermal ablation targets heretofore not possible with current electrodes. 

Comparisons of Lumbar Facet Radiofrequency Neurotomy Using a Conventional Monopolar versus Multitined Electrode2

R. Burnham, MD. Pain Medicine, Volume 16, Number 8, 2015, page 1650-51

Background: 

Strategies to expand radiofrequency(RF) lesion size to accommodate medial branch nerve location variability include multiple lesions using a conventional monopolar electrode and the use of a multitined (Nimbus) electrode.

Objective: 

To compare the effect of electrode type (conventional monopolar versus multitined) on relief of pain and disability, procedure time and fluoroscopy exposure. 

Methods: 

25 consecutive patients underwent lumbar facet RF using a single multitined thermal lesion per medical branch nerve. Each had previously undergone successful lumbar facet RF using 2 conventional monopolar lesions over the same medial branch nerves. Prospectively gathered Pain Disability Questionnaire (PDQ) scores were recorded prior to and at 2 months post RF for both groups and at 6 months post RF for the multitined electrode group. RF procedure duration and fluoroscopy times were also recorded. Data were analyzed using Analysis of Variance.

Results: 

PDQ scores dropped significantly and comparably at 2 months post RF in both the monopolar and multitined electrode groups {pre:postmean(sd) scores – monopolar 28.8(5.5):11.6(6.1); multitined 28.6(5.6):11.0(6.7)}. The 6 month post RF PDQ score remained significantly improved the multitined group {14.9(7.5)}.  Pain scores also dropped significantly and comparably in both groups {pre:post mean(sd) scores – monopolar 6.4(1.8):2.6(1.4); multitined 6.3(1.6:2.3(1.4)}. The 6 month post RF pain score remained significantly improved in the multitined group {3.3(2.1)}. At 2 months post RF, 76% and 72% of the monopolar and multitined groups respectively had experienced 50% or more pain relief.  Procedure time was significantly shorter with the multitined electrode {in minutes – monopolar 45 (15.2); multitined 25.5(8.2)}.  Fluoroscopy exposure was comparable {in seconds – monopolar 117 (49.8); multitined 98.4(34.4)}.  

Conclusions: 

Pain and disability relief from lumbar facet radiofrequency neurotomy are significant and comparable whether using a conventional monopolar or multitined electrode. The procedure is significantly quicker when using the multitined electrode. Fluoroscopy exposure is comparable.

An Ex Vivo Study On Radiofrequency Tissue Ablation Using a Novel Multitined Expandable Electrode4

R.E. Wright, S.A. Brandt; Pain Medicine, Volume 12, Number 9, 1446, 2011
Presented at International Spine Intervention Society 19th Annual Meeting in Chicago, Illinois (Best Basic Science Abstract)

Radiofrequency (RF) ablation has been effectively used to interrupt nociception arising from various spinal pain generators1. Anatomic variation in the targeted neural pathways and suboptimal electrode placement may result in technical failure and poor patient outcomes. Intuitively, larger lesions mean a larger tolerance for both errors in electrode placement as well as the inevitable variation in the anatomic position of target nerves2. A novel multitined expandable RF electrode was developed.

Objective: 

Investigate the evolution in typography of a thermal lesion produced by a novel RF electrode. 

Methods: 

Sections of raw muscle tissue were allowed to equilibrate to 37°C in a distilled water bath. RF electrode with tines deployed was positioned to contact tissue surface in 10 trials, and was inserted into tissue in 10 trials. A Radionics RFG 3C RF generator energy source was set at 75°C for 80 seconds. Propagation of tissue coagulation was documented with video and calibrated Flir T-400 thermal camera. Tissue samples were sectioned and coagulation zones measured.

Results: 

Infrared observation demonstrated symmetric and homogenous lesion progression without hot spots or focal over-impeding. Calculated volume averaged 467 +/- 71 mm3/lesion. Topography was elongate spheroid offset from the central axis toward tines. 

Conclusions: 

A novel RF electrode prototype using dual deployable tines for electrical field diffusion reliably produces a lesion potentially useful in spinal applications.

References:  

1. Dreyfuss P, Halbrook B, Pauza K, Joshi A, McLarty J, Bogduk N. Efficacy And Validity Of Radiofrequency Neurotomy For Chronic Lumbar Zygaphysial Joint Pain. Spine 2000; 25:1270-7. 2. Lord S, McDonald G, Bogduk N. Percutaneous Radiofrequency Neurotomy of the Cervical Medial Branches: A Validated Treatment for Cervical Zygapophysial Joint Pain. Neurosugery Quarterly 1998; 8(4): 288-308.  

This is the first description of a multitined, expandable electrode designed for use in spinal radiofrequency procedures. It is manufactured by Nimbus Concepts, LLC in Austin, Texas. This novel radiofrequency electrode was developed using dual deployable tines for electrical field diffusion and increased functional electrode surface area. The lesion it produces is geometrically predictable and thermally stable. 

Technical Efficacy of a Direction Specific Radiofrequency Device in the Performance of Lumbar Medial Branch Neurotomies – An MRI and EMG Confirmation Study (Interim Analysis)5

J.S. Bainbridge, MD, R.E. Wright, MD, C.D. Pappas, MD, S. Light, BA, RC, R.B. McQueen, PhD, Pain Medicine, Volume 16, Number 8, 2015, page 1650

Background/Objective: 

Lesion position and geometry are cardinal in maximizing safety and efficacy when performing lumbar medial branch radiofrequency ablation (LMBRFA). Technical efficacy of a multi-tined expandable electrode (MEE), with perpendicular approach, was demonstrated using a novel LMRI validation protocol and corroborated with paraspinous EMG (PEMG) findings in this IRB approved study.

Methods: 

Patients (n=6 MRI, n=5 EMG) chosen for LMBRFA underwent pre and post LMRI and PEMG[1]. Post-ablation LMRI using a previously described[2] protocol was obtained 7 days following RFA and used to quantify lesion size and provide lesion topography and anatomic relationship information. Post-LMBRFA EMG was obtained at 3-6 weeks. Monitoring of possible complications was carried out. 

Results:

Lesions were achieved, incorporating the target MB/SAP wall, in all cases*. Mean lesion volume was 601.7mm3 (n=40, 95%CI: 522.6, 680.8). No bony edema or complications were noted. EMG evidence of target medial branch ablation was achieved in 88%* (n=34, 95%CI: 77-99) of targets which compares favor- ably with EMG % ablation of Dreyfuss, et al [3] of 90.5%. *One subject underwent repeat procedure, adding one additional MRI/EMG positive ablation site – included in these results. There were no complications. 

Comments: 

Post-MBRFA LMRI, supported by PEMG, was used to demonstrate technical efficacy and safety of a multi-tined expandable RF electrode, using a new technique (perpendicular approach) that simplifies this ablative procedure for this common target. This validation method is an extension of all ex-vivo RF work done to date, and may be used for future research, as well as being a useful tool for educational purposes. 

References:

1) Haig, A.J., et al., Paraspinal mapping: quantified needle electromyography in lumbar radiculopathy. Muscle Nerve, 1993. 16(5): p. 477-84. 2) Wright, R., Bainbridge, JS, Allan, KJ, MRI Protocol for Analysis of Tissue Ablation Following Dorsal SIJ Radiofrequency Denervation, in ISIS ASM July, 2013 Poster Session. 2013. 3) Dreyfuss, P., et al., Efficacy and validity of radiofrequency neurotomy for chronic lumbar zygapophysial joint pain. Spine, 2000. 25(10): p. 1270-7. 

In and Ex Vivo Validation of a Novel Technique for Radiofrequency Denervation of the Dorsal Sacroiliac Joint – Including a Case Study6

R.E. Wright, K.J. Allan, J.S. Bainbridge, Regional Anesthesia and Pain Medicine, Volume 38, Number 5, Supplement 1, September-October 2013, E161-E162. 
Presented at the 32nd Annual ESRA Congress in Glasgow, United Kingdom, September 4-7, 2013

Purpose:

A technique was developed for radiofrequency (RF) ablation of the L5 dorsal ramus (L5DR) and S1-3 lateral branches (LBs) making use of a novel (FDA approved Nimbus Multi-tined Expandable Electrode) RF electrode.

Materials/Methods: 

The typical distance between lateral walls of adjacent S1-3 foramina is 18-22mm. Tissue coagulation in chicken breast using Nimbus electrodes in bipolar configuration with 20mm gap (and in vivo simulation with 37°C water bath) was observed thermographically. A Baylis RF generator produced parameters of 80°C for 120 seconds (30 sec. ramp time). Tissue samples were sectioned and geometric measurements were made at 10mm from either electrode (lesions >10mm in diameter). The experiment was replicated using the palisade bipolar strip lesion method, for comparison of data. Consented adults underwent the Nimbus Continuum strip lesion technique, and MRI assessment was obtained 13 days post-RF. Lesion (edema) size was scored with an axial fat suppressed proton density sequence (echo train 8, TR 3000ms, TE 26ms) and the tubular (diam. 11.7mm) tissue change extended from L5-S1 through S4 segment inclusive, and overlapped the known dorsal sacroiliac join (SIJ) innervation.

Results:

Bench and in vivo findings thus far support the Nimbus Continuum technique as a method for the ablation of the L5DR and S1-3 lateral branches for dorsal SIJ denervation.

Conclusions: 

This new RF technique appears to be technically effective and time efficient as a method for successful dorsal SIJ denervation.

MRI Protocol for Analysis of Tissue Ablation Following Dorsal SIJ Radiofrequency Denervation7

R.E. Wright, M.D., J. Weingardt, M.D., J. Scott Bainbridge, M.D., K.J. Allan, M.D
Poster Presentation at the International Spine Intervention Society 21st Annual Meeting in New York, New York, July 2013

Purpose:

The sacroiliac joint (SIJ) is a challenging radiofrequency target owing to variant anatomy of the S1, S2, and S3 lateral branches1. Bipolar RF techniques have been described to expand lesion volume potentially increasing the likelihood of target ablation, currently there is no objective test for evaluating technical success following dorsal SIJ RF denervation. MRI may be useful to correlate the ablation zone with target anatomy. An MRI protocol was developed to quantify volume, and evaluate the spatial characteristics of tissue change pursuant to dorsal SIJ RF denervation.

Materials/Methods:  

After consent a 64-year-old male underwent right-sided dorsal SIJ RF denervation. Electrodes (1.45 mm OD) were paired starting at the base of the S1 SAP progressively caudad<progressively 20mm gaps. The Baylis Pain Management generator in bipolar mode delivered an 80°C x150 seconds heat cycle.

Fourteen days post procedure an MRI study was optimized for both spatial and contrast resolution. A sequence sensitive to edema with preserved spatial resolution for accurate volumetric analysis was obtained. Lesion size was scored with an axial fat suppressed proton density sequence (echo train 8, TR 3000ms) at a slice thickness of 5mm with a 1mm gap. A region interest curve was drawn around edematous tissue on each slice providing an area, which was totaled for all of the slices. The total was multiplied by an effective slice thickness of 6mm providing the total volume of edematous tissue.

Results:

Right posterior parasacral edema extended from L5-S1 through S4 segments. Total volume of tissue change was 24.4cm3. The lesion was tubular with average diameter of 11.7mm. Tissue change incorporated described dorsal SIJ innervation.

 

Conclusions:  

An MRI protocol is described which demonstrates RF induced tissue changes following dorsal SIJ denervation.

1. Yin W, et al sensory stimulation-guided sacroiliac joint radiofrequency neurotomy: technique based on neuroanatomy of the dorsal sacral plexus. Spine 2003; 28:2419-25.

Radiofrequency Neurotomy for Sacroiliac Joint Pain; Twelve Month Outcomes and Comparison Between Two Techniques8

R.E. Wright, M.D., DABPM, FIPP, Metro Pain Group, Melbourne, Australia.
Poster Presentation at the 11thAnnual Congress of the European Pain Federation in Valencia, Spain, September 2019

Method: 

Retrospective chart review n=182.

Purpose:

The Sacroiliac Joint (SIJ) is an acknowledged pain generator; various descriptions of variable joint innervation inform Radiofrequency ablation (RFA) practices. Many practitioners target S1-S3 lateral branches (LBs) with a “strip lesion” RFA technique while others include the L4 medial branch (MB) and L5 dorsal ramus (DR) in their tactic (1).

Objective:

Ascertain whether RFA of the SIJ results in a durable (twelve month) benefit and determine if including RFA of the L4 MB and L5 DR improved outcomes.

Methods:

One hundred and eighty-two (n=182) patient charts were reviewed. 103 female 79 male average age 52 years. All patients presented with >5/10 on pain VAS index pain below the belt-line and positive Fortin’s finger test. Fluoroscopically guided contrast-confirmed intra-articular injection with >70% relief of index pain and confirmatory multi-site multi-depth lateral branch blocks with >70% relief of index pain was required for RFA. Ninetly-three (93) patients underwent bipolar ablation of S1-S3 lateral branches using a multitined expandable electrode (Nimbus) based on the technique described by Wright et al (2). The author modified his technique and subsequently eighty-nine (89) patients underwent monopolar RFA of the L4 MB and L5 DR in addition to the S1-S3 LB bipolar RFA. Patient’s pain VAS and global PDQQS (3) scores were obtained at baseline, one, six, and twelve months. Only twelve-month data was used to assess “durable” benefit.

Results: 

Global baseline pain VAS was 7.2+/- 1.1 and global PDQQ-S score was 79.6 +/- 11.2. At twelve months pain VAS decreased to 2.6 +/- 1.2 and PDQQ-S 35.2 +/- 14.8. (P values <0.001). Subset analysis of the S1-S3 RFA only group showed baseline pain VAS of 7.2 +/- 1.0 and global PDQQ-S of 38.2 +/- 14.2. The group including RFA of L4 MB and L5 DR had baseline pain VAS of 7.1 +/- 1.2 and PDQQ-S of 75.9 +/- 11.5. At twelve months pain decreased to VAS of 2.4 =/- 1 and global PDQQ-S of 32 +/-15.

Conclusion:

RFA of the S1-S3 sacral lateral branches in a well selected population using an anatomically accurate bipolar strip lesion technique producing the necessary and sufficient lesion topography provides highly significant pain reduction and improvement in PDQQ-S at twelve months follow up. Including L4 MB and L5 DR may provide additional benefit and further study is encouraged.

Nimbus: A Novel Multi-Tined Expandable Electrode For Percutaneous Radiofrequency Lesioning Of The Sacroiliac Joint9

A. Al-Kaisy, D. Pang. The British Editorial Society of Bone & Joint Surgery: Orthopaedic Proceedings, Vol. 96-B, No. Supp. 4, February 2018.

Introduction:

Percutaneous radiofrequency lesioning of the lateral branches of the sacroiliac joint has become a recognised method of treating chronic pain arising from this joint. Due to the large and varied innervation from the S1-3 lateral branches success has been achieved with large lesions that has a high chance of covering these nerves. Such lesions require specialised and expensive equipment and the NIMBUS needle is a large 17G electrode with expandable tines at the tip. It is compatible with all standard radiofrequency probes and it produces a large lesion at the tip. It has been in use in the USA in over 100 cases and we describe its use in the UK.

Methods:

Patients were identified as having sacroiliac joint pain by clinical assessment and positive pain response to local anaesthetic sacroiliac joint lateral branch blocks.

Under fluoroscopic control, the needle is inserted at the lateral edge of the sacral S1-3 posterior foramen. Three lesions at the lateral edge of the foramen are made at 80°C for 90s. A further lesion is made at the L5 dorsal ramus.

Results:

4 patients achieved very good pain relief >50% reduction in pain scores on the NRS scale at 6 weeks follow up. No complications were noted and there were no technical difficulties.

Conclusion:

Lesioning with the NIMBUS needle is feasible and allows clinicians a method of treating chronic sacroiliac joint pain using existing radiofrequency equipment. Further large, long term studies are warranted to establish clinical efficacy.

Comparisons of Lesion Volumes and Shapes Produced by a Radiofrequency System with a Cooled, a Protruding, or a Monopolar Probe3

D.L. Cedeño, A. Vallejo, Courtney A.K., D.M. Tilley, and N. Kumar, Millennium Pain Center, Bloomington, Illinois; Illinois Wesleyan University, Bloomington, Illinois; University of Illinois at Urbana-Champaign, Champaign, Illinois, Illinois; Pain Physician: September/October 2017: 20:E915-E922 

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