A Novel Modality for Facet Joint Denervation: Cooled Radiofrequency Ablation for Lumbar Facet Syndrome. A Case Series

Research Article

Phys Med Rehabil Int. 2014;1(5): 5.

A Novel Modality for Facet Joint Denervation: Cooled Radiofrequency Ablation for Lumbar Facet Syndrome. A Case Series

Zachary McCormick1*, Jeremy Walker2, Benjamin Marshall1, Robert McCarthy2, David R Walega2

1The Rehabilitation Institute of Chicago/Northwestern University Feinberg School of Medicine, Department of Physical Medicine and Rehabilitation, USA

2Northwestern University Feinberg School of Medicine, Department of Anesthesiology, USA

*Corresponding author: Zack McCormick, MD Department of Physical Medicine and Rehabilitation, Rehabilitation Institute of Chicago, McGaw Medical Center, Northwestern University Feinberg School of Medicine, USA

Received: November 13, 2014; Accepted: December 19,2014; Published: December 23, 2014


Background: While cooled radiofrequency ablation (C-RFA) appears to be a promising technology for joint denervation, outcomes of this technique for the treatment of lumbar facet syndrome have not been described. We report clinical outcomes in a case series of patients treated with C-RFA for lumbar facet syndrome.

Methods: Consecutive patients aged 18-60 years diagnosed with lumbar facet syndrome, confirmed by =75% symptom relief with at least one set of diagnostic medial branch nerve blocks, who underwent C-RFA between January 2007 and December 2013 in an urban academic pain center were included. The respective proportions of participants who reported =50% improvement in pain in function were calculated. Change in median NRS score, daily morphine equivalent consumption (DME), and medication quantification scale III (MQS III) score were measured.

Results: Twelve patients underwent C-RFA; three were lost to follow-up. The median and 25%-75% inter quartile range (IQR) for age was 44 years (35, 54). The median duration of follow-up was 34 months, IQR (21, 55). The percentage and 95% confidence interval (CI) of patients who reported =50% improvement in pain was 33% CI (12%, 64%) and in function was 78%, CI (41%, 96%). There was no change in DME or MSQ III score. Approximately 50% of patients sought additional healthcare by long-term follow-up. No complications were reported.

Conclusions: This case series suggest that C-RFA may improve function and to a lesser degree pain at long-term follow-up. A randomized, controlled trial is warranted.

Keywords: Zygapophyseal joint; Denervation; Low back pain


CI: Confidence Interval; C-RFA: Cooled Radio Frequency Ablation; DME: Daily Morphine Equivalents; G: Gauge; Hz: Hertz; IQR: Inter Quartile Range; IVP: Intra Venous Push; MBN: Medial Branch Nerve; MQSIII: Medication Quantification Scale III; NRS: Numerical Rating Scale; T-RFA: Conventional Thermal Radiofrequency Ablation


Lumbar zygapophyseal or "facet" joint pain accounts for 15-30% of low back pain cases in the adult population [1-3]. When facetmediated pain fails to improve with conservative treatment including non-steroidal anti-inflammatory drugs, physical therapy and postural re-education, interventional treatment may be indicated. Radiofrequency ablation (RFA) of the lumbar medial branch nerves provides significant improvement in pain, function and analgesic use for 6-12 months in individuals with facet-mediated low back pain [4-3-16]. RFA has also been shown to be a cost effective pain management modality [11].

The pain mediator in lumbar facet syndrome is the medial branch nerve of the dorsal ramus (MBN), which supplies the facet joints and multifidi muscles at each spinal segment. Thermal MBN lesioning interrupts these afferent nociceptive pathways by applying radiofrequency energy through an electrode placed at the target MBN. In contrast to conventional thermal radiofrequency ablation (T-RFA) wherein the target is heated to 80 degrees C for 90 seconds, cooled radiofrequency ablation (C-RFA) uses a constant flow of ambient water circulated through the electrode via a peristaltic pump to maintain a lower tissue temperature by creating a heat sink, but still allowing neurolysis to occur. By removing heat from tissues immediately adjacent to the electrode tip, a lower lesioning temperature is maintained, resulting in less tissue charring adjacent to the electrode and therefore less tissue impedance [17, 18]. The volume of tissue heated and the resultant thermal lesion size is substantially larger with C-RFA as compared to T-RFA [19]. C-RFA lesions are spherical and project several millimeters beyond the electrode tip as compared to T-RFA, thereby increasing the probability of successful denervation of the target MBN. The lesion characteristics in C-RFA also allow the electrode to be positioned at any angle to make contact with the target neural structure [20]. Together, these make the technique easier to perform.

C-RFA has been used to successfully treat cardiac arrhythmia [21- 23] and solid tumors [24, 25]. More recently introduced for chronic pain indications, a number of studies have demonstrated improved pain and functional outcomes when C-RFA is used to treat chronic sacroiliac joint pain [26-29]. No published study has investigated C-RFA for the treatment of lumbar facet syndrome. In this case series, we describe the clinical outcomes of 12 patients with lumbar facet syndrome treated with C-RFA.


This is a longitudinal cohort study. The study protocol (STU00090028) was approved by the local Institutional Review Board and was conducted at a single-site interventional pain management practice in an urban tertiary academic medical center. Inclusion criteria were: age 18-60 years, lumbar facet syndrome corroborated by history, physical examination, imaging, and confirmation with >75% reduction in back pain following at least one set of diagnostic MBN blocks and C-RFA procedure between January 1, 2007 and December 31, 2013. Exclusion criteria were: radicular symptoms by history, nerve root tension signs, lower extremity strength or reflex asymmetry.

The medical records of participants were reviewed and demographic data (age, sex, and body mass index), duration of pain and anatomic levels of C-RFA, pre-C-RFA pain scores and pre C-RFA medication usage were recorded. After C-RFA, participants were contacted by telephone by a research assistant and followup outcome data (NRS pain score, duration of pain reduction, functional improvement, opioids and non-opioids medication use, and other healthcare utilization information) were collected using of a standardized questionnaire (Appendix A). If a patient could not be contacted by phone upon at least three attempts, on different days, at different times of the day, then the individual was considered "lost to follow up". Our primary outcome measure was the rate of =50% pain improvement at long-term follow up. We chose to use a categorical definition of "clinically significant" pain relief rather than the difference in group means studies of low back pain interventions have consistent show that there are "responders" and "non-responders," such that, when using group means, significant pain reduction in a subset of the study group can be masked [30-31].


Based on history, physical examination and imaging studies, the treating physican selected the facet joints to be diagnostically blocked and performed MBN blocks to fucntionally anesthetize these joints. A needle was placed at each target location (described below) and following confirmation of appropriate needle placement with fluoroscopy, 0.5 cc of 0.5% bupivacaine or 2% lidocaine was injected. The maximum number of MBNs blocked for any diagnstic injection was limited to six.

At the time of the C-RFA procedure, patients were positioned prone on a fluoroscopy table and the lumbar region was prepped with chlorhexidine and draped in a standard sterile manner. Conscious sedation was used in some cases (midazolam 1-4 mg IVP and /or fentanyl 50-100 mcg IVP). After local anesthesia to the skin and subcutaneous tissues superficial to a planned target site, an 17 G C-RFA electrode (Lumbar Cool (R) Cooled Radiofrequency Kit, Kimberly-Clark, LLC, Roswell, GA) was positioned using fluoroscopic guidance at the medial, middle third of the transverse process at the anatomic transition to the pedicle for the L1-L4 medial branches and inferior to the concavity of the sacral ala for the L5 medial branch. Motor testing was performed at 2 Hz to confirm integrity of the corresponding exiting spinal nerve at each target. As the C-RFA electrode placement is anatomically different compared to a conventional lumbar T-RFA procedure, patients were not expected to experience concordant low back pain with sensory testing at 50 Hz. When appropriate C-RFA electrode positioning was confirmed, 1cc of 2% lidocaine was injected through the introducer needle for anesthesia during the ablation. C-RFA lesioning was performed at each target site at 60°C for 150 seconds. Following the ablation, 0.5- 1.0 cc of 0.5% bupivacaine was injected to provide post-procedure analgesia. No corticosteroids were used. Following the procedure, patients were observed for approximately 30 minutes and were then discharged. Patients were asked to follow up in 4-6 weeks after the C-RFA procedure was performed for clinical re-evaluation.

Data analysis

All collected data was entered into a password protected database. Opioids medication doses for each patient were converted to daily morphine equivalents (DME) at each follow up time point for direct comparison purposes. In addition, the Medication Quantification Scale (MQS) III, a validated equation used to objectively quantify all medications use for pain management (including opioid and non-opioid medications), [32-33] was calculated for each patient at follow-up time points.

The number of individuals reporting =50% reduction in pain, the number of individuals reporting =50%improvement in function, the change in median DME and MSQIII score were calculated and analyzed, and post C-RFA healthcare utilization for pain management was evaluated.

Statistical analysis

All data were checked for distributional form using summary statistics and graphical displays. Data were not normally distributed, so medians and 25%-75% inter quartile ranges were calculated for each continuous variable. Proportions and 95% confidence intervals were calculated for categorical variables. Statistical software was used to analyze the data (SPSS, Version 22; Chicago, IL).


Twelve consecutive patients underwent C-RFA for the treatment of lumbar facet syndrome during the study time-frame. Three patients were lost to follow-up. Demographic, clinical, and procedural characteristics of the study population are shown in Table 1. The median and 25%-75% inter quartile range (IQR) for age was 44 years (35, 54). Patients' duration of pain at presentation was categorized: <2 years in 3 (25%), 2-5 years in 3 (25%), >5 years in 6 (50%). The median baseline pre C-RFA NRS pain score was 6, IQR (5, 8).

Citation: McCormick Z, Walker J, Marshall B, McCarthy R, Walega DR. A Novel Modality for Facet Joint Denervation: Cooled Radiofrequency Ablation for Lumbar Facet Syndrome. A Case Series. Phys Med Rehabil Int. 2014;1(5): 5. ISSN:2471-0377