Advances in radiofrequency ablation for thoracic spine pain

Introduction

Background

Radiofrequency ablation (RFA), also known as rhizotomy or neurotomy, utilizes electrical current to generate heat and cause damage to nerves via thermal energy (1). The resultant damage to nerve fibers prevents the transmission of information to the central nervous system, interrupting nociception (2,3). RFA includes (I) continuous radiofrequency (CRF), (II) pulsed radiofrequency (PRF), and (III) cooled radiofrequency ablation (CRFA). These methods can be utilized in conjunction with pharmacologic agents for multimodal pain management and analgesia (4).

RFA subtypes

CRF was introduced in 1974 and is a modality of pain management that uses an electrical generator to produce heat at 90 ℃ for 90–120 seconds to damage peripheral and central nerves (2,3,5,6). Historically, CRF has been used to treat facet joint disease, cancer pains, and neuralgias (5,6). CRF tends to be a very precise and minimally invasive procedure, as temperature and probe size can be modified based on size of the target lesion (5,6). However, early modalities of this analgesic technique were limited in their application due to the risk of deafferentation syndrome, in which patients experience pain in sites other than where they had been treated, and regional motor deficits (2,5,7).

PRF was introduced as an alternative to CRF with the advantage of avoiding the complications of deafferentation pain syndrome (2,6). Here, low intensity, short duration pulses are delivered proximate to sensory nerves at a maximum temperature of 45 ℃ for 2–4 minutes (2,6). This temperature will dampen but not destroy the nerves, in part explaining the preference for this modality over CRF (1). CRF can be used to target the dorsal root ganglion within the central nervous system at all spinal levels or target peripheral nerves both inside and outside of the brachial plexus (1).

CRFA is an alternative to both CRF and PRF. This technique utilizes a larger probe size and a lower temperature than those used in CRF and PRF, thus allowing for larger tissue swaths to be targeted (2,8). Like CRF, probe size, temperature, and duration of the current can all be modified to control the size of the lesion produced (1).

Indications, contraindications and complications

RFA is oftentimes utilized when more conservative efforts at pain management, including pharmacological therapies or other surgical interventions, have failed (9). The procedure is relatively safe, and there are few contraindications. Absolute contraindications of ablation procedures include patient refusal and local infection (1,9). Relative contraindications include bacteremia or aberrant anatomy which would complicate the procedure (1,9).

Complications of the procedure include the potential for unintentional thermal burns, bleeding, infection, and nerve damage, including deafferentation pain syndrome (9). The most common complication following this procedure is reported to be patient discomfort, though this side effect tends to subside with time (1).

Rationale and knowledge gap

The thoracic spine is the least common site for complaints of back pain, with a predominance of patients experiencing pain in the cervical or lumbar regions (10). Research on nerve targets in this region for the resolution of back pain is therefore limited, as the literature has tended to focus on the cervical and lumbar spine (10,11). However, recent advances in pain management technologies suggest that the thoracic facet joints may account for pain in 34–48% of patients with chronic mid-back and upper-back pain (11). The thoracic spine is therefore an optimal target for future denervation technologies such as radioablation for treatment of chronic back pain.

That said, the literature on the effectiveness of RFA for the thoracic spine is inconclusive in terms of the long-term and short-term outcomes of this procedure for the resolution of back pain. One systematic review of nine studies on RFA at all spinal levels, including the thoracic spine, suggests that this modality of denervation can offer short-term relief for chronic back pain with moderate evidence for long-term relief (12). These findings are consistent with other reviews of the literature that comment on RFA for the thoracic spine, where there has been limited evidence for short- and long-term pain relief with denervation of the medial branches (12-14).

In 2021, the American Society of Pain and Neuroscience (ASPN) published best practice guidelines for radiofrequency neurotomy and provided a summary of the available literature on thoracic spine ablation, but only cited four studies. The US Preventive Services Task Force recommendation criteria, which grades the certainty of evidence against the risks and benefits of offering an intervention, gave thoracic RFA a grade C, which defers utilization of this therapy to clinical judgment and individual circumstance (15). In other words, though the authors consensus statement recommends the therapy if facet joints are implicated as the cause of pain, a paucity of primary literature on this therapy makes it difficult to ascertain its clinical utility and safety (15). Thus, the purpose of this paper is to summarize existent primary literature on thoracic RFA to provide more robust and comprehensive evidence on RFA for thoracic spine.

Objective

The purpose of this paper is to describe RFA and its utilization in the thoracic spine. To the authors knowledge, no review articles have summarized the primary evidence for RFA with focus on only the thoracic spine. For each study, N.R. and M.M. extracted methods, participations, outcomes, results, and conclusions (Table 1). This paper will also cover medial branch blocks and different radiofrequency modalities, with a focus on the anatomy of medial branches for the thoracic spine.

Discussion

Neuroanatomy of thoracic medial branches and facet joints

The neuroanatomy of the thoracic spine is complex and makes for a unique target for RFA. All vertebrae of the cervical, thoracic, and lumbar spine articulate with adjacent vertebrae at facet joints (10,24). Facet joints, including those of the thoracic spine, are thoroughly innervated by nerves of the medial branches of dorsal rami (25-31). Through cadaveric studies in 1995, Chua and Bogduk found that medial branches of the thoracic dorsal rami follow similar courses across all spinal levels, with some exceptions at specific levels (25). The medial branch separates within 5 mm after the dorsal rami exits the intervertebral foramen. The branch then traces posterior to the superior costotransverse ligament, following a lateral, dorsal, and inferior course through the intertransverse space. As it continues through the intertransverse space, the medial branch curves dorsally, directed at the superolateral corner of the transverse process.

From the intertransverse space, the medial branch travels between the multifidus and semispinalis muscles as it tracts caudally along the posterior aspect of the end of the transverse process to enter the posterior compartment of the back. The medial branch provides numerous filaments as it travels inferomedially along the dorsal fascicles of the multifidus. At superior thoracic levels, a cutaneous nerve branch forms from one of the filaments, but this is not observed at more inferior thoracic levels. Ascending and descending articular branches form the medial branch to innervate the facet joints of adjacent superior and inferior spinal levels, respectively. The inferior portion of each facet joint is innervated by rami of the ascending articular branch from the medial branch of the adjacent inferior spinal segment (25). The superior portion of each facet joint is innervated by the descending articular branch from the medial branch of that spinal level after it crosses the superolateral corner of the transverse process (25). Accordingly, each thoracic facet joint is dually innervated by the medial branches from adjacent superior and inferior spinal levels (25,27,32).

Thoracic medial branch course variations

Chua and Bogduk found the medial branches to consistently follow the course described above at levels T1–T4 and T9–T10, with some variation at levels T5–T8 and T11–T12 (25). At levels T5–T8, the medial branch follows a parallel course to other levels but does not maintain consistent contact with the transverse process. Rather than crossing at the superolateral corner of the transverse process, the medial branches at T5–T8 cross the transverse process into the posterior compartment of the back just medial to the intertransverse muscle. This separation between the transverse process and medial branch is maintained by the multifidus muscle fibers as the branch continues along a medial and slightly inferior course into the posterior compartment (25).

In 2022, Koutp et al. conducted a cadaveric study of the neuroanatomy of the medial branch at levels T10–T12 (27). They found that in 70% of their cadaver population, the T10 medial branch followed the same course as the medial branches at levels T1–T4 and T9–T10 as described by Chua and Bogduk, where close contact was maintained with the transverse process before crossing at the superolateral corner (25,27). However, in 30% of their cadaver population, the T10 medial branches followed the more superior course as described by Chua and Bogduk for levels T5–T8, where space was maintained between the transverse process and medial branch before crossing dorsally while suspended within the intertransverse space (25,27).

The course of the medial branch at T11–T12 varies from the superior thoracic segments due to differing osseous anatomy (25,27). At these levels, the transverse processes more closely resemble those of the lumbar vertebrae where they are separated into two smaller processes—one dorsal to the superior articular process and one just lateral to that (27). At T11, the medial branch travels through a fissure between these two smaller transverse processes before crossing into the posterior compartment of the back at the superolateral corner of the transverse processes. The medial branch is contained within the T11 transverse process fissure by an equivalent to the mamillo-accessory ligament that spreads within this potential space. Mirroring the courses of the lumbar-level medial branches due to shared vertebral morphology, the medial branch at T12 crosses the transverse process at its junction with the superior articular process. Fibers of the mamillo-accessory ligament cover the medial branch dorsally as it courses through the mamillary and accessory processes (27). At T10–T12, the medial branches split into many muscular branches and two articular branches that follow similar courses to other thoracic levels upon entering the posterior compartment (25,27).

Utilization of medial branch blocks in the thoracic spine

Though successful use of denervation techniques for back pain can be traced back to as early as 1971, the first primary study on RFA was published in 1976 by Lora et al. (16,33). In their prospective outcome study, nine patients with intractable thoracic spine pain underwent RFA with 33% of them reporting an improvement of pain greater than 50% (10,16). Despite the obvious limitation of small sample size, this landmark paper set the stage for future studies on RFA. They provided two recommendations for patient selection for RFA that subsequent studies have continued to follow: (I) failure of conservative therapy and (II) evidence of response to medial branch blocks via lidocaine or another local anesthetic blockade of target region prior to RFA (16).

In 1993, Stolker et al. published one of the first prospective studies on percutaneous radiofrequency denervation of the thoracic facet joints in 40 patients (10). They found that after 2 months, nearly half of their patients were pain-free while 18% reported no difference. After an average follow-up of 31 months, 44% of the remaining 36 patients reported resolution of their pain—the remaining patients either had some or no change in symptoms (10). Just one year later, Stolker et al. published another study on 45 patients with at least 6 months of irradiating back pain that could be localized to the T8–T12 region of the spine that had failed conservative treatment (17). The patients underwent posterior percutaneous partial rhizotomy and then were evaluated 2 months after treatment on a numeric rating scale (NRS), where pain was assessed on a scale of 1 (no pain) to 10 (worst possible pain) (17). Nearly 67% of patients reported being pain-free after this period, with 24% reporting improvement of at least 50% or greater, and 9% reporting no change in the pain (17). In terms of long-term pain relief, the patients were followed for a median of 24 months, at which point 41 patients remained in the study (17). Of those, nearly half reported excellent long-term results, with about 15% reporting poor results. Of note, five patients required re-intervention (17).

In 2000, Tzaan and Tasker published their retrospective study of 17 patients who had undergone percutaneous facet denervation of the thoracic spine (18). The authors defined success of this procedure as being complete elimination of pain or a subjective reduction of pain greater than 50 percent (18). Patients were followed for a mean of 5.6 months, and the authors found that six out of 15 patients reported success of the procedure for thoracic pain (18). When compared to other spinal levels with the same procedure, there was no statistically significant difference in reported success of the procedure (18). Of note, several patients in this study who underwent RFA for other spinal levels required repeat RFA, and the authors found that repeat radiofrequency was not effective in improving results, calling into question the potential long-term benefits of this procedure given the relatively short follow-up period (18).

In 2011, a prospective cohort study conducted from 2001 to 2010 was published. In this study, authors recruited 28 patients with zygapophysial and sacroiliac joint pain for a study on percutaneous radiofrequency neurotomy (19). They found that of these patients, 19 patients reported success of the procedure, which was defined as at least 50% reduction in pain in the treated joint region for at least 2 months (19). Between 6 and 11 months following the procedure, at least 11 patients reported total relief of pain and four patients reported no relief in pain—no patient in this study reported worsened pain following the procedure (19). Between 6 and 36 months, 18 patients remained in the study and authors reported average pain relief during this period to be 85% for an average duration of nine months, suggesting potentially long-lasting benefits of RFA for these patients (19).

One of the first randomized trials on RFA for thoracic spine pain was published in 2013. The authors conducted a prospective, randomized, controlled clinical study from January 2006 to December 2007 and recruited 40 patients with recurrent thoracolumbar joint pain following initial successful treatment with RFA (20). The study was to compare the effects of alcohol ablation versus repeat thermal RFA of medial nerve branches for patients experiencing recurrent paint (20). Initial success of RFA was defined as a >50% reduction in pain at 6 months following RFA along with patient-stated satisfaction (20). Recurrence of pain was defined as ≥7/10 on a numeric pain scale and an Oswestry disability index (ODI) rating of >22% (20). Patients were evenly randomized to alcohol ablation or repeat RFA (20). They found that the median effective period was significantly longer in the alcohol ablation group [24 (range, 16.8–24) months] when compared to the repeat RFA group [10.7 (range, 5.4–24) months] (P<0.001) (20). In terms of pain relief, they again found that alcohol ablation provided longer pain relief when using the log rank test with 24 months censored (P<0.001), with one patient in the RFA group without recurring pain compared to 17 in the alcohol ablation group at the end of the study (20).

Two studies were published in 2018 on RFA for thoracic spine. The first was a prospective case series of 20 patients with thoracic facet joint pain who first underwent pulsed RFA (21). They found a statistically significant reduction in self-reported pain from six on the NRS at baseline to four at three months follow-up (21). A larger retrospective cohort study of 71 patients found that nearly 82% of their patients reported pain relief of greater than 50% at one year follow-up, a statistically significant decrease from an NRS of 7.75 at baseline to 2.82 at one year (22). The long follow-up and significant reductions in pain for patients in this study provides promising evidence for the potential of RFA to have longer lasting analgesic effect (22).

In 2020, another retrospective cohort study was published on cooled RFA in the thoracic spine. Here, 23 patients underwent RFA with authors comparing NRS scores at baseline and at three follow-up periods after treatment: (I) 4–8 weeks; (II) 2–6 months; and (III) 6–12 months (23). Authors found that patients reported 21%, 53%, and 38% reductions in pain for each follow-up period respectively (23). Furthermore, authors stratified their findings by patients’ age and baseline reported pain and found that patients under the age of 50 years with a baseline NRS of >7 experienced the most significant pain relief in the 2–6 months follow-up period (23). Patients over the age 50 years and with a baseline NRS of ≤7 found the most pain relief in the 2–6 months follow-up period and the 6–12 months follow-up period (23). These findings suggest that the short- and long-term effects of RFA for thoracic pain may exhibit some heterogeneity depending on patient age and baseline pain (23).

Strengths and limitations

This paper has provided an expansive look at RFA for thoracic spine pain with detailed discussions of the neuroanatomy relevant for the procedure and a historical summary of primary literature on this neuromodulation technique. To the authors knowledge, no other paper has been written that focuses specifically on RFA for the thoracic spine. A limitation of this paper is that results are reported in composite for patients who underwent RFA without delineation of whether patients underwent just one RFA or multiple. Reporting in this manner was due to how study authors presented their findings without specifying how many RFA procedures each patient in their cohort underwent during the study period.

Conclusions

Primary literature published on RFA-naive patients with thoracic facet joint pain has provided evidence in support of RFA for short-term and long-term pain relief in this spinal region, though most of these studies have been cohort studies. One randomized controlled trial on this topic compared repeat RFA versus alcohol ablation in patients who had undergone RFA but had a recurrence of symptoms. This study did not provide strong evidence in support of the longevity of RFA pain relief and found that patients had better outcomes with alcohol ablation. Future studies with larger patient cohorts and randomized control trial study designs are crucial to better establish the effectiveness and long-term utility of this neuromodulation technique for thoracic spine pain.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Palliative Medicine, for the series “Advances in Radiofrequency Ablation”. The article has undergone external peer review.

Peer Review File: Available at https://apm.amegroups.com/article/view/10.21037/apm-24-86/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://apm.amegroups.com/article/view/10.21037/apm-24-86/coif). The series “Advances in Radiofrequency Ablation” was commissioned by the editorial office without any funding or sponsorship. A.A.E. served as the unpaid Guest Editor of the series and serves as an unpaid editorial board member of Annals of Palliative Medicine from June 2024 to May 2026. He is also a consultant of Avanos. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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