Radiofrequency ablation for shoulder pain: an updated systematic review

Introduction

Background

Shoulder pain is reported as the second most common musculoskeletal disorder in adults, affecting 15–30% of the adult population over their lifetime (1,2). Its onset is either acute, sub-acute, or chronic and may have an associated decrease in range of motion. In those affected, shoulder pain can significantly decrease quality of life and function (1,3). Etiology of shoulder pain can result from various conditions including rotator cuff disorders, adhesive capsulitis, osteoarthritis, glenohumeral instability, and acromioclavicular joint pathology. These conditions can lead to pain with activity, motion, and difficulty with activities of daily living. If left unmanaged, these conditions can become quite severe and ultimately leading to critical impairment of the patient (4). Management of shoulder pain is often a multidisciplinary approach involving physical therapy, pharmacotherapy, and if necessary, more invasive procedures such as intra-articular steroid injection, regional anesthesia, surgery, or neurolysis (5-12).

Rationale and knowledge gap

Suprascapular nerve (SSN) block has become an increasingly common technique to treat shoulder pain given that the SSN supplies 70% of the shoulder’s sensory innervation (13,14). The SSN arises from the upper trunk of the brachial plexus (C5–C6) and supplies sensation to the acromioclavicular region, joint capsule, and superior and posterior shoulder regions (15). It also supplies motor function to the supraspinatus and infraspinatus muscles. The SSN can be targeted for blockade in a variety of ways, typically by pulsed radiofrequency (PRF) neuromodulation or radiofrequency ablation (RFA) (6,16). The advantages of PRF include longer-lasting duration of action and decreased destruction to tissues. It therefore has the benefit of long-lasting pain relief, increased patient satisfaction, reduced painful protective muscle spasms, and decreased analgesic use (11,17,18).

Objective

Several case reports, case series, prospective studies, and retrospective studies have addressed the use of PRF for chronic shoulder pain refractory to conventional treatment modalities. The aim of this systematic review is to provide a summary of the current literature on PRF and its efficacy in the management of shoulder pain. We present this article in accordance with the PRISMA reporting checklist (available at https://apm.amegroups.com/article/view/10.21037/apm-23-529/rc).

Methods

Search strategy

The authors conducted a literature search through PubMed, MEDLINE, and Cochrane databases identifying all potentially relevant published articles until the date June 15th, 2023. The following MeSH terms were searched: “radiofrequency ablation”, “radiofrequency”, “RF”, “ablation”, “neurolysis”, “pulsed radiofrequency”, “radiofrequency therapy”, and “shoulder pain”, “shoulder osteoarthritis”.

Inclusion criteria

The inclusion criteria included adults with chronic shoulder pain, RFA-related technology (continuous or pulsed), and original studies. Review articles that were identified were reviewed for additional sources. Studies utilizing the visual analog scale (VAS) and numeric rating scale (NRS) pain scores were included in the analysis. If papers did not assess the pain scores, then the paper was analyzed further in the discussion. Functional, physical disability, and patient satisfaction scores were analyzed if present. If use of medical analgesic therapy was assessed in an article, it was also added to the results of this review.

Exclusion criteria

Papers were excluded if they were animal studies, non-English, non-RFA technologies, non-shoulder pain related, if the targeted nerve was not relevant to treat shoulder pain, and if the research was only available in poster or abstract form.

Quality of assessment of studies

Study quality and eligibility was determined by two researchers. In the case of different opinions regarding article relevance, all authors reviewed and reached a consensus. The information extracted includes the following: publication year, author’s last name, clinical diagnosis, study design, sample size, ablation technique used, RFA settings utilized (temperature and duration) if available, mean pain improvement, mean duration of improvement, side effects, secondary outcome if analyzed, and significant conclusions. The articles were additionally assessed through quality through the risk of bias in non-randomized studies of interventions tool (ROBINS) (Figure 1) and risk of bias visualization tool (ROBVIS) (Figure 2) (19).

Figure 1 Traffic plot detailing risk of bias in non-randomized studies (ROBINS-I).

Figure 2 Traffic light plots of the risk of bias assessment of the RCT studies (ROBVIS). RCT, randomized control trial.

Results

Through the search strategy, 386 studies were initially identified: 247 in PubMed, 77 in MEDLINE, and 62 in the Cochrane Database. Ten studies were found in the references of relevant articles found through the search.

The PRISMA flow diagram is shown in Figure 3. Non-English articles with animal studies were excluded. Based on initial screening through title and abstract, 117 articles were excluded. A total of 29 full-text articles were included (Table 1).

Figure 3 PRISMA flow diagram showing literature search.

Characteristics of the studies and quality assessment

The studies included with their characteristics are shown in Table 1. The studies compared included 4 retrospective studies, 4 prospective studies, 1 cross-sectional observation study, 6 case series, 2 case reports, and 12 randomized control trials (RCTs). The sample sizes for quantitative studies ranged from 1 to 160 (20-22). Study quality ranged from low risk of bias to serious risk of bias. Most studies focused on chronic shoulder pain for at least three months (6,10,16,17,20,23-28). There were 6 studies from the United States (21,29-33) and 23 from other countries [8 from Turkey, 7 from China (3 from Taiwan), 2 from United Kingdom, 1 from Ireland, 1 from India, 1 from Korea, 1 from Switzerland, 1 from Spain, 1 from Australia] (6,10,14,16,17,20,22-28,34-43).

Evidence associated with the use of RFA in treatment of chronic shoulder pain

Targeted nerves

Twenty-two of the 29 studies solely targeted the SSN. Two studies additionally targeted the axillary nerves (33,43). Four of the studies targeted the intrabursal area (32), subacromial space (22,34), and the maximally tender area of the shoulder (25). The remaining study did not specify (42).

Pain scores

All included studies collected pain scores of the patients at various time points to assess RFA or PRF treatment outcomes. Seven of the 29 studies sought to investigate the efficacy of RFA or PRF alone (10,21,22,28,38,39,41). Five studies performed diagnostic nerve blocks to assess if patients would be candidates for RFA or PRF (24,27,33,35,40). Five of the 29 studies performed RFA through slightly altered approaches (25,30,34,37,42). The remaining 11 studies were compared to alternative treatments of chronic shoulder pain (6,14,16,17,20,23,26,29,31,36,43).

Duration of analgesia

Short-term and long-term relief was documented in all 29 studies. Three of the 29 studies found RFA provided more short-term pain relief (17,40,42). Most studies followed patients up to three months (6,14,16,23,25,29,30,34,36,41), four to five months (21,22,35,43) or six months (10,20,24,26-28,31-33,37-39).

Functional outcomes

Three studies examined passive shoulder range of motion (14,17,32,43). Active range was measured in four studies after PRF (21,27,32,35). Eight of the 29 studies examined functional outcomes of RFA or PRF through Shoulder Pain and Disability Index (SPADI) scores (6,16,24,26,28,31,34,42). Constant-Murley Shoulder (CMS) scores were assessed in four studies (25,31,37,38). The remaining studies used functional measurements including the Oxford shoulder scores (38,41), Modified MacNab scores (39), Goal Attainment scale (23), and American Shoulder and Elbow Surgeons score (33).

Patient satisfaction levels

Patient satisfaction was observed in 10 studies and reported through various scales including the Likert scale, general patient satisfaction, quality of life, Pain, Enjoyment of life, and General activity (PEG) scores, European Quality of Life Five Dimension (EQ-5D) and the beck depression inventory (BDI) scores (6,20,23,25,28,31,34,38,42,43).

Discussion

This review sought to investigate and characterize the outcomes of RFA on patients with chronic shoulder pain. We found 29 studies that suggest that RFA can reduce pain scores, provide lasting pain relief, increase function, and increase patient satisfaction. Nearly all studies had a reduction in VAS or NRS scores at all time points reflecting short-term and long-term improvement of pain relief. Similarly, most studies showed improvement of disability scores or functional scores of patients after RFA. Lastly, several of these studies examined patient satisfaction of RFA treatment suggesting that RFA was associated with high levels of satisfaction.

Targeted nerves

The majority (22) of the 29 studies solely targeted the SSN suggesting that this nerve can be targeted for chronic shoulder pain. The studies additionally targeted the axillary nerves and found improvement in shoulder pain (33,43). Of the studies targeting shoulder areas including the intrabursal area (32), subacromial space (22,34), and the maximally tender area of the shoulder (25), the intrabursal area (32) and the maximally tender area of the shoulder (25) were successfully targeted for shoulder pain. Although Sluijter et al. (22) showed the subacromial space can serve as a target for ablation, Avendano et al. found there were no significant differences found between groups (P=0.37) suggesting that RFA targeting the subacromial area may not be effective in shoulder pain (34). The remaining study did not specify (42) but found that ultrasound-guided PRF did benefit patients with pain from frozen shoulder.

Pain relief scores

Regarding pain relief, all included studies collected pain scores of the patients at various time points to assess RFA or PRF treatment outcomes. Pain scores were measured through the VAS and NRS.

When only RFA or PRF was performed, pain scores before and after treatment were significantly reduced. Luleci et al. found PRF treatment decreased Verbal Numerical Rating Scale (VNRS) scores by >50% in 42 out of 57 (73.7%) patients (39). Taverner et al. found 25 patients who received transcutanous-PRF (t-PRF) had reductions of 24/100 in pain at night and 20/100 of pain with activity at 4 weeks, and 18/100 and 19/100 at 12 weeks (41). Liliang et al. found in 11 patients with chronic shoulder pain who received PRF, baseline mean VAS was 7.5, 1-month was 2.8, and 6-month follow-up was 2.5 (10). These results could suggest that in patients with chronic shoulder pain with contraindications or refractory pain to other interventions, RFA or PRF may be an efficacious treatment option (10,21,22,28,38,39,41).

Several studies performed diagnostic nerve blocks to assess if patients would be candidates for RFA or PRF. If patients had 50% or greater reduction in pain after their block, they were deemed candidates for RFA or PRF (24,27,33,35,40). For example, Chang et al. found RFA decreased mean VAS for shoulder pain from 7.3 to 2.0 in six patients with malignancy associated shoulder pain (35). In each study, after being characterized as candidates through diagnostic blocking, VAS scores were significantly reduced at all time points after RFA or PRF treatment. This suggests a predictive value in performing a diagnostic nerve block prior to ablation (24,27,33,35,40).

Altered approaches of RFA included combining RFA treatment with platelet-rich plasma (PRP), different RFA temperatures, transcutaneous RFA, ultrasound-guided RFA (UGRFA), and RFA of the subacromial area (25,30,34,37,42). When RFA is combined with PRP, VAS scores decreased significantly at 1 month with no significant increase in VAS scores after 3 and 6 months (37). Similarly, when cooled RFA is compared to traditional monopolar RFA, pain was significantly reduced in both groups, however, there was no significant difference among groups. This suggests that there is no difference between RFA types (30). When comparing transcutaneous electrical nerve stimulation (TENS) to transcutaneous RFA, there were significantly lower PEG scores in the RFA group thus demonstrating the utility of RFA (25). When UGRFA was compared to a sham group, UGRFA was superior in reducing VAS scores (42). In this study, UGRFA VAS scores decreased by 3.1 after 6 weeks and 4.6 after 12 weeks, compared to the sham group that found decreases of 1.3 and 1.7 over the same interval (P<0.01) (42). In contrast, when administering RFA treatment to the subacromial space, there was no significant difference in pain scores (34).

When RFA or PRF was compared to alternative interventional treatments, RFA or PRF had both superior and inferior outcomes (6,14,16,17,20,23,26,29,31,36,43). When PRF was compared to lidocaine nerve blocks, NRS scores were significantly reduced in PRF patients (20,23,31). Similarly, when RFA was compared to an intra-articular steroid and nerve block, RFA was superior in reduction of NRS scores. Cetingok et al. found that one month post-intervention, the RFA group exhibited a significantly lower median NRS score of 1.0 compared to the steroid and nerve block group that had a median NRS score of 3.0 (P<0.05) (20). When PRF with anesthetic was compared to PRF with steroid, Gabrhelik et al. found there was no significant reduction in pain scores suggesting PRF is sufficient. In the anesthetic alone group, 71% reported VAS 0–2 at rest and 64% during active shoulder movement, while in anesthetic and steroid group, 79% reported VAS 0–2 at rest and 64% during active shoulder movement (P=0.323 for rest and P=0.944 for active) (36). Likewise, when PRF was compared to physical therapy alone, PRF had a significant reduction in VAS scores. Wu et al. found in patients with adhesive capsulitis, VAS at week 1 decreased by 40% in physical therapy with RFA vs. 4.7% with physical therapy only (14). In contrast, when comparing intra-articular steroids to PRF, although both treatments significantly reduce pain, intra-articular steroids were significantly favorable in score reduction when compared to PRF (6,17). Eyigor et al.’s RCT of 50 patients determined mean VAS score of 1.2 at 12 weeks post-treatment for the steroid group and mean VAS score of 1.65 for the PRF group (P<0.01) (6). Kim et al.’s RCT found NRS scores in the PRF groups to be 5.9±0.8 at baseline, 5.0±2.2 at one month, and 5.2±2.0 at two months post-treatment compared to the intra-articular corticosteroid injection group of 6.2±1.1 at baseline to 2.8±0.9 at one month and 3.2±1.1 at two months post-treatment (P<0.001) (17).

Similarly, when PRF was compared to suprascapular or axillary nerve blocks (43), TENS (16), photobiomodulation with exercise (26), and peripheral nerve stimulation (PNS) (29), there was no significant difference in VAS scores (16,26,29,43). These results suggest that alternative forms of intervention may be used for chronic shoulder pain.

Duration of analgesia

Short-term pain relief is defined as duration of three months whereas long-term relief is defined as beyond three months (44). Most studies documented duration of pain relief through pain scores obtained at follow-up. Several studies demonstrated RFA provided more short-term pain relief ranging from two weeks (40) to 1–2 months (17) to 3 months (42). These studies did not perform long-term follow-up in their patient cohorts thus limiting the measurement of maximum pain relief. Most studies followed patients up to three months (6,14,16,23,25,29,30,34,36,41), four to five months (21,22,35,43) or six months (10,20,24,26-28,31-33,37-39) and found RFA or PRF provided long term relief for chronic shoulder pain. This suggests that duration of pain relief for patients can be expected for at least 3–6 months.

Functional status

Functional status was assessed in most studies through a range of motion and shoulder function scores such as the SPADI and CMS. Four studies examined passive shoulder range of motion (14,17,32,43). Yang et al. found a significant difference in passive shoulder abduction and external rotation between SSN block and PRF-treated patients (43). Although Kim et al. found intra-articular steroid range of motion measurements were significantly higher than PRF, PRF patients had a significant increase in range of motion from baseline (17). Additionally, Wu et al. demonstrated an improvement in passive range of motion in PRF patients with physical therapy compared to physical therapy alone (14). Similarly, active range of motion significantly improved after PRF (21,27,32,35).

• Functional outcomes of RFA or PRF were assessed through SPADI scores (16,24,26,28,31,34,42). There was no significant difference in SPADI scores when comparing thermal, sub-thermal, and sham groups for RFA (34) and photobiomodulation and RFA (26). Despite these studies, all others showed significant improvement in SPADI scores at time of follow-up (6,16,24,28,31,42).
• Similarly, CMS scores were assessed in several studies (25,31,37,38). All studies showed a significant improvement in CMS scores secondary to RFA or PRF treatment suggesting that treatment does improve patient function.

The remaining studies showed significant improvement in functional measurements including the Oxford shoulder scores (38,41), Modified MacNab scores (39), Goal Attainment scale (23), and American Shoulder and Elbow Surgeons score (33). Regardless of scale type, RFA or PRF treatments show observed improvement of function.

Patient satisfaction

Patient satisfaction was observed in several studies and was reported through various scales (6,20,23,25,28,31,34,38,42,43). Sir et al. observed significant improvement in Likert scores at 3 weeks and 6 months following PRF suggesting patients were significantly more satisfied with PRF (28). Similarly, patients reported significantly more satisfaction with PRF treatment when compared with lidocaine block (31). Additionally, Kane et al. and Çetingök et al. found patient satisfaction increased with PRF (20,38). Two studies reported that PRF and RFA resulted in significantly higher ratings of quality-of-life scores suggesting that treatment compared to sham will improve patient satisfaction (34,42). Lastly, Lin et al. measured PEG scores and found that PEG scores were significantly lower in the PRF group meaning better quality of life (25). In contrast, no significant difference was found in studies measuring EQ-5D and the BDI scores (6,43).

Strengths and limitations

This study serves as an update to the literature of the evidence associated with RFA for management of chronic shoulder pain. Previous systematic reviews have been performed on this particular topic (45); however, this study provides specific outcomes of ablation such as the targeted nerves, pain scores, pain relief duration, functional status, and patient satisfaction levels. Understanding these various outcomes is important in order to guide clinicians and patients to numerous treatment options. This review had several limitations including the lack of consistent approach to ablation, the retrospective nature of most studies, and difference in follow up duration. Further studies are needed to investigate functional status and patient satisfaction of ablation of shoulder pain.

Conclusions

This study reviewed the current published literature assessing RFA as a treatment of chronic shoulder pain. The consensus found was that RFA is a favorable treatment for shoulder pain, and it has shown benefit through pain scores, duration of pain relief, functional outcomes, and patient satisfaction levels. Many of the included studies show positive outcomes towards RFA for management of chronic shoulder pain. This study was limited by its retrospective nature as each study had varying methodologies. Additional large RCT trial studies are needed to better analyze the efficacy and safety of RFA in patients with chronic shoulder 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.

Reporting Checklist: The authors have completed the PRISMA reporting checklist. Available at https://apm.amegroups.com/article/view/10.21037/apm-23-529/rc

Peer Review File: Available at https://apm.amegroups.com/article/view/10.21037/apm-23-529/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://apm.amegroups.com/article/view/10.21037/apm-23-529/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 2022 to May 2024. A.A.E. received consulting fees from 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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