Analgesic effects of a capacitive-resistive monopolar radiofrequency in patients with myofascial chronic neck pain: a pilot randomized controlled trial

Background / Purpose

Chronic neck pain caused by myofascial trigger points (MTrPs) is a major source of disability, often leading to stiffness, pain radiating to the shoulders, and reduced range of motion. Conventional treatments—such as dry needling, electrotherapy, and medication—can be limited by invasiveness or side effects. This pilot study investigated the immediate and short-term effects of monopolar capacitive–resistive radiofrequency (448 kHz) on pain intensity, neck disability, and cervical range of motion (CROM) in patients with chronic myofascial neck pain, compared with a placebo application.

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Methods

A randomized, double-blind, placebo-controlled trial (NCT02353195) enrolled 24 patients aged 18–60 with chronic myofascial neck pain persisting ≥ 6 months and an active MTrP in the upper trapezius. Participants were assigned to:

• Radiofrequency Group (RFG, n = 14): eight sessions of INDIBA® Activ 902 monopolar CR radiofrequency (448 kHz) applied to the painful trapezius region (12 minutes / session, twice weekly for 4 weeks).
• Placebo Group (PG, n = 10): identical procedure, but the device was deactivated.

Assessments were made at baseline, immediately after the first session, and after the eighth session:

• Pain: Visual Analog Scale (VAS, 0–10 cm)
• Disability: Neck Disability Index (NDI, 0–50)
• Mobility: Cervical Range of Motion (CROM device).
  Statistical tests included non-parametric Wilcoxon, Mann-Whitney U, and repeated-measures ANOVA (p < 0.05 significance).

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Results

Participants in the RFG experienced a significant and clinically meaningful reduction in pain intensity, both after the first treatment and after the full 8-session protocol.

• VAS pain: Median decreased from 4.9 cm (IQR 2.8–6.4) at baseline to 2.0 cm after the first session and 0.5 cm after eight sessions (p < 0.001). No significant changes occurred in the placebo group (p > 0.05).
• NDI: Decreased significantly within each group (p < 0.05), with ≈ 40% improvement in the RF group and ≈ 30% in the placebo group, though inter-group differences were not significant (p = 0.25).
• CROM: Only right-side cervical rotation improved significantly after treatment (+8.1° in RFG vs +6.8° in PG, p = 0.03), while other movements showed no statistical change.
  No adverse effects were reported.

Discussion

Although both groups showed improvements—likely reflecting expectation-related placebo response—the active radiofrequency treatment achieved a greater magnitude of pain relief and functional gain. The approximately 4.4 cm reduction in VAS exceeds the minimal detectable change, indicating meaningful clinical improvement. The analgesic effect may result from localized vasodilation, reduced ischemia, and decreased release of sensitizing neurotransmitters at the trigger-point level. Additionally, the mild thermal gradient and subthermal electrical effects of 448 kHz stimulation may trigger antinociceptive and regenerative cellular responses, such as enhanced metabolic activation and improved microcirculation in the trapezius.

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Conclusion

Monopolar capacitive–resistive radiofrequency (448 kHz) produced a notable short-term reduction in myofascial neck pain intensity and mild functional gains in cervical motion, without side effects. While between-group differences did not reach statistical significance due to the pilot sample size, the findings support the feasibility and safety of Tecar therapy for chronic myofascial neck pain. Future large-scale trials should include more participants, follow-up evaluations, and additional objective measures of muscle sensitivity and blood flow to confirm Tecar’s analgesic and neuromodulatory potential.