Abstract
Percutaneous needle electrolysis (PNE) applies low-voltage direct current to human tissue, inducing localized electrolysis. This process triggers controlled inflammation and promotes tissue repair. Hydrogen gas, a byproduct of electrolysis, appears as hyperechoic spots on ultrasound imaging, whereas other products such as sodium hydroxide and chlorine gas are less visible. PNE has demonstrated effectiveness in cases resistant to conventional therapies, including chronic lateral epicondylitis. Written informed consent were obtained from the patient.
Dear Editor:
The ionic composition and unique cellular structure of human tissue make it an ideal environment for electrolysis. When applied to injured tissue, percutaneous needle electrolysis (PNE) initiates specific biochemical responses that support healing. The procedure generates a localized electric field (galvanic current), which disrupts cellular homeostasis and triggers a controlled inflammatory response [1]. This response leads to a cascade of cellular events, including macrophage activation, fibroblast proliferation, and remodeling of the extracellular matrix. Recent studies using real-time ultrasound imaging suggest that PNE enhances tissue healing and improves pain and function in musculoskeletal injuries [2]. In addition to previously cited studies, recent high-impact publications have further elucidated the mechanisms and clinical outcomes of PNE. These studies support the role of PNE in promoting tissue regeneration and reducing pain in chronic tendinopathies [3].
During PNE, a limited degree of electrolysis involving water (H2O) and sodium chloride (NaCl) occurs within human tissue. The application of low-voltage direct current induces the electrolysis of NaCl and water present in body fluids. However, this reaction remains minimal due to the low current intensity typically used in clinical practice. The generated NaOH, H+, and Cl− ions migrate under the influence of the electric field, triggering a localized inflammatory response at the cellular level and promoting a cascade of biochemical reactions that facilitate tissue repair [4]. While this low-intensity electrolysis contributes to PNE's biochemical mechanism, the amount of gas generated typically remains below clinically observable levels. Occasionally, hyperechoic spots observed in ultrasound imaging may be attributed to microbubbles generated by these reactions. However, these bubbles generally dissipate rapidly and do not interfere with the healing process. Thus, while minor electrolysis of H2O and NaCl occurs during PNE therapy, this process primarily serves as a secondary effect of the treatment. The primary therapeutic effect is derived from the controlled induction of inflammation and the facilitation of tissue repair mechanisms.
Evidence from the literature suggests that the hyperechogenicity observed during ultrasound imaging is primarily linked to the presence of hydrogen gas (H2) generated during the electrolysis process. This phenomenon is attributed to the formation of gas bubbles, which enhance the echogenicity observed in ultrasound images. Limited information exists regarding the direct contribution of chlorine gas (Cl2) to hyperechoic imaging during PNE. Although Cl2 is potentially produced as a byproduct of the electrolysis process, its effects on ultrasound imaging remain unclear. Chloride ions (Cl−), also generated during the procedure, do not appear to cause significant changes in ultrasound visibility. Dissolved ions, such as NaOH, are not directly visualized with ultrasound due to their lack of significant reflectivity against ultrasound waves. However, NaOH can locally elevate pH levels, causing protein denaturation in tissue structures and potentially altering echogenicity in the surrounding tissue. In summary, while hydrogen gas play a significant role in generating hyperechogenicity, additional studies are required to elucidate the specific contributions of chlorine and its compounds to ultrasound imaging during PNE [5]. This report highlights the hyperechoic appearance of H2 gases observed as a result of electrolytic reactions induced by galvanic current during US-guided PNE.
A 45-year-old female patient presented with lateral epicondylitis. Over the previous year, she had received multiple treatments, including painkillers, extracorporeal shock wave therapy, splinting, and steroid injections, all of which provided minimal or temporary relief. Physical examination revealed tenderness over the lateral elbow and a positive Cozen's test. Neurological examination was normal, and the absence of trauma suggested overuse as the likely cause. Due to persistent symptoms, the patient underwent three sessions of PNE therapy at one-week intervals. Each session involved a current of 350 μA for 80 seconds. Pain intensity was assessed using the Visual Analog Scale (VAS), with a baseline score of 8/10. After three sessions, the VAS score decreased to 2/10 at the four-week follow-up. Functional status was evaluated using the QuickDASH questionnaire (a validated tool for upper limb function), improved from 56 to 18 post-treatment. These results indicate both a substantial reduction in pain and a marked improvement in upper limb function. Fig. 1 shows the ultrasound-guided PNE procedure, while supplementary Video 1 offers a detailed visualization of the procedure.
Fig. 1.
Ultrasound-guided PNE procedure in a patient with lateral epicondylitis. The image shows the needle (arrow) passing through the common extensor tendon, with hyperechoic foci (asterisk) indicating gas formation along the needle tract. LE = lateral epicondyle; CET = common extensor tendon.
Supplementary data related to this article can be found online at https://doi.org/10.1016/j.inpm.2025.100593
The following are the Supplementary data related to this article.
Video 1. This video demonstrates the ultrasound-guided PNE procedure. The procedure was performed using an in-plane approach with a 40 × 0.25 mm acupuncture needle. (A) The needle's entry point is visualized. (B) Hyperechogenicity along the needle trajectory is attributed to hydrogen gas (H2) generated during electrolysis. Although NaOH is important for tissue regeneration, it cannot be visualized on ultrasound.
Although the biochemical mechanisms of PNE have been described previously, this report adds to the literature by providing real-time ultrasound video documentation of gas formation during the procedure. The use of standardized outcome measures and detailed follow-up in a patient with refractory lateral epicondylitis further enhances the clinical value of this case. These findings support the potential utility of PNE in cases unresponsive to conventional therapies.
Potential adverse effects of PNE include transient post-procedural pain, mild erythema, and, rarely, infection at the needle entry site. In this case, no complications were observed. Compared to other modalities such as corticosteroid injection or extracorporeal shock wave therapy, PNE is a minimally invasive alternative with a favorable profile. However, the absence of large-scale randomized controlled trials limits the generalizability of these findings. Further research is needed to establish the long-term efficacy and safety of PNE.
In conclusion, PNE induces the electrolysis of water (H2O) and sodium chloride (NaCl), resulting in the production of sodium hydroxide (NaOH), chlorine gas (Cl2), and hydrogen gas (H2). Ultrasound imaging enables visualization of these reaction products, reflecting the ionic and biochemical changes during PNE. Ultrasound guidance is essential for real-time visualization of needle placement and tissue response, potentially increasing procedural accuracy. However, the clinical benefits observed in this single case should be interpreted with caution. Further studies with larger patient cohorts are necessary to confirm these preliminary findings.
Author contributions
All authors contributed to the study conception and design. All authors read and approved the final manuscript.
Funding
None.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
Not applicable.
Footnotes
Supplementary data related to this article can be found at https://doi.org/10.1016/j.inpm.2025.100593.
Appendix A. Supplementary data
The following are the supplementary data related to this article:
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Supplementary Materials
Video 1. This video demonstrates the ultrasound-guided PNE procedure. The procedure was performed using an in-plane approach with a 40 × 0.25 mm acupuncture needle. (A) The needle's entry point is visualized. (B) Hyperechogenicity along the needle trajectory is attributed to hydrogen gas (H2) generated during electrolysis. Although NaOH is important for tissue regeneration, it cannot be visualized on ultrasound.