Comparing the analgesic efficacy between 100 Hz and 2 Hz electroacupuncture on patients with lumbar osteoarthritis

This was a two-arm parallel, double-blind randomized controlled trial conducted from September 2018 to July 2019. We enrolled 124 inpatients with CLBP due to lumbar osteoarthritis who came to the Traditional Medicine Hospital at Ho Chi Minh City. This study followed the Declaration of Helsinki Good Clinical Practice guidelines for trial conduct. All patients were able to read, to understand the informed consent, the questionnaire, and all had written informed consent. The study protocol was approved by the Ethics Board in Biomedical Research of the University of Medicine and Pharmacy at Ho Chi Minh City.

Patients were enrolled in the study when they met the inclusion criteria, including (1) having pain in the lower back region lasting for at least 3 months, (2) being in the age range 30-70 years old, (3) receiving ≥ 32 points of Questionnaire Douleur Saint Antoine (QDSA) score at enrolment, and (4) being confirmed osteoarthritis by radiographic evidence such as osteophyte formation, joint space narrowing, or subchondral sclerosis. Patients with blood pressure ≥160/90 mmHg or with CLBP which required surgery were excluded.

Patients who were admitted to the Traditional Medicine Hospital as osteoarthritis would be invited to participate in the study. Those who met the inclusion criteria would be enrolled in the intervention. Two arms of the intervention included electroacupuncture at the frequency of 100 Hz (Arm A) and electroacupuncture at the frequency of 2 Hz (Arm B). Study participants did not know which group they belonged to. They agreed to spend 14 days since the enrolment in the hospital.

Eligible patients were randomly assigned to either the intervention group receiving 100 Hz frequency electroacupuncture or the control group receiving 2 Hz frequency electroacupuncture. Acupuncture was administered in 14 sessions over 14 days (one section per day), with the needle retention time of 20 minutes in each session by conventionally trained physicians. All patients were treated at bilateral Hua Tuo Jia Ji acupoints of lumbar spine L1-S1 following the WHO Standard Acupuncture Locations [8,9]. Patients with radiating dermatome pain were treated at relating Ashi points. Acupuncture needles were inserted 1.5 – 2 cm into the skin with an angle of 90° and then attached to the electrical acupuncture device for stimulation. The maximum intensity of 5 – 10 mA with the frequency of 2 Hz or 100 Hz was applied until the patient achieved an irradiating needling sensation (‘de qi’).

Patients in both groups also administered Du Huo Ji Sheng Tang decoction daily adopted from the internal guideline. The medication included: 12 grams of Radix Angelicae Pubescentis, 12 grams of Herba Taxilli, 12 grams of Radix Gentianae Macrophyllae, 10 grams of Radix Saposhnikoviae, 8 grams of Poria, 12 grams of Cortex Eucommiae, 12 grams of Radix Rhemanniae, 12 grams of Radix Codonopsis pilosulae, 4 grams of Herba Asari, 12 grams of Radix Achysanthis bidentatae, 8 grams of Radix Paeoniae alba, 12 grams of Radix Angelicae sinensis, 6 grams of Cortex Cinnamomi, and 4 grams of Rhizoma Glycyrrhizae. This formula adopted from the internal guideline issued by the Traditional Medicine Hospital in 2017 [4]. Participants were not allowed to take pain medicines during the intervention course.

Figure 1: Study design

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The primary outcome was QDSA scale obtained by interview at baseline (day 1), day 7, and day 14 (D1, D7, and D14 in the questionnaire). The scale had 37 questions in 16 domains, ranked from 0 (no impairment) to 4 (severe impairment) [10]. In addition, the secondary outcomes included the percentage of pain relief (PPR) and the lumbar flexion range of motion (LFROM). The PPR was calculated based on the QDSA score, in which:

A tape measure was used to determine the LFROM at baseline and day 14 using the Schober method. The study also recorded the adverse symptoms due to electroacupuncture such as dizziness, sweating, nausea, or vomiting, cold hands and feet. Blinded observers who did not know which treatment group a patient belonged to were used to record the outcomes.

Data were processed by Epidata 3.1 and statistical analysis was performed by Stata version 13, with p <0.05 signifying statistical significance. The quantitative data which were consistent with the normal distribution were expressed as mean ± standard deviation (SD). When assumptions of normal distribution were not met, the non-parametric test would be used instead. T-test was used to compare means between the two-groups. Qualitative data were expressed by frequency and be compared using χ² test or Fisher’s Exact test, depending on the distribution. For evaluating treatment effect, two sample t-tests were used to compare two groups’ means of QDSA score on day 1 and day 14.

In the present study, both frequencies of 2 Hz and 100 Hz electroacupuncture at Hua Tuo Jia Ji acupoints combined with the Du Huo Ji Sheng Tang decoction for 14 days showed improvements in QDSA score and lumbar flexion range of motion in patients with CLBP due to lumbar osteoarthritis. However, the 100 Hz electroacupuncture had superior analgesic effects to the 2 Hz, which confirmed the hypothesis that electroacupuncture with low and high frequencies produced different therapeutic effects.

To our knowledge, this was the first trial to investigate the efficacy of electroacupuncture with two frequencies, 2 Hz and 100 Hz, for CLBP. After 14-day treatment, the proportion of patients with PPR improvement ≥70% in 100 Hz electroacupuncture was 87%, including 29% had no pain remained, while in the 2 Hz group it was only 45% with no fully recovered case. Although the previously published articles had different combinations of therapies, our results were similar to the previous studies in respect to the efficacy of electroacupuncture. In 2012, Phan QCH and Truong TH reported that 78.85% of patients with CLBP treated with electroacupuncture at the Hua Tuo Jia Ji acupoints combined with lumbar spinal decompression therapy had PPR improvement ≥70% [10]. Another study of Kim HJ using only electroacupuncture showed that PPR improvement ≥70% in the intervention group was 71.4% [11].

The analgesic efficacy of electroacupuncture at different frequencies on CLBP could be explained by several mechanisms [5,6,7,12]. Some studies indicated that various endogenous opioids in the central nervous system, which played a crucial role in mediating analgesic effect, were released in different ways depending on the electrical frequency. At 2 Hz, electroacupuncture increases the release of enkephalin, beta-endorphin and endomorphin, but beta-endorphin has short-term analgesic effect which lasts for only 3 to 4 hours. Meanwhile, 100 Hz electroacupuncture increases the release of dynorphin which has primary effects on receptors K1 and K3 and produces long-term analgesic effect. Electroacupuncture at Hua Tuo Jia Ji acupoints of L5-S1 is also associated with relaxation of surrounding muscles such as the latissimus dorsi and longissimus thoracis. It also increases circulation and affects cutaneous sensory distribution of nerve roots [9, 13].

CLBP is one of the most frequently encountered musculoskeletal disorders in today’s society. The goal of treatment is to control or reduce pain, to improve structure impairment of the spine, and to help patients return to their normal daily activities as soon as possible. In fact, patients with CLBP often have to stay in hospitals for a long time [3]. Our research findings suggest that the combination of electroacupuncture with other therapies may shorten treatment time and reduce the use of painkillers for patients with CLBP due to lumbar osteoarthritis. Moreover, electroacupuncture using the frequency of 100 Hz is recommended to ultimate the treatment effects.

This study has some limitations, including the lack of an untreated control group because of ethical considerations. In fact, when patients come to a traditional medicine hospital, they all want to receive medications as well as acupuncture. Hence, it is unethical to conduct a control group with only decoction or only acupuncture. Secondly, the intervention period was only 2 weeks, which was a limited time for treatment responses. This is a common situation for inpatients at traditional medicine hospitals in Vietnam since patients rarely stay longer in hospitals. Further studies should evaluate the long-term effects of 100 Hz electroacupuncture on patients with CLBP.