1. INTRODUCTION
Chronic lower back pain (CLBP), which refers to pain in the lower back region, lasts for at least 3 months [1]. More than 70% of people in developed countries will experience low back pain at some point in their life, which usually improves within two weeks. However, about 10 percent remain unable to work and about 20 percent have persistent symptoms at one year [1]. Among the main causes of CLBP globally, lumbar spine osteoarthritis accounts for 40–85% and such gap is mostly due to differences in definitions between studies, a wide range of ages and other demographic factors, and subject recruitment [2]. Current therapies for CLBP include analgesics and non-steroidal anti-inflammatory drugs (NSAIDs) for conventional treatment. Local injections are reported to have adverse effects such as headache, dizziness, transient local pain, tingling and numbness, and nausea in small numbers of people [1]. Furthermore, CLBP patients often dissatisfied because of the drug-related side effects, so they seek non-pharmacological interventions such as complementary and alternative medicine (CAM) [3].
In the Traditional Medicine Hospital, lumbar osteoarthritis accounted for 29% of musculoskeletal diseases in 2017 [4]. When patients with lumbar spine osteoarthritis come to the hospital, they are treated by electroacupuncture combined with Du Huo Ji Sheng Tang decoction [4]. Electroacupuncture has been used for a wide range of pain management, including CLBP. The mechanism is not fully elucidated, but its actions on the endogenous opioids system through multiple neuronal pathways and gate-control effects have been identified [5, 6]. Previous (observational) studies have revealed that electroacupuncture at 2 Hz may increase endorphin, a natural pain reliever. Meanwhile, the therapy at 100 Hz may increase dynorphin with primary effects on receptors K1 and K3 causing neurotransmitters reduction and increasing pain threshold [7]. However, up to now, no clinical study has been conducted to compare the analgesic effect of the 100 Hz electroacupuncture to the 2 Hz electroacupuncture in CLBP. In this study, we aim to investigate whether electroacupuncture with two frequencies, 2 Hz and 100 Hz, can reduce pain and improve lumbar flexion range of motion. We also investigate the differences in therapeutic effects between the 2 Hz and the 100 Hz electroacupuncture in patients who have CLBP due to the lumbar osteoarthritis.
2. MATERIALS AND METHOD
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.
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.
3. RESULTS AND DISCUSSION
We screened 232 inpatients with CLBP due to lumbar osteoarthritis who went to the Traditional Medicine Hospital at Ho Chi Minh City, and 124 of them satisfied the inclusion criteria. Complete follow-up data were available for all patients at the end of week 2. Table 1 indicates the baseline characteristics of the patients. Most patients were above 45 years old, and females accounted for 73% of the total participants. The baseline average QDSA score of the intervention group and the control group was 44 ± 5 and 43 ± 4, respectively. Up to half of the patients in both groups had gastritis and more than 60% of patients suffered CLBP for more than 5 years. Overall, baseline characteristics were similar among the two study groups (p >0.05) (Table 1).
The QDSA score decreased from baseline to day 7 and continued decreasing until day 14 by a mean of 35 ± 4 in the 100-Hz electroacupuncture group and 27 ± 4 in the 2-Hz electroacupuncture group (Figure 2) (Table 2). The difference between the 100-Hz and the 2-Hz electroacupuncture group was statistically significant (p <0.001).
| Change in QDSA score | 100-Hz electroacupuncture Mean ± SD | 2-Hz electroacupuncture Mean ± SD | p |
|---|---|---|---|
| Day 1 – Day 7 | 17 ± 4 | 14 ± 3 | <0.001 |
| Day 7 – Day 14 | 18 ± 4 | 13 ± 2 | <0.001 |
| Day 1 – Day 14 | 35 ± 4 | 27 ± 4 | <0.001 |
Table 3 shows results of secondary outcomes. After 2 weeks, the PPR in the two groups were significantly different (p <0.001) The proportion of patients in the 100 Hz electroacupuncture group with PPR improvement ≥70% was 87%, while it was only 45% in the 2 Hz group. The result of LFROM in the 100 Hz electroacupuncture group tended to be better than in the 2 Hz group (91.9% and 87% of patients had LFROM ≥13 cm, respectively), but there was no statistically significant difference between the two groups. (Table 4 and 5)
| 100-Hz electroacupuncture | 2-Hz electroacupuncture | p | |||
|---|---|---|---|---|---|
| n | % | n | % | ||
| Percentage of pain relief | <0.001 | ||||
| ≥ 90% | 18 | 29 | 0 | 0 | |
| 70 − 90% | 36 | 58 | 28 | 45 | |
| 50 − 70% | 8 | 13 | 29 | 47 | |
| < 50% | 0 | 0 | 5 | 8 | |
| 100-Hz electroacupunture | 2-Hz electroacupunture | |||
|---|---|---|---|---|
| Day 1 | Day 14 | Day 1 | Day 14 | |
| Lumbar flexion range of motion (cm) | 11 ± 0,8 | 15 ± 0,5 | 11 ± 0,9 | 14 ± 0,8 |
| p | <0.001 | <0.001 | ||
| 100-Hz electroacupuncture | 2-Hz electroacupuncture | p | |||
|---|---|---|---|---|---|
| n | % | n | % | ||
| Lumbar flexion range of motion | <0.092 | ||||
| ≥ 14 cm | 30 | 48.4 | 20 | 32.3 | |
| 13 − 14 cm | 27 | 43.5 | 30 | 48.4 | |
| 12 – 13 cm | 5 | 8.1 | 12 | 19.4 | |
| < 12cm | 0 | 0 | 0 | 0 | |
During 14 days of treatment, both groups did not experience any serious adverse events (dizziness, sweating, nausea or vomiting, cold hands and feet, etc.). No case was discontinued due to undesirable side effects.
4. DISCUSSION
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.
CONCLUSION
In our study of 124 patients with chronic low back pain due to lumbar osteoarthritis, the combination of 100 Hz electroacupuncture at Hua Tuo Jia Ji acupoints and Du Huo Ji Sheng Tang decoction had superior analgesic effects on chronic low back pain due to lumbar osteoarthritis compared to the combination of 2 Hz electroacupuncture at Hua Tuo Jia Ji points and Du Huo Ji Sheng Tang decoction. The PPR in the two groups were significantly different (p <0.001). Result of LFROM in 100 Hz electroacupuncture group tended to be better than in 2 Hz group, but there was no statistically significant difference. One of the potential fields for studies in the future may consist of performing long-term effects of 100 Hz electroacupuncture combined with other therapies in patients with CLBP.
