Clinical Study on Extracorporeal Shock Wave Therapy plus Electroacupuncture for Myofascial Pain Syndrome

Huang Fang, Chen Xiong, Mu Jing-ping

1 Department of Acupuncture and Moxibustion, Taihe Hospital, Hubei University of Medicine, Shiyan 442000, China

2 Hubei University of Chinese Medicine, Wuhan 430061, China

CLINICAL STUDY

Clinical Study on Extracorporeal Shock Wave Therapy plus Electroacupuncture for Myofascial Pain Syndrome

Huang Fang1, Chen Xiong2, Mu Jing-ping1

1 Department of Acupuncture and Moxibustion, Taihe Hospital, Hubei University of Medicine, Shiyan 442000, China

2 Hubei University of Chinese Medicine, Wuhan 430061, China

Author: Huang Fang, attending nurse

Objective: To observe the clinical effect of extracorporeal shock wave plus electroacupuncture (EA) on myofascial pain syndrome (MPS) and to investigate its treatment mechanism.

Methods: Ninety cases who met the inclusion criteria were randomly allocated into an EA group, an extracorporeal shock wave therapy (ESWT) group and a combined therapy group, 30 in each group. EA was employed in the EA group, extracorporeal shock wave therapy in the ESWT group and EA plus extracorporeal shock wave therapy in the combined therapy group. The VAS, tenderness threshold and therapeutic efficacy were evaluated after three months of treatment.

Results: After 2 weeks, 4 weeks and 3 months of treatment, the VAS scores in all three groups were significantly reduced and the tenderness threshold significantly elevated. The recovery rate and total effective rate were 23.3% and 83.3% respectively in the EA group, versus 40.0% and 90.0% in the ESWT group and 63.3% and 96.7% in the combined therapy group, showing statistical differences (P＜0.05).

Conclusion: EA combined with EWST works remarkably well for MPS.

Acupuncture Therapy; Electroacupuncture; Myofascial Pain Syndromes; High-energy Shock Waves

Myofascial pain syndrome (MPS), also known as chronic myofascial pain (CMP), is a syndrome characterized by chronic muscle pain accompanied by one or multiple trigger points[1]. Often seen in adults and elderly population, myofascial pain can occur in distinct, isolated areas of the body following a traumatic injury and cause a variety of localized pain such as the neck, back, soft tissue and surrounding areas of the joints. It’s believed MPS is a common cause for pain in the low back, neck, shoulder and joints[2]. In 1988, some scholars first pointed that MPS involves muscles and fascia, especially on the neck, shoulder and low back. Chronic persistent pain is mainly caused by local adhesion and constriction resulting from aseptic inflammation of muscles and fascia[3]. Today, the nomenclature of an affected muscle has been accepted, such as the piriformis syndrome, infraspinatus trigger-point syndrome, gluteus medius syndrome and scalenus syndrome. An American professor has found that most non-organic fibromyalgia are caused by myofascial trigger points[4]. MPS can be managed by many therapies. Acupuncture is often used to relieve pain[5]. Over the recent years, the extracorporeal shock wave therapy (ESWT) has been proven effective for this condition. However, its action mechanism is not clear yet. In order to observe the clinical effect of different treatmentprotocols and investigate their action mechanism, we have treated MPS with electroacupuncture (EA) plus ESWT and compared with either EA or ESWT alone. The results are now summarized as follows.

1 Clinical Materials

1.1 Diagnostic criteria

There are no unified diagnostic criteria for MPS yet. The diagnostic criteria for MPS in Western medicine issued in 1990 have been employed in clinical practice[6-7]. Discrepancy in diagnostic criteria can affect the comparability of documentation data and epidemiological survey. A unified diagnostic criterion is therefore necessary. The diagnostic criteria in this study are made referring to theMusculoskeletal Rehabilitation[8]: a local regional pain, muscle pain due to recurrent or chronic overuse or unknown muscle pain; paresthesia in distributed area of pain or referred pain associated with trigger points; palpable taut bands and contraction nodules over the affected muscles; local twitching induced by fast palpation or needling trigger points; exclusion of pain due to organic or other system conditions such as nonmyofascial pain (skin and scar pain, periosteal pain, acupuncture point tenderness and motor end plate pain), disorders of skeletal system, nervous system and visceral system, infectious diseases, neoplasm and psychogenic pain; autonomous potential at the trigger points and depolarized electric wave at the motor end plate nerve endings recorded in electromyography (EMG); limited range of motion and stretch of affected muscles and slight muscle weakness; the symptoms aggravated upon insufficient sleep.

1.2 Inclusion criteria

Those who met the above diagnostic criteria and had MPS for less than 3 years; aged between 20 and 65 years; having not received other medications or therapies during the last week; having non-allergic constitution or no history of drug allergy; willing to participate in this trial and sign the informed consent.

1.3 Exclusion criteria

Those who didn’t meet the above diagnostic and inclusion criteria; exclusion of myofascial pain due to tumor, surgery, trauma, acute soft tissue injury, cervical or lumbar disc herniation and rheumatism by medical history, signs, symptoms, X-ray, MRI scan and laboratory biochemical examinations including blood sedimentation, anti-streptolysin O, rheumatoid factor and HLA-B27; having severe life-threatening primary conditions involving the cardio-cerebrovascular, liver, kidney and hematopoietic systems; psychotic patients; unwilling or unable to comprehend the treatment protocol; and those who are contraindicated to EA and ESWT.

1.4 Criteria for termination, rejection and dropout

Severe complications during the treatment; having failed to follow the treatment protocol and doctors’instructions; those who recovered before completion of the treatment course (calculated as clinical recovery); having severe adverse events or reactions; and those who voluntarily dropped out.

1.5 General data

Ninety MPS cases treated in our hospital between January 2010 and May 2013 were recruited and randomly allocated into an EA group, a ESWT group and a combined therapy group by their visit sequence numbers, 30 in each group.

The clinical procedure flow chart in three groups is shown in Figure 1.

Figure 1. Clinical procedure flow chart in three groups

There were no statistically significant differences in gender, age, duration and affected area among three groups (P＞0.05), indicating that the three groups were comparable (Table 1).

2 Treatment Methods

2.1 Combined therapy group

2.1.1 EA

Points: Ashi points.

Method: Ask the patient to choose a comfortable prone position and to fully expose the neck and back.The doctor then pressed the neck and back using the thumb to search for painful points, subcutaneous nodules and other reaction areas. These areas can be determined as Ashi points when the patient felt pain or comfort. After routine sterilization, insert stainless steel filiform needles of 0.25 mm in diameter and25-40 mm in length rapidly. After arrival of qi, reducing manipulation by lifting, thrusting and twirling wad conducted. Then connect needles with G-6805 electric stimulator, using the sparse-dense wave and tolerable intensity. Retain the needles for 30 min and slowly withdraw afterwards[9-10]. It’s advised not to apply EA on the same day of ESWT. Other than that, the EA was conducted 30 min for each treatment, once every day, 7 d made up one course of treatment. There was an interval of 1 d between two courses of treatment. The therapeutic efficacy was evaluated after 3 months of treatment.

Table 1. Inter-group comparison of general data

2.1.2 EWST

Seeking the trigger points: Palpate the affected area using four fingers to search and locate specific areas that can trigger pain or referred pain, known as trigger points or painful points[11].

Shock wave therapy: The ESWO-AJ extracorporeal shock wave therapeutic apparatus was employed to impact approximately 700 times towards the trigger points of muscle pain, coupled with approximately 300 times towards the surrounding area. The working voltage (7-10 kV), shock wave (60 times/min) dose and energy density (0.18-0.25 mJ/mm) were adjusted according to the patient’s condition and tolerance. The treatment was conducted once every 3 d for 3 months.

2.2 EA group

Patients in this group were treated with same EA therapy alone (including the method and course of treatment) as that in the combined therapy group.

2.3 EWST group

Patients in this group were treated with same EWST therapy (including the method and treatment course) alone as that in the combined therapy group.

3 Treatment Results

3.1 Criteria for therapeutic efficacy

Currently there are no unified criteria for therapeutic efficacy of MPS. By referring to relevant literature, this study concludes that the key to therapeutic efficacy of MPS lies in absence of pain. Consequently the therapeutic efficacy was evaluated according to pain scores.

3.1.1 Pain assessment

The visual analogue scale (VAS): Operationally a VAS was usually a horizontal line, 10 cm in length, anchored by word descriptors at each end. One end read 0, representing no pain. The other end read 10, representing severe pain. The part in between 0 and 10 represent pain in different severities. The patient marked on the line the point that they felt representing their perception of the current state and the values were recorded before treatment and 2 weeks, 4 weeks and 3 months after treatment[9].

Pain threshold detection: Gradually exert pressure on pain threshold detector over the patients’ finger joints, get the patients’ reaction and record the required pain-inducing pressure, i.e., pain tolerance threshold (N/cm2) for patients’ pain tolerance.

3.1.2 Criteria for therapeutic efficacy

The VAS reduction rate was calculated by the VAS scores before and after treatment.

VAS reduction rate ﹦ (Pre-treatment VAS score –Post-treatment VAS score) ÷ Pre-treatment VAS score × 100%.

Clinical recovery: VAS reduction rate ≥75%.

Marked effect: VAS reduction rate ≥50% but＜75%.

Improvement: VAS reduction rate ≥25% but＜50%.

Failure: VAS reduction rate ＜25%.

3.2 Statistical analysis

The SPSS 19.0 software was employed for statistical management,for expression of measurement data,t-test for intra-group comparison, one-factor analysis of variance for inter-group comparison and Chi-square test for ratio comparison. APvalue＜0.05 indicated a statistical significance.

3.3 Results

3.3.1 VAS scores

The VAS scores were reduced in all three groups after 2 weeks, 4 weeks and 3 months of treatment (P＜0.05); after 2 weeks of treatment, the VAS scores in the combined therapy group were more significantly reduced than those in the other two groups (P＜0.05); after 4 weeks of treatment, the VAS scores in the ESWT group and the combined therapy group were further reduced; however, the VAS score in the EA group was slightly increased (Table 2).

3.3.2 Tenderness threshold

The tenderness thresholds were elevated in all three groups after 2 weeks, 4 weeks and 3 months of treatment; and the elevation in the combined therapy group was more significant than that in the other two groups. In addition, the tenderness threshold in the combined therapy group was further elevated as time went on; however the elevation was insignificant in the other two groups (Table 3).

3.3.3 Total effective rate

After three months of treatment, the recovery rate and the total effective rate were 23.3% and 83.3% respectively in the EA group, versus 40.0% and 90.0% in the ESWT group and 63.3% and 96.7% in the combined therapy group, showing statistically significant differences (P＜0.05), (Table 4).

Table 2. Inter-group comparison of VAS scores before and after treatment (point)

Table 2. Inter-group comparison of VAS scores before and after treatment (point)

Note: Compared with the intra-group before treatment, 1) P＜0.05; compared with the intra-group result after 4 weeks of treatment, 2) P＜0.05; and compared with EA and ESWT groups at the corresponding time period, 3) P＜0.05

Table 3. Inter-group comparison of tenderness threshold before and after treatment (，N/cm2)

Table 3. Inter-group comparison of tenderness threshold before and after treatment (，N/cm2)

Note: Compared with intra-group result before treatment, 1) P＜0.05; compared with intra-group result 4 weeks after treatment, 2) P＜0.05; compared with the EA and ESWT groups at the corresponding time period, 3) P＜0.05

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Table 4. Inter-group comparison of clinical effects (case)

4 Discussion

Muscular fasciae are compact connective tissue and characterized by thick dense collagen fibers and less elastic and reticular fibers. MPS is often diagnosed on the basis of trigger points，i.e. tenderness points of myofascial pain that can trigger muscle pain and referred irritating pain in surrounding or distal areas. Contributing factors of trigger points include neuromuscular dysfunctions, subsequent malnutrition of tissues, increased local metabolism but decreased blood flow. This may result in uncontrolled metabolic areas in muscles. Nerve activating substances in metabolic products such as histamine, 5-hydroxytryptamine, kinin and prostanoid can cause severe vasoconstriction. Through central or sympathetic nerve reflex, the local response can cause muscle tension and responsive pain areas[12]. Some people diagnose MPS into ‘myofascitis’. However, ‘myofascitis’ refers to infection or inflammatory reactions of muscle tissue and cannot supersede MPS. Some people misdiagnosed MPS because they confused trigger points with tenderness points[5]. Recently, acupuncture has been used more and more in pain management. Previous studies have proven the very good effects of painful Ashi points on MPS[13-15]. On one hand, acupuncture can release local spasm, increase blood circulation, improve local metabolism and inhibit or eliminate local inflammatory substances. On the other hand, acupuncture can inhibit pain center in cerebral cortex, block transmission of neurotransmitters and enhance the analgesic effect. In treating MPS, trigger points with maximum reactions are primary options for needling[16-17].

Extracorporeal shock wave device can transform the impulse sound wave into accurate trajectory shock wave, producing an effective pain-relief effecton extensive human tissue through the orientation and shifting of the therapeutic probe. Upon entering the body, the shock wave can increase the local microcirculation, unblock physiologically closed capillaries, accelerate capillary circulation, improve oxygen contents in cells and help to heal the injured soft tissue[18]. On one hand, this therapy can change the chemical environment of the affected area, help to generate and release pain-inhibiting chemical substances such as endorphin, disrupt the cell membrane of pain receptor, inhibit the generation and conduction of pain signal and thus reduce the pain sensitivity. On the other hand, this therapy can improve the function of trigger point affected area, decompose metabolic products, stimulate regional muscle groups and block concentric pain conduction.

Combined EA and shock wave therapy can directly work on the trigger point area and points, improve local metabolism, alleviate inflammatory reaction, accelerate the healing of tissue and thus work well for MPS.

In summary, MPS is a complex chronic condition with a high incidence. However, its treatment effect has been limited by lack of diagnostic methods and unknown pathomechanism[19]. So far many therapies can eliminate or alleviate MPS pain and improve the patients’ quality of life but all therapies have their limitations. As a result, it’s of great urgency to come up with a safe, effective, and low-cost therapy. The easy-to-operate extracorporeal shock wave therapy and EA are effective, free of adverse reactions and easily accepted by patients. The combined therapy therapy can reduce the pain sensitivity of myofascial trigger points, improve the patients’ quality of life and obtain better effect than EA or extracorporeal shock wave therapy alone.

Conflict of Interest

There is no potential conflict of interest in this article.

Acknowledgments

This work was supported by Project of Hubei Provincial Health Department (No. JX4C08).

Statement of Informed Consents

All of the patients signed the informed consent.

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Translator:Han Chou-ping

Mu Jing-ping, M.D., associate chief physician.

E-mail: mjpll@163.com

R246.2

: A

Date:September 25, 2013