Dry needling versus magnesium sulfate iontophoresis of active trigger points of the axioscapular muscle in neck pain: a single blind randomized controlled trial

Abstract

Objective:

To compare the effects of dry needling (DN) and magnesium sulfate (MgSO4) iontophoresis on pressure pain threshold (PPT), neck disability, pain intensity and muscle activity/amplitude in patients with upper-trapezius active myofascial trigger points (MTrPs) and neck pain.

Methods:

Sixty subjects with neck pain and cervical myofascial pain syndrome (MPS) of the upper trapezius muscles were randomly assigned into a DN group that received DN and stretching of all cervical muscles, an iontophoresis group that received MgSO4 iontophoresis and stretching of all cervical muscles or a control group C that received only stretching of all cervical muscles. The subjects received the treatment twice a week for 4 weeks. PPT, Arabic neck disability index (ANDI), pain intensity visual analogue scale (VAS) and cervical muscle amplitude (assessed by electromyography and expressed as a normalized root mean square (RMS)) were measured before and after completion of the treatment.

Results:

In the within-group analysis, there were statistically significant differences pre- versus post-treatment in all variables in both experimental groups (p < 0.05) but no significant differences in the control group with the single exception of pain intensity. In the between-group analysis post-treatment, there were statistically significant differences between all three groups. Compared with the iontophoresis group, the DN group showed significant improvements in VAS (mean difference (MD) −2.0, 95% confidence interval (CI) −2.84 to −1.36; p < 0.01), RMS (MD −1.32, 95% CI −1.79 to −0.85; p < 0.001), ANDI (MD −2.60, 95% CI −4.50 to −0.70; p = 0.004) and PPT (MD 1.48, 95% CI 1.01–1.95; p < 0.001).

Conclusion:

DN and MgSO4 iontophoresis both had positive effects on PPT, ANDI, VAS and muscle amplitude in the treatment of neck pain subjects with upper-trapezius MTrPs. DN had a superior effect than MgSO4 iontophoresis for all outcomes studied.

Keywords

dry needling electrophoresis iontophoresis myofascial trigger points neck pain

Introduction

Neck pain (NP) is one of the most common public health issues, affecting approximately one-third of the adult population, with an incidence of 10.4%–21.3% among office and computer workers.^1,2 This pain is felt from the superior nuchal line to an imagined transverse line passing through the spinous process of the first thoracic vertebra.² In patients with neck pain, myofascial pain syndrome (MPS) has been reported to be the most common etiology.³ MPS is a painful muscular condition that occurs as a result of trauma or repetitive stress and is characterized by the presence of myofascial trigger points (MTrPs).⁴ Simons and Travell defined an MTrP as a hypersensitive spot located in a taut band of skeletal muscle, stimulation of which induces referred pain symptoms and motor phenomena.⁵ Psychological disorders—including personality traits (especially neuroticism), anxiety and depression, fear of motion, pain fear-avoidance, catastrophism and central sensitization—may be associated with the presence of MTrPs.⁶ Chiarotto et al. found that MTrPs in the upper trapezius were the most common finding in individuals suffering from neck pain.⁷ MTrPs are frequently painful and can cause changes in a variety of muscular properties, including altered muscle activation, increased muscle tension, decreased range of motion (ROM), muscle weakening and fatigability.^8,9 People of all ages are liable to have MTrPs, but most documented cases occur in adults aged 21–50 years; although both sexes are affected, MPS appears to be more common in females than males.¹⁰

Treatment options for MTrPs include deactivating techniques such as ischemic compression,¹¹ spray and stretch,¹² strain and counter strain,^13–15 muscle energy techniques,¹⁶ MTrP release,¹¹ transverse friction massage,^11–13 integrated neuromuscular inhibition technique (INIT),¹⁷ and dry needling (DN),^18,19 as well other physical modalities such as thermotherapy,²⁰ ultrasound therapy,²¹ phonophoresis,²¹ laser therapy,²² and iontophoresis.²³

DN has received particular attention as a method of deactivating trigger points in the past decade; it involves the passage of a small filiform needle through the skin to stimulate the underlying MTrPs, muscle and connective tissues for the treatment of neuromusculoskeletal discomfort and mobility deficits. Multiple clinical trials and systematic reviews have reported on the positive role of DN in patients with MTrPs.^24–27 The use of DN leads to a change in the biochemical state around the MTrPs,²⁸ through elicitation of a local twitch response (LTR) that corrects the increased levels of several biochemical mediators—for example bradykinin, calcitonin gene-related peptide (CGRP) and substance P (SP)—at the site of the MTrP.²⁹ The LTR is an involuntary spinal cord-mediated reflex contraction of muscle fibers in a taut band that occurs in response to needling of MTrPs.³⁰ DN can also break the cycle of neuromuscular dysfunction through different processes, including a reduction of muscle tone, modulation of neurochemical pathways in muscle, increases in local blood flow and restoration of ROM at the neck, and thus may improve quality of life.²⁷

Iontophoresis involves ion transfer of medical substances to the body via direct current as an alternative to oral administration and is being increasingly used in the treatment of MTrPs.²³ Iontophoresis has several advantages including the prevention of absorption variation associated with oral administration by bypassing hepatic “first pass” metabolism and reducing the possibility of dosing variation by providing programmed delivery of medications, potentially overcoming issues of compliances and ensuring that the medication reaches the circulation without delay.³¹ Magnesium sulfate (MgSO4) acts as a muscle relaxant, vasodilator and analgesic and has been found to have a superior analgesic effect to lidocaine due to its capacity to enter undamaged skin as well as its efficacy in raising serum magnesium levels; MgSO4 delivery via iontophoresis could potentially result in a more effective MTrP treatment.³² Mizutani et al. investigated the analgesic effect of MgSO4 iontophoresis and revealed that pain recognition time was greatly extended and lasted for 60 min, demonstrating that MgSO4 possesses analgesic and pain-relieving properties.³³ However, to the best of our knowledge, the existing data are insufficient to conclude whether DN or MgSO4 iontophoresis is superior for the treatment of patients with upper-trapezius MTrPs. Accordingly, the aim of this study was to directly compare these two interventions.

Methods

Study design

A single-masked randomized controlled trial was performed in accordance with the Helsinki Declaration (1964) and reported in line with the Consolidated Standards of Reporting Trials (CONSORT) guidelines.³⁴ The trial was performed at the Faculty of Physical Therapy outpatient clinic at Cairo University from April to August 2021. Before engaging in the study, each patient provided voluntary written informed consent. The protocol was approved by the Faculty of Physical Therapy’s research ethics committee (P.T.REC/012/003108) and was prospectively registered at ClinicalTrials.gov (NCT04809038) on 18 March 2021.

Inclusion and exclusion criteria

An orthopedist diagnosed 70 participants with neck pain including cervical MPS of the upper-trapezius muscle. Subjects were included in the study if they reported pain at rest for <3 months and had active MTrPs of the upper trapezius muscle on the dominant side, as well as a LTR, jump sign, reduced ROM, referred pain over the lateral aspect of the upper trapezius fibers and superior to the ipsilateral occiput, and a normal body mass index (BMI).³⁵ Subjects were excluded if they had: significant clinical problems other than neck pain, such as cervical spine lesions, radiculopathy or myelopathy; fractures or history of cervical spinal surgery; or cervical spinal instability. They were also excluded if they had: received physical therapy within the previous 3 months; non-rheumatologic diseases such as multiple sclerosis; rheumatologic conditions such as systemic lupus erythematosus, even if mild;³⁶ BMI ⩾ 25 kg/cm² (given there is a correlation between the thickness of skin and fascia and location of MTrPs);³⁷ or needle phobia. In addition, those who were unwilling to participate, were on anticoagulant therapy or who had thrombocytopenia,^38,39 were ineligible.

Randomization and blinding

After signing the consent form, subjects were allocated randomly to one of three groups using an opaque sealed envelope: group A (DN group), group B (iontophoresis group) and group C (control group). Group A received DN and stretching of all cervical muscles, group B received MgSO4 iontophoresis and stretching of all cervical muscles and group C received only stretching of all cervical muscles. The process of randomization was performed by the first author who was not involved in gathering data. The third author, who has 10 years of experience in the assessment of pressure pain threshold (PPT) and electromyography (EMG), collected the data and was blinded to the allocation stage. The second author opened the opaque sealed envelopes and applied the allocated treatment twice a week for 4 weeks.

Interventions

Dry needling

For participants in group A, active MTrPs were detected by pincer palpation and marked for DN using a pen.^35–40 During the examination, a taut band needed to be present and at least one of the following clinical signs had to be observed: spot tenderness within the taut band; reproduction of pain; or referred pain complaints during mechanical stimulation of the tender spot.⁴⁰ The existence of an LTR during taut band palpation was regarded as a confirmatory criterion for an active MTrP.^40,41 Subjects were placed in a comfortable prone position and asked to relax completely. The area around the active MTrPs was cleaned with an alcohol pad, and thin filiform needles (0.30 mm × 50 mm) with plastic guide tubes (Tony, China) were inserted over the active MTrPs and retained for 30–60 s (Figure 1(a)). In weak responders, the needle could be left for up to 2 min. The needle was advanced to a depth of 5–10 mm using a tapping motion, the needle angulation was changed in order to generate a LTR, which typically takes 30 s to 2 min to elicit, then the needle was withdrawn.⁴² All patients were advised to apply ice massage up to a total of 24 h after needling.²⁴

Figure 1.

(a) Dry needling application, (b) iontophoresis application and (c) assessment of pressure pain threshold.

Iontophoresis

Participants in group B received MgSO4 iontophoresis using a Phoresor_II Auto iontophoresis machine (PM850; IOMED, Salt Lake City, UT, USA). Subjects underwent marking of MTrPs and were placed in a relaxed prone position as in group A. Using a syringe, MgSO4 at a concentration of 100 mg/cm² was administered to the active positive electrode, which was positioned immediately over the previously marked area containing the sensitive MTrPs. The dispersive electrode was placed 6 inches away from the active electrode on the skin (Figure 1(b)). The device was set to the required dose of 75 mA-min and the current intensity (direct current) was gradually increased based on the subject’s tolerance (ranging from 2 mA to 4 mA). The device computed the required time for the selected dose automatically.⁴³

Passive stretching exercises

Participants in all three groups underwent stretching of all cervical muscles (flexor, extensor, rotator and side bending muscles). The subjects were seated in a relaxed and comfortable manner, with their backs supported. One of the practitioner’s hands applied a stretching force to the side of the patient’s head, while the other hand applied shoulder stability to the patient’s shoulder. Flexion, side bending to the other side and rotation to the same side were the directions of stretched force. The stretched position was held for 30 s and this was followed by a 30 s relaxation period. This procedure was carried out three times every session for two sessions per week for 4 weeks.¹³

Primary outcomes

Pain intensity

Pain was assessed by visual analogue scale (VAS), which is a valid and reliable tool for pain assessment. The VAS consists of a line with no pain at one end and the worst imaginable pain at the other. Each subject was asked to mark a point on a line to indicate the level of their pain.⁴⁴

Muscle activity

Upper-trapezius muscle activity/amplitude was measured using a MyoSystem 1400A (Noraxon, Scottsdale, AZ, USA) and expressed as a normalized root mean square (RMS). The assessment started by decreasing the skin resistance, and it was recommended that electrode insertion areas be shaved and cleaned with alcohol. The upper-trapezius active electrode was positioned 2 cm lateral to the middle of a line drawn between the C7 spinous process and the posterolateral acromion on the dominant side of each subject. The reference electrode was placed over the C7 spinous process.⁴⁵ Before filtering, data bias was removed and full wave rectification was performed. As described by Ekstrom et al.,⁴⁶ the maximum voluntary isometric contraction (MVIC) was assessed using a manual isometric shoulder shrug; each contraction was maintained for 7 s, then the shoulder shrug was performed three times against manual resistance, with the participant resting for 30 s between each repeat. Following the MVIC evaluation, the upper trapezius was assessed during movement by performing shoulder abduction at 120° from a standing position.⁴⁷ The normalized RMS was determined as follows: normalized RMS percent = EMG amplitude during activity / (average of three MVIC trials) × 100.⁴⁸

Secondary outcomes

Pain threshold

A Commander algometer (JTECH Medical, Midvale, UT, USA), which is a hand-held tool that uses manual pressure to test pain sensitivity in deeper structures, was used to measure PPT, which is considered to be a valid and reliable tool for assessing PPT in patients with MTrPs and mechanical neck pain.⁴⁹ The tip of the algometer was positioned on the MTrP area, and pressure was increased at a rate of 1 kg/s (Figure 1(c)). When the patient expressed discomfort and verified it verbally, the pressure measurement was recorded in kg/cm². The technique was repeated three times at 60 s intervals.

Neck function

The Arabic neck disability index (ANDI), which is a tool with a moderate degree of validity and reliability in neck function evaluation, was used to assess neck function.^50,51 The ANDI consists of 10 classes/categories, with six choices per category (0–5). A score of 0–4 indicates no disability, 5–15 indicates mild disability, 15–24 indicates moderate disability, 25–34 indicates severe disability and >34 indicates complete disability.^50–52

Estimation of sample size

The required sample size was estimated in G* Power version 3.1.9.2 (Franz Faul, Uni Kiel, Germany) based on an unpublished pilot study of 15 subjects, using a mixed multivariate analysis of variance (MANOVA) with repeated measures and between-group factors. We estimated that 45 patients would be needed to detect an effect size of 0.42 in the VAS (one of the primary outcomes) at 80% power and allowing for a type I error rate of 5%. This number was increased by 30% (to n = 60 subjects) in order to accommodate anticipated dropouts.

Statistical analysis

Categorical data (sex and affected side) were compared between groups using the Chi-square test. After confirming normality of distribution (using the Shapiro-Wilk test), one-way analysis of variance (ANOVA) was used to analyze baseline demographic data, while multivariate ANOVA (MANOVA) was used to determine the effects of the different treatments and the interaction between time and treatment. When significant differences were identified between groups, pairwise comparisons were performed using post hoc Bonferroni tests (including correction for multiple testing). The magnitude of between-group differences was assessed using partial eta square (η)². All analyses were conducted using the Statistical Package for the Social Sciences (SPSS) version 23 (IBM Corp., Armonk, NY, USA). The adjusted p value for statistical significance in our primary outcome measures was 0.025 (= 0.05 ÷ number of primary outcomes (2)). Per convention, secondary outcomes measures were considered exploratory in nature.

Results

Seventy subjects with neck pain were screened at outpatient physical therapy clinics, of which 10 were excluded because they had received treatment in the prior 3 months. Ultimately, 60 subjects were recruited and randomly allocated in a 1:1:1 ratio to the three experimental groups (Figure 2).

Figure 2.

Consolidated Standards of Reporting Trials (CONSORT) flow diagram.

Demographic data

As shown in Table 1, the subjects were similarly matched across groups (p > 0.05) in terms of age, weight, height, BMI and chronicity of symptoms (assessed by ANOVA), as well as sex and affected side (assessed by Chi-square test). During treatment, no adverse effects were reported in any of the three groups.

Table 1.

Baseline demographic data.

	Dry needling group	Iontophoresis group	Control group	p-value
Age (years)	21.4 ± 2.58	22.5 ± 2.92	23.3 ± 1.37	0.53
Weight (kg)	68.9 ± 7.86	65.8 ± 6.6	65.4 ± 6.01	0.38
Height (cm)	166.0 ± 7.12	169.4 ± 15.62	169.5 ± 12.36	0.83
Body mass index (kg/m²)	23.6 ± 0.23	22.7 ± 0.65	23.0 ± 0.32	0.67
Chronicity of symptoms (weeks)	7.5 ± 1.27	7.7 ± 1.11	7.0 ± 1.41	0.55
Sex distribution
Male	8 (40%)	6 (30%)	9 (45%)	0.61
Female	12 (60%)	14 (70%)	11 (55%)	0.61
Affected side
Right	17 (85%)	18 (90%)	19 (95%)	0.57
Left	3 (15%)	2 (10%)	1 (5%)	0.57

Data are mean ± standard deviation or n (%).

As shown in Table 2, there were no significant differences in either of the two primary outcomes at baseline; however, after the interventions there were significant differences between the groups in VAS and RMS, both of which met our adjusted threshold for statistical significance (p < 0.025). The same was true for the secondary outcome measures PPT and ANDI (Table 3). The general mixed MANOVA also detected significant differences attributable to time (p = 0.001) and a significant interaction between group and time (p = 0.001).

Table 2.

Primary outcomes: within- and between-group analysis.

	Dry needling group	Iontophoresis group	Control group	p-value (between groups)	f-value (between groups)	η ²
Pain intensity (VAS)
Pre-treatment	8.5 ± 0.99	8.5 ± 1.00	8.6 ± 0.76	0.94	0.058	0.002
Post-treatment	2.0 ± 0.79	4.1 ± 0.98	7.5 ± 0.51	0.001	169.72	0.85
p-value (within group)	<0.001	<0.001	0.01
% change	76%	52%	13%
MD	6.45	4.40	1.10
95% CI	5.89 to 7.01	3.84 to 4.95	0.54 to 1.65
Muscle activity (RMS)
Pre-treatment	4.3 ± 0.59	4.3 ± 0.67	4.3 ± 0.72	0.97	0.02	0.001
Post-treatment	1.8 ± 0.47	3.1 ± 0.67	4.3 ± 0.63	0.001	83.65	0.75
p-value (within group)	<0.001	<0.001	0.39
% change	58%	26%	1%
MD	2.47	1.13	0.05
95% CI	2.37 to 2.58	1.03 to 1.24	−0.06 to 0.15

Data are mean ± standard deviation. Bold text indicates significant differences. VAS: visual analogue scale; RMS: root mean square; CI: confidence interval; MD: mean difference; η^2: partial Eta square.

Table 3.

Multiple pairwise comparisons.

	Dry needling group vs. iontophoresis group		Dry needling group vs. control group		Iontophoresis group vs. control group
	MD (95% CI)	p-value	MD (95% CI)	p-value	MD (95% CI)	p-value
Primary outcomes
VAS	−2.10 (−2.84 to −1.36)	<0.001	−5.45 (−6.19 to −4.71)	<0.001	−3.35 (−4.09 to −2.61)	<0.001
RMS	−1.32 (−1.79 to −0.85)	<0.001	−2.46 (−2.92 to −1.99)	<0.001	−1.14 (−1.6 to −67)	<0.001
Secondary outcomes
ANDI	−2.60 (−4.50 to −0.70)	0.004	−20 (−21.9 to −18.1)	<0.001	−17.4 (−19.3 to −15.5)	<0.001
PPT	1.48 (1.01 to 1.95)	<0.001	2.63 (2.16 to 3.11)	<0.001	1.16 (0.68 to 1.63)	<0.001

PPT: pressure pain threshold; ANDI: Arabic neck disability index; VAS: visual analogue scale; RMS: root mean square; CI: confidence interval; MD: mean difference.

Table 3 shows the results of multiple pairwise comparisons between the three groups, which were performed using post hoc Bonferroni tests to minimize the risk of type 1 error. Pre-treatment there were no differences in any of the four outcomes. Post-treatment, VAS, ANDI and RMS scores were significantly lower and PPT values were significantly higher in both DN and iontophoresis groups relative to the control group, as well as in DN versus iontophoresis groups, suggesting superiority of the DN intervention.

Within-group analysis revealed statistically significant differences pre- versus post-treatment in all measured outcome variables in the DN and iontophoresis groups (Tables 2 and 3) but only for VAS scores within the control group (Table 2).

Discussion

The purpose of this study was to compare the effects of DN and MgSO4 iontophoresis of active MTrPs of the upper trapezius muscle in patients with neck pain. To our knowledge, this is the first trial to directly compare the effects of these two interventions for this indication. According to our results, the DN and iontophoresis groups exhibited improvements in PPT, NDI, VAS scores and muscle activity over the course of the study, while the control group (receiving passive stretching exercises only) only demonstrated significant changes in VAS scores. Moreover, the improvement in the DN group was significantly greater than that in both the iontophoresis group and the control group. The minimal clinically important differences (MCIDs) for pain intensity (VAS), neck disability (NDI) and pain threshold (PPT) have been reported as −3.1 points,⁵³ −7.5 points⁵⁴ and +1.1,⁵⁵ respectively. Accordingly, changes in pain intensity and disability within both experimental groups (pre- versus and post intervention) were both statistically and clinically significant, while the changes in PPT within both experimental groups were statistically significant but not clinically significant. In the control group, there was a statistically significant difference in pain intensity; however, this difference did not reach the MCID. When comparing across groups, differences in pain intensity and disability in both DN and iontophoresis groups versus the control group were both clinically and statistically significant, while those for DN versus iontophoresis groups were statistically significant but not clinically significant for pain intensity and disability. For PPT, there were both statistically and clinically significant differences between three groups. To the author’s knowledge, this is the first study to compare the effects of DN and MgSO4 iontophoresis on upper-trapezius MTrPs.

DN group

Several previous research and systematic reviews on the management of MTrPs have concluded that DN is an effective method for alleviating pain, raising PPT and improving functional impairment in patients with neck pain.^26,56–58 Although DN research is ongoing, the exact mechanisms of action of direct needling in the deactivation of MTrPs are still unknown. Furthermore, the majority of our existing knowledge of the systemic physiologic effects of DN comes directly from the acupuncture literature.^59,60

One possible explanation for the improvement in pain in the DN group may relate to “gate control theory” as needling of an MTrP stimulates large-diameter sensory afferent fibers, which can cause inhibition of neural transmission in the dorsal horn of the spinal cord and thereby block pain signals.⁶¹

In addition, inserting a needle into an MTrP and stimulating it by rotation is hypothesized to reduce pain via a variety of other mechanisms, the first of which is rapid depolarization of the affected muscle fibers, exhibited as an LTR. After the muscle has stopped twitching, spontaneous electrical activity ceases, and discomfort and dysfunction are significantly reduced.⁶² Second, Aδ nerve fiber stimulation activates enkephalinergic inhibitory dorsal horn interneurons, resulting in opioid-mediated pain suppression and pain alleviation.⁶³

Some investigations have shown that the elevated levels of bradykinin, SP and CGRP at the site of MTrPs are directly reversed by generation of a LTR after DN.⁶⁴ Another potential explanation is that DN suppresses or disables the sympathetic nervous system; MTrP patients have sympathetic hyperactivity, which can impact skin resistance by altering submotor fibers.⁶⁵ It is known that the sympathetic skin response, which is a polysynaptic reflex under spinal and supraspinal control, is responsible for the suppression of sympathetic activity following DN.⁶⁶ The autonomic nervous system and various regions of the brain cortex, thalamus, hypothalamus and limbic system are involved in the facilitation or suppression of pain.⁶⁷ Needle stimulation of active TrPs via Aδ and C fibers may be associated with modulation of activity in higher brain centers that affect the dynamic balance of supraspinal descending facilitation and autonomic nervous system inhibition. The findings of this study support the notion that descending inhibitory autonomic effects could result in local MTrP deactivation.⁶⁷

Regarding the effect of DN on muscle activity, DN decreases muscle activity by lowering the degree of overlap between actin and myosin filaments, and a precisely placed needle could offer a localized stretch to the constricted cytoskeletal structures, disentangle the myosin filaments from the titin gel at the Z-band and allow the sarcomere to restore its resting length.⁶³ This is in keeping with the findings of Chen et al.⁶⁸ and Hsieh et al.,⁶⁹ who revealed that spontaneous electrical activity (SEA) is successfully reduced when DN is applied to a MTrP and an LTR is triggered. They hypothesized that inserting a needle into the endplate region would result in increased discharges and, as a result, an immediate drop in accessible acetylcholine (ACh) reserves, with a later decrease in SEA. Another potential underlying mechanism is muscle fiber discharge following sufficient mechanical needle stimulation near the endplate area, resulting in an LTR. In addition, local ischemia and hypoxia at the core of a MTrP could be caused by sustained contractures of taut muscular bands. Needling has been shown in various studies to enhance muscle blood flow and oxygenation.^61,70,71 The local muscle response to blood flow during needle stimulation could be explained in several ways. The most probable scenario is the release of vasoactive substances such CGRP and SP, which stimulate A and C fibers via the axon reflex, resulting in small vessel vasodilation and increased blood flow.⁷²

In contrast to our findings, De Meulemeester et al. studied the short- and long-term therapeutic benefits of DN and myofascial pain release in participants suffering from myofascial neck and shoulder discomfort.⁷³ They determined that both treatment approaches have short- and long-term effects; however, DN was less effective than myofascial pain release in the treatment of myofascial neck-shoulder pain. This possible contradiction may be explained by differences in the sample, as he performed his study on only female MPS patients and did not specify the active MTrPs. Moreover, Irnich et al. examined the immediate effect of DN (compared with a sham procedure) on motion-related pain and cervical spine mobility in neck pain patients and found that DN enhanced ROM but did not improve pain-related motion.⁷⁴

Iontophoresis group

The improvements observed in this group may have been due to the ability of MgSO4 to penetrate undamaged skin, which was demonstrated by raised serum magnesium levels. Due to a high diffusion coefficient, the lower the molecular weight the deeper the drug penetration.⁷⁵ Thus, a low molecular weight is the optimum physicochemical property for transdermal administration, and MgSO4 has a low molecular weight of 120.36 g/mol.⁷⁵ It is also known that transdermal absorption of MgSO4 increases linearly with solution concentration and skin surface area. When combined with iontophoresis, the latter qualities of MgSO4 become much more effective.⁷⁶ As a result, MgSO4 may be preferred over other medications, and it can also be utilized to treat deeper structures. An increased firing threshold of myelinated and unmyelinated axons caused by magnesium ions increasing the transmembrane potential (causing hyperpolarization) is one possible explanation for the decrease in pain level. As the concentration of magnesium ions increases, the blockade of pain becomes more noticeable.⁷⁷

According to Sirvinskas and Laurinaitis, MgSO4 is a vasodilator that can reverse vasoconstriction in numerous vascular beds; this could explain why pain levels are reduced by improving blood flow to the MTrP and removing the irritating chemical that causes pain.⁷⁷ An increase in blood flow may be an indirect cause of decreased muscle activity because hypoxia is a primary cause of the creation of MTrPs, according to the energy crisis hypothesis.⁷⁸ The findings of the current study are consistent with those of Ibrahim et al.,³² who conducted a study on 60 patients and employed MgSO4 iontophoresis on upper-trapezius MTrPs and discovered a rise in PPT, which was related to a decrease in both NDI and VAS.

These findings are in agreement with those of Mizutani et al., who conducted a study on 14 healthy adult volunteers in which the analgesic impact of iontophoresis with MgSO4 was investigated.⁷⁹ Iontophoresis with a 1.0 mA electric current for 10 min was used to give 0.5 mg MgSO4 locally. A pain thermometer was used to quantify pain recognition time before, after and 5, 15, 30, 60 and 120 min following iontophoresis, and it was found that pain recognition time was dramatically extended, lasting 60 min.⁷⁹ Their findings support the theory that MgSO4 has an analgesic effect and provides good pain relief with a long duration of block duration in clinical trials. Sirvinskas and Laurinaitis investigated the use of MgSO4 in anesthesiology and found that it can be used to decrease the amount of analgesic medication required, since it improves their action, and can also be utilized as an adjuvant to anesthesia, demonstrating its usefulness in reducing pain.⁷⁷

Study limitations and recommendations

We cannot generalize about long-term effects because this study only reported the post-treatment effect of both DN and MgSO4 so. Accordingly, further research with a longer duration of follow-up is needed. Assessment of cervical ROM is also needed and the fact that we did not include it is a further limitation of this trial.

Conclusion

DN and MgSO4 iontophoresis had positive effects on PPT, NDI, VAS and muscle amplitude in the treatment of neck pain subjects with upper-trapezius active MTrPs. Directly comparing DN and MgSO4 iontophoresis, DN had superior effects on PPT, NDI, VAS and muscle amplitude.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors received no financial support for the research, authorship and/or publication of this article.

ORCID iD

Alshaymaa S Abd El-Azeim

References

Fejer

Kyvik

Hartvigsen

. The prevalence of neck pain in the world population: a systematic critical review of the literature. Eur Spine J 2006; 15: 834–848.

Hoy

Protani

, et al. The epidemiology of neck pain. Best Pract Res Clin Rheumatol 2010; 24: 783–792.

Mohandoss

Sharan

Ranganathan

, et al. Co morbidities of myofascial neck pain among information technology professionals. Ann Occup Environ Med 2014; 26: 21.

Gerwin

. Myofascial pain syndromes from trigger points. Curr Rev Pain 1999; 3: 153–159.

Donnelly

Fernandez de las Penas

Finnegan

, et al. Travell, Simons & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. 3rd ed. Philadelphia, PA: Wolters Kluwer, 2019.

San-Antolín-Gil

López-López

Becerro-de-Bengoa-Vallejo

, et al. Chapter 36—influence of psychological factors on myofascial pain. In: Rajendram

Patel

Preedy

, et al. (eds) The neurobiology, physiology, and psychology of pain. Cambridge, MA: Academic Press, 2022, pp 405–415.

Chiarotto

Clijsen

Fernandez-de-Las-Penas

, et al. Prevalence of myofascial trigger points in spinal disorders: a systematic review and meta-analysis. Arch Phys Med Rehabil 2016; 97: 316–337.

Hong

Simons

. Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points. Arch Phys Med Rehabil 1998; 79: 863–872.

Kuan

. Current studies on myofascial pain syndrome. Curr Pain Headache Rep 2009; 13(5): 365–369.

10.

Hou

Tsai

Cheng

, et al. Immediate effects of various physical therapeutic modalities on cervical myofascial pain and trigger-point sensitivity. Arch Phys Med Rehabil 2002; 83(10): 1406–1414.

11.

Moraska

Schmiege

Mann

, et al. Responsiveness of myofascial trigger points to single and multiple trigger point release massages: a randomized, placebo-controlled trial. Am J Phys Med Rehabil 2017; 96: 639–645.

12.

Gulick

. Evidence-based interventions for myofascial trigger points. Phys Med Rehabil Res 2016; 1(3): 41–47.

13.

Simons

Travell

Simons

. Travell & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Volume 1. Upper Half of Body. 2nd ed. Baltimore, MD: Williams & Wilkins, 1999, pp. 12–93.

14.

D’Ambrogio

Roth

. Positional release therapy: assessment and treatment of musculoskeletal, dysfunction. St Louis, MO: Mosby, 1997, pp. 383–387.

15.

Jones

. Strain and counter-strain. Newark, OH: American Academy of Osteopathy, 1981.

16.

Chaitow

. Effect of muscle energy technique with nontraumatic neck pain. In: Muscle energy techniques. 2nd ed. Edinburgh: Churchill Livingstone, 2001; 141, pp. 432–439.

17.

Jyothirmai

Kumar

Raghavkrishna

, et al. Effectiveness of integrated neuromuscular inhibitory technique (INIT) with specific strength training exercises in subjects with upper trapezius trigger points. Int J Physiother 2015; 2(5): 759–764.

18.

Lewit

. The needle effect in the relief of myofascial pain. Pain 1979; 6: 83–90.

19.

Vulfsons

Ratmansky

Kalichman

. Trigger point needling: techniques and outcome. Curr Pain Headache Rep 2012; 16: 407–412.

20.

Lee

Lin

Hong

. The effectiveness of simultaneous thermotherapy with ultrasound and electrotherapy with combined AC and DC current on the immediate pain relief of myofascial trigger points. J Musculosk Pain 1997; 5: 81–90.

21.

Gam

Warming

Larsen

, et al. Treatment of myofascial trigger points with ultrasound, combined with massage and exercise-a randomized controlled trial. Pain 1998; 77: 73–79.

22.

Pontinen

Airaksinen

. Evaluation of myofascial pain and dysfunction syndromes and their response to low level laser therapy. J Muskuloskele Pain 1995; 3(2): 149–154.

23.

Kaya

Kamali

Ardicoglu

, et al. Direct current therapy with/without lidocaine iontophoresis in myofascial pain syndrome. Bratisl Lek Listy 2009; 110(3): 185–191.

24.

Rayegani

Bayat

Bahrami

, et al. Comparison of dry needling and physiotherapy in treatment of myofascial pain syndrome. Clin Rheumatol 2014; 33(6): 859–864.

25.

Liamas-Ramos

Pecos-Martin

Gallego

, et al. Comparison of short-term outcome between trigger point dry needling and trigger point manual therapy: a randomized clinical trial. J Orthop Sports Phys Ther 2014; 44: 852–861.

26.

Kietrys

Palombaro

Azzaretto

, et al. Effectiveness of dry needling for upper-quarter myofascial pain: a systematic review and meta-analysis. J Orthop Sports Phys Ther 2013; 43: 620–634.

27.

Liu

Huang

Liu

, et al. Effectiveness of dry needling for myofascial trigger points associated with neck and shoulder pain: a systematic review and meta-analysis. Arch Phys Med Rehabil 2015; 96(5): 944–955.

28.

Shah

Danoff

Desai

, et al. Biochemicals associated with pain and inflammation are elevated in sites near to and remote from active myofascial trigger points. Arch Phys Med Rehabil 2008; 89: 16–23.

29.

Shah

Philips

Danoff

, et al. A novel microanalytical technique for assaying soft tissue demonstrates significant quantitative biochemical differences in 3 clinically distinct groups: normal, latent, and active. Arch Phys Med Rehabil 2003; 84: A4.

30.

Hong

. Persistence of local twitch response with loss of conduction to and from the spinal cord. Arch Phys Med Rehabil 1994; 75: 12–16.

31.

Clijsen

Taeymans

Baeyens

, et al. The effects of iontophoresis in the treatment of musculoskeletal disorders -a systematic review and meta-analysis. Drug Deliv Lett 2012; 2(3): 180–194.

32.

Ibrahim

Abdel Raoof

Mosaad

, et al. Effect of magnesium sulfate iontophoresis on myofascial trigger points in the upper fibres of the trapezius. J Taibah Univ Med Sci 2021; 16(3): 369–378.

33.

Mizutani

Taniguchi

Miyagawa

, et al. The analgesic effect of iontophoresis with magnesium sulfate. Masui 1995; 44(8): 1076–1079.

34.

Schulz

Altman

Moher

, et al. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ 2010; 340: c332.

35.

Simons

Travell

Simons

. Travell & Simons’ myofascial pain and dysfunction: the trigger point manual, volume 1: upper half of body. 2nd ed. Baltimore, MD: Williams & Wilkins, 1998.

36.

Gary

Hodgson

. The effect of manual pressure release on myofascial trigger points in the upper trapezius muscle. J Bodyw Mov Ther 2005; 9(4): 248–255.

37.

Salavati

Akhbari

Takamjani

, et al. Reliability of the upper trapezius muscle and fascia thickness and strain ratio measures by ultrasonography and sonoelastography in participants with myofascial pain syndrome. J Chiropr Med 2017; 16(4): 316–323.

38.

American Physical Therapy Association. Physical therapists & the performance of dry needling: an educational resource paper. Alexandria, VA: American Physical Therapy Association, 2012.

39.

White

Cummings

Filshie

. An introduction to western medical acupuncture. Edinburgh: Churchill Livingstone, 2008.

40.

Myburgh

Larsen

Hartvigsen

. A systematic, critical review of manual palpation for identifying myofascial trigger points: evidence and clinical significance. Arch Phys Med Rehabil 2008; 89(6): 1169–1176.

41.

Simons

. Clinical and etiological update of myofascial pain from trigger points. J Musculoskele Pain 1996; 4: 93–122.

42.

Baldry

. Superficial versus deep dry needling at myofascial trigger point sites. J Musculoskele Pain 1995; 3: 117–126.

43.

Teslim

Olaogun

MOB

Obembe

, et al. Electromotive drug administration of magnesium sulphate on spastic biceps brachii of stroke survivors: a technical report. J Med Med Sci Res 2013; 2(4): 38–43.

44.

Boonstra

Preuper

Reneman

, et al. Reliability and validity of the visual analogue scale for disability in patients with chronic musculoskeletal pain. Int J Rehabil Res 2008; 31(2): 165–169.

45.

McLean

. The effect of postural correction on muscle activation amplitudes recorded from the cervicobrachial region. J Electromyogr Kinesiol 2005; 15(6): 527–535.

46.

Ekstrom

Soderberg

Donatelli

. Normalization procedures using maximum voluntary isometric contractions for the serratus anterior and trapezius muscles during surface EMG analysis. J Electromyogr Kinesiol 2005; 15(4): 418–428.

47.

Khan

Bhati

, et al. Influence of forward head posture on cervicocephalic kinesthesia and electromyographic activity of neck musculature in asymptomatic individuals. J Chiropr Med 2020; 19(4): 230–240.

48.

Nicoletti

Spengler

Läubli

. Physical workload, trapezius muscle activity, and neck pain in nurses’ night and day shifts: a physiological evaluation. Appl Ergon 2014; 45(3): 741–746.

49.

Kinser

Sands

Stone

. Reliability and validity of a pressure algometer. J Strength Cond Res 2009; 23(1): 312–314.

50.

Shaheen

Omar

Vernon

. Cross-cultural adaptation, reliability, and validity of the Arabic version of Neck Disability Index in patients with neck pain. Pain 2013; 38(10): 609–615.

51.

Vernon

Mior

. The Neck Disability Index: a study of reliability and validity. J Manipul Physiol Ther 1991; 14(7): 409–415.

52.

MacDermid

Walton

Avery

, et al. Measurement properties of the neck disability index: a systematic review. J Orthop Sports Phys Ther 2009; 39(5): 400–417.

53.

Katz

Paillard

Ekman

. Determining the clinical importance of treatment benefits for interventions for painful orthopedic conditions. J Orthop Surg Res 2015; 10: 24.

54.

Young

Walker

Strunce

, et al. Responsiveness of the Neck Disability Index in patients with mechanical neck disorders. Spine J 2009; 9(10): 802–808.

55.

Walton

Levesque

Payne

, et al. Clinical pressure pain threshold testing in neck pain: comparing protocols, responsiveness, and association with psychological variables. Phys Ther 2014; 94(6): 827–837.

56.

Tekin

Akarsu

Durmuş

, et al. The effect of dry needling in the treatment of myofascial pain syndrome: a randomized double-blinded placebo-controlled trial. Clin Rheumatol 2013; 32(3): 309–315.

57.

Tough

White

Cummings

, et al. Acupuncture and dry needling in the management of myofascial trigger point pain: a systematic review and meta-analysis of randomised controlled trials. Eur J Pain 2009; 13(1): 3–10.

58.

Edwards

Knowles

. Superficial dry needling and active stretching in the treatment of myofascial pain–a randomised controlled trial. Acupunct Med 2003; 21: 80–86.

59.

Leung

. Neurophysiological basis of acupuncture-induced analgesia–an updated review. J Acupunct Meridian Stud 2012; 5(6): 261–270.

60.

Zhao

. Neural mechanism underlying acupuncture analgesia. Prog Neurobiol 2008; 85(4): 355–375.

61.

Cagnie

Barbe

De Ridder

, et al. The influence of dry needling of the trapezius muscle on muscle blood flow and oxygenation. J Manipul Physiol Ther 2012; 35(9): 685–691.

62.

Garcia-de-Miguel

Pecos-Martin

Larroca-Sanz

, et al. Short-term effects of PENS versus dry needling in subjects with unilateral mechanical neck pain and active myofascial trigger points in levator scapulae muscle: a randomized controlled trial. J Clin Med 2020; 9(6): 1665.

63.

Dommerholt

. Dry needling in orthopedic physical therapy practice. Orthopaedic Practice 2004; 16(3): 15–20.

64.

Shah

Heimur

. New frontiers in the pathophysiology of myofascial pain. Pain 2012; 22(2): 26–30.

65.

Bolel

Hizmetli

Akyüz

. Sympathetic skin responses in reflex sympathetic dystrophy. Rheumatol Int 2006; 26(9): 788–791.

66.

Vetrugno

Liguori

Cortelli

, et al. Sympathetic skin response: basic mechanisms and clinical applications. Clin Auton Res 2003; 13: 256–270.

67.

Sakai

Hori

Umeno

, et al. Specific acupuncture sensation correlates with EEGs and autonomic changes in human subjects. Auton Neurosci 2007; 133: 158–169.

68.

Chen

Chung

Hou

. Inhibitory effect of dry needling on the spontaneous electrical activity recorded from myofascial trigger spots of rabbit skeletal muscle. Am J Phys Med Rehabil 2001; 80(10): 729–735.

69.

Hsieh

Chou

Joe

, et al. Spinal cord mechanism involving the remote effects of dry needling on the irritability of myofascial trigger spots in rabbit skeletal muscle. Arch Phys Med Rehabil 2011; 92(7): 1098–1105.

70.

Kubo

Yajima

Takayama

, et al. Changes in blood circulation of the contralateral achilles tendon during and after acupuncture and heating. Int J Sports Med 2011; 32(10): 807–813.

71.

Kubo

Yajima

Takayama

, et al. Effects of acupuncture and heating on blood volume and oxygen saturation of human Achilles tendon in vivo. Eur J Appl Physiol 2010; 109(3): 545–550.

72.

Sato

Shimura

, et al. Calcitonin gene-related peptide produces skeletal muscle vasodilation following antidromic stimulation of unmyelinated afferents in the dorsal root in rats. Neurosci Lett 2000; 283(2): 137–140.

73.

De Meulemeester

Castelein

Coppieters

, et al. Comparing trigger point dry needling and manual pressure technique for the management of myofascial neck/shoulder pain: a randomized clinical trial. J Manipul Physiol Ther 2017; 40(1): 11–20.

74.

Irnich

Behrens

Gleditsch

, et al. Immediate effects of dry needling and acupuncture at distant points in chronic neck pain: results of a randomized, double-blind, sham-controlled crossover trial. Pain 2002; 99(1–2): 83–89.

75.

Ruela

Perissinato

Sousa Lino

, et al. Evaluation of skin absorption of drugs from topical and transdermal formulations. Braz J Pharm Sci 2016; 52(3): 527–544.

76.

Chu

Bruyninckx

Neuhauser

. Transdermal magnesium sprays for myofascial pain relief and facilitation of autonomous twitch elicitation with electrical twitch-obtaining intramuscular stimulation (ETOIMS). Eur J Pharm Med Res 2018; 5(2): 148–156.

77.

Sirvinskas

Laurinaitis

. Use of magnesium sulphate in anesthesiology. Medicina (Kaunas) 2002; 38(7): 695–698.

78.

Borg-Stein

Simons

. Focused review: myofascial pain. Arch Phys Med Rehabil 2002; 83(3): S40–S49.

79.

Mizutani

Taniguchi

Miyagawa

.et al The analgesic effect of iontophoresis with magnesium sulfate. Masui 1995; 44(8): 1076–1079.