Effectiveness of Percutaneous Microelectrolysis in the Decrease of Pain in Myofascial Trigger Points: Evaluation Through Algometry and Visual Analog Scale. Randomized Controlled Trial.
Phase: NA
Conditions: Myofascial Trigger Point Pain (MTrP)
Sponsor: Quiropraxia y Equilibrio

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STUDY PROTOLOL 
Identifiers: NCT03636386 
Protocol ID: 60312069 
Date of the document: August 15, 2019 
Brief 
Title: Percutaneous Microelectrolysis on Myofascial 
Trigger Points Pain. (MEP) 
Official Title: Effectiveness of Percutaneous Microelectrolysis in 
the Decrease of Pain in Myofascial Trigger Points: Evaluation 
Through Algometry and Visual Analog Scale. Randomized 
Controlled Trial. 
 
 
 
ABSTRACT. 
 
Background: Percutaneous electrotherapy is today a therapeutic alternative in 
musculoskeletal conditions. In that sense, percutaneous microelectrolysis (MEP) stands out 
as treatment for tendinopathies and musculoskeletal pain, such as myofascial trigger points 
(MTrPs), although more studies are needed to support it. 
Objective: Investigate effectiveness of MEP in reducing painful pressure threshold (PPT) 
and pain intensity (PI) in MTrPs. 
Method: Controlled randomized clinical trial. Research was performed at Physiotherapy 
Laboratory of Andrés Bello University. Participants were forty-eight volunteers with MTrPs 
presence in upper trapezius muscle. Both groups received a baseline ultrasound treatment, 
adding MEP to experimental group. Intervention consisted of a MEP intervention and tree 

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reevaluation sessions (at day one, three and seven). Direct current was delivered with 
acupuncture needle directly to MTrP and PPT and PI was reevaluated before and after 
application. Main outcomes were PPT and PI differences (PPTdiff and PIdiff) between 
evaluation sessions. 

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Results: MEP demonstrated positive changes increasing PPT (PPTdiff1-1, p=0,0000, 
PPTdiff2-1, p=0,0000, PPTdiff3-1, p=0,0000) and decreasing PI (PIdiff1-1, p=0,0001, 
PIdiff2-1, p=0,0001, PIdiff3-1, p=0,0008) in experimental group, and significant differences 
in PPT at second reevaluation session compared to control group (PPTdiff2-1, p=0,0032). 
Conclusion: MEP is a good analgesic treatment for MTrPs compared to therapeutic 
ultrasound, although neither of two therapies seems to be better than other in long term. Two 
treatments improvements PPT and PI, so MEP can be considered as an effective alternative 
treatment for MTrPs pain. 
Keywords: electrotherapy; electrolysis; pain threshold; myofascial pain syndromes; analog 
visual scale. 

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Material and Methods 
 
Present design represents a randomized double-blind clinical trial. Study was approved on 
June 18, 2019 by Eastern Metropolitan Health Service of Santiago (SSMO) ethics committee. 
Study was registered at www.clinicaltrials.gov. Participants were divided in two groups 
assessed in both presences of MTrPS in shorter upper trapezius muscle. It was recording the 
PPT and PI before and after intervention. Both groups received therapeutic ultrasound as 
baseline treatment. Experimental group received microelectrolysis additionally. A 
reassessment of PPT and PI was done on day one, three and seven post intervention. 
Subjects. forty-eight healthy volunteers were recruited (23 men, 25 women, average age 22 
years). Participants were students of Science Rehabilitation Faculty (SRF) of Andrés Bello 
University, Santiago de Chile. Number of participants was selected by convenience. An 
invitation was extended to students through formal communication channels (mailing), 
student representatives and social networks, summoning two hundred and seven potential 
participants. Selection was based on a survey whose first part was structured in relation to 
general demographic participant’s data, including name, age, sex, body mass index (BMI), 
career year, and personal information contact (e-mail and cell phone number). Second part 
of survey consisted of closed questions constructed by eligibility criteria. Inclusion criteria 
considered participants over 18 years old, students of SRF and positive hypersensitive 
MTrPs. Exclusion criteria include neck or shoulders pathologies in the last 6 months (as 
fractures, sprains, tendinopathies, dislocations or muscle tears), cervical pain, sensitivity 
alterations such as hyposthesia, anesthesia or hyperesthesia in neck, shoulders and/or arms, 
wounds or skin alterations in shoulder as psoriasis, scars or keloids, fear to electrotherapy 
application and analgesic pharmacological treatment at recruitment time (non-steroidal anti- 

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inflammatory or steroidal drugs). Elimination criteria considered non-tolerance 
electrotherapy intervention and non-completion of evaluation protocol (attendance at all 
scheduled sessions). Demographic data were tabulated in Microsoft excel® 2016 program 
(Table 1, characterization of study groups). 
Variable MEP (n = 24) Control (n = 24) 
p-value 
Sample 
distribution 
sex (%) 
men 
women 
11 (22,9%) 
13 (27,1%) 
12 (25,0%) 
12 (25,0%) 
p = 0,7730* 
Normal* 
Age (mean,+/-DS) 
22,5+/-1,9 
22,0+/-1,6 
p = 0,2993** 
Normal** 
BMI (Kg/m2) 
(mean +/-DS) 
24,5 +/- 3,4 
22,9+/-2,3 
p =0,0616** 
Normal** 
Short trapezius 
muscle laterality 
(%) 
right 
left 
17 (70,8%) 
7 (29,2%) 
20 (83,3%) 
4 (16,7%) 
p = 0,2470*** 
Normal*** 
SP-AC distance 
(cm) 
(mean+/-DS) 
9,2+/-1,8 
8,4+/-1,7 
p = 0,1241** 
Normal** 
PPTpre 1 
(Kg/cm2) 
(mean +/-DS) 
1,4+/-0,2 
1,4+/-0,2 
p = 0,5734** 
Normal** 
PIpre1 (mm) 
(mean +/- DS) 
32,1+/-13,6 
31.4 +/- 15.1 
p = 0,8729** 
Normal** 
Table 1. Characterization of study groups.Variable sex and short trapezius muscle laterality is 
represented in frequencies (%). Values for continuous variables are in means with their 
corresponding standard deviation (DS). Variable sex was analyzed using xi2 test*. For the 
analysis of continuous variables, the T-Student test was used**. Variable short trapezius 
laterality was analyzed with the F-Fisher test***. 
BMI: body mass index, SUTL: short upper trapezius muscle laterality, SP-AC distance: 
distance spinous process from C7 to acromion, PPTpre: pain pressure threshold pre 
intervention at day one, PIpre: pain intensity pre intervention at day one. p > 0.05**** 
Secondary variables as short upper trapezius muscle laterality (SUTL) and sex were 
represented as frequencies, while MTrP location distance (MLD) and age was represented as 
median and BMI in averages. Primary variables included PPT and PI pre-intervention 

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(PPTpre and PIpre) were expressed as averages with their corresponding standard deviation 
(x, SD). Data were analyzed to compare homogeneity of groups with STATAv.13 program. 
Equipment. GYMNA´s COMBI 500 electric stimulator was used for ultrasound application 
at 1MHz, 1.5Watts/cm2, 100% duty cycle, 5cm2 ERA and 15 minutes.24 SVELTIA´s DC 
equipment was used for MEP application. It was used a dispersing electrode (area 28.26cm2) 
and an acupuncture needle (0.3x25millimeters). Circuit was closed by placing dispersing 
electrode in contralateral arm to trapezius muscle to be treated. Current intensity was 600µA 
at the needle (current density of 1.71mA/cm2). 
Measurement tools. BASELINE® pressure algometer was used to measure PPT (1cm2 
 
surface area).25 Algometry was applied after shortness upper trapezius assessment by placing 
algometer at the MTrP exerting a perpendicular pressure until user reported pain. Kilograms 
of pressure per square centimeter (Kg/cm2) was registered. PI was evaluated with VAS. VAS 
was applied after algometry recording pain perceived with algometry test. 
 
 
Procedure. 
 
1. Participants 
 
207 surveys were analyzed obtaining 59 potential participants, dropping out five. 54 
participants agreed to participate and gave their written consent. Six participants were 
excluded due absence of MTrPS, obtaining 48 participants (23 men, 25 women). Principal 
investigator assigned a number to each participant to perform randomization. Conformation 
of groups was carried out by simple randomization by dark envelopes. Participants didn´t 
know assigned group and were individually cited in following two weeks to physiotherapy 
laboratory of SRF to be evaluated. 

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2. Groups. 
 
Sample was divided by a simple randomization process performed with a random number 
table, assigned participants to one of two study groups. Sequence of randomization and 
participants of each group was only known by principal investigator. Working groups were 
designated as experimental (MEP group, n = 24) and control group (n = 24). None subjects 
knew the treatment that would be applied. Each participant was evaluated registering their 
age, BMI and SUTL. Location of MTrP was determined at shortness trapezius muscle, taking 
as reference a line between superior acromion´s midpoint surface and C7 spinous process 
(PE-AC distance). Algometry and VAS was subsequently applied obtaining the PPT and PI 

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pre intervention (PPTpre y PIpre). Variables described were compared between groups to 
assess the homogeneity of them (Table 1). Data reflect the homogeneity of groups at the 
beginning of the study. 
 
 
3. Pain pressure threshold (PPTpre) and pain intensity (PIpre) preintervention evaluation. 
 
A blinded physiotherapist registered PPT and PI before and after participant’s intervention. 
Evaluation station consisted of a chair and a table with the algometer and VAS. The subjects 
sat with their backs supported with both feet on the floor. Evaluator proceeded to measure 
both upper trapezius muscles length manually, choosing the shortest. Subsequently a line was 
drawn between C7 spinous process and upper acromion midpoint face of ipsilateral shoulder. 
Most sensitive palpation´s point was searched on the line and then marked with a cross 
measuring distance from C7 to this point. Algometry was applied at selected point exerting 
a perpendicular pressure until the user referred pain. Participants were instructed to raise 
slightly contralateral hand when feeling pain in algometry test. A PPT less than 3Kg/cm2 was 
recorded as a positive MTrP. This was same protocol used for participants pre-selection 
where 6 of 54 were excluded. Next pain intensity was assessed with VAS, recording pain 
magnitude in millimeters produced by algometry. PPTpre and PIpre data were tabulated in 
Microsoft excel® program sheet. 
 
 
4. Therapeutic ultrasound application. 
 
Participants of both groups received a therapeutic ultrasound treatment. Experimental group 
received first ultrasound and subsequently MEP, while control group was treated only with 
ultrasound. Ultrasound intervention protocol was performed in the same way for both groups. 
Application was performed in an adjoining room by another physiotherapist who didn´t know 

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groups. Treatment was carried out with participant in sitting position applying ultrasound at 
sensitive point marked by examiner of evaluation station. Ultrasound therapy was delivery 
at 1MHz, 1.5 Watts/cm2, 100% duty cycle (SATP: 1.5Watts/cm2 and SATA:1.5W/cm2), 
ERA 5cm2 and 15 minutes.24 Once ultrasound intervention was finished, participants of MEP 
group were taken to microelectrolysis box, while participants of control group returned to 
evaluation station. 
 
 
5. Microelectrolysis application. 
 
Microelectrolysis was performed by another physiotherapist. Before intervention, puncture 
area was cleaned with alcohol. Procedure was performed with latex gloves. Acupuncture 
needle was introduced perpendicular to demarcated point of trapezius with 0.14mA intensity. 
Dispersing electrode was placed in external surface of contralateral arm once chosen 
trapezius muscle. Inside tissue intensity was raised to 0.6mA. Each participant was instructed 
to indicate to physiotherapist appearance of burning, pain or great local pressure in order to 
pause emission. Emission time was recorded until symptoms appeared, indicating T1 time, 
pausing emission for 30 seconds. Then a second emission was made until participant referred 
again discomfort symptoms. Second emission time was recorded as T2, pausing application 
again for 30 seconds. Third and last emission was delivered for same time obtained for T2 or 
if discomfort appeared before completing that time. 
 
 
6. Pain pressure threshold (PPTpre) and pain intensity (PIpre) postintervention evaluation. 
 
Completing intervention, participants returned to evaluation station. Evaluator repeated the 
same assessment protocol made before ultrasound and MEP application, recording PPT and 
PI postintervention. Variables PPTdiff1-1 and PIdiff1-1 were created based on differences 

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between algometry and pain intensity measurements before and after intervention. 
Participants were cited for a reevaluation on day three and seven obtained variables PPT2, 
PI2, PPT3 and PI3. This allowed to create PPTdiff2-1, PPT3-1, PIdiff2-1 and PIdiff3-1 
variables, that represented differences obtained between the measurements of days three and 
seven with those obtained on day one before intervention.