Comparing Deep and Superficial Dry Needling for Neck Pain: An Ultrasound and EMG Study

The musculoskeletal system, the largest in the human body, is highly susceptible to pain, affecting up to 80% of individuals (Bourgaize et al., 2018; Weller et al., 2018). Among these disorders, myofascial pain syndrome (MPS) is one of the most prevalent and costly conditions, affecting approximately 85% of the general population at least once in their lifetime (Pal et al., 2014). The economic burden of MPS is substantial, with estimated costs of 522 million dollars in Canada and around 57.51 million dollars in the United States (Berger et al., 2007). MPS was described by Simons and Travell (1983) as a regional pain condition associated with one or more myofascial trigger points (MTrPs)-hyperirritable nodules in taut muscle bands (Barbero et al., 2019). These trigger points may result from trauma or repetitive strain, producing an energy crisis characterized by motor endplate dysfunction, sustained contraction, and local hypoxia (Zhang et al., 2020).

The upper back region is the most frequent site of MTrPs; 65% occur in the levator scapulae and trapezius muscles, and 50% in the suboccipital muscles (Lluch et al., 2015). Notably, 38.8% of individuals with neck pain have MTrPs in the upper trapezius (Cohen \& Hooten, 2017). Electromyography (EMG) studies revealed that MTrPs exhibit higher amplitude and longer duration of motor unit potentials compared with normal muscle (Audette et al., 2004; Wytrążek et al., 2011). Ultrasonographic investigations found band-like hypoechoic regions, reduced entropy, and increased stiffness in active MTrPs (Ballyns et al., 2012; Turo et al., 2013; Adigozali et al., 2017; Ball et al., 2022). Doppler ultrasound studies demonstrated increased retrograde diastolic blood flow, indicating altered local circulation (Sikdar et al., 2010; Ballyns et al., 2011). In addition, microdialysis research revealed lower pH and elevated levels of substance P and calcitonin gene-related peptide in active MTrPs, reflecting a pro-inflammatory biochemical milieu (Shah et al., 2005; Shah et al., 2008; Gerdle et al., 2014).

Among treatment modalities, dry needling (DN)-introduced by Lewit (1979)-is one of the most widely used. Two main approaches exist: superficial DN, involving shallow insertion without reaching the MTrP (Baldry, 2002; Legge, 2014), and deep DN, in which the needle penetrates into the muscle to mechanically deactivate the MTrP (Griswold et al., 2019). Superficial DN is thought to activate Aδ nerve fibers that inhibit nociceptive transmission (Bowsher, 1998; Karavis, 1997; Baldry, 2002), whereas deep DN may disrupt dysfunctional endplates, normalize acetylcholine activity, and improve blood flow and oxygenation (Fernández-de-Las-Peñas \& Nijs, 2019; Cagnie et al., 2012).

Although both techniques reduce pain and disability effectively (Sedighi et al., 2017; Sarrafzadeh et al., 2018; Ezzati et al., 2019; Griswold et al., 2019; Hoseininejad et al., 2023), no studies have compared their effects on ultrasound-measured muscle properties and electromyographic activity. Therefore, the present study aims to compare deep versus superficial dry needling on the ultrasound and EMG characteristics of MTrPs in the upper trapezius among patients with neck pain.

Objective:

To investigate impact of deep and superficial dry needling on the ultrasound properties and electromyography muscle activity of trapezius muscle points in patients with neck pain by conducting randomized clinical trial.

Expected Results:

In this study, deep dry needling will be more affective to make change in the ultrasound properties of the myofascial trigger points and electromygraphic activity than superficial dry needling and there will be no correlations between primary outcomes (ultrasonographic and EMG findings) and secondary outcomes (pain intensity and neck disability).

Materials and Methods:

Title:

Effect of deep vs. superficial dry needling on myofascial trigger point characteristics in neck pain: A triple-blind randomized controlled trial with ultrasonography and electromyography.

Study Design:

Triple-blind Randomized Clinical Trial (RCT)

Sample size calculation and participants:

The sample size calculation was conducted using G*Power 3.1.9.6 statistical software (G*Power©; University of Dusseldorf, Dusseldorf, Germany), employing the subsequent parameters: analysis of variance, repeated measures design, within-between interaction, a moderate effect size (f) of 0.25, a significance level (alpha) of 0.05, statistical power (1-β) of 90%, a correlation among repeated measures (rmcorr) of 0.5, involving 2 groups and 3 measurements (time points), and incorporating a non-sphericity correction (Є) of 1. The estimated required sample size was determined to be 18 participants per group. Considering an anticipated attrition rate of 20%, a total number of 44 participants, with 22 participants per group was deemed necessary.

The study sample will consist of patients with neck pain and at least one active MTrP in the upper trapezius muscle that meets the following qualifying criteria: tender point, presence of a palpable taut band, presence of familiar pain during compression on the tender point and/or referred pain recognized by the patient as a "familiar" sensation and restricted range of motion of the neck (Fernández-de-Las-Peñas and Dommerholt, 2018). The identification of MTrPs by both different raters and the same rater has been observed to be moderately to highly reliable (Mayoral del Moral et a., 2018; Gerwin et al., 1997). Identified MTrPs must directly induce pain in the specific region and generate a localized twitch response on palpation (Gerwin et al., 1997; Myburgh et al., 2011). These diagnostic criteria were developed by Simons and Travell, and an international consensus was reached on their use in a Delphi study published in 2018 (Simons et al., 1999; Fernández-de-Las-Peñas and Dommerholt, 2018). To qualify for participation, patients will need to meet the following inclusion criteria: aged 18-65 years, have cervical pain, and have at least one active MTrP in the upper trapezius muscle. The exclusion criteria will be as follows: whiplash injury, prior cervical surgery, cervical radiculopathy, fibromyalgia, analgesic treatment (e.g., physiotherapy or medication) within the week preceding participation, psychiatric disorders, or any contraindication to dry needling (e.g., needle phobia and/or anticoagulant use).

Setting and Ethical Considerations:

Potential participants will be screened for eligibility and data will be collected at Qatif Central Hospital, Eastern Province, Saudi Arabia. This study will be conducted in accordance with the principles outlined in the Declaration of Helsinki. The study protocol will be approved by Gatif Central Hospital. Each participant will be provided with both written and verbal information about the study. Prior to their participation in the study, each participant will submit a signed informed consent form. This study will be registered on the ClinicalTrials.gov platform, and the reporting will meet the CONSORT guidelines. The dry needles utilized in this study have been approved by the Saudi Food and Drug Authority (SFDA) with authorization number MDMA-1-2020-1097.

Risk Factors:

Dry needling is a therapeutic technique that involves the insertion of a thin, solid filament needle into specific points within the muscle tissue. While it shares similarities with acupuncture, dry needling is primarily performed by healthcare professionals like physiotherapists to address musculoskeletal conditions.

Dry needling is generally considered safe and its use in the medical field is well established (Gattie et al., 2020). However, dry needling does carry some risks, albeit minor. Common adverse events include soreness, bruising, or bleeding at the needle insertion site. These effects, however, are typically mild and temporary, often resolving within a few days (Zugasti et al., 2014; Martín-Pintado-Zugasti et al., 2018). To minimize risks, healthcare providers take several precautions:

• Sterile techniques are employed to prevent infection.
• Patients are positioned comfortably to reduce discomfort and the likelihood of complications.
• Pressure is applied to the needle insertion site to control bleeding.
• Post-treatment care, such as ice or stretching, can help alleviate soreness.
• Patients are advised to rest for a specified period after treatment to allow the body to recover.

Randomization:

The participants will be randomly assigned to one of two groups: deep dry needling group or superficial dry needling group. An independent researcher will use the Research Randomizer platform (version 4.0) to generate a randomized series of numbers, which will be written on individual cards. The card will be then folded and placed in sealed opaque envelopes to ensure that the contents are concealed. The participants will then select an envelope to determine their intervention allocation. Consequently, each participant will be assigned to the relevant intervention group. The assessors and participants will be unaware of the group assignment, and the therapist will be unaware of the outcome measures.

Intervention:

The primary investigator who is certified therapist in dry needling with five years of experience will perform the intervention. Both deep and superficial dry needling will be administered twice per week for 2 weeks, with at least 48 hours between sessions (Zugasti et al., 2014; Martín-Pintado-Zugasti et al., 2018), for a total of 4 sessions (Gattie et al., 2020). Patients will then be followed up after 4 weeks to measure the outcomes. Tender point, presence of a palpable taut band, presence of familiar pain during compression on the tender point, referred pain recognized by the patient as a "familiar" sensation, and restricted range of motion of the neck. The identification of MTrPs by both different raters and the same rater has been observed to be moderately to highly reliable (Mayoral del Moral et a., 2018; Gerwin et al., 1997). Identified MTrPs must directly induce pain in the specific region and generate a localized twitch response on palpation (Gerwin et al., 1997; Myburgh et al., 2011). These diagnostic criteria were developed by Simons and Travell, and an international consensus was reached on their use in a Delphi study published in 2018 (Simons et al., 1999; Fernández-de-Las-Peñas and Dommerholt, 2018).

Deep dry needling intervention. The patient will be asked to lie in the supine position and identify the active MTrPs in the upper trapezius muscle. If many active MTrPs are found, the therapist will choose the one that causes the most severe symptoms, as reported by the patient. Alcohol will be used to clean the skin before a single-use, sterile, dry needle with a diameter of 0.25 mm and a length of 50 mm (APS, C/Casp158, Barcelona, Spain) will be deeply inserted into the MTrP using the fast-in and fast-out technique that was described by Hong (1994, 1997, 2006). After the initial local twitch response is observed, the needle will be moved vertically up and down for three to five repetitions (Abbaszadeh-Amirdehi et al., 2016; Behrangrad et al., 2020).

Superficial dry needling intervention. The active MTrPs in the upper trapezius muscle will be identified while the patient is in the supine position. Then, a single-use, sterile, dry needle with a diameter of 0.25 mm and a length of 15 mm (APS, C/Casp158, Barcelona, Spain) will be inserted using the fast-in and fast-out technique that was described by Hong (1994, 1997, 2006)

Outcome Measures:

Measure outcomes will be collected at three time of points: baseline, post-treatment (end of week 2), and 4-week follow-up. In our study, the primary clinical endpoint prompting withdrawal of participants is bleeding at the needle site.

Primary Outcome Measures:

These outcome measures will be measured at baseline, immediately post-treatment (end of week 2) and 4 weeks post-treatment.

Ultrasonography:

An Ultrasound (model LOGIQ E9 R6, GE Medical Systems Ultrasound and Primary Care Diagnostics, LLC, Wauwatosa, WI, USA) will be used to examine the upper trapezius muscle MTrP characteristics such as stiffness, thickness and speed of blood flow. The participants will be instructed to maintain a relaxed upright posture while sitting in a chair with their forearms resting in a downward-facing position on the chair armrests. A musculoskeletal sonographer with seven years of experience will capture three types of images:

1. Shear wave elastography will be used to measure tissue stiffness. Images will be obtained with the transducer positioned longitudinal to the muscle fibers. Multiple characteristics, such as Young's modulus (kPa) and local shear wave speed (m/s) will be measured. This technique has moderate inter-rater reliability level (ICC= 0.74) and inter-session reproducibility (ICC = 0.66-0.71) and good to excellent intra-session repeatability (ICC = 0.82-0.91)
2. B-mode sonography measures the thickness of the upper trapezius muscle by calculating the greatest distance between the lower and upper boundaries of the muscle, expressed in millimeters. The ultrasonic probe will be positioned in alignment with the muscle fibers of the upper trapezius muscle. The MTrP should appear as a concentrated area with reduced echogenicity (darker) and an uneven echotexture (Taheri et al., 2016; Adigozali et al., 2017). The sensitivity and specificity of the ultrasonographic assessment of MTrPs in the trapezius muscle are 91% and 75%, respectively, and inter-rater reliability is excellent (ICC = 0.94) (Taheri et al., 2016; Adigozali et al., 2017).
3. Doppler ultrasonography visualizes blood vessels and measures the speed of blood flow at both active MTrPs and muscle throughout both the systolic and diastolic periods. The sonographer will use the ultrasound transducer to apply two distinct levels of pressure to the muscle fibers of the upper trapezius muscle. The first level involves minimum pressure, with the transducer barely making contact with the skin surface. The second level provides moderate pressure and visible squeezing of the muscle. The peak systolic velocity (PSV; m/s), end diastolic velocity (EDV; m/s or cm/s), and resistance index (RI; ratio or percentage) (Adigozali et al., 2017) will be calculated. The inter-rater reliability of doppler ultrasound is moderate to excellent (ICC = 0.67-0.87) (Sikdar et al., 2010; Adigozali et al., 2017).

Surface Electromyography:

In this study, Delays Trigno Wireless EMG system (Delays Incorporations, 23 Strathmore Road Natick, MA 01760 USA) will be used to measure muscle activity dysfunction, particularly in muscles with active MTrPs. The raw EMG signals underwent analog-to-digital conversion with a resolution of 16 bits with a sampling rate of 1500 Hz. Additionally, the signals were pre-amplified with an overall gain of 500, a common mode rejection ratio of 100 dB, and a signal-to-noise ratio of less than 1 microvolt (μV) root mean square (RMS) baseline noise (De Meulemeester et al., 2017). As the patient remained seated on a chair, the skin will first be shaved, scrubbed, and cleaned with alcohol to reduce skin impedance. Next, three bipolar surface electrodes will be used, two of which will be positioned medially and laterally relative to the MTrP location, namely at the midpoint between the posterolateral edge of the acromion and the spinous process of the seventh cervical vertebra. The distance between the electrodes will be 20 mm. The third electrode will be used as reference electrode and will be positioned on the affected side of the body over the clavicle (De Meulemeester et al., 2017; Ustun et al., 2024). The accuracy of the placement of the electrodes will be verified via visual examination of the sEMG signals shown on the computer screen (Hermens et al., 2000). Patients will be received instructions to keep their trapezius muscle in a rested state for a duration of 6 seconds. The resting EMG activity will be assessed by calculating the average of three recordings, which will be performed with 1-minute intervals. Following this, patients will be asked to elevate shoulder in affected side and maintain an isometric contraction for 6 seconds. the highest and average amplitude values obtained from the three repeated recordings will be calculated (Ustun et al., 2024). The reliability of surface EMG for trapezius muscle is excellent (ICC = > 0.81) (Cid et al., 2018).

Secondary Outcome Measures:

These outcome measures will be measured at baseline, immediately post-treatment (end of week 2) and 4 weeks post-treatment.

Current pain intensity:

Will be assessed using a visual analog scale (VAS) consisting of a 10 cm horizontal line. A score of 0 corresponds to "no pain," and a score of 10 corresponds to "the highest level of pain." The VAS is a reliable (ICC = 0.97) and valid tool to assess musculoskeletal pain. (Bijur et al., 2001; Boonstra et al., 2008).

Neck Disability Index (NDI):

Is used to evaluate the impact of neck pain on person's daily activities. The instrument consists of 10 items and is divided into 10 sections, and each item is assigned up to 5 points, with 0 points corresponding to "no limitation" and 5 points corresponding to "complete limitation." The highest achievable score is 50 points. The score is then converted into a percent value (e.g., 50 points = 100%) to determine the disability classification. The disability classifications vary from "no disability" (0-8%) to "full disability" (70-100%) (MacDiarmid et al., 2009). The NDI is reliable (ICC = 0.68) and valid (Cleland et al., 2006).

Statistical Analysis:

Statistical Package for the Social Sciences (SPSS) statistics software version 29.0 (IBM Corporation, Armonk, New York, USA) will be used to analyze all data. Normality will be tested using the Shapiro-Wilk test. In addition, mean and standard deviation values will be used for descriptive analysis. Linear Mixed Model (LMM) will be used to analyze the outcome measures at different time points (baseline, post-needling, and one week later), and post hoc tests will be used if significant differences are found. To determine whether there are relationships between the primary and secondary outcomes, Pearson or Spearman correlation will be used. 95% confidence interval and Cohen's d will be used to indicate the magnitude of treatment effects between groups. The significance of the results will be determined at P value < 0.05.