Ultrasound-Guided Acupotomy Release With Biomechanical Assessment For Trapezius Myofascial Pain Syndrome

Summary

This protocol describes ultrasound‑guided acupotomy release for trapezius myofascial pain syndrome, using shear wave elastography and digital palpation to quantify biomechanical changes. It enables real‑time fascial visualization, precise release, reduced operator dependence, and reproducible metrics, offering a safe, repeatable workflow for clinical practice and mechanistic research.

Abstract

Trapezius myofascial pain syndrome (MPS) is a highly prevalent musculoskeletal disorder. Conventional acupotomy release relies heavily on operator experience and lacks objective quantitative outcomes, thus severely limiting its reproducibility and mechanistic research. This protocol establishes a standardized ultrasound-guided acupotomy release combined with an objective biomechanical assessment system, detailing standardized patient positioning, ultrasound localization of pathological fascial layers, precise needle insertion, and layered superficial/deep fascial release. Shear wave elastography (SWE) and digital palpation were applied to quantitatively assess soft tissue biomechanical properties under both resting and passive stretching conditions. Results from 27 affected sides in patients with trapezius MPS who underwent ultrasound-guided acupotomy release demonstrated that: VAS scores at 1 week and 2 weeks post intervention were significantly reduced compared with both baseline and immediately after intervention (all P < 0.001); resting-state shear modulus (G-value) immediately, at 1 week, and at 2 weeks post-intervention was significantly improved compared with baseline (P < 0.05 or P < 0.01); muscle tone and stiffness at both resting and passive stretching positions, as well as resting elasticity, were significantly improved at 1 and 2 weeks compared with immediately after intervention (P < 0.05 or P < 0.01); elasticity at both passive stretching and resting positions was significantly improved at 2 weeks compared with baseline and immediately after intervention (P < 0.05 or P < 0.01). These representative short-term results suggest that the protocol can be applied reproducibly to perform ultrasound-guided acupotomy release and to quantify associated clinical and biomechanical changes. The workflow may support standardized clinical practice, technical training, and mechanistic studies of acupotomy in trapezius MPS.

Introduction

Myofascial pain syndrome (MPS) is characterized by fascial contractile thickening and hyper-reactive nodules¹, with a prevalence of 30%–93% in pain clinic settings². Current diagnosis relies heavily on subjective methods, such as palpation, lacks objective criteria, and suffers from poor reproducibility³. The trapezius muscle, due to its constant role in maintaining head and neck posture, is particularly susceptible⁴. Acupotomy release, integrating traditional Chinese acupuncture theory with modern anatomy, has become a commonly used characteristic therapy in Traditional Chinese Medicine for treating MPS, owing to its advantages of minimal trauma, mild discomfort, and effective release of adhesions⁵. Nevertheless, conventional blind acupotomy carries the risk of damaging surrounding nerves and blood vessels, and its efficacy is evaluated solely on patients' subjective reports and practitioners' empirical judgment, lacking objective quantitative metrics, which severely limits its standardization and clinical promotion.

Recent advancements in ultrasound imaging offer promising solutions to these challenges. Ultrasound not only clearly and objectively visualizes thickened fascia but also provides real-time guidance, thereby substantially enhancing the precision and safety of acupotomy release. Concurrently, shear wave elastography (SWE) can non-invasively quantify the elastic modulus of muscle tissue by measuring shear wave propagation speed, offering an objective basis for assessing the biomechanical properties of soft tissue⁶. SWE has been successfully used to quantify muscle stiffness in trapezius MPS and has established a diagnostic threshold of 9.08 kPa, demonstrating promising utility in both the diagnosis and efficacy evaluation of trapezius MPS⁷. Therefore, this protocol proposes a standardized ultrasound‑guided acupotomy release combined with SWE and digital palpation technology, achieving real‑time fascial visualization, precise layered release, and reproducible biomechanical metrics—advantages over conventional blind acupotomy. This protocol is applicable to clinical practice, mechanistic studies, and technical training.

Protocol

This protocol was approved by the Medical Ethics Committee of Xiyuan Hospital (Approval No.: 2025XLA024-1). All participants provided written informed consent. The following steps describe the ultrasound-guided acupotomy release procedure and the concomitant biomechanical assessments using shear wave elastography (SWE) and a digital palpation device for patients diagnosed with trapezius MPS according to established criteria^8,9.

1. Intervention methods

1. Pretreatment preparation
   1. Perform a pretreatment screening: Review the patient’s history for contraindications (e.g., bleeding disorders, anticoagulant use, pregnancy); assess the treatment area; and ensure the patient is in a comfortable, relaxed state.
   2. Gather the following materials: a disposable dressing change kit, povidone-iodine solution, disposable sterile medical gloves, disposable acupotomy needles (loop-handle type, size 0.6 mm × 40 mm), and sterile fenestrated drapes.
      ​CAUTION: Povidone iodine may irritate skin and eyes; avoid contact with eyes and mucous membranes; wear sterile gloves during use. Acupotomy needles are sharp, and single use devices; handle carefully to prevent needle stick injury; discard used needles immediately in a designated sharps container. See Figure 1A.
   3. Position the patient in a relaxed sitting posture with the back upright, gaze directed forward, both arms resting naturally on the anterior thighs, and feet flat on the floor. Ensure the affected trapezius region is fully exposed.
   4. Ask the patient to identify the most painful area, then apply gradual vertical pressure (2–3 kg) within the trapezius taut band to locate the maximal tender point.
   5. Use a sterile gentian violet skin marker to draw a 0.5 cm diameter circle at the target point. Perform marking before sterile disinfection to maintain aseptic technique.
   6. Disinfect the skin in a circular motion from the center outward with povidone iodine (diameter ≥ 10 cm). Repeat three times, giving 30 s for drying each time. Finally, cover with a sterile fenestrated drape centered on the marked point.
   7. Power on the color Doppler ultrasound system. Connect the high-frequency linear-array probe (4–18 MHz; set to 17 MHz). Select the MSK extremity preset and enable tissue harmonic imaging (THI). Set depth = 3–4 cm, power = 95%, frame rate = 35 Hz, gain = 60–70 dB, and adjust TGC for uniform brightness. Position the focus at the deep fascia (1.5–2 cm depth).
   8. Apply 2–3 mL of medical ultrasound coupling gel to the probe surface.
   9. Cover the probe with a disposable sterile medical glove; expel air for a smooth surface and secure the distal end with two finger stalls. Disinfect the glove outer surface with sterile povidone iodine.
   10. Instruct the patient to inform the physician immediately of any discomfort during the procedure.
2. Treatment procedure
   1. Place the ultrasound probe along the direction of the trapezius muscle fibers (i.e., the long axis of the probe is parallel to the fiber orientation), perpendicularly on the skin over the marked point, maintaining stable probe-to-skin contact (skin indentation < 0.5 cm).
   2. Slowly move the probe along the fiber direction to scan and identify areas of locally thickened fascia, then center the thickest part of the thickened fascia under the probe.
      NOTE: Thickened fascia is defined on ultrasound as: thickness increase > 2 mm compared to adjacent normal fascia, with heterogeneous echogenicity and restricted sliding. See Figure 2D.
   3. Insert the acupotomy needle percutaneously at a point 0.5 cm lateral to the probe's long-axis marker.
   4. Under real-time ultrasound guidance, advance the needle from medial to lateral, with the needle tip pointing toward the shoulder joint, at an angle of 10°—15° relative to the skin, within the plane parallel to the long axis of the trapezius muscle. Guide the needle tip to the superficial fascial layer.
   5. Perform 3–5 oblique release motions (5 mm longitudinal movement, 1 Hz frequency) until a palpable “loss of resistance” is felt, or ultrasound shows fascial separation and improved sliding.
   6. Withdraw the needle to the subcutaneous level, adjust the insertion angle to approximately 45°, and advance the needle tip to the deep fascial layer under ultrasound guidance. Perform 3–5 oblique release motions using the same 5 mm longitudinal movement and 1 Hz frequency until loss of resistance is felt or ultrasound shows fascial separation and improved sliding.
   7. Withdraw the needle completely, apply firm pressure to the needle site with a sterile cotton ball for 30 s and cover the site with a sterile adhesive dressing, and assist the patient in adjusting their clothing.
      ​NOTE: Throughout the needle insertion and release procedure, continuously monitor the patient’s responses and verbal feedback for any signs of discomfort or adverse reactions.
3. Posttreatment Instructions
   1. Instruct the patient to keep the needle site dry for 24 h and avoid lifting heavy objects exceeding 5 kg for 48 h.
4. Safety monitoring
   1. Adverse event (AE) grading
      1. Define mild AE as transient local pain (VAS 1–3), small ecchymosis (<2 cm), or mild soreness, resolving spontaneously within 24 h.
      2. Define moderate AE as local pain (VAS 4–6), ecchymosis (2–5 cm), or mild vasovagal reaction; this is relieved with rest and hydration.
      3. Define severe AE as severe pain (VAS ≥7), large hematoma (>5 cm), syncope, nerve injury, pneumothorax, or hospitalization-requiring events.
   2. Patient response thresholds (intraoperative stopping criteria)
      1. Stop the procedure immediately if: VAS pain ≥ 7 during needling; presyncopal symptoms (pallor, dizziness, HR < 50 or >100 bpm, SBP < 90 mmHg); or active bleeding is visualized.
   3. Adverse event recording and reporting methods
      1. Record all AEs in the CRF with type, onset, duration, severity, management, and outcome.
      2. Report moderate/severe AEs to the Ethics Committee within 24 h.
      3. Follow patients until AE resolution and document the final outcome.
         ​CAUTION: Vasovagal syncope is a potential moderate adverse event. If presyncopal symptoms occur, stop the procedure, place the patient in a supine position with legs elevated, and monitor until symptoms resolve.

2. Assessment procedures

NOTE: To reduce measurement error, all measurements are performed in a quiet, temperature controlled (22–24 °C), privacy protected environment. The patient is instructed to wear loose clothing that allows easy exposure of the shoulder area and to rest quietly in the waiting area for 10 min before the assessment.

1. Visual Analog Scale assessment
   1. Present the Visual Analog Scale to the subject. Instruct the subject as follows: “On this scale, 0 represents ‘no pain at all,’ and 10 represents ‘the worst pain imaginable.’ Please mark the point that best represents the average pain intensity in your trapezius muscle.”
2. Shear wave elastography measurement
   ​NOTE: All SWE measurements should be performed by operators with over 75 h of specific training in the technique. Before data collection, each operator completes standardized practice on healthy volunteers and patients with trapezius MPS to achieve consistent probe positioning, fiber alignment, and ROI placement. During SWE acquisition, use minimal probe pressure: just enough for a clear B mode image with skin indentation < 0.5 cm.
   1. Equipment preparation and subject positioning
      1. Power on the portable ultrasound diagnostic system. Select and connect the 8.5 MHz linear array probe.
         NOTE: See Figure 1B.
      2. Position the subject in a sitting posture in front of an adjustable treatment bed. Instruct the subject to place their forearms parallel on the bed surface, approximately shoulder-width apart.
      3. Adjust the bed height to align with the level of the subject’s thoracolumbar junction.
      4. Ensure the subject’s feet are flat on the floor, back is upright, and gaze is forward. Confirm the shoulders are in a naturally relaxed position, with only the weight of the arms resting on the bed (see Figure 2A).
   2. Measurement point localization
      1. Palpate to identify the spinous process of the seventh cervical vertebra (C7) and the most lateral point of the ipsilateral acromion.
      2. Mark the midpoint of the line connecting these two anatomical landmarks. This point corresponds to the acupuncture point Jianjing (GB21)10 and serves as the standardized measurement site.
   3. SWE measurement in the resting state
      1. Apply 2–3 mL of ultrasound coupling gel to the surface of the ultrasound probe.
      2. Align the probe parallel to the trapezius muscle fibers at the marked point. In B mode, adjust the orientation until the fascicles appear as continuous, parallel hypoechoic bands; do not acquire SWE if they appear oblique, discontinuous, or poorly visualized. Maintain minimal probe to skin contact (ultrasound image shows skin indentation < 0.5 cm) and avoid additional pressure (see Figure 2C).
      3. Activate the SWE mode on the ultrasound system. Set the imaging depth to 3–4 cm to ensure the middle portion of the trapezius muscle is centered in the image.
      4. Instruct the subject to remain relaxed and breathe normally. After the subject remains motionless for 2–3 s, acquire the SWE data frame.
      5. Record at least 10 valid repeated measurements per side and take the average as the final shear modulus (G value) for that side.
   4. SWE measurement in the passive stretching state
      1. With the subject maintaining the base sitting position (steps 2.2.1.2 to 2.2.1.4), have a second operator stabilize the subject‘s ipsilateral shoulder to prevent elevation.
      2. Ask the second operator to passively laterally flex the subject's head to the contralateral side to an angle of 30°–45° (measured by goniometer), achieving a "mild stretch sensation without pain". Maintain this passive stretching position for 1 min.
      3. Simultaneously, have the first operator repeat the SWE measurement process (steps 2.2.3.1 to 2.2.3.5) at the identical measurement point marked in step 2.2.2.
         NOTE: Ensure the stretched position is completely passive and does not elicit any voluntary guarding or contraction from the subject. See Figure 2B for an illustration of the positioning.
   5. Image analysis and data recording
      1. Select the frame with the highest motion stability and reliability index for analysis.
      2. On the selected frame, draw a rectangular Region of Interest (ROI) measuring 2.5 mm × 20 mm within the muscle tissue, beneath the fascia.
         NOTE: Position the ROI to carefully avoid inclusion of visible blood vessels, tendons, or fascial boundaries.
      3. Record the mean shear modulus (G-value, in kPa) provided by the system software for that ROI.
3. Soft tissue tension measurement
   ​NOTE: Use a digital palpation device to obtain three key parameters: Oscillation Frequency (F, Hz, reflecting muscle tone), Dynamic Stiffness (S, N/m, reflecting resistance to deformation), and Logarithmic Decrement (D, reflecting elasticity) (see Figure 1C).
   1. Measurement procedure
      1. Ensure that the testing posture and measurement point are identical to those used for the SWE measurements (step 2.2).
      2. Position the device probe perpendicular to the skin at the designated measurement point. Gently press until the device indicator light changes from red to green (contact force approximately 2–3 N).
      3. Hold the probe steady. The device will automatically deliver three mechanical impulses and records the above parameters.
      4. If the coefficient of variation exceeds 3%, repeat the measurement.
         ​NOTE: The assessments for VAS, SWE, and soft tissue tension are performed at the prescribed time points according to the trial design. In this study, these outcome measures are evaluated at baseline (pretreatment), immediately post treatment (30 min after the completion of the acupotomy release), and at the 1 week and 2 week follow ups.
4. Quality control, device calibration, and operator consistency
   1. Perform equipment checks before each testing day. For the ultrasound system, confirm probe integrity, image uniformity, depth calibration, and SWE mode availability. For the digital palpation device, perform the manufacturer-recommended calibration or function check and confirm stable probe movement and contact-force indication.
   2. Use the same ultrasound system, probe model, SWE preset, ROI size, and digital palpation device throughout the study whenever possible. If equipment replacement is unavoidable, document the change and perform cross-check measurements before continuing data acquisition.
   3. Assign trained operators to fixed roles: one for SWE acquisition, one for passive stretching assistance, and one for digital palpation measurements. Blinding to group allocation is maintained whenever feasible.
   4. Before formal data collection, assess intraoperator and interoperator reliability using the same standardized posture, measurement site, and acquisition settings as in the main study. Use the following reliability thresholds: poor, ICC < 0.50; moderate, ICC 0.50–0.75; good, ICC 0.75–0.90; and excellent, ICC > 0.90.
   5. Record all deviations from the standardized acquisition procedure (e.g., excessive probe pressure, unstable SWE maps, inability to maintain passive stretching, repeated CV >3%, equipment malfunction, operator change). Correct the cause and repeat the measurement; if valid measurements cannot be obtained, document as a protocol deviation.

Results

A total of 44 subjects were initially enrolled. One subject was subsequently excluded due to a concomitant diagnosis of frozen shoulder identified post-enrollment. Consequently, 43 subjects were included in the final analysis, comprising 6 subjects with unilateral pain and 37 subjects with bilateral pain, resulting in a total of 80 affected sides, with bilateral cases counted as two affected sides. The final distribution was 27 sides in the acupotomy group, 27 in the sham acupotomy group, and 26 in the blank control group. Randomization was performed centrally using a computer-generated 1:1:1 block sequence with variable block sizes of 4 or 6, and allocation was concealed using sealed opaque envelopes. For participants with bilateral pain, each affected side was randomized independently. No stratification was used. The sham acupotomy group received ultrasound-guided subcutaneous needling without fascial penetration, while the blank control group received no needle intervention and completed the same assessments at the corresponding time points. Patients were not blinded because of the difference in penetration depth between active and sham procedures, whereas outcome assessors and statisticians were blinded to group allocation.

All subjects diagnosed with trapezius myofascial pain syndrome had unilateral or bilateral active trigger points. No statistically significant differences were found among the three groups in baseline characteristics, including sex, age, and BMI, indicating comparability (see Table 1). The needle tip was clearly visualized at the superficial and deep fascial layers under ultrasound, and the operator perceived a distinct loss of resistance during release. Valid and stable biomechanical measurements, together with post-intervention changes in tissue stiffness and pain, indicated successful protocol execution. In a reliability assessment of 10 volunteers and 20 sides, inter-operator reliability was excellent (ICC = 0.970; SEM/MDC95 = 0.55/1.53), and intra-operator reliability was also excellent (ICC = 0.984; SEM/MDC95 = 0.41/1.15). Conversely, abnormal or unstable measurements suggest deviations in patient positioning, probe handling, or needle insertion, requiring repeated data acquisition or procedural adjustment in accordance with the quality control criteria of this protocol.

VAS scores, used to assess average pain intensity, were non-normally distributed and are presented as median (interquartile range). No significant differences in VAS scores were observed among the three groups at baseline (P > 0.05). Within-group comparisons revealed that in the acupotomy group, VAS scores at both 1 week and 2 weeks post-treatment were significantly lower than baseline (P < 0.001) and 0 week (immediately post treatment) (P < 0.001). No significant changes in VAS scores were observed at any time point within the sham acupotomy group or the blank control group (P > 0.05). Between-group comparisons demonstrated that VAS scores in the acupotomy group at 1 week and 2 weeks were significantly lower than those in both the sham group and the blank control group (P < 0.001 for all comparisons) (see Table 2 and Figure 3A).

SWE was employed to assess tissue stiffness, quantified as the shear modulus (G-value, in kPa), under both resting and passive stretching states. The G-value data for the acupotomy group followed a normal distribution and are presented as mean ± standard deviation. Data for the sham and control groups were non-normally distributed and are presented as median (interquartile range). Within-group comparisons in the acupotomy group showed that the resting-state G-value decreased significantly immediately post-treatment (0 week) compared to baseline (P < 0.01) and remained significantly lower than baseline at both 1-week and 2-week follow-ups (P < 0.05 for both). In the passive stretching state, a transient but significant increase in G-value was observed at 1 week compared to the 0-week measurement (P < 0.05), with no other significant changes compared to baseline. No significant within-group changes in G-value were observed at any time point in either state for the sham or blank control groups (P > 0.05). Between-group comparisons at baseline revealed significant differences in G-values, indicating a lack of baseline comparability for this parameter (see Table 3 and Figure 3B,C).

Measurements were obtained using the digital palpation device, recording muscle tone (Hz), stiffness (N/m), and elasticity (Logarithmic Decrement) under both resting and passive stretching states. Data conforming to a normal distribution are presented as mean ± SD, and non-normally distributed data are presented as median (IQR). In the acupotomy group, muscle tone under both resting and stretching states was significantly lower at 1 and 2 weeks compared to 0 week (P < 0.05 or P < 0.01). Stiffness in both states also showed significant decreases at 1 and 2 weeks versus 0 week (P < 0.01 for resting state; P < 0.05 for stretching state). For elasticity, resting-state elasticity at 1 week was significantly lower than at 0 week (P < 0.05). By 2 weeks, elasticity in both resting and stretching states was significantly lower than at both 0 week and baseline (P < 0.01 for comparisons with 0 week; P < 0.05 for comparisons with baseline). In the sham acupotomy group, only stretching-state stiffness showed a transient, isolated increase at 1 week compared to baseline (P < 0.05). No other parameters changed significantly at any time point. The blank control group showed no significant changes in any parameter (tone, stiffness, elasticity) across all time points. Between-group comparisons showed significant baseline differences in muscle tone and stiffness, precluding direct comparability at baseline. Specifically, the acupotomy group exhibited significantly higher resting-state tone than both control groups (P < 0.05 or P < 0.01) and higher resting-state stiffness than the sham group (P < 0.05). Under the stretching state, the acupotomy group’s tone and stiffness were both significantly higher than those of the sham group (P < 0.05 for both). Baseline elasticity was comparable across all groups. At the 2-week follow-up, the acupotomy group’s elasticity in the stretching state was significantly lower than that of the blank control group (P < 0.05). No other statistically significant between-group differences were observed at other time points (see Table 4 and Figure 3D-I).

During the treatment period, two adverse events were reported in the acupotomy group, both of which were cases of vasovagal syncope (needle fainting) occurring after needle withdrawal. The patients were promptly assisted into a supine position with the head lowered and legs elevated to promote cerebral blood flow, leading to rapid symptom resolution. No other adverse events were reported among the remaining participants.

Figure 1. Materials and equipment used in the study. (A) Required materials for the procedure: disposable dressing change kit, disposable sterile medical gloves, povidone‑iodine solution, disposable acupotomy needles (size 0.6 mm x 40 mm), and sterile fenestrated drapes. (B) Shear wave elastography was performed using a portable ultrasound diagnostic system. (C) The digital palpation device for soft‑tissue tension measurement. Please click here to view a larger version of this figure.

Figure 2. Measurement positions, measurement points, and ultrasound anatomy of the trapezius fascia. (A) Resting position and measurement points; (B) Passive stretch position; (C) Measurement of shear modulus G at resting position. (D) Representative ultrasound image (B‑mode) of the trapezius muscle showing the SF (arrow) and DF (arrowhead). Abbreviations: SF = superficial fascia; DF = deep fascia. Please click here to view a larger version of this figure.

Figure 3. Comparisons of VAS, SWE, and soft tissue tension properties among the three groups at different time points. (A) VAS scores. (B) SWE values at resting position (kPa). (C) SWE values under passive stretch (kPa). (D) Resting tone (Hz). (E) Resting stiffness (N/m). (F) Resting elasticity. (G) Passive stretch tone (Hz). (H) Passive stretch stiffness (N/m). (I) Passive stretch elasticity. Timepoint “0 wk” indicates measurements taken immediately post-intervention. ^*P<0.05, ^**P<0.01, ^***P<0.001 for within-group comparisons; ^#P < 0.05, ^##P < 0.01, ^###P<0.001 for between-group comparisons. Abbreviations: VAS= Visual Analog Scale; SWE = Shear wave elastography. Please click here to view a larger version of this figure.

Group	Sex (Male/Female)	Age (years)	BMI（kg/m2）
Acupotomy Group (n=27)	8-19	28.15 ± 7.21	20.71 ± 2.33
Sham Acupotomy Group (n=27)	6-21	27.37 ± 7.37	22.18 ± 3.15
Blank Control Group (n=26)	5-21	27.50 ± 7.48	22.16 ± 3.21
Statistic value	χ2 = 0.8434	F = 0.0864	F = 2.2205
P-value	0.6559	0.9173	0.1155

Table 1: Comparison of baseline data among the three groups.

Group	Baseline	0 week	Week 1	Week 2
Acupotomy Group (n=27)	4.00(3.00,5.00)	3.00(3.00,4.00)	2.00(1.00,3.00)*^sb	2.00(1.00,2.00)*^sb
Sham Acupotomy Group (n=27)	5.00(3.00,6.00)	–	5.00(3.00,5.75)	4.00(3.25,5.75)
Blank Control Group (n=26)	4.00(3.00,6.00)	–	4.00(3.00,6.00)	4.50(3.00,6.00)
Data are presented as median (interquartile range). 0 week, immediately post-intervention. –, not applicable. *P < 0.001 vs. baseline within the same group; ^P < 0.001 vs. 0 wk within the same group; bP < 0.001 vs. the blank control group at the same time point; sP < 0.001 vs. the sham acupotomy group at the same time point.

Table 2: Comparison of Visual Analog Scale scores among three groups before and after Intervention. Data are presented as median (interquartile range). 0 week, immediately post intervention. –, not applicable. ^*P < 0.001 vs. baseline within the same group; ^{^}P < 0.001 vs. 0 week within the same group; ^bP < 0.001 vs. the blank control group at the same time point; ^sP < 0.001 vs. the sham acupotomy group at the same time point. 

Group	Time Point	SWE at Rest (kPa)	SWE at Passive Stretch (kPa)
Acupotomy Group (n=27)	Baseline	10.79±4.78#	11.86±4.83
	0 wk	7.01±2.99**	9.75±3.23
	Week 1	8.46±3.01*	12.42±4.70^
	Week 2	8.51±2.99*	10.20±3.50
Sham Acupotomy Group (n=27)	Baseline	8.47(6.56, 10.40)	9.88(7.37, 13.57)#
	Week 1	8.73(6.95, 11. 11)	11.20(8.98, 14.30)
	Week 2	7.93(6.34, 11.62)	8.92(6.90, 11.59)
Blank Control Group (n=26)	Baseline	8.74(5.96,9.40)	11.49(10.31, 17.04)
	Week 1	7.82(5.81, 11.00)	10.95(10.12, 13.70)
	Week 2	9.88(7.18, 12. 12)	10.80(6.91, 12.03)
Data are presented as mean ± SD (x̄± SD) or median (interquartile range). SWE, shear wave elastography (kPa). 0 wk, immediately post-intervention. *P < 0.05, **P < 0.01 vs. baseline within the same group; ^P < 0.05 vs. 0 wk within the same group; #P < 0.05 vs. the blank control group at the same time point.

Table 3: Comparison of SWE values at different positions among the three groups before and after intervention. Data are presented as mean ± SD (x̄± SD) or median (interquartile range). SWE, shear wave elastography (kPa). 0 wk, immediately post-intervention. ^*P < 0.05, ^**P < 0.01 vs. baseline within the same group; ^P < 0.05 vs. 0 wk within the same group; ^#P < 0.05 vs. the blank control group at the same time point.

Group	Time Point	Tone (Hz)		Stiffness (N/m)		Elasticity
		Rest	Passive Stretch	Rest	Passive Stretch	Rest	Passive Stretch
AG (n=27)	Baseline	18.80±1.81ssb	21.35±1.88s	369.52±58.6 5s	441.00(407. 25,486.75)s	1.14±0.16	1.15±0.21
	0 wk	19.71±1.97	22.13±2.37	394.78±62.0 6	456.00(424. 00,491.50)	1.16±0.11	1.15±0.19
	Week 1	18.21±1.52^^	20.67±1.59^	347.56±50.1 6^^	428.00(379. 50,462.25)^	1.08±0.16^	1.07±0.15
	Week 2	18.08±1.88^^	20.27±2.20^^	333.81±86.2 2^^	422.00(351. 50,474.75)^	1.04±0.16*^^	1.03±0.13*^^ b
SAG (n=27)	Baseline	17.30(15.85, 18.48)	19.80(19.10, 21.17)	327.78±67.8 6	389.00(372. 50,431.50)	1.11±0.13	1. 12(1.01, 1. 21)
	Week 1	17.90(16.92, 19.95)	20.90(19.65, 22.08)	357.78±60.4 5	436.00(402. 25,472.50)*	1.12±0.12	1.09(1.02, 1. 14)
	Week 2	17.50(16.90, 18.30)	20.00(19.45, 21.95)	342.96±49.0 1	421.00(383. 75,477.50)	1.09±0.14	1.08(0.99, 1. 19)
BCG (n=26)	Baseline	17.63±1.66	19.95(18.80, 21.70)	332.50(310. 00,357.00)	416.42±69.2 0	1.09(1.01, 1. 20)	1.10±0.11
	Week 1	17.62±1.70	19.85(18.60, 21.50)	324.00(298. 00,354.00)	413.38±65.6 0	1.07(0.97, 1. 13)	1.08±0.13
	Week 2	17.85±2.03	19.65(18.30, 20.70)	340.50(312. 00,363.00)	405.19±47.5 8	1.08(1.02, 1. 22)	1.11±0.15
Data are presented as mean ± SD (x̄± SD) or median (interquartile range). AG: Acupotomy Group; SAG: Sham Acupotomy Group; BCG: Blank Control Group. 0 wk, immediately post-intervention. *P < 0.05 vs. baseline within the same group; ^P < 0.05, ^^P < 0.01 vs. 0 wk within the same group; bP < 0.05 vs. the blank control group at the same time point; sP < 0.05,ssP < 0.01 vs. the sham acupotomy group at the same time point.

Table 4: Comparison of soft tissue tension values at different positions among the three groups before and after intervention. Data are presented as mean ± SD (x̄± SD) or median (interquartile range). AG: Acupotomy Group; SAG: Sham Acupotomy Group; BCG: Blank Control Group. 0 wk, immediately post-intervention. ^*P < 0.05 vs. baseline within the same group; ^{^}P < 0.05, ^{^^}P < 0.01 vs. 0 wk within the same group; ^bP < 0.05 vs. the blank control group at the same time point; ^sP < 0.05,^ssP < 0.01 vs. the sham acupotomy group at the same time point. 

Problem	Possible Cause	Solution
Unstable SWE signals or invalid shear modulus (G-value)	Patient movement; excessive probe pressure; probe not parallel to muscle fibers	Ask the patient to rest quietly for 10 min before measurement; control probe pressure (skin indentation < 0.5 cm); align the probe parallel to trapezius muscle fibers
No “loss of resistance” during acupotomy release	Needle tip fails to reach the targeted fascial layer	Adjust needle angle under real-time ultrasound guidance; reconfirm the depth of superficial and deep fascia
Abnormally high biomechanical values under passive stretching	Head lateral flexion angle > 45°; patient’s voluntary muscle contraction	Control flexion angle at 30°–45° using a goniometer; stabilize the patient’s shoulder to avoid compensatory contraction
Unclear visualization of fascial layers	Non-standardized ultrasound parameters; insufficient sterile coupling gel	Reset ultrasound settings (17 MHz, THI on, focus at 1.5–2 cm); apply adequate sterile coupling gel between probe and sterile cover
Vasovagal reaction (dizziness, pallor) during procedure	Patient anxiety; insufficient preoperative rest	Provide psychological comfort; extend preoperative rest to 15 min; stop procedure and place patient in supine position with legs elevated

Table 5: Troubleshooting table.

Discussion

Neck pain is one of the most common health problems worldwide, affecting approximately 70% of individuals at some point in their lives and ranking among the top four causes of years lived with disability^11,12, and trapezius myofascial pain syndrome (MPS) is a major contributor. Acupotomy release, integrating acupuncture and minimally invasive techniques, offers advantages of minimal trauma and effective adhesion release. This protocol establishes, for the first time, a standardized procedure that combines ultrasound‑guided layered acupotomy release with quantitative biomechanical assessment under both resting and passive stretching conditions. This approach converts the traditional “blind needling” into a visualizable and precise operation, thereby improving the safety and reproducibility of acupotomy treatment.

In the acupotomy group, VAS scores at 1 and 2 weeks post intervention were significantly reduced (P < 0.001) and were superior to those in the sham acupotomy and blank control groups, supporting a short-term clinical effect of targeted release of pathologically thickened fascia. The analgesic mechanism is related to direct release of abnormal tension bands, modulation of local microcirculation and energy metabolism, reduction of nociceptive signal input, and elevation of the pain threshold^13,14.

Within-group comparisons showed sustained improvement in the resting-state shear modulus (G-value), muscle tone, stiffness, and elasticity under both resting and passive stretching states following the acupotomy intervention. Previous studies have confirmed that shear wave speed (which reflects tissue stiffness) is significantly higher in muscles with a taut band or trigger point, reflecting mechanical restriction¹⁵, and that muscle stiffness is generally increased in chronic neck pain and correlates with pressure pain threshold^16,17. In between-group comparisons, except for a significantly better elasticity in the passive stretching state in the acupotomy group at 2 weeks compared to the blank control group (P < 0.05), no other significant differences were found. This is primarily attributable to baseline imbalances in G‑value, muscle tone, etc., among the three groups, rather than protocol failure. Muscle elasticity is an important biomechanical property for maintaining normal function and mobility¹⁸, and the observed improvement in elasticity at 2 weeks reflects restoration of tissue compliance. The biomechanical changes observed in this study may reflect the release of mechanical restriction and restoration of fascial‑muscle unit balance. For troubleshooting, see Table 5.

Because skeletal muscle is anisotropic and shear wave speed varies with fiber direction, strict probe‑fascicle alignment was enforced for all SWE acquisitions, especially during passive stretching where fascicle orientation may shift with head/neck position; alignment was verified in B‑mode before each acquisition, and frames with oblique fascicles or unstable elastography maps were excluded. Additionally, the individualized treatment target (tender point and thickened fascia) and the standardized measurement point (GB21) did not always coincide. Although this design enhances cross‑participant reproducibility, it may limit spatial specificity for causal inference; therefore, observed biomechanical changes should be interpreted as regional alterations in upper trapezius properties rather than direct measures at the released fascial segment. Future studies should systematically record the target‑to‑measurement distance and compare outcomes at both sites. Finally, significant baseline differences in SWE and soft tissue tension parameters existed among the three groups. Consequently, unadjusted between‑group comparisons were considered exploratory; we focused on within‑group temporal changes and protocol feasibility. Postintervention differences may partly reflect pre‑existing disparities rather than pure treatment effects. Future confirmatory trials should apply baseline‑adjusted mixed‑effects models and account for within‑participant clustering in bilateral cases.

This protocol has some limitations. Operators require musculoskeletal ultrasound skills and standardized training; passive stretching must be strictly controlled for angle and posture, otherwise, measurement bias may occur; the sample size is relatively small and follow‑up limited to 2 weeks, precluding assessment of long‑term efficacy; baseline imbalances affect between‑group comparisons. Future studies should increase sample sizes, enforce strict baseline matching, extend follow‑up periods, and extend the dual‑state SWE evaluation model to other common myofascial pain sites such as the infraspinatus, quadratus lumborum, and piriformis muscles.

The core innovation of this study is the combined use of SWE and digital palpation under both resting and passive stretching states, providing objective biomechanical evidence for acupotomy release. Musculoskeletal ultrasound can display the needle tip path in real time, avoiding nerves and vessels, and accurately guide the acupotomy to the diseased fascia^19,20. This protocol may help reduce safety risk of inaccurate targeting and unclear tissue layers associated with conventional blind acupotomy, and is applicable to clinical treatment, mechanistic research, and standardized technical training.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Adjustable Treatment Bed	Guangdong Qiyunjian Intelligent Technology Co., Ltd.	C401	For patient positioning and support during the procedure.
Color Doppler Ultrasound System	Konica Minolta Medical Technology Co., Ltd.	SONIMAGE HS1	Used with L18-4 high-frequency linear array probe for real-time guidance of acupotomy release.
Disposable Sterile Acupotomy Needle (0.6 mm × 40 mm)	Ma'anshan Bond Medical Devices Co., Ltd.	CBR	For releasing fascial adhesions.
Disposable Sterile Dressing Change Kit	Beijing Haokang Technology Co., Ltd.	HK-C2	Contains cotton balls, forceps, etc.
Disposable Sterile Medical Gloves	Beijing Ruijing Latex Products Co., Ltd.	Textured, powder-free, curved type	Prevents cross-infection between practitioner and patient.
L18-4 High-frequency Linear Array Probe	Konica Minolta Medical Technology Co., Ltd.	L18-4	To be used with the Color Doppler Ultrasound System.
Medical Skin Marker Pen	Dongguan Tangde Medical Technology Co., Ltd.	Medical skin marker pen	For marking the treatment point on the skin.
Medical Ultrasound Coupling Gel	Beijing Huarun Kangtai Hi-Tech Development Institute	General type	Conductive medium between ultrasound probe and skin.
MyotonPRO Digital Palpation Device	Myoton AS	MyotonPRO	Measures soft tissue tension (tone, stiffness, elasticity).
Portable Ultrasound Diagnostic System	Beijing Xijian Technology Co., Ltd.	T5C1A304W	For Shear Wave Elastography (SWE) measurement.
Povidone-iodine Disinfectant Solution	Shandong Zhuojian Medical Technology Co., Ltd.	Effective iodine content 5 g/L ± 0.25 g/L, 60 mL/bottle	For skin disinfection prior to acupotomy.
Sterile Adhesive Dressing	Jiangxi Hengbang Medical Devices Co., Ltd.	PKT-PE	Covers the needle puncture site.
Sterile Fenestrated Drape	Henan Xianghongrui Nursing Supplies Co., Ltd.	XHR-188	Establishes a local sterile operating field.