High-versuslow-energyextracorporealshock-wavetherapyformyofascialpainsyndromeofuppertrapezius:Aprospectiverandomizedsingleblindedpilotstudy

Myofascial pain syndrome (MPS) is a common cause of musculoskeletal pain, with an estimated prevalence of 12%. It is characterized by myofascial trigger points—hyperirritable spots in taut bands of skeletal muscle that are tender, painful on compression, and associated with referred pain patterns. The upper trapezius is a frequently affected muscle, and MPS in this region can cause significant neck pain and functional limitation. While various treatments exist, including pharmacotherapy, trigger point injections, and physical therapy, extracorporeal shock wave therapy (ESWT) has emerged as a promising non-invasive option.

However, a critical question remained unanswered: what energy level of ESWT provides the best outcomes? Previous studies had demonstrated efficacy of ESWT for MPS, but no prior research had directly compared high-energy versus low-energy ESWT in this patient population. This gap in knowledge motivated the investigators to conduct a prospective randomized trial to determine whether higher energy levels yield superior clinical results.

The researchers conducted a prospective, single-blind, randomized pilot study at an outpatient musculoskeletal pain clinic. They enrolled 30 patients (3 men, 27 women) with MPS of the upper trapezius, diagnosed using established clinical criteria including palpable tender nodules in taut bands, typical referred pain patterns, local twitch responses, and pain onset within 3 months. Participants had baseline verbal numeric pain scale (VNS) scores of 4 or higher out of 10.

Patients were randomly assigned to receive either high-energy ESWT at 0.210 mJ/mm² or low-energy ESWT at 0.068 mJ/mm². Both groups received 1500 pulses once weekly for 2 weeks, for a total of 2 sessions. To minimize pain during treatment, all patients received subcutaneous infiltration of 5 mL of 1% lidocaine. A transparent film and coupling gel were used during ESWT application.

Rescue medication (acetaminophen, up to 2 g per day) was permitted if needed.

Outcome assessments were performed by an independent observer blinded to treatment assignment at baseline and 2 weeks after the final treatment. Measures included: VNS (0-10 scale), Neck Disability Index (NDI, 0-50 scale), cervical range of motion (ROM) in six directions using an inclinometer, and pressure threshold (PT) measured with an algometer at a standardized point on the upper trapezius.

Both groups showed statistically significant improvements in several outcomes. In the high-energy group, VNS decreased from 5.67±1.63 to 3.00±1.56 (P=.001), NDI improved from 11.27±4.04 to 4.20±1.78 (P=.001), and pressure threshold increased from 1.63±0.37 to 2.32±0.55 kg/cm² (P=.001). Neck rotation to the sound side, lateral bending to the affected side, and lateral bending to the sound side also improved significantly (all P<.05). Notably, neck flexion ROM improved from 56.53±14.49° to 65.47±10.09° (P=.001) and neck extension ROM improved from 61.67±12.84° to 68.93±11.47° (P=.015)—but only in the high-energy group.

In the low-energy group, VNS improved from 5.40±1.64 to 3.07±1.49 (P=.001), NDI improved from 9.20±3.75 to 6.47±2.48 (P=.001), and pressure threshold increased from 1.67±0.49 to 2.05±0.55 kg/cm² (P=.017). Neck rotation to the sound side, lateral bending to the affected side, and lateral bending to the sound side also improved significantly. However, neck flexion and extension ROM did not show statistically significant improvements.

When comparing the two groups directly after treatment, statistically significant differences favored the high-energy group for NDI (4.20±1.78 vs. 6.47±2.48, P=.008) and neck flexion ROM (65.47±10.09° vs. 55.93±11.07°, P=.029). No significant between-group differences were found for VNS, neck extension, rotation, lateral bending, or pressure threshold. No major adverse effects were reported in either group.

This pilot study suggests that both high-energy and low-energy ESWT can effectively reduce pain and improve some functional measures in patients with upper trapezius MPS. However, high-energy ESWT appears superior for functional improvement, as evidenced by greater reductions in neck disability and improvements in neck flexion range of motion. This finding is clinically meaningful because the NDI captures real-world functional limitations—such as ability to perform daily activities, work, and sleep—rather than just pain intensity.

For clinicians, these results suggest that when using ESWT for upper trapezius MPS, higher energy levels (around 0.210 mJ/mm²) may be preferable when the goal is functional restoration, particularly for neck flexion. However, low-energy ESWT remains a viable option for pain reduction with fewer potential side effects and less need for local anesthesia. The study also confirms that ESWT is generally well-tolerated, with no serious adverse events.

For patients, this means that shock wave therapy—delivered at appropriate energy levels—may help not only reduce pain but also improve ability to move the neck and perform daily activities. However, the small sample size and short follow-up period mean these findings should be considered preliminary. Patients should discuss with their healthcare providers whether ESWT is appropriate for their specific situation and what energy level might be optimal for their treatment goals.

The investigators appropriately note that larger, longer-term studies with control groups are needed to confirm these findings and to better understand the dose-response relationship of ESWT in myofascial pain syndrome.