Effectivenessofultrasoundguidedinterfascialhydrodissectionwiththeuseofsalineanestheticsolutionformyofascialpainsyndromeoftheuppertrapezius:asingleblindrandomizedcontrolledtrial

Myofascial pain syndrome (MPS) is one of the most common causes of chronic musculoskeletal pain, affecting up to 85% of the general population. It is characterized by the presence of myofascial trigger points—hyperirritable spots within taut bands of skeletal muscle that cause local and referred pain. The upper trapezius is a frequently affected muscle, and standard treatments include both pharmacologic and non-pharmacologic approaches. Among interventional treatments, dry needling has been widely used as a mainstay therapy, though its mechanism is not fully understood.

More recently, interfascial hydrodissection (IH) has emerged as a novel technique where anesthetic saline solution is injected between muscle fascia layers under ultrasound guidance. This approach is theorized to block nerve branches, reduce inflammatory mediators, improve fascial gliding, and decrease muscle friction. However, prior studies on interfascial injection were limited, with no randomized controlled trials directly comparing IH to dry needling for upper trapezius MPS. This study aimed to fill that gap by evaluating both short-term and long-term effects on pain and quality of life.

The researchers conducted a single-blind randomized controlled trial at a hospital in the Philippines. They recruited 46 adults aged 20–50 years who were newly diagnosed with MPS of the upper trapezius based on established clinical criteria (taut band, tenderness, pain reproduction). Participants were randomly assigned to one of two groups: interfascial hydrodissection with self-stretch exercises (IH+SSE, n=23) or dry needling with self-stretch exercises (DN+SSE, n=23). The IH procedure involved ultrasound-guided injection of 1cc 2% lidocaine mixed with 5cc normal saline solution between the trapezius fascia and the fascia of the underlying muscle.

Dry needling was performed using a solid filament needle with dynamic pistoning motion into the trigger point. All participants received daily self-stretching exercises with weekly text message reminders and were instructed not to pursue other MPS treatments during the study period. A blinded assessor evaluated outcomes at baseline, immediately after treatment, 10 and 30 minutes post-procedure, and at 1 week, 2 weeks, 4 weeks, 3 months, and 6 months follow-up. Pain was measured using the visual analogue scale (VAS, 0–10), and quality of life was assessed with the EQ-5D-5L questionnaire across five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression.

Two participants dropped out (one due to a vehicular accident, one due to undiagnosed cervical radiculopathy), but all 46 were included in the final intention-to-treat analysis.

Both treatment groups showed significant pain reduction from baseline across all time points, but with notable differences in timing and magnitude. The IH+SSE group had significantly lower VAS scores than the DN+SSE group immediately after the procedure (mean difference 2.00±2.00 vs. -0.26±3.06, Cohen's d=2.05 vs. -0.17), at 10 minutes (Cohen's d=2.88 vs. 0.45), and at 30 minutes (Cohen's d=2.88 vs. 1.08). However, from one week through four weeks post-treatment, the DN+SSE group showed larger effect sizes (Cohen's d=2.98, 3.52, and 3.32 respectively, vs. 2.25, 2.25, and 3.22 for IH+SSE). By three months and six months, the IH+SSE group again demonstrated larger effect sizes (Cohen's d=3.21 and 4.39 vs. 2.74 and 2.69).

The mixed two-way ANOVA revealed a significant main effect of time on VAS scores [F(8,352)=39.00, p<0.000, partial η²=0.47] and a significant time-by-group interaction [F(8,352)=6.20, p<0.000, partial η²=0.12]. The main effect of intervention approached significance [F(1,44)=3.80, p=0.058, partial η²=0.08].

For quality of life, no statistically significant differences were found between groups on any EQ-5D-5L dimension. However, effect sizes favored the IH+SSE group for usual activities (larger effect size at all baseline comparisons), pain/discomfort (larger effect sizes at 2 weeks, 4 weeks, and 6 months), and anxiety/depression (larger effect sizes at 2 weeks, 4 weeks, 3 months, and 6 months). The only statistically significant between-group difference in EQ-5D-5L was for anxiety/depression at one week, where the IH+SSE group had a higher (worse) mean score (1.17±0.39 vs. 1.00±0.00, p=0.037). Self-care showed significant improvements from baseline in the IH+SSE group at 2 weeks through 3 months, but not in the DN+SSE group.

Adverse events were minimal: one IH+SSE participant (4.3%) had neck stiffness at two weeks, while two DN+SSE participants (4.3% each) experienced heaviness at the injection site immediately post-procedure and neck stiffness at two months. All adverse events resolved within one week with exercises alone.

This study provides the first randomized controlled trial evidence that ultrasound-guided interfascial hydrodissection with lidocaine-saline solution is a viable alternative to dry needling for myofascial pain syndrome of the upper trapezius. The immediate and superior short-term pain relief with IH suggests it may be particularly useful when rapid analgesia is desired—such as in acute flare-ups or when patients need quick functional recovery. The crossover pattern, where dry needling performed better at 1–4 weeks while IH showed advantages at 6 months, suggests these treatments may work through different mechanisms with distinct temporal profiles. IH's long-term benefits may stem from improved fascial gliding, washout of algesic substances, and reduced mechanical friction between muscle layers, while dry needling's mid-term superiority may reflect more direct trigger point deactivation.

For clinicians, this offers evidence to consider IH when patients are needle-phobic (though both use needles), when trigger points are difficult to localize precisely, or when longer-term outcomes are prioritized. The minimal adverse events in both groups support the safety of both approaches. The mandatory self-stretching component in both groups, reinforced by weekly reminders, likely contributed to sustained benefits and should be considered an essential adjunct rather than optional. The lack of a true sham or no-treatment control group limits definitive conclusions about absolute efficacy, and the absence of cervical range of motion assessment leaves functional impact partially unexplored.

Future research should include sham controls, larger samples, and objective measures like elastography to better understand fascial changes. For patients with chronic upper trapezius MPS, this study suggests that interfascial hydrodissection is a reasonable option to discuss with their healthcare provider, particularly if prior dry needling results have been disappointing or if they seek a treatment with potentially more durable long-term effects.