Efficacy of Ultrasound-Guided Interfascial Hydrodissection for Myofascial Pain Syndrome of the Gluteus Maximus in Patients With Piriformis Syndrome: A Double-Blind Randomized Controlled Trial.

Piriformis syndrome (PS) is a neuromuscular condition characterized by compression or irritation of the sciatic nerve at the piriformis muscle level. Patients frequently present with unilateral gluteal pain that worsens with prolonged sitting, hip movement, or palpation over the piriformis locus. Although the neuropathic component of PS is attributed to sciatic nerve irritation, the somatic pain component is believed to arise from myofascial dysfunction within gluteal structures, particularly the piriformis muscle.

Recent clinical observations indicate that many patients diagnosed with PS also exhibit features of gluteus maximus myofascial pain syndrome (GM-MPS). The gluteus maximus muscle has a large fascial interface with the piriformis muscle, and nociceptive stimulation originating from this interface may contribute to persistent gluteal pain in PS. Despite this, the fascial contribution to symptom persistence remains poorly investigated, and therapeutic interventions are largely directed toward the piriformis alone.

Interfascial hydrodissection is an emerging ultrasound-guided technique in which liquid is injected between tissue planes to mechanically separate fascial layers, improve gliding, and modulate sensory nociceptive fibers. Dextrose solutions have been increasingly used in ultrasound-guided interfascial injections based on their proposed neuromodulatory and regenerative effects. However, evidence regarding its long-term efficacy in gluteal myofascial pain, particularly when coexisting with PS, is limited.

This prospective, randomized, double-blind clinical trial aims to evaluate the therapeutic effectiveness of interfascial hydrodissection using 10% dextrose solution between the gluteus maximus and piriformis muscles in patients with PS diagnosed through positive diagnostic injection response. Patients with ≥50% pain reduction one hour after diagnostic piriformis injection will be randomized into two treatment groups. Randomization will be performed by an independent co-investigator using a pre-prepared 1:1 allocation list. Outcome assessment will be conducted by an investigator blinded to treatment allocation. Patients will then be assigned to one of the following treatment groups: (1) ultrasound-guided interfascial hydrodissection and (2) dry needling of the gluteus maximus muscle.Both interventions will be performed under ultrasound guidance to ensure accuracy and standardization.

Outcome assessment will include numerical pain scoring, percentage pain reduction, and clinical improvement at one hour, one week, one month, and three months post-intervention. The first assessor will be blinded to treatment allocation, ensuring independent measurement of outcomes. It is hypothesized that interfascial hydrodissection will provide superior long-term pain relief compared with dry needling by separating adhered fascial planes, improving local mobility, and reducing nociceptive drive through dextrose-mediated neuromodulation.