The gluteus maximus overlies the piriformis muscle and forms a broad fascial interface with it. Restricted movement, increased tension, or adhesions between these tissue layers may contribute to persistent buttock pain in piriformis syndrome. Interfascial hydrodissection is an ultrasound-guided procedure in which fluid is introduced between the gluteus maximus and piriformis muscles to gently separate restricted fascial planes, improve tissue gliding, reduce local mechanical irritation, and potentially modulate nociceptive input from pain-sensitive nerve endings within or adjacent to the fascial interface.
The goal of this clinical trial is to learn whether adding ultrasound-guided interfascial hydrodissection to a piriformis injection provides better pain relief and improves function in adults with piriformis syndrome.
Piriformis syndrome can cause buttock pain that may spread to the back of the thigh or leg. Interfascial hydrodissection is a procedure in which fluid is injected between the gluteus maximus and piriformis muscles. The fluid gently separates the tissue layers and may help them move more freely.
The main questions this trial aims to answer are:
* Does adding interfascial hydrodissection to a piriformis injection lower overall pain more than the piriformis injection alone at 3 months after treatment? * Does it provide greater improvement in pain at earlier follow-up visits, hip-related function, and overall recovery?
All participants will first receive one ultrasound-guided local anesthetic injection into the piriformis muscle. The early pain response will help support the diagnosis, and the same injection will serve as the common treatment received by both groups. Participants whose pain improves by at least 50 percent will be randomly assigned to either continue with the piriformis injection alone or receive additional interfascial hydrodissection. After the 1-week assessment, participants in both groups will begin the same home-based piriformis stretching program.
Participants will:
* Receive one ultrasound-guided piriformis injection and, depending on group assignment, may also receive interfascial hydrodissection * Have follow-up assessments later on the treatment day and at 1 week, 1 month, and 3 months * Follow the same home-based stretching program after the 1-week assessment * Report their pain, daily function, overall improvement, pain medicine use, additional treatment needs, and any side effects
Age 18 to 70 years.
Buttock or gluteal pain that may radiate to the posterior thigh and/or leg.
Medical history and physical examination findings consistent with piriformis syndrome.
Tenderness on palpation over the piriformis muscle.
Active lumbar radiculopathy, clinically significant lumbar disc herniation, spinal stenosis, or another spinal disorder that could explain the participant's symptoms.
Clinically significant neurological deficit.
Marked limitation of lumbar spine and/or hip range of motion.
Previous surgery involving the lumbar spine or hip region.
Parallel
Ultrasound-Guided Piriformis Injection
Procedure/SurgeryBefore randomization, participants who meet the initial clinical eligibility criteria will receive one ultrasound-guided injection of 5 mL of 2% lidocaine into the piriformis muscle. The injection will have both diagnostic and therapeutic intent. The early pain response will be used to support the diagnosis and determine eligibility for randomization. In participants who demonstrate at least a 50 percent reduction in overall pain and proceed to randomization, the same injection will constitute the common active treatment received by both arms.
Ultrasound-Guided Interfascial Hydrodissection
Procedure/SurgeryAfter assessment of the early pain response and randomization, participants assigned to the experimental arm will receive one ultrasound-guided interfascial hydrodissection of the tissue plane between the gluteus maximus and piriformis muscles. Hydrodissection will be performed using a total volume of 20 mL consisting of 18 mL of 0.9% sodium chloride and 2 mL of 1% lidocaine.
Standardized Home-Based Piriformis Stretching Program
BehavioralAfter completion of the 1-week assessment, participants in both arms will begin the same standardized home-based piriformis stretching program and will continue the program for 6 weeks. The exercise will be demonstrated by a member of the rehabilitation team, written instructions will be provided, and adherence will be recorded during follow-up.
Change From Pre-Injection Baseline in Overall Pain Intensity on the 11-Point Numeric Rating Scale at 3 Months
Overall pain intensity will be measured using an 11-point Numeric Rating Scale ranging from 0 (no pain) to 10 (worst imaginable pain). The change score will be calculated as the 3-month score minus the pre-injection baseline score. More negative change scores indicate greater improvement in pain.
Change From Pre-Injection Baseline in Overall Pain Intensity at Earlier Follow-Up Time Points
Overall pain intensity will be measured using an 11-point Numeric Rating Scale ranging from 0 (no pain) to 10 (worst imaginable pain). Change scores will be calculated separately at 1 hour, 1 week, and 1 month by subtracting the pre-injection baseline score from the score at each follow-up time point. More negative change scores indicate greater improvement in pain.
Change From Pre-Injection Baseline in the Situation-Specific Pain Profile
The situation-specific pain profile consists of 6 prespecified component ratings: pain at rest, during activity, at night, while sitting, while standing, and while lying down. Each component will be measured separately using an 11-point Numeric Rating Scale ranging from 0 (no pain) to 10 (worst imaginable pain). Change scores for each component will be calculated separately by subtracting the pre-injection baseline score from the score at each follow-up time point. More negative change scores indicate greater improvement. The component scores will be reported separately, and no total or combined pain score will be calculated.
Change From Baseline in Hip-Related Function Measured by the Non-Arthritic Hip Score
Function will be assessed using the Non-Arthritic Hip Score, a 20-item participant-reported questionnaire scored from 0 to 100. Higher scores indicate better hip-related function. Change scores will be calculated separately at each follow-up time point by subtracting the baseline score from the follow-up score. More positive change scores indicate greater functional improvement.
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