An interventional study of Ultrasound-Guided Piriformis Injection and Ultrasound-Guided Interfascial Hydrodissection in Piriformis Syndrome, sponsored by Haydarpasa Numune Training and Research Hospital. Recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-09-28.
Sponsored by Haydarpasa Numune Training and Research Hospital · Not applicable, Interventional, and Treatment
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:
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:
Piriformis syndrome is a clinical pain condition characterized by buttock pain that may radiate to the posterior thigh or leg. Symptoms may be associated with dysfunction of the piriformis muscle, irritation of the sciatic nerve, and abnormalities within the surrounding soft-tissue planes. Because its clinical presentation may resemble lumbar radiculopathy or primary hip disorders, diagnosis is generally based on clinical examination, exclusion of other important causes of symptoms, and response to an ultrasound-guided piriformis injection.
The gluteus maximus overlies the piriformis muscle and forms a broad fascial interface with it. In some participants, restricted gliding, increased tension, or adhesions within this plane may contribute to persistent gluteal pain in addition to abnormalities involving the piriformis muscle itself. Despite the potential clinical importance of this interface, most interventional treatments for piriformis syndrome are directed primarily toward the piriformis muscle.
Ultrasound-guided piriformis injection is used in clinical practice for both diagnostic and therapeutic purposes. Interfascial hydrodissection is an emerging ultrasound-guided technique in which fluid is introduced between adjacent tissue layers. The procedure may separate restricted fascial planes, improve gliding between the gluteus maximus and piriformis muscles, reduce local mechanical irritation, and modulate nociceptive input from pain-sensitive free nerve endings and small sensory nerve branches within or adjacent to the fascial plane. However, the additional clinical benefit of hydrodissection over piriformis injection alone remains uncertain.
This is a prospective, randomized, assessor-blinded, parallel-group, active-controlled, single-center clinical trial. Adults with clinical findings consistent with piriformis syndrome will undergo a detailed clinical assessment and review of available routine imaging to exclude lumbar radiculopathy, major hip pathology, and other important causes of buttock or leg pain. The clinical examination will include palpation of the piriformis muscle and the FAIR, Freiberg, Pace, and Beatty maneuvers.
Participants who meet the initial eligibility criteria will receive a single ultrasound-guided local anesthetic injection into the piriformis muscle. This injection will have both diagnostic and therapeutic intent. The early pain response will be used to support the diagnosis and determine eligibility for randomization, while the same injection will serve as the common active treatment received by both randomized groups. Approximately 110 participants are expected to undergo the pre-randomization diagnostic-therapeutic piriformis injection, of whom approximately 96 are expected to demonstrate at least a 50 percent reduction in overall pain and proceed to randomization.
Participants who demonstrate at least a 50 percent early reduction in overall pain compared with their pre-injection pain level will be randomly assigned in a 1:1 ratio to one of two parallel groups. The active-control group will receive no additional invasive procedure. The intervention group will receive ultrasound-guided interfascial hydrodissection of the tissue plane between the gluteus maximus and piriformis muscles after the early response assessment. All invasive procedures will be completed during the same study visit under standardized sterile conditions.
The early pain assessment used to determine eligibility for randomization will be recorded separately from the post-randomization outcome assessments. The first comparative follow-up assessment will be performed 1 hour after hydrodissection in the intervention group and at the corresponding post-randomization time point in the active-control group. Subsequent assessments will be performed at 1 week, 1 month, and 3 months.
The piriformis injection and, when assigned, the hydrodissection procedure will be performed by a physical medicine and rehabilitation physician experienced in ultrasound-guided interventions. Baseline and follow-up outcome assessments will be conducted by a different physical medicine and rehabilitation physician working in the same clinic. The outcome assessor will not participate in the procedures, will not have access to treatment allocation records, and will remain unaware of treatment allocation throughout follow-up. Participants will be instructed not to disclose their group assignment to the outcome assessor.
After completion of the 1-week assessment, participants in both groups 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.
The primary objective is to determine whether adding interfascial hydrodissection produces a greater reduction in overall pain intensity from the pre-injection baseline to 3 months than the piriformis injection alone.
Secondary evaluations will include changes in overall pain at 1 hour, 1 week, and 1 month; pain at rest, during activity, at night, while sitting, while standing, and while lying down; hip-related function measured using the Non-Arthritic Hip Score; participant-reported global improvement; analgesic medication use; the need for additional or repeat treatment; and adverse events.
By comparing a diagnostic-therapeutic piriformis injection and standardized home-based stretching program with the same care supplemented by interfascial hydrodissection, this study aims to determine whether addressing the gluteus maximus-piriformis fascial interface provides additional and sustained clinical benefit in participants with piriformis syndrome.
58 studies on the registry are indexed under Piriformis Muscle Syndrome; 23 are open to participants now.
This study's planned enrollment of 110 is above the median of 42 across 52 interventional studies indexed under Piriformis Muscle Syndrome.
Browse Piriformis Muscle Syndrome studies →Haydarpasa Numune Training and Research Hospital is the lead sponsor of 33 studies on the registry; 7 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Additional criterion for randomization:
- At least a 50 percent early reduction in overall pain after the single ultrasound-guided local anesthetic piriformis injection.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before randomization, participants will receive a single ultrasound-guided injection of 5 mL of 2% lidocaine into the piriformis muscle with both diagnostic and therapeutic intent. The early pain response will be used to determine eligibility for randomization. Participants with at least a 50 percent reduction in overall pain who are assigned to this arm will receive no additional invasive procedure. After completion of the 1-week assessment, participants will begin the standardized 6-week home-based piriformis stretching program.
Procedure: Ultrasound-Guided Piriformis Injection · Behavioral: Standardized Home-Based Piriformis Stretching Program
Before randomization, participants will receive an ultrasound-guided injection of 5 mL of 2% lidocaine into the piriformis muscle with both diagnostic and therapeutic intent. The early pain response will be used to determine eligibility for randomization. Participants with at least a 50 percent reduction in overall pain who are assigned to this arm will receive a single ultrasound-guided interfascial hydrodissection between the gluteus maximus and piriformis muscles using 18 mL of 0.9% normal saline and 2 mL of 1% lidocaine. Hydrodissection will be performed after the early response assessment during the same study visit. After completion of the 1-week assessment, participants will begin the same standardized 6-week home-based piriformis stretching program.
Procedure: Ultrasound-Guided Piriformis Injection · Procedure: Ultrasound-Guided Interfascial Hydrodissection · Behavioral: Standardized Home-Based Piriformis Stretching Program
Before 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.
After 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.
Also known as: Gluteus Maximus-Piriformis Interfascial Hydrodissection
After 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.
Time frame: Pre-injection baseline and 3 months after randomization
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.
Time frame: Pre-injection baseline and 1 hour, 1 week, and 1 month after randomization
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.
Time frame: Pre-injection baseline and 1 week, 1 month, and 3 months after randomization
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.
Time frame: Baseline and 1 week, 1 month, and 3 months after randomization
Plan to share: No — There is currently no plan to share de-identified individual participant data with external researchers. Study results will be reported in aggregate form.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Haydarpasa Numune Training and Research Hospital