Ultrasonographic Evaluation of the Sciatic Nerve in Patients With Piriformis Syndrome (Sciatica)

February 28, 2026 updated by: Busra Sezer Kıral, Istanbul University - Cerrahpasa
Piriformis syndrome (PS) is defined as a neuropathy of entrapment resulting from compression and irritation of the sciatic nerve at the level of the piriformis muscle (PM) at the pelvic outlet, causing sciatica radiating to the leg. The neuropathic component of PS is the compression of the sciatic nerve in or around the PM, while the primary cause of the somatic component is myofascial pain of the PM. PS accounts for 6-8% of all hip and sciatic pain cases. It is more common in middle-aged patients, and the most common etiological cause is trauma. There are various methods for the diagnosis of Piriformis Syndrome. Clinically, tenderness on palpation of the PM is the most common symptom. The FAIR test (passive flexion abduction and internal rotation of the hip), the Freiberg test (forceful internal rotation of the thigh in the supine position), the Pace test (abduction of the leg against resistance while sitting) and the Beatty maneuver (active abduction of the thigh on the affected side in the lateral decubitus position) are maneuvers that help in diagnosis. It is known that there is a delay in proximal nerve conduction (H-reflex) on the pathological side compared to the healthy side in the FAIR maneuver on EMG in PS, and it is not a sufficient test for diagnosis alone. Some studies have reported increased piriformis thickness on the pathological side in MRI. None of these clinical and imaging methods are sufficient for diagnosis alone, and today ultrasonography (US) has become one of the most important imaging methods for musculoskeletal clinicians in the diagnosis of PS. Imaging with US and the diagnostic injection test applied to the piriformis muscle with US guidance are quite important for diagnosis. There are a number of studies in the literature evaluating PM with US. These studies have shown that the piriformis muscle thickness and echogenicity increase on the pathological side. However, there is a lack of studies in the literature focusing on the evaluation of the sciatic nerve with US in patients with PS. Our aim in this study is to compare the thickness of the PM and the sciatic nerve by measuring US on both the pathological and painless sides in patients with unilateral hip pain who were diagnosed with PS clinically, to record the variations present in the sciatic nerve, and to determine whether the myofascial pain or the neuropathic component is dominant in the disease.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

The sciatic nerve is the largest nerve in the body and is formed by the ventral roots of the lumbosacral plexus (L4-S3), passes through the foramen ischiadicum majus under the piriformis muscle (PM) and enters the gluteal region. It is controversial whether anatomical variations in the sciatic nerve and PM predispose to the development of Piriformis syndrome (PS). The sciatic nerve passes under the PM as a single branch in almost 90% of cases. However, there are some variations where it passes above and through the muscle or divides into tibial and peroneal branches, with one branch passing under the piriformis. There are a number of studies in the literature evaluating the PM with US. These studies have shown that the PM thickness and echogenicity increase on the pathological side. In addition, it has been mentioned that the sciatic nerve has a coarse and blurry image in patients complaining of sciatic pain. In one study, cross-sectional area measurement was performed instead of PM thickness measurement. However, this was criticized in later studies, and it was stated that it was difficult to calculate muscle volume exactly with two-dimensional US due to the irregular shape of the PM, which is anatomically pear-shaped, and that thickness measurement would provide more accurate results instead of cross-sectional area. In the first study in the literature focusing on the sciatic nerve in PS and the neuropathic pain it causes, it was found that the sciatic nerve was significantly enlarged (75%) on the symptomatic side and had decreased echogenicity in some patients when compared to healthy volunteers.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
19

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Turkey (Türkiye)
      • Istanbul, Turkey (Türkiye)
        • İstanbul Üniversitesi - Cerrahpasa (IUC)

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Probability Sample

Study Population

Patients aged between 18 and 70 years with unilateral hip and/or leg pain, positive FAIR (flexion, adduction, internal rotation) test, and tenderness to palpation in the PM will be included in our study.

Description

Inclusion Criteria:

  • Patients aged between 18 and 70 years with unilateral hip and/or leg pain
  • Positive FAIR (flexion, adduction, internal rotation) test
  • Tenderness to palpation in the Piriformis muscle

Exclusion Criteria:

  • Patients with a history of previous surgery involving the lumbar and/or hip region
  • A history of malignancy or infection in the pelvic region
  • Body mass index (BMI) Greater than 30 kg/m2
  • Psychiatric diseases
  • Vascular disease
  • Uncontrolled diabetes, hypertension or heart failure,
  • Disc pathologies that may cause radiculopathy
  • History of rheumatic disease.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
symptomatic hip
Patients aged between 18 and 70 years with unilateral hip and/or leg pain, positive FAIR (flexion, adduction, internal rotation) test, and tenderness to palpation in the PM will be included in our study.
Other: Ultrasound
The ultrasound probe will be placed parallel to the body of the piriformis muscle on an imaginary line drawn from the sacrum to the greater trochanter of the femur. This area is also the sensitive area of the patients during the examination with pressure, and when the US probe is in this position, the subcutaneous fat tissue, gluteus maximus muscle, piriformis muscle, and the upper and lower borders of the sciatic nerve will be displayed in order from superficial to deep. First, the maximum thickness of the piriformis muscle body will be measured, then the thickness of the sciatic nerve will be measured, and the same measurements will be applied to the patient's asymptomatic hip, and the measurements will be recorded.
asymptomatic hip
Patients aged between 18 and 70 years with unilateral hip and/or leg pain, positive FAIR (flexion, adduction, internal rotation) test, and tenderness to palpation in the PM will be included in our study.
Other: Ultrasound
The ultrasound probe will be placed parallel to the body of the piriformis muscle on an imaginary line drawn from the sacrum to the greater trochanter of the femur. This area is also the sensitive area of the patients during the examination with pressure, and when the US probe is in this position, the subcutaneous fat tissue, gluteus maximus muscle, piriformis muscle, and the upper and lower borders of the sciatic nerve will be displayed in order from superficial to deep. First, the maximum thickness of the piriformis muscle body will be measured, then the thickness of the sciatic nerve will be measured, and the same measurements will be applied to the patient's asymptomatic hip, and the measurements will be recorded.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
numeric scale
Time Frame: five months
Tenderness in the piriformis muscle will be assessed by palpation using the numerical scale (NRS). The numerical scale is a pain score and is evaluated between 0 and 10.
five months
Sciatic nerve thickness (measurement with US)
Time Frame: five months
Sciatic nerve thickness will be measured with ultrasound on the symptomatic and asymptomatic sides in the same patient.
five months
Piriformis muscle thickness (measurement with US)
Time Frame: five months
Piriformis muscle thickness will be measured with ultrasound on the symptomatic and asymptomatic sides in the same patient.
five months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Istanbul University - Cerrahpasa

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Istanbul Physical Medicine Rehabilitation Training and Research Hospital

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Selim Sezikli, Istanbul Physical Medicine Rehabilitation Training and Research Hospital

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 1, 2024

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
April 1, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
April 1, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
January 7, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
January 14, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
January 20, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
March 3, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
February 28, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 2024-69
  • Istanbul PMR (Other Identifier: Istanbul PMR Training and Research Hospital)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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