Effect of Ultrasound-guided Piriformis Muscle Corticosteroid Injection Versus Extracorporeal Shock Wave Therapy for Piriformis Syndrome: a Randomized Control Trial

Effect of Ultrasound-guided Piriformis Muscle Corticosteroid Injection Versus Extracorporeal Shock Wave Therapy for Piriformis Syndrome

In this study, the investigators aim to compare the effect of extracorporeal shockwave therapy with ultrasound-guided piriformis coticosteroid injection in treatment of PS.

Piriformis syndrome (PS) is one of the common etiology of low back pain. The cause of PS is due to myofascial syndrome of piriformis muscle, leading to piriformis muscle spasm, string-like taut band, and trigger point. Consequently, it may compresses the sciatic nerve which arise from sciatic notch and passes under the piriformis muscle. Conservative treatment of PS includes therapeutic exercise, diathermy, and local steroid injection. Among them, as radiology techniques advance, ultrasound-guided piriformis injection becomes popular for diagnosis block and treatment. Nowadays, extracorporeal shockwave therapy has widely applied in musculoskeletal disease such as plantar fasciitis, tennis elbow, and calcific tendinitis of the shoulder. However, to the investigators best knowledge, there is no study comparing the therapeutic effect between local steroid injection and shockwave. In this study, the investigators aim to compare the effect of extracorporeal shockwave therapy with ultrasound-guided piriformis corticosteroid injection.

This is a randomized controlled trial. 70 participants will be randomly divided into shockwave group and injection group. The participant in the shockwave group will receive one time extracorporeal shockwave therapy, and injection group will receive one time ultrasound-guided piriformis muscle corticosteroid injection. After the intervention, participant in both groups will receive home-based stretch exercise. Evaluation will be performed at baseline, 1 week, and 5 weeks after intervention. Outcome measures include the pain visual analog scale (VAS), hip range of motion, change of pressure pain threshold, and Oswestry Disability Index (ODI).

Inclusion Criteria:

1. Age from 20 to 80
2. Unilateral buttock involvement without leg pain or paresthesia
3. Duration of symptoms ≥1 month
4. Positive trigger point or taut band at piriformis muscle, confirmed by palpation and ultrasound examination
5. Positive FAIR (flexion, adduction, internal rotation) test
6. Positive piriformis resistive test (patient actively abducts and/or externally rotates the hip while the examiner resists these movements

Exclusion Criteria:

1. Having received hip, pelvis, or lumbar spine surgery
2. Low back pain or buttock pain due to lumbosacral spine, hip or pelvis lesion other than piriformis syndrome
3. Having received shock wave therapy or corticosteroid injection for buttock pain within the past one month
4. Neurologic deficit in in the lower limbs
5. History of drug allergy to local anesthetics or corticosteroids
6. Pregnancy