Long-term assessment of clinical outcomes of ultrasound-guided steroid injections in patients with piriformis syndrome.

Purpose: The purpose of this study was to evaluate the long-term efficacy of ultrasound (US)guided steroid injections in patients with piriformis syndrome. Methods: Between January 2010 and October 2012, 63 patients (23 men and 40 women; average age, 63.2 years; range, 24 to 90 years) were diagnosed with piriformis syndrome based on clinical history, electromyography, and flexion-adduction-internal rotation test results. They were divided into two groups. The first group (37 subjects) received a US-guided steroid injection around the piriformis muscle. The second group (26 subjects) received both piriformis muscle and spinal epidural injections. The therapeutic effect was categorized as improvement, partial improvement, or failure depending on the degree of symptom alleviation one month after injection, based on a review of each patient's medical records. Results: In the first group, 15 patients (40.5%) showed improvement, seven (18.9%) showed partial improvement, and 15 (40.5%) failed to respond to the initial treatment. In the second group, eight patients (30.8%) showed improvement, 11 (42.3%) showed partial improvement, and seven (26.9%) failed to respond to the initial treatment. A second piriformis injection was performed in four cases, after which two patients showed improvement within 3 years, but the other two showed no therapeutic effect. Conclusion: US-guided steroid injection may be an effective treatment option for patients with piriformis syndrome.