Background/Purpose: Piriformis syndrome (PS), which is characterized by pain radiating to gluteal region and posterior leg, is accepted as one of the causes of sciatica. Although the importance of local piriformis muscle injections whenever PS is clinically suspected has been shown in many studies, there is not enough study considering the clinical efficacy of these injections. The objective of this study was to compare the effectiveness of ultrasound (US)-guided local anesthetic (LA) and corticosteroid (CS) injections for the treatment of PS.

Methods: Fifty-seven patients with a pre-diagnosis of PS after clinical evaluation were included in this prospective randomized double-blind study. After baseline assessments that were done by the first physiatrist, subjects who were blinded to group allocation, were randomized by the second physiatrist. US-guided injections of 4 cc of lidocaine 2% (LA group) and 4 cc of lidocaine 2%+1 cc of betametazone dipropionate (LA+CS group) with a 22-gauge 88 mm Spinocan were done by the third physiatrist with a Diasus dynamic imaging US equipped with a 5- to 10- MHz multifrequency transducer. The patients whose pain resolved 50% and more were included in the study. Seven patients whose injection tests were negative were excluded from the study. Each group contained 25 patients with a diagnosis of PS. The subjects were re-assessed by the first physiatrist with physical examination and Likert Analogue Scale (LAS) and Numeric Rating Scale (NRS) at the 1st week, the 1st and 3rd months after the injection.  

Results: The difference between two groups was analyzed with Pillai’s Trace, which is a multivariate analysis from general linear models. No statistically significant difference (p>0,05)  was detected between the groups in NRS score values at resting (p=0.814), night (p=0.830) and in motion (p=0.145) and LAS values with long duration of sitting (p=0.547), standing (p=0.898) and lying (p=0.326) with evaluations at the baseline, 1st week, 1st and 3rd months after the injection. Each group was compared within itself by Friedman test, which is used for non-parametric repeated measures. A statistically highly significant (p<0,005) reduction of pain was evaluated through NRS scores at resting (p=0.001), in motion (p=0.001)  and at night (p=0.001) and and LAS values with long duration of sitting (p=0.001), standing (p=0.001) and lying (p=0.001) in both of the groups. 

Conclusion: LA injections for the PS were found to be clinically effective. However, addition of CS to LA did not give an additional benefit. This gives us the idea that PS has similar features with the other myofascial pain syndromes and responds well to trigger point injections.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-the-effectiveness-of-local-anesthetic-and-corticosteroid-injections-for-the-treatment-of-piriformis-syndrome/