An 83-yr-old man had left gluteal and posterior thigh pain for 1 yr. He had undergone L4-5 laminectomy and internal fixation for L4-5 spondylolisthesis, but his symptoms did not improve. On physical examination, palpation of the piriformis line elicited trigger-point tenderness, flexion, adduction, and internal rotation, Freiberg's and Pace's signs were positive. Straight leg raise test as well as flexion, abduction, and external rotation were negative. There were no neurological deficits. The tentative diagnosis was piriformis muscle pain (and not piriformis syndrome given the absence of pseudo sciatica). The patient decided to receive ultrasound (US)-guided injection after discussion on various treatments.
On US examination, there was no obvious sonographic abnormality such as gluteus maximus (GMax) atrophy or piriformis hypoechoic changes. Ultrasound-guided needling with injection to GMax and piriformis muscles with triamcinolone 10 mg, lidocaine 1% 5 ml, and 0.9% sodium chloride solution 4 ml was performed. Local twitch responses were elicited in GMax but not in piriformis (Video). Immediate gluteal pain relief by 50% was observed after the procedure. In the authors' experience, isolated needling with injection of GMax seems to provide important relief in many cases of buttock pain often labeled as piriformis syndrome.
Piriformis syndrome remains a controversial diagnosis for sciatic pain, whereas piriformis myofascial pain is well recognized.1 A piriformis injection may be considered for diagnostic and/or therapeutic purposes, and US guidance has been recommended to improve safety and accuracy because of the deep location the piriformis muscle and its close proximity to important neurovascular structures.2 Although most literatures described injection within or superficial to the piriformis muscle, we noted that local twitch responses were much more likely to be induced during needling of GMax, rather than piriformis. Ultrasound-guided needling of gemelli and obturator internus muscles has been reported to relieve piriformis syndrome symptoms in a patient who had remained unresponsive to repeated piriformis injections.3 It implies that the piriformis muscle may not be the only pain generator in piriformis syndrome. In our experience, isolated injection to piriformis muscle might not entirely relieve the symptoms in cases of presumed piriformis syndrome.
To better discriminate the pain generators, the superimposed GMax and piriformis could be injected on separate sessions. However, if both are presumed to be involved in buttock pain, they can easily be injected/needled at the same time with the same needle entry point (Video).
By presenting this case, we would like to propose the idea that GMax should not be neglected when treating patients with buttock pain.
1. Jankovic D, Peng P, van Zundert A: Brief review: piriformis syndrome: etiology, diagnosis, and management. Can J Anaesth
2. Payne JM: Ultrasound-guided hip procedures. Phys Med Rehabil Clin N Am
3. Vas L, Pai R, Pawar KS, et al.: “Piriformis syndrome”: is it only piriformis? Pain Med