Piriformis muscle block
by Baheti Dwarkadas K, Bakshi Sanjay, Gupta Sanjeeva, Gehdoo Raghbir Singh

Interventional Pain Management: A Practical Approach

by Sanjay Bakshi, Sanjeeva Gupta, Dwarkadas K Baheti, Raghbir Singh P Gehdoo
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This video demonstrates a technique to inject the piriformis muscle under fluoroscopic guidance with nerve stimulator. The patient is placed on the fluoroscopy table in prone position with a pillow under pelvis and acetabular region. Now place metal marker on most inferior aspect of the SI joint and of the most superior-lateral aspect of the acetabulum. On this line, about one-third of the way medial from acetabular landmark is the needle entry point. After painting and draping, inject 1% lignocaine; care must be taken to avoid the deeper structures to prevent loss of stimulating ability of the nerve stimulator by the local anesthetic. A 4-inch Stimuplex insulated needle is inserted and advanced under fluoroscopic guidance. Now, stimulation output is obtained at 1.5–2.0 mA and 2 Hz frequency to obtain contraction of the gluteus maximus muscle. Then, the stimulator output is reduced until only a moderate gluteal twitch is observed. Now, advance needle until contraction of the gluteus is markedly diminished. The output is reduced to less than 0.6 mA and the needle tip adjusted until there is just a discernable twitch noted at the needle hub and at the hip, which identifies the piriformis muscle. Inject 1 mL of radiopaque contrast to obtain myogram of piriformis muscle. Contrast should flow in a diagonal pattern from cephalad to caudad as it goes toward the femoral attachment site of the piriformis muscle. Now, inject 3 cc mixture of 0.25% bupivacaine with or without steroid into the piriformis muscle after negative aspiration for blood. In patients that are refractory to local and/or steroid medication, injection botulinum toxin 100 IU is beneficial.

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