BL54 ACUPUNCTURE LANDMARK TO FACILITATE ULTRASOUND-GUIDED PIRIFORMIS MUSCLE INJECTION: S. Sorrenti1, M. Ciuffreda1, E. Pisello1, C. Pellegrino2, A. Monacelli2, G. Cucè3, L. Angelelli1, C. Piangatelli1, D. Galante4 | 1U.O.C. Anestesia Rianimazione Terapia del Dolore, AST Ancona, Fabriano (AN), Italy; 2Scuola di Specializzazione in Anestesia Rianimazione, Terapia Intensiva e del Dolore, Università Politecnica delle Marche, Ancona, Italy; 3Scuola di Specializzazione in Igiene e Medicina Preventiva, Università degli Studi di Messina, Italy; 4U.O.C. Anestesia e Rianimazione, ASL Foggia, Cerignola (FG), Italy

Introduction. Piriformis syndrome is an entrapment neuropathy caused by compression or irritation of the sciatic nerve by the piriformis muscle, frequently resulting from muscle hypertrophy, spasm, or anatomical variations described by the Beaton and Anson classification (1). Patients typically present with deep gluteal pain radiating along the posterior thigh, often worsened by prolonged sitting, hip flexion, or uphill walking. Ultrasound-guided piriformis muscle injection is an effective therapeutic option; however, accurate identification of the target muscle remains highly operator-dependent, particularly in patients with challenging anatomy. This study evaluated the usefulness of the Bladder 54 (Zhibian, BL54) acupuncture point as an anatomical landmark to facilitate ultrasound-guided piriformis muscle identification and injection.Methods. A prospective observational study included 30 consecutive patients (15 women and 15 men; age range 16–45 years) diagnosed with piriformis syndrome and referred for ultrasound-guided piriformis muscle injection. The BL54 acupuncture point was identified approximately 3 cun lateral to the midline at the level of the sacral hiatus. The individualized 3-cun measurement was converted into centimeters for each patient and marked on the skin. A convex ultrasound probe was then used to evaluate the underlying anatomy, identify the piriformis muscle, and assess its morphology before performing the ultrasound-guided injection.Results. In all 30 patients, ultrasound examination performed from the BL54 landmark enabled rapid identification of the piriformis muscle regardless of body habitus. The muscle was consistently visualized at the thickest portion of its muscle belly, facilitating optimal needle targeting and procedural planning. The combined use of an individualized acupuncture landmark and ultrasound guidance improved anatomical orientation and simplified localization of the target muscle during the procedure.Conclusions. The BL54 (Zhibian) acupuncture point appears to be a reliable anatomical landmark for ultrasound-guided piriformis muscle injection. Combining individualized acupuncture-based surface anatomy with ultrasound imaging may facilitate target identification, personalize the procedure, and reduce operator dependency. Larger comparative studies are warranted to evaluate the impact of this approach on procedural accuracy, clinical outcomes, and reproducibility.