{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T07:44:46Z","timestamp":1782719086308,"version":"3.54.5"},"reference-count":21,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2026,6,27]],"date-time":"2026-06-27T00:00:00Z","timestamp":1782518400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Japanese Non-surgical Orthopedics Society","award":["JNOS202401"],"award-info":[{"award-number":["JNOS202401"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medical Sciences"],"abstract":"<jats:p>Background\/Objectives: Ultrasound-guided fascial hydrorelease (FHR) occasionally elicits a brief localized contraction (\u201clocal twitch\u201d) at the moment the needle tip contacts a fascial layer; the anatomical basis of this reaction has not yet been systematically characterized. To examine local twitch occurrence relative to stacking fascia (yes\/no) at the needle tip (primary outcome), as well as the anatomical distribution and per-video capture rate (secondary outcomes). Methods: We retrospectively analyzed 11,205 ultrasound videos from a single pain clinic (October 2015\u2013March 2026). Twitches were identified by prospective clinical observation and computational screening (frame-difference-based Profile Match classifier; 417 candidates over 30 review rounds). The stacking fascia status was independently determined by two FHR-experienced clinicians, with discordant cases jointly adjudicated. Results: Inter-rater agreement was 86\/90 (95.6%; 95% CI 89.0\u201398.8%); one case was reassessed, deemed to not be a twitch, and excluded. In the final cohort (n = 89), local twitches occurred at stacking fascia in 89\/89 (100%; 95% CI 95.9\u2013100%). Events were concentrated in gluteal\/pelvic (51%) and lumbar paraspinal (29%) regions, with a per-video capture rate of 0.98% (110\/11,205; 95% CI 0.81\u20131.18%). Conclusions: Local twitches during ultrasound-guided FHR essentially always coincide with the needle tip lying within stacking fascia, identifying this as the structural locus within this cohort. This figure represents inclusion-criterion-bound selectivity within the twitch-positive subset, not the positive predictive value of stacking fascia for twitch occurrence.<\/jats:p>","DOI":"10.3390\/medsci14030350","type":"journal-article","created":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T05:49:33Z","timestamp":1782712173000},"page":"350","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Local Twitches During Ultrasound-Guided Fascial Hydrorelease Occur Within Stacking Fascia: A Retrospective Analysis of a Large Video Archive"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-8959-5748","authenticated-orcid":false,"given":"Hiroaki","family":"Kimura","sequence":"first","affiliation":[{"name":"Kimura Pain Clinic, Maebashi 371-0013, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-6303-8666","authenticated-orcid":false,"given":"Tadanao","family":"Hiroki","sequence":"additional","affiliation":[{"name":"Department of Anesthesiology, Isesaki Municipal Hospital, 12-1 Tsunatori-honmachi, Isesaki 372-0817, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2001-4464","authenticated-orcid":false,"given":"Tadashi","family":"Kobayashi","sequence":"additional","affiliation":[{"name":"Development of Community Healthcare, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hideaki","family":"Obata","sequence":"additional","affiliation":[{"name":"Department of Anesthesiology, Saitama Medical Center, Saitama Medical University, Kawagoe 350-8550, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,27]]},"reference":[{"key":"ref_1","unstructured":"Kimura, H., Imagita, H., Kobayashi, T., Asaka, R., Obata, H., Kawashima, K., Kurosawa, R., Suzuki, S., Suda, M., and Zenita, Y. 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