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Published on: January 31, 2025
Ultrasound-Guided Approach for L5 Dorsal Ramus Block and Fluoroscopic Evaluation in Unpreselected Cadavers
Manfred Greher1, Bernhard Moriggl, Philip W H Peng
1From the *Department of Anesthesiology, Intensive Care and Pain Therapy, Sacred Heart of Jesus Hospital, Vienna; and †Department of Anatomy, Histology and Embryology, Division of Clinical and Functional Anatomy, Medical University of Innsbruck, Innsbruck, Austria; ‡Department of Anesthesia and Pain Management, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada; §Pain Therapy Service and ∥Department of Radiology, Foundation IRCCS Policlinico San Matteo, Pavia, Italy; and #Department of Anaesthesiology, St. Anna Clinic, Lucerne, Switzerland.
Background And Objectives:
Medial branch blocks are frequently performed to diagnose lumbar facet-joint-mediated pain. Ultrasound guidance can increase practicability and eliminate exposure to ionizing radiation when compared with fluoroscopy. However, ultrasound-guided L5 dorsal ramus block, which, together with L4 medial branch block is necessary to anesthetize the most commonly affected facet joint L5/S1, has not been described so far. The objective of this study was to develop a technique and to evaluate its accuracy with standard fluoroscopy in unpreselected cadavers.
Methods:
Twenty ultrasound-guided L5 dorsal ramus block approaches were performed with a new oblique out-of-plane technique in a rotated cross-axis view bilaterally in 10 cadavers. After checking the needle position in a second perpendicular sonographic plane, the final needle position was confirmed with conventional fluoroscopy by an independent observer.
Results:
All cadavers had significant degenerations of the lumbar spine, and 5 of them had moderate to severe spondylolisthesis. Skin-to-target distances were 42 ±7 mm. Sixteen L5 dorsal ramus block attempts were located at the exact radiological target, 1 was slightly too lateral, and 3 were slightly too caudal (3-10 mm away). The overall success rate in unpreselected cadavers reached 80% (95% confidence interval, 56%-94%) and in the subgroup of corpses without spondylolisthesis 100% (95% confidence interval, 69%-100%).
Conclusions:
This is the first study to show that ultrasound-guided L5 dorsal ramus block is accurate and feasible in the absence of significant spondylolisthesis when performed with an oblique out-of-plane technique.
