Anatomical and Clinical Validation of a Novel Ultrasound-Guided Approach to Lumbar Transforaminal Epidural Injection "Lambda Sign over Horizontal Line".

Authors

Sachiko Kawasaki, Manabu Maeda, Nana Maeda, Takamasa Shimizu, Naoki Minami, Yurito Ueda, Kenji Kawamura

Published in

Spine surgery and related research. Volume 10. Issue 4. Pages 577-584. Jul 27, 2026. Epub Feb 16, 2026.

Abstract

Transforaminal epidural injection (EI) is an effective treatment for lumbar disorders. We used a novel ultrasound (US)-guided approach to identify the lumbar transforaminal epidural space without radiation or electrical stimulation. This technique shows a characteristic "Lambda sign over Horizontal Line (LHL)" view focused on the pars interarticularis. Therefore, we aimed to determine the anatomical background of the intervertebral foramen and clinical outcomes of this technique.
In one cadaver, indigo carmine was injected into the sacral hiatus, and the L3 vertebra was removed with the L3/4 facet joint. The specimens were sectioned longitudinally along the L3 spinal nerve and examined using hematoxylin-eosin staining. For clinical analysis, 18 individuals with lower limb pain underwent our novel US-guided lumbar transforaminal EI. The Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) was assessed before and at one, two, and four weeks after the first intervention, and scores for three visual analog scales (VASs) and five domains were compared between baseline and 4 weeks. Additionally, patients were divided into two groups based on the number of injections (single-trial versus multiple-trial), and baseline demographic data were compared between them.
Histological sections revealed oblique ligamentous tissue on the laterodorsal edge of the pars interarticularis, with the epidural space extending laterally. Among 15 complete follow-up cases, VAS scores for low back pain, lower limb pain, and all JOABPEQ domains except mental health improved significantly. Only the diagnosis differed significantly between the single-trial and multiple-trial groups.
Our novel US-guided transforaminal EI approach ("LHL") may improve pain and quality of life. However, multiple trials are required for cases of bony stenosis.

PMID:
42605389
Bibliographic data and abstract were imported from PubMed on 17 Aug 2026.

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