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  • Retrodural space of Okada in the posterior ligamentous complex region: clinical and anatomical findings relevant to lumbar interlaminar epidural injection

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Original research
Retrodural space of Okada in the posterior ligamentous complex region: clinical and anatomical findings relevant to lumbar interlaminar epidural injection
  1. Shin Hyung Kim1,2,
  2. Tae-Hyeon Cho2,3,
  3. Hee Jung Kim1,2,
  4. Hyun-Jin Kwon2,3,
  5. Hyun-Ho Kwak4,
  6. Kang-Jae Shin5,
  7. Yong Suk Lee1 and
  8. Hun-Mu Yang2,3,6
  1. 1Department of Anesthesiology and Pain Medicine, Yonsei University College of Medicine, Seoul, Korea
  2. 2Translational Research Unit for Anatomy and Analgesia, Yonsei University College of Medicine, Seoul, Korea
  3. 3Department of Anatomy, Yonsei University College of Medicine, Seoul, Korea
  4. 4Department of Oral Anatomy, Pusan National University School of Dentistry, Busan, Korea
  5. 5Department of Anatomy and Cell Biology, Dong-A university school of medicine, Busan, Korea
  6. 6Surgical Anatomy Education Centre, Yonsei University College of Medicine, Seoul, Korea
  1. Correspondence to Dr Hun-Mu Yang, Anatomy, Yonsei University College of Medicine, Seodaemun-gu, Seoul, Korea (the Republic of); yanghm{at}yuhs.ac

Abstract

Background The retrodural space of Okada is a potential space posterior to the ligamentum flavum that allows communication with the bilateral facet joints. However, the actual anatomy of this space has not been clearly visualized to date. We sought to investigate the characteristics of patients showing contrast spreading to the facet joint space during epidural injection and to clarify the anatomical structures of the retrodural space and adjacent ligamentous tissues in cadaveric specimens.

Methods Fluoroscopic images of patients who underwent fluoroscopy-guided lumbar interlaminar epidural injection were assessed for contrast flow to the facet joints. Patient demographics, preprocedural imaging study findings, and epidural approaches were analyzed. The anatomical study included the sectional dissection, micro-CT imaging, and histological evaluation of lumbar spine specimens from 16 embalmed cadavers.

Results Fluoroscopic images of 605 epidural injections were analyzed. Among them, 36 with inadvertent spread into the facet joints (5.9%) were identified. Multivariate analysis revealed that facet joint pathologies were significantly associated with inadvertent spread into the facet joints (OR 4.382; 95% CI 1.160 to 16.558; p=0.029). Micro-CT and histological findings consistently showed a retrodural space between the ligamentum flavum and interspinous ligament. Various anatomical communication routes in the posterior ligamentous complex leading to this space were observed in specimens with degenerative and pathological changes.

Conclusion Degenerative and pathological facet joint changes were associated with a higher incidence of spread into the retrodural space during epidural injection. Our findings confirm anatomical evidence for a false loss of resistance before the needle enters the epidural space.

  • regional anesthesia
  • pain management
  • nerve block

Data availability statement

Data are available on reasonable request. Data are available on reasonable request. Deidentified data will be made available on reasonable written request submitted to the corresponding author.

https://doi.org/10.1136/rapm-2022-103765

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    Data availability statement

    Data are available on reasonable request. Data are available on reasonable request. Deidentified data will be made available on reasonable written request submitted to the corresponding author.

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    Footnotes

    • SHK and T-HC contributed equally.

    • Contributors SHK and T-HC (these authors contributed equally to this work) were involved with study conception, design, clinical and anatomical data acquisition, data analysis, interpretation, and figure preparation, drafting of the paper. HJK was involved with clinical data acquisition, clinical data analysis/interpretation and drafting of the paper. H-JK was involved with anatomical data acquisition, anatomical data analysis, interpretation, and figure preparation. H-HK was involved with anatomical data acquisition, anatomical data analysis, interpretation, and figure preparation. K-JS was involved with anatomical data acquisition, anatomical data analysis, interpretation, and figure preparation. YSL was involved with clinical data acquisition, clinical data analysis/interpretation. H-MY: study conception, design, anatomical data acquisition, anatomical data analysis, interpretation, figure preparation, and drafting of the paper and is guarantor. All authors read and gave final approval of the version to be published.

    • Funding This work was supported by grants from the National Research Foundation Korea, funded by the Korean government (No. 2020R1F1A1058123 to H-MY and No. 2021R1F1A1045873 to SHK).

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.