Epidural Space Boundaries — FRCA Primary MCQ
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Correct answer: D — Ligamentum flavum
The correct answer is **A, ligamentum flavum**. The posterior boundary of the lumbar epidural space is formed by the ligamenta flava together with the laminae and facet-joint structures. In a midline epidural approach, the needle traverses the supraspinous ligament and interspinous ligament before penetrating the ligamentum flavum and entering the epidural space; therefore, those first two ligaments are superficial to, rather than boundaries of, the space. The posterior longitudinal ligament lies anterior to the epidural space, covering the posterior surfaces of the vertebral bodies and intervertebral discs. The pedicles contribute to the lateral boundaries of the vertebral canal and epidural space, not its posterior boundary.
Reference: Royal College of Anaesthetists. Guide to the FRCA Examination—The Final, Fourth Edition. SOE 1 Answers: Anatomy of the epidural space at L3/4, p. 216. 2020. https://www.rcoa.ac.uk/media/49226