During lumbar epidural anesthesia, which ligament must be traversed to reach the canal?

During lumbar epidural anesthesia, which ligament must be traversed to reach the canal?

• A. Interspinous ligament
• B. Ligamentum flavum
• C. Supraspinous ligament
• D. Posterior longitudinal ligament

Answer: (B)

Access to the epidural space hinges on passing through the ligament that forms its posterior boundary—the ligamentum flavum. This thick, elastic barrier is what you feel as you advance the needle and experience loss of resistance, signaling entry into the epidural space inside the vertebral canal. The supraspinous and interspinous ligaments lie more superficially and are encountered earlier in a midline approach, but they aren’t the barrier to the canal itself. The posterior longitudinal ligament sits inside the canal anterior to the dural sac, not at the posterior route used for epidural anesthesia.

Access to the epidural space hinges on passing through the ligament that forms its posterior boundary—the ligamentum flavum. This thick, elastic barrier is what you feel as you advance the needle and experience loss of resistance, signaling entry into the epidural space inside the vertebral canal. The supraspinous and interspinous ligaments lie more superficially and are encountered earlier in a midline approach, but they aren’t the barrier to the canal itself. The posterior longitudinal ligament sits inside the canal anterior to the dural sac, not at the posterior route used for epidural anesthesia.