Epidural Steroid Injection, Lateral View

Description

Seen in lateral profile, the lumbar vertebral column is oriented with the spinous processes posterior and the vertebral bodies anterior, while the interlaminar window between adjacent laminae opens toward the epidural space. A spinal needle advances from posterior to anterior, passing through skin and subcutaneous tissue, traversing the supraspinous and interspinous ligaments, then piercing the ligamentum flavum to enter the posterior epidural space. The animation tracks the needle tip in sequence as it approaches the dural sac, keeping the trajectory shallow enough to avoid the subarachnoid space. Depth matters. Clinically, this is the working anatomy behind interlaminar epidural steroid injection for lumbar radicular pain from disc herniation or foraminal stenosis, where medication needs to spread along the posterior epidural compartment around the exiting nerve roots. Layer-by-layer motion clarifies why loss-of-resistance occurs at the ligamentum flavum, and why a few extra millimeters can convert a therapeutic epidural placement into inadvertent dural puncture with post-dural puncture headache. The lateral perspective also reinforces the relationship of the epidural space to the posterior longitudinal ligament and the anterior border of the spinal canal, a common point of confusion in trainees. Use this animation in anesthesiology and pain medicine teaching, procedure guides for residents, or patient-facing education that explains where the needle goes without overpromising outcomes; it also fits spine module content in musculoskeletal anatomy and neuraxial techniques curricula. Anatomical accuracy verified by SciePro's Medical Advisory Board.