Lateral View of epidural injection Lateral view of L3-L4 Interspace.
In the illustration above, a 'single shot' epidural injection is being performed in the Lumbar 3-4 interspace.

The needle is advanced progressively through the supraspinous and interspinous ligaments, before entering the ligamentum flavum. As the needle enters the epidural space, resistance is lost and air, or saline can be easily injected into the space. The required dose of local anaesthetic solution is now injected, and can be seen spreading through the epidural space - which envelops the spinal cord.