Interlaminar Epidural Injection
An interlaminar epidural is the simplest approach to epidural injection. With this technique, the pain specialist advances the needle into the epidural space from the midline back-side of the spine through the bony opening called the ‘interlaminar window’. This approach has been used without x-ray guidance for the past 100 years to create surgical anesthesia, stop the pain of labor and to treat acute and chronic spinal pain conditions like disc herniation.
The advent of fluoroscopic guidance (real time x-ray imaging) in the 1990s allowed pain specialist physicians to precisely target interlaminar epidurals to specific spinal levels and today the interlaminar approach is used throughout the cervical, thoracic and lumbar spine. Interlaminar epidurals can be performed with minimal discomfort because the needle is placed into the back side of the spine, far away from the irritated spinal nerve roots and the medication indirectly targets the disc-nerve root interface which is in the front and side of the spinal canal.
View an example of an interlaminar epidural injection in the lumbar spine.
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Transforaminal Epidural Injection
To target irritated spinal nerve roots more directly, pain specialist physicians are increasingly using the transforaminal approach to epidural injection. Transforaminal epidural injections are technically more difficult than interlaminar epidurals, require fluoroscopic guidance and are sometimes done at more than one level in a single procedure.
Transforaminal epidural injections deposit medication directly onto irritated spinal nerve root so it may be more effective but may also be more uncomfortable compared to interlaminar technique.
View an example of a transforaminal epidural injection in the lumbar spine.