Background and indications: Lumbar transforaminal epidural steroid injections are common interventional procedures used in the treatment of lower extremity radicular pain. Injections are performed at the level that corresponds with the dermatomal pain pattern described by the patient. Nerve root irritation can be a result of direct compression from a herniated disk, spondylosis causing neural foraminal narrowing, or disk rupture causing a chemical irritation.

Anatomy: Transforaminal epidural steroid injections are typically done for radicular pain. Placement of a corticosteroid along the appropriate nerve root rather than in the dorsal aspect of the epidural space provides better results in treating radicular pain. The lumbar foramina, where the nerve roots exit from, face laterally and are bordered by the vertebral body superiorly, the inferior articular process (IAP) posterosuperiorly, the superior articular process (SAP) posteroinferiorly and the pedicles above and below. Injury to the artery of Adamkiewicz, entering the spinal canal from T7-L4, can cause anterior spinal artery syndrome and paraplegia if injured in the performance of injections, and thus, one should ensure not to traverse or inject particulate steroids into this artery as well as the smaller radicular vessels.

Patient position: Prone with towel rolls placed under the abdomen for alleviation of lumbar lordosis.

Probe: Broadband curved or linear array transducer depending on the depth expected.