Lumbar Selective Epidural Injection

Lumbar selective injection is also performed with the patient in prone position. The neural foraminal level to be injected is localized fluoroscopically, and the beam is tilted laterally approximately 25° so that the superior articular process is directly below the adjacent pedicle (Fig. 2). Craniocaudal angulation of the image intensifier is performed to "look down the barrel" of the pedicle, the lower margin of which is about halfway between the end plates. A slightly cranial course of the needle tract will help avoid the transverse process. The skin is widely prepped and draped; the skin entry site is localized fluoroscopically and subcutaneous lido-caine is administered. Deeper, lidocaine is administered along the angle of the X-ray beam. The nerve root passes just beneath the medial margin of the pedicle and extends inferiorly, so the needle (22-gauge 3 in. needle for thin-to-average build patients, 6-7 in. needle for obese patients) is advanced to the area just below the inferior margin of the pedicle. The needle is advanced to bone (the posterolateral aspect of the vertebral body) or until radicular pain is elicited. With significant radicular pain, the needle should be repositioned.

FIGURE 2 Lumbar selective epidural injection. (A) Fluoroscopic image showing optimal obliquity for needle placement. Note vertebral pedicle (letter "P") and needle (arrow) in place. Care must be taken not to pass the needle medial to the medial edge of the pedicle (arrowhead), which forms the margin of the spinal canal. (B) Needle tip position within the neural foramen is verified using a frontal projection. Optimally, the needle should be positioned just inferior to the six o'clock point on the pedicle (letter "P"). Nonionic iodinated contrast is injected to verify position; note opacification of the sheath of the exiting nerve root (arrow) and extension to the medial epidural space (arrowhead). Medication can then be injected with intermittent fluoroscopic observation.

FIGURE 2 Lumbar selective epidural injection. (A) Fluoroscopic image showing optimal obliquity for needle placement. Note vertebral pedicle (letter "P") and needle (arrow) in place. Care must be taken not to pass the needle medial to the medial edge of the pedicle (arrowhead), which forms the margin of the spinal canal. (B) Needle tip position within the neural foramen is verified using a frontal projection. Optimally, the needle should be positioned just inferior to the six o'clock point on the pedicle (letter "P"). Nonionic iodinated contrast is injected to verify position; note opacification of the sheath of the exiting nerve root (arrow) and extension to the medial epidural space (arrowhead). Medication can then be injected with intermittent fluoroscopic observation.

Next, contrast injection is performed to verify satisfactory positioning. The contrast should extend centrally into the epidural space of the spinal canal and peripherally around the nerve root. If there is vascular opacification, the needle should be repositioned. If the patient complains of an acute onset of severe radicular pain immediately upon injection, an intraneural injection may have occurred; injection should be stopped immediately and the needle should be repositioned. After proper positioning is verified, approximately 3 cc of a combination of anesthetic and steroid is injected with intermittent fluoroscopic observation.

A coaxial technique can also be used, with placement of a larger gauge needle with a more straight parasagittal orientation, through which a curved 25-gauge needle is passed to attain access to the neural foramen. This technique is especially helpful in patients with a fusion mass obstructing direct access to the foramen. CT may be required for localization in this setting.

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