Lumbar Transforaminal Epidural Steroid Injection—Infraneural Approach: Fluoroscopic Guidance

Keywords

disc herniation, infraneural, lumbar epidural steroid injection, preganglionic, radiculopathy, retrodiscal, spinal stenosis, transforaminal

Note: Please see pages ii , iii for a list of anatomic terms/abbreviations used throughout this book.

Infraneural Approach

Some authors suggest that transformainal epidural steroid injection needle placement infraneurally, in the inferior aspect of the foramen (i.e., Kambin’s triangle,), is a theoretically safer approach, as the probability of encountering the radicular artery in the inferior foramen may be less likely. However, vascularity has been shown in this region as well. This alternative transforaminal injection is called the infraneural technique (also known as retrodiscal or preganglionic) where the needle stays in the lower third of the foramen or “low in the hole.”

This technique may be used in place of the traditional supraneural technique or when anatomic changes compromise a safe injection. This technique has been described as retrodiscal because the needle is placed just posterior to the disc’s posterior annulus; inadvertent disc injection is not uncommon due to close proximity to the disc. Some authors describe the infraneural approach as preganglionic because the needle tip lies proximal to the DRG along the transiting nerve root. The infraneural approach may be beneficial for injecting the nerve at the same disc level as a central herniation since injectate tends to flow along the nerve root as it transits inferiorly past a centrally herniated disc.

Of note, the initial trajectory of the infraneural injection is similar to the trajectory used in lumbar discography.

Trajectory View

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Confirm the level (with the use of the anteroposterior view) before obtaining the trajectory view.
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Tilt the fluoroscope to optimize end plate visualization.
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  A caudad or cephalad tilt is used to line up both the superior end plate (SEP) and inferior end plate (IEP) of the adjacent lumbar vertebrae. (Preferentially line up SEP inferior to the target.)
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Oblique the fluoroscope ipsilaterally ( Fig. 13C.1 ):
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  The C-arm is then obliqued toward the symptomatic side so that the superior articular process (SAP) bisects the IEP of the superior vertebral body (VB). The target is the junction of SAP and SEP of the inferior VB.
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  This setup is similar to lumbosacral discography (see Chapter 17 ).
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  This is the trajectory view; needle entry should be parallel to the C-arm angle.
Fig. 13C.1

A, Fluoroscopic image of trajectory view with needle in position. B, Radiopaque structures, trajectory view. C, Radiolucent structures, trajectory view.

Notes on Positioning in the Trajectory View

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Maintain the needle in the lower third of the foramen or “low in the hole.”
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This view is not optimal for visualizing an inadvertent disc injection. Alternate between anteroposterior and lateral views as the target position is approached.
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The needle may be placed as low as possible in the lower third of the foramen.