Lumbar Transforaminal Epidural Steroid Injection—Supraneural (Traditional) Approach: Fluoroscopic Guidance

Key Words

back pain, disc herniation, epidural steroid injection, fluoroscopy, lumbar, radiculopathy, transforaminal

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

Traditionally, the transforaminal approach to epidural steroid injection is accomplished with a supraneural (subpedicular or retroneural) needle position. The target resides within the “safe triangle” location which is where a lumbar transforaminal injection can be accomplished with minimal risk of intrathecal or neural injury. ^11,12The technique described in this chapter differs from the subpedicular approach described elsewhere, ¹⁵since the needle is not advanced completely to the ventral aspect of the vertebral body. Avoiding the vertebral body theoretically reduces the likelihood of vascular injection, but vascular compromise may still occur. Although complications are rare, conus infarct has been reported with this approach. ^13,14Catastrophic events are thought to be from embolization caused by particulate corticosteroids entering the spinal cord and/or brain arterial supply. ^13,14For this reason, we advocate strong consideration for using non-particulate steroids since their “noninferiority” has been demonstrated. ^15,16

Trajectory View

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Confirm the level (see Chapter 1 ).
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Tilt the fluoroscope cephalad or caudad to line up the superior end plate (SEP) corresponding to the vertebra at which the injection is being performed. SEP should appear as a straight line ( Fig. 13A.1 ), rather than an elliptical structure, indicating that the fluoroscope beam is aligned with the superior end plate (SEP).

Fig. 13A.1

A, Fluoroscopic image of the trajectory view with needle in position. B, Radiopaque structures, trajectory view. Note the “Scotty Dog”: P = eye, TP = nose, PI = neck, IAP = front and rear legs, SAP = ear, SP = tail, and Lam = body. C, Radolucent structures. Note the “safe triangle” formed inferomedially by the SN and superiorly by the P.
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Preferentially lining up the SEP rather than the inferior end plate (IEP) will favor an inferior-to-superior needle trajectory (with the final needle tip position more likely to target the supraneural location).
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Oblique the fluoroscope ipsilateral to allow for proper visualization of the target point and, therefore, optimal trajectory for supraneural needle placement avoiding encountering the spinal nerve (SN) (see Fig. 13A.1 ).
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Note the following anatomic landmarks that create the “Scotty dog”: Pedicle (P) = eye, transverse process (TP) = nose, pars interarticularis (PI) = neck, inferior articular process (IAP) = front and rear legs, superior articular process (SAP) = ear, spinous process (SP) = tail, and lamina (Lam) = body.
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The target needle destination is just below the “chin” of the “Scotty dog” (i.e., adjacent to the pars interarticularis and inferior to the pedicle) where there is no periosteum (SAP, TP, Lam, PI) obstructing the target point.
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Avoid advancing the needle too far medially to prevent penetration of the dural sheath.
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A more medial final needle tip placement requires a more oblique approach.
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Identify a direct path to reach the target needle position.
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Place the needle parallel to the fluoroscopic beam.

Notes on Trajectory View Setup (See Chapter 13D for additional diagrams)

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Oblique ipsilaterally until there is no periosteum (SAP, TP, lamina, and PI) obstructing the target point beneath the “chin” of the “Scotty Dog.”
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A more oblique trajectory results in a more medial final needle tip position (on the anteroposterior [AP] view) and a less ventral final needle tip position (on the lateral view). This approach may facilitate access to the neural foramen in individuals with foraminal stenosis.
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A less oblique trajectory results in a less medial final needle tip position (on the AP view) and a more ventral final needle tip position (on the lateral view).
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In a scoliotic spine, lining up the SEP may not result in an optimal needle trajectory. The needle trajectory may need to be further “tuned” by adjusting the fluoroscope tilt cephalad or caudad to optimize SEP visualization (see Chapter 3 , “Tuning” an Oblique View for Optimal Needle Trajectory, Figs. 3.27A to 3.27C .)
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For L5, the iliac crest may obstruct a clear trajectory. Adjust the C-arm to a more cephalad tilt and/or reduce the oblique angle until an unobstructed trajectory is achieved.

Trajectory View Safety Considerations

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Avoid the spinal nerve by staying in the superior one-sixth of the foramen. This “safe triangle” is formed inferomedially by the SN and superiorly by the P. This needle tip position minimizes neural compromise; however, vascular penetration is still common in this position ( Simon et al., 2015 ).