The transforaminal approach to the epidural space is very similar to the approach used for selective nerve root blocks. With the patient in the prone or prone oblique position, fluoro-scopy is used to identify the appropriate neural foramen. Using C-arm equipment, the fluoroscope can be angled to "open" the neural foramen. This usually requires 30-40° ipsilateral angulation. The needle is then advanced through the neural foramen immediately inferior to the pedicle (Fig. 10). The epidural space can be encountered at the medial margin of the pedicle as seen on the anterior-posterior plane. Contrast epidurogram can
be obtained to confirm the epidural location, the lack of subarachnoid puncture, and to document that there is adequate epidural spread for the intended treatment area. If the needle is not in the epidural space, one can see a perineural injection, with the contrast outlining the exiting nerve root sleeve. This sleeve will many times communicate with the epidural space, so it is possible to see both the exiting nerve root and the epidural space. Mixtures similar to those used in the interlaminar technique are used for the transforaminal approach, typically 40-80 mg of Depo-Medrol or 2-3 cc of Celestone with 3-5 cc of local anesthetic. The transforaminal approach is most frequently used in treating radicular pain, especially in patients with previous back surgery and thereby limited access to the epidural space using the easier sublaminar approach.
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