Thoracic spine discography can be performed in the prone semioblique 45° position (using a wedge) with the less painful side up. Alternatively, the patient may be placed prone and anteroposterior images obtained with the endplates in alignment. The C-arm is rotated to the side of injection until a lucent zone directly in line with the beam
is seen projecting over the thoracic disc (Fig. 13). This usually requires approx 20° of rotation. The needle should enter the disc lateral to the interpedicular line and medial to the costovertebral joints to avoid potential complications, such as accidental puncture of the lung or thecal sac. Generally a single-needle technique is used in the thoracic spine. Usually 25-gauge needles will suffice for small individuals; however, 3.5-in., 23-gauge needles are often preferred because they are stiffer and can negotiate better around nerve roots and/or the osseous structures if necessary. The thoracic disc normally accepts a small volume of injectant (<1.0 mL). Fluoroscopic images may be difficult to interpret because of the superimposition of osseous structures, difficulty in obtaining a true lateral projection, and the presence of a small amount of injectant (Fig. 14). Therefore, post-discography CT imaging is often a useful adjunct to delineate IDDs and HNPs (Fig. 15).
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