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clinical examination, and surgical options, and should be discussed with the referring physician before the procedure is performed. Injection generally includes L3-4, L4-5, and L5-S1. The patient is positioned in a prone or prone-oblique position with the less painful side up. Each level is set up fluoroscopically so the disc is parallel to the beam and obliqued so that the superior articular process of the overlying facet joint is slightly posterior to the center of the endplate (30-50% zone). Lidocaine is administered under the skin. Next a 22- or 23-gauge 3.5-in. needle is advanced along the X-ray beam toward the disc, past the anterior margin of the superior articular process. Anes-

Fig. 8. (A, B) Annular injection demonstrated by contrast in the periphery of the disc. (C) A mixed injection with contrast in the periphery and central portion of the disc. Annular injections may lead to a false-positive pain response.

thetic is injected as the needle is withdrawn, thus fully anesthetizing the path to the disc. Care must be exercised with respect to the depth of the injection, so as not to inject the annulus or nerve root sheath.

A coaxial technique is used to place the discography needles into each disc. This reduces trauma to the annu-lus, and may reduce the risk of infection. The larger outer needle allows rapid positioning at the disc margin, with a small-gauge needle used to penetrate the annular fibers. At the L3-4 and L4-5 levels, a 20-gauge 3.5-in. outer needle can be used in conjunction with a 6- to 8-in. 25-gauge inner needle (Fig. 10). The L5-S1 disc may be located below the pelvic rim and can be difficult to access. Generally, the X-ray beam is oriented with more caudal angulation than the higher levels and is rotated slightly to open a small triangle of access over the iliac crest (Fig. 11). When this window is achieved, one needs to determine if the lumbosacral IVD can be punctured in the central portion with a direct approach or if the orientation is more parasagittal. If the course of the outer needle is parasagittal, a curved-needle technique is required to position the inner needle centrally. Prior to insertion of the inner needle, a bend (or curve) may be applied along the distal tip so that when it emerges from the guide needle, the inner needle deflects toward the center of the disc. Alternatively, precurved coaxial needle systems are available. Typically, a 22-gauge inner needle through an 18-gauge outer needle is used for most cases that require

Discogram Needle Placement

Fig. 9. Lumbar spine discography needle placement. Each level is set up fluoroscopically so that the disc is parallel to the beam and obliqued so that the superior articular process of the overlying facet joint is slightly posterior to the center of the endplate (30-50% zone) (star). The needle is then directly advanced along this path, being located slightly closer to the inferior endplate and superior articular process to avoid injury to the exiting nerve root.

Fig. 9. Lumbar spine discography needle placement. Each level is set up fluoroscopically so that the disc is parallel to the beam and obliqued so that the superior articular process of the overlying facet joint is slightly posterior to the center of the endplate (30-50% zone) (star). The needle is then directly advanced along this path, being located slightly closer to the inferior endplate and superior articular process to avoid injury to the exiting nerve root.

a curve. In addition, particularly at the lumbosacral junction, longer needles may be required.

Positioning of all needles during placement is checked frequently in the plane along the trajectory of the needle and is supplemented with the anteroposterior and lateral planes as the tip approximates the disc. The tip of the inner needle should be positioned as close as possible to the center of the disc, so that injection is into the nucleus pulposus instead of the innervated annular fibers, which can result in a false-positive pain response (Fig. 8). After all needles are placed, 1-2 mL of contrast (mixed with antibiotic) is injected at each level, with fluoroscopic monitoring and evaluation of any pain elicited. A morphologically normal disc demonstrates a central globule of contrast collection or "hamburger bun" configuration and degeneration is indicated by a horizontal, linear distribution of contrast (Fig. 7). An annular tear is diagnosed if contrast extends into the periphery of the disc in the expected region of the AF (Fig. 7). CT imaging may be used to complement projectional imaging techniques, and grading systems are available to characterize IDD as outlined in the preceding (33) (Fig. 12).

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