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Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
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The sacroiliac joint has a well developed joint space lined by synovial membrane with typical hyaline articular cartilage on the sacral side and a thinner layer of fibrocartilage on the iliac side of the joint. Anteriorly, the joint capsule is well developed, forming the thin anterior sacroiliac ligament. There is no joint capsule posteriorly, and the joint space is in continuity with the interosseous sacroiliac ligament. Immediately posterior to the interosseous sacroiliac ligament is the large and strong posterior sacroiliac ligament ( Fig. 40-2 A ). The joint surfaces can rotate 3 to 5 degrees in younger, symptom-free patients, and the joint provides elasticity to the pelvic rim and serves as a buffer between the lumbosacral joint and the hip joint.

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Figure 40-2a  A, Sacroiliac joint anatomy.


The patient’s position depends on whether fluoroscopy is used to confirm the position of the needle. When fluoroscopy is used, the patient is placed prone, with the contralateral hip raised slightly on a pillow (∼20 degrees off the horizontal). This position allows the anterior and posterior orifices of the lower third of the joint to be superimposed, maximizing visualization of the joint. If fluoroscopy is not used, a pillow can simply be placed underneath the pelvis and lower abdomen with the patient prone (see Fig. 40-2 B ).

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Figure 40-2b  B, Clinical cross-sectional sacroiliac joint anatomy in a position similar to that used during the block technique.

The anesthesiologist can approach the technique in one of two ways. He or she can stand on the side of the sacroiliac joint undergoing injection. This allows palpation of the sacroiliac joint with the fingers of the dominant hand from a lateral position and frees more space medially for joint injection ( Fig. 40-3 A ). Conversely, the anesthesiologist can stand opposite the sacroiliac joint to be blocked, allowing needle insertion with the dominant hand (see Fig. 40-3 B ).

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Figure 40-3a  Sacroiliac block technique. A, Palpation of the ipsilateral sacroiliac joint when the anesthesiologist is positioned on the side being blocked.

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Figure 40-3b  B, Needle insertion for the block when the anesthesiologist is positioned opposite the side being blocked.

Needle Puncture.

When fluoroscopy is used for needle guidance, the patient is placed in the slightly oblique position described under patient position. Fluoroscopy is used to superimpose the lower third of the anterior and posterior orifices of the sacroiliac joint, which should appear as a Y-shaped image ( Fig. 40-4 ). After aseptic skin preparation and skin infiltration with local anesthetic, a 22-gauge, 7- to 9-cm needle is advanced into the lower third of the joint; its position is confirmed with a radiocontrast solution. If inadequate spread of contrast medium is noted, the needle can be repositioned under fluoroscopic guidance and the cycle repeated. If no fluoroscopic needle guidance is planned, after aseptic skin preparation and local anesthetic skin infiltration a 22-gauge, 7- to 9-cm needle on a 10-mL three-ring control syringe is inserted in an anterolateral direction into the region between the posterosuperior and the posteroinferior iliac spines. The needle may be repositioned along an arc extending between the posterosuperior and the posteroinferior iliac spines, and the solution can be reinjected incrementally (see Fig. 40-3 B ). Again, it is typical to use approximately 5 to 10 mL of solution during these injections. For nonfluoroscopic needle insertion, the local anesthetic-steroid solution is directed primarily at and deep to the posterior sacroiliac ligament, and some of the solution may find its way into the joint. Verification of joint injection is possible only with fluoroscopy, although clinical care does not demand its use for this block.

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Figure 40-4  Sacroiliac joint fluoroscopic anatomy. The needle is in the inferior aspect of the sacroiliac joint. A small amount of contrast material is seen outlining the joint and spilling out inferiorly.

Potential Problems.

Like any block performed near the sacrum, sciatic or sacral root block is a possible outcome, especially if large volumes of local anesthetic are used. Misdiagnosis is also possible when fluoroscopy is not used to guide needle placement and the patient reports no pain relief. In this situation, it may simply be that the drug did not reach the sacroiliac joint.

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