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The sacroiliac joint (SIJ) is the largest axial joint in the body with an abundance of nociceptive pain fibers within the joint and surrounding ligaments. SIJ dysfunction or syndrome is pain originating in the sacroiliac joint without demonstrable anatomic lesion and is presumed to be due to a biochemical abnormality.1 Predisposing factors include conditions causing stress on the joint such as spinal deformity, previous spinal surgery, and leg length discrepancy. Symptoms of SI joint dysfunction include pain in the superior medial quadrant of the buttock, the lateral buttock, and inferior to the posterosuperior iliac spine, with radiation to the greater trochanter, upper lateral thigh, and groin (Figure 26-1).
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Two types of injections have been performed for SIJ pain relief: an injection of local anesthetic or corticosteroids (or both) into the intra-articular space and the periarticular region, in particular into the posterior ligamentous structures. Both types of injection can be effective in the treatment of SIJ pain. It is still controversial as to which type of injection is more effective.
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Several studies have evaluated periarticular vs. intra-articular. A study by Borowsky and Fagen2 retrospectively showed that patients who received intra-articular and periarticular injections did better than the patients receiving intra-articular injections only. However, only 51.25% of patients who received the combination of injections experienced relief at 3 months. Luukkainen et al evaluated the role of periarticular injections in two randomized trials.3,4 Both studies showed periarticular injection of local anesthetic with steroids to be superior, though only in a short-term follow-up.
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The SI joint is the largest axial joint in the body, also supported by a network of muscles that help to deliver regional muscular forces to the pelvic bones.
Dorsally there is raised median crest with irregular surface of lateral sacrum.
The S1 foramen too is close to PSIS and the location of S3 foramen is inferior to SIJ.
There are ligamentous gaps on dorsal surface that extend superolaterally (Figure 26-2).
The muscles, such as the gluteus maximus, piriformis and biceps femoris are functionally connected to SI joint ligaments. The sacroiliac joint is innervated at its anterior and posterior aspects.
Posteriorly, the joint is innervated by the lateral branches of the posterior primary ramus of the L4 to S4 dorsal rami.5,6
The predominant innervation is from the dorsal ramus of S1 and isolated dorsal innervations from S1-4 (Figure 26-3).
The anterior innervation is from the ventral rami of L5 to S2 and via branches from the sacral plexus.5
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