Sacroiliac Joint Block and Neuroablation

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Chapter 11 Sacroiliac Joint Block and Neuroablation

Kyung-Hoon Kim, MD, PhD, Sang-Wook Shin, MD, PhD

The sacroiliac joint (SIJ) is the largest axial joint in the body with an average surface area of 17.5 cm2 [1]. It is a large, auricular-shaped, diarthrodial synovial joint. However, only the anterior third of the interface between the sacrum and ilium is a true synovial joint; the rest of the junction is comprised of an intricate set of ligamentous connections. If the joints become painful, they may cause pain in the low back, buttocks, abdomen, groin or legs (Figs. 11-1 and 11-2).

image

Figure 11–1 Density of referral zones for sacroiliac joint pain. 0.5+ is the least common referral zone, 4+ the most common.

image

Figure 11–2 Common referral zones for sacroiliac joint pain. The sacroiliac joint can become inflamed from an acute injury or from chronic postural abnormalities. Undue stress on the joint following low back fusion surgery can also cause inflammation and pain here. Pain from sacroiliac joint abnormalities occurs in the low back, buttock/hip, abdomen, groin, or legs.

The primary function of the sacroiliac joint is to lend stability, which it accomplishes through the following mechanisms:

image The transmission and dissipation of truncal loads to the lower extremities
image Limiting of x-axis rotation
image Facilitation of parturition

The biomechanics of the SIJ withstand a medially directed force six times greater than the lumbar spine, but only half of the torsion and 1/20 of the axial compression load.

Sacroiliac joint dysfunction

Typically, SIJ dysfunction is initially symptomatic after a minor traumatic event, such as a fall onto the buttocks or a slip while pushing a heavy object. It is then aggravated by transitional activities, such as climbing stairs, getting up from a chair, and getting out of a car. Pain in the SIJ can also be provoked by activities requiring asymmetrical loading through the lower extremities or pelvis, such as skating, gymnastics, golfing, and step aerobics.

Dreyfuss and colleagues [2] have shown that the pain referral pattern in asymptomatic volunteers consists of the following areas:

image The buttock, the groin, and the entire lower limb, but not the back above the L5 level
image An area extending 10 cm caudally and 3 cm laterally from the posterior superior iliac spine

The diagnostic criteria for sacroiliac joint syndrome, as defined by the International Association for the Study of Pain (IASP), are as follows:

image Pain in the region of the SIJ with possible radiation to the groin, medial buttocks, and posterior thigh
image Reproduction of pain by physical examination techniques that stress the joint
image Elimination of pain with intra-articular injection of a local anesthetic
image An ostensibly morphologically normal joint without demonstrable pathognomonic radiographic abnormalities

One of the most consistent physical findings in patients with SIJ dysfunction is point-specific tenderness over the sacral sulcus as well as the posterior sacroiliac spine.

The prevalence of SIJ pain in carefully screened patients with low back pain (LBP) is in the range of 15% to 25%. 39% of patients with SIJ dysfunction were also diagnosed [3] with an associated spinal disorder. Of these spinal disorders complicated by SIJ dysfunction, the most common are as follows:

image Facet joint syndrome (41%)
image Spondylolisthesis (29%)

SIJ dysfunction can stem from both intra-articular and extra-articular sources, although extra-articular sources such as enthesopathy and fractures are more common. Nociception in the SIJ can also be caused by pathologic changes affecting many different SIJ structures, such as the following:

image Capsular or synovial disruption
image Capsular and ligamentous tension
image Hypomobility or hypermobility
image Extraneous compression or shearing forces
image Abnormal joint mechanics
image Microfractures or macrofractures
image Chondromalacia
image Soft tissue injury
image Inflammation

The following factors predispose an individual to SIJ dysfunction:

image Degenerative joint disease
image Joint (ligamentous) laxity and pregnancy
image A history of minor direct trauma, such as a fall onto the buttocks

The average mechanical threshold of the SIJ nociceptive unit is shown in Table 11.1.

Table 11.1 Average Mechanical Threshold of Sacroiliac Joint and Other Nociceptive Units

Nociceptive Unit Average Mechanical Threshold (g)
Sacroiliac joint 70
Lumbar facet joint 6
Anterior lumbar disc 241

SIJ treatment options are injections, nerve blocks, and denervation. A sacroiliac joint injection serves the following two purposes:

image Injecting anesthetic medication into the joint confirms whether or not pain comes from the joint.
image The local anesthetic and cortisone can help break a pain cycle, possibly facilitating a rehabilitative exercise program.

The evidence for the effectiveness of SIJ block and denervation as diagnostic and therapeutic methods for SIJ dysfunction is shown in Table 11.2.

Table 11.2 Level of Evidence for Intra-articular Injection and Neurotomy

Intra-articular injection:  
Diagnostic method Moderate evidence for diagnosis of pain from the sacroiliac joint (SIJ)
Therapeutic method Moderate evidence for short-term relief (<3 months)
Limited evidence for long-term relief
Radiofrequency neurotomy Indeterminate evidence for managing SIJ pain

Indications

The primary indication for treatment with SIJ block and neuroablation is intra-articular sacroiliac joint pain. The diagnostic criteria for identifying idiopathic intra-articular sacroiliac joint pain are as follows:

image Absence of neurologic deficits
image Absence of dural tension signs
image Absence of laboratory, imaging, or clinical evidence of medical causes of sacroiliac joint pain
image Maximal pain below L5
image No evidence of lumbar pain generators (if indicated, this can be confirmed through negative results of zygapophys-eal joint block and discography)
image At least 75% relief with controlled, dual, fluoroscopically guided, contrast-enhanced intra-articular SIJ injections

Several major diagnostic tests are used to confirm a diagnosis of intra-articular SIJ pain; they are described in Table 11.3 and Box 11.1, and shown in Figures 11-3 through 11-5.

Table 11.3 Sensitivity and Specificity of Major Diagnostic Tests Used to Identify Patients with Intra-articular Sacroiliac Joint Pain

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Test Sensitivity Specificity
Sacroiliac joint pain ++++ +
Groin pain + +++
Buttock pain ++++ +

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