January/February 2008
Volume 4, Issue 1

Click on the icon to view the newsletter as a pdf.

The Sacroiliac Joint

An Original Contribution by Jimmy Henry, M.D. & Tony Al-Amin, M.D.

Low back pain (LBP) has a lifetime prevalence approaching 95%. A definite pain generator can be indentified in 75% of cases of LBP and the significance of sacroiliac joint syndrome (SIJS) has been previous under recognized. The sacroiliac joint (SIJ) is a common source of LBP and is thought to account for 15-30% of cases. The SIJ, once thought to be the most common cause of sciatica, may be affected in cases of trauma, infection, malignancy, pregnancy, arthritis, and inflammatory arthritis.

The SIJ is a synovial joint formed from the junction of the sacral spine and pelvis that serves to maintain normal biomechanics between the sacrum and ilium. The SIJ aids in the absorption of vertical forces from the spine and dissipates these forces to the pelvis and lower extremities. The intrinsic stability of the SIJ is provided by the intra-articular ridges and anterior, interosseous, and posterior sacroiliac ligaments. Dynamic stabilizers include the piriformis, biceps femoris, gluteus maximus and minimus, erector spinae, latissimus dorsi, quadrates lumborum, and iliopsoas muscles. Repetitive loading and asymmetrical force transmission may result in maladaptive compensatory patterns, degenerative joint changes, and SIJ dysfunction. These imbalanced or unilateral loads may jeopardize the interlocking sacral mechanics by impeding balanced transiliac boney fixation and ligamentous tension across the sacrum.

Patients with SIJS report pain or tenderness in the area of the posterior superior iliac spine (PSIS) with or without radiation to other areas. A positive Fortin finger test is confirmed when a patient points to the area of pain just medial and inferior to the PSIS. Pain is often worse with prolonged sitting or standing and rotational activities. Maneuvers that stress the SIJ may elicit pain. A thorough history and physical examination are key to the evaluation of any patient with LBP however, these have proven to be unreliable in accurately identifying SIJ mediated pain and therefore should not be used alone. Suspicion for SIJS may be increased if three or more tests are positive on physical exam and should prompt further diagnostic work-up for inflammatory arthritis, metabolic or infectious etiologies.

SIJS pain may have several referral zone patterns that may include the buttock, upper lumbar, lower lumbar, groin, abdomen, thigh, leg, and/or foot. The great variability in localization of SIJ pain is in part due to its complex neural network. Innervation to the anterior portion of the SIJ is from the posterior rami of the L2-S2 roots with possible contribution from the obturator and superior gluteal nerves and lumbosacral trunk, while the posterior portion of the SIJ receives innervation form the posterior rami of L4-S3 and possibly L4 (Slipman). Pain originating from the SIJ is mediated via neuropeptides such as calcitonin gene-related peptide and substance P that are transmitted by nocioceptive nerve fibers which innervate the intraarticular joint capsule and periarticular ligaments.

The International Association for the Study of Pain (IASP) proposes three criteria in diagnosing the SIJS: pain in that anatomic region, reproduction of pain with provocative testing, and symptomatic relief with administration of local anesthetic. Due to the low positive predictive value of provocative SIJ stress maneuvers, confirmatory SIJ injection is required for definitive diagnosis. Intra-articular SIJ injections are performed using fluoroscopic guidance to ensure proper placement of a local anesthetic after needle position is confirmed by a contrast arthrogram. In the absence of imaging, intra-articluar placement occurs only 22% of the time. Ultrasound and computerized tomography guidance have also been described for injection. A positive response is considered to be a significant (50-70%) reduction in symptomatic SIJ pain.

Treatment of SIJ pain includes conservative measures, intra-articular injections, radiofrequency (RF) neurotomy, prolotherapy, and cryotherapy. Conservative treatment includes cold application, anti-inflammatory medications, and relative rest in the acute stages. Once pain has subsided, further efforts should be employed to restore normal mechanics, including: manual medicine techniques, pelvic stabilization exercises, and muscle balancing of the trunk and lower extremities. SIJ belts or pelvic stabilization orthoses will provide confidence and proprioceptive awareness for SIJ dysfunction and will limit sacroiliac motion and thereby decrease pain.

Intra-articular injections are reserved for patients who have failed conservative treatments. To optimize diagnostic and therapeutic value, fluoroscopic guidance is employed. The patient is draped and prepped in sterile fashion. Contrast is injected into the SIJ for needle verification. Next, a small amount of a mixture of steroid and anesthetic are injected into the SIJ.

If intra-articular injections provide only temporary relief, RF neurotomy may be considered. The approach is the same as the intra-articular injection. Under fluoroscopic guidance the SIJ is visualized, anesthetized, then the RF probe is placed into the SIJ and the nerve endings ablated.

Prolotherapy is based on the principle of stabilizing weakened joints and ligaments. Injection of chemical irritants into ligamentous tissue incites collagen proliferation thereby scaring and tightening the ligament resulting in stabilization of the joint.

With cryotherapy, the lateral branches of the SIJ are exposed to liquid or gas nitrogen resulting in necrosis of the nerve endings. This may also cause a response similar to prolotherapy.

Post procedure care includes post procedural instructions, activity modification, application of ice packs to the area, and analgesic medications.

The SIJ is a pain generator that should be considered in all cases of low back pain. Definitive diagnosis is by positive response to SIJ intra-articular injection. Treatment may involve conservative and/or invasive measures. Treatment of chronic or refractory cases with RF ablation, prolotherapy or cryotherapy may provide lasting therapeutic effect.