Clinical Trials SquareSacroiliitis is a condition in which one or both of the sacroiliac joints become inflamed. These joints are located on either side of the lower spine (sacrum) and connect the lower spine to the pelvis. Sacroiliitis can develop for a number of reasons including traumatic injury, general arthritis (osteoarthritis), arthritis of the spine (ankylosing spondylitis), pregnancy and infection.

Sacroiliitis commonly manifests as pain in the back or buttocks that gets worse after long periods of standing or sitting. Running and climbing stairs have also been known to aggravate the condition. Pain can also be felt in the legs, groin and feet. However, the pain usually improves with activity. Proper diagnosis is important as complications can arise, particularly with sacroiliitis caused by ankylosing spondylitis, which can lead to breathing difficulties, heart and lung problems and spinal deformities.

In the US, 13 million people go to the doctor for chronic back pain annually. Sacroiliitis is a major cause of disability, accounting for 10-27% of patients with low back pain below the level L5. This number will only continue to grow as the population becomes increasingly older.

Current Treatment

There are a few treatment options for sacroiliitis but none of them are permanent or overwhelmingly successful. Medications such as over-the-counter pain relievers and muscle relaxants are often prescribed to alleviate symptoms. In more severe cases, prescription medications can be used. Tumor necrosis factor inhibitors have also been used to treat sacroiliitis resulting from ankylosing spondylitis.

Physical therapy is commonly recommended by physicians to loosen and stabilize the muscles surrounding the sacroiliac joints, and can help to increase the effectiveness of prescribed medications.

Joint injections of a corticosteroid can be given to help resolve more serious cases. Repeated injections are often necessary as relief is not permanent. However, repeated injections are known to weaken bones and tendons and can only be given a few times a year.

Electrical stimulation can be performed in cases that fail to respond to medication or therapy. This involves implanting an electrical device into the sacrum. The device then sends out electrical pulses to interfere with the brain’s pain signals. This treatment is not always successful and risks include weakness, numbness, battery failure and allergic reactions to implanted materials.

Radiofrequency denervation is another treatment option for patients unresponsive to more conventional therapies. The outpatient treatment involves using radiofrequency impulses to heat a special needle that is inserted directly into the back. The heat thermally ablates part of the nerve that is causing the pain.

The most aggressive treatment for sacroiliitis is joint fusion, where the sacrum (lower spine) and ilium (pelvis bone) are fused together with titanium plates. Historically, this procedure has been rarely prescribed because it requires open surgery. However, advancements have now given doctors a way to perform minimally invasive joint fusion, involving minimal risks.

Focused Ultrasound Research

Focused ultrasound has not been approved for the treatment of sacroiliitis. However, it has been approved for the treatment of pain in patients with bone metastasis. Feasibility studies have repeatedly shown that targeted heating of the bone periosteum with focused ultrasound has provided pain relief for these patients. In much the same way, focused ultrasound, if aimed at the nerve supplying the sacroiliac joint, should be able to thermally ablate tissue and alleviate symptoms. The ability of focused ultrasound to focus on a very precise target without damaging surrounding tissue should provide a solution to problems associated with less accurate forms of denervation (RF).

An upcoming clinical trial at the University of Virginia aims to test the safety and efficacy of focused ultrasound for the treatment of sacroiliitis in 10 patients. The patients will be followed for 12 months after the procedure to observe the permanency of the treatment. This clinical trial builds upon similar work conducted in a pilot study at Saint Mary’s Hospital in England where 18 patients with low back pain stemming from facet disease were treated with focused ultrasound. No significant adverse events were reported, and over half of patients experienced either a decrease in pain or increased mobility.

Notable Papers

Sin Yuin Yeo, Andrés J. Arias Moreno, Bert van Rietbergen, Natalie D. ter Hoeve, Paul J. van Diest, and Holger Grüll. Effects of magnetic resonance-guided high-intensity focused ultrasound ablation on bone mechanical properties and modeling. Journal of Therapeutic Ultrasound 2015, 3:13  doi:10.1186/s40349-015-0033-8

Weeks E., et al., MRI-guided focused ultrasound (MRgFUS) to treat facet joint osteoarthritis low back pain-case series of an innovative new technique. Eur Radiol, 2012.

Muhlner SB., et al. Review article: radiofrequency neurotomy for the treatment of sacroiliac joint syndrome. Curr Rev Musculoskelet Med, 2009; 2:10-14.

Hansen HC., et al. Sacroiliac joint interventions: a systemic review. Pain Physician, 2007; 10: 165-84.

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