I had my sacroiliac joint injected with a steroid and got good pain relief for about six months. Now my surgeon wants to use radio waves instead of the steroid. What’s the difference?

Identifying pain that is coming from the sacroiliac joint can be quite a challenge. For one thing, the symptoms aren’t always present just in the sacral area. Pain is often felt in the low back, leg, pelvis, or buttocks instead. That’s because the nerves to the sacrum and sacroiliac area are complex and vary from one person to the next.

Injecting a steroid with a numbing agent into the sacroiliac joint is both a diagnostic test and a treatment. If it successfully stops the pain, then you know the source of the pain was the sacroiliac joint. And once the pain is alleviated, your treatment has been successful!

But because the cause of the underlying problem has not been identified, the chances are your pain will eventually return. A second steroid injection is often offered as a treatment option. It worked once (and for quite a long time), so the chances are it will work again — and maybe for an even longer time.

For chronic, confirmed sacroiliac joint pain, an alternate treatment approach is the use of radiofrequency denervation (also known as radiofrequency ablation). The surgeon inserts a long, thin probe into the area under the guidance of a type of real-time X-rays called fluoroscopy. The offending nerve(s) are hit with high voltage radio waves that heat up the tissue and destroy the sensory nerve (the one that sends pain messages).

Radiofrequency can be delivered in several different forms (e.g., conventional, pulsed, cooled-probe, bipolar). The pulsed form doesn’t cause a rise in tissue temperature. Instead, it sets up an electromagnetic field around the nerve. The result is pain relief that may last six months or more. But because the nerve remains intact, the painful symptoms can come back.

The cooled-probe technique allows the target tissue to be heated up while keeping the surrounding tissue cool. This method makes it possible to heat up a slightly larger area than the conventional probe but without damaging other nerves in the area. There is also less tissue trauma with the cooled-probe because of the way the needle enters the tissue (perpendicular rather than parallel).

Whereas a steroid injection most often targets the joint, radiofrequency denervation directly attacks the nerve(s) to the joint. Diagnostic SI joint steroid injections are usually performed before radiofrequency ablation is recommended.