How can patients with pain in the low back pain, leg, sacrum, pelvis, or buttocks coming from the sacroiliac joint (SIJ) get relief? For the last 10 years, radiofrequency denervation (using radio waves to destroy nerve tissue) has been used as an alternative treatment. It's time to evaluate the results and see if this new approach is working and who might benefit from it the most.
The sacroiliac joint (SIJ) is a complex joint with ligaments to support and stabilize it (hold it in its proper place) and muscles to move the pelvis. It is formed by the two iliac (pelvic) bones on either side of the triangular-shaped sacrum.
The sacrum is located at the lower end of the spine, just below the lumbar spine. It is actually formed by the fusion of several vertebrae during development. The sacroiliac (SI) joint is formed where the sacrum and the iliac bones meet (thus the name "sacroiliac" joint). You can see these joints from the outside as two small dimples on each side of the lower back at the belt line.
The SI joint is one of the larger joints in the body. The surface of the joint is wavy and doesn't always line up exactly. There is some (but not much) motion in the SI joint. The motion that does occur is a combination of sliding, tilting and rotation. Even a small change in alignment can cause shearing forces and considerable pain.
When nothing short of surgery helps relieve the pain, then radiofrequency ablation is considered. 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).
The results of using bipolar radiofrequency for chronic SI joint pain was only reported in one study. This technique is done by passing radiofrequency power between two points on either side of the nerve tissue. There are some concerns using this technique because the tissue's ability to transmit or impede (keep out) the radio waves varies so much. More studies are needed before this form will be used routinely.
Whenever a new form of treatment arrives on the scene, physicians want to know: 1) How well does it work? and 2) Who would benefit most from this treatment? Let's start with the answer to the second question. Patient selection is always a key factor in the success of any treatment like this.
What we know so far is that people with sacroiliac joint pain who get some relief from a steroid injection into the joint seem to respond best to radiofrequency ablation. Younger patients have the best results.
How well does it work? That's harder to say for a number of reasons. First, the SI joint can vary considerably from patient to patient. Likewise, the number, size, shape, and location of the nerves are equally variable.
Finding the most affected nerve can be a challenge. Then getting to the involved nerve is the next dilemma. Some of the nerves are right on the bone, while others are embedded in the soft tissues around the joint. Often more than one nerve is involved requiring more than one procedure.
And evaluating the results of studies already published isn't as clear and easy as physicians would like. For example, different surgeons use different techniques, select their patients using different criteria, and have different standards by which to judge "success" or "failure". Those kinds of differences make it difficult to compare one study to another and/or report overall trends for this treatment technique.
After reviewing the studies that have been published, the authors made the following observations. Radiofrequency does have some potential in the successful treatment of chronic sacroiliac joint pain. The most effective nerves to target for most patients are between the L5 and S3 levels. Cooled-probe radiofrequency seems to have the best outcomes but more studies are needed to compare the different techniques.
Reference: Anita Gupta, DO, PharmD. Evidence-Based Review of Radiofrequency Ablation Techniques for Chronic Sacroiliac Joint Pain. In Pain Medicine News. December 2010. Vol. 8. No. 12. Pp. 69-77.