SI Joint Fusion in St. Louis

The sacroiliac joints sit where the base of the spine meets the pelvis, one on each side. They move very little. They are built to pass load along, not to give range of motion. When one starts causing pain, the usual tools of spine care often miss it entirely, because it is not the spine.

Minimally invasive SI joint fusion locks that joint in place. The surgeon works through a small cut at the side of the buttock, guided by live X-ray. Implants are placed across the joint to stop the painful tiny movements and let bone grow across. It is surgery, done in one outpatient session.

This is different from the sacroiliac joint injection, which both finds and treats the problem. The injection tells you whether the joint is the source. Fusion is the next step when the answer is yes and the relief from the injection does not hold.

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The sacroiliac joint is a known source of pain in a sizable minority of people with low back pain. Published estimates range from about 10 to 30 percent. The spread is not sloppiness — it reflects how the diagnosis was made. Studies that required two confirming blocks report different figures from those that accepted one. That is the same point made in the diagnosis section below. Either way, it is a large share of a very large group, and it is routinely missed.

Part of the reason is where it sits. SI joint pain is low and to one side, often over the back of the pelvis. It spreads into the buttock, groin or back of the thigh. It is easy to mistake for a disc problem or sciatica. Lumbar imaging looks at the lumbar spine. A joint that is not in the picture cannot be found in it.

Two patterns should raise the question right away. One is pain that lasts after a lumbar fusion — where load shifts to the joint below — and the other is pain that began during or after pregnancy, when loose ligaments changed how the pelvis handles load.

Imaging alone cannot make the diagnosis. Wear-and-tear changes at the SI joint are common in people with no pain at all. The diagnosis comes from an exam plus a diagnostic block.

During the exam, we press and move the joint in set directions to stress it. When several of these tests are positive together, suspicion rises. Proof comes from an image-guided injection of local anesthetic into the joint. If the pain reliably drops while the anesthetic works and comes back as it wears off, the joint has given itself away.

This step is not optional, and it is not a formality. Every major trial of SI joint fusion required a confirming diagnostic block before a patient could enroll. Coverage policy usually requires it as well. A fusion done on a joint never proven to be the pain source is a procedure with no reason to work.

The evidence here is stronger than for many interventional procedures. It comes from randomized trials, not case series.

A 2015 multicenter randomized controlled trial in Neurosurgery put 148 patients with SI joint dysfunction into one of two groups. One got minimally invasive fusion with triangular titanium implants. The other got non-surgical care. At six months, success rates were 81.4 percent in the surgical group against 26.1 percent with non-surgical care. The Oswestry Disability Index measures how much pain limits daily life. A clinically important gain on it — a fall of at least 15 points — came in 73.3 percent of the fusion group against 13.6 percent of the non-surgical group. The gains held at twelve months. Patients who switched from non-surgical to surgical care improved about the same.

A 2016 European randomized trial in the European Spine Journal compared fusion against conservative care at nine sites in four countries. At six months, low back pain improved by 43.3 points in the fusion group against 5.7 with conservative care. Disability scores improved by 26 points against 6. Rates of side effects and complications did not differ between the groups.

Both of the trials above compared fusion against non-surgical care. Neither compared it against a sham operation. That gap matters more in surgery than in most fields, because the placebo response to an operation is large and well documented.

Researchers in Norway and Sweden thought it mattered enough to run a double-blind, sham-controlled trial just to find out. They wrote plainly that it remains unclear how much of the benefit seen reflects the placebo effect. That trial exists because the question is open, not because the procedure is doubted.

It is also worth knowing that industry paid for the major fusion trials, and the implant maker helped write them. That does not make the results wrong — they are randomized, multicenter and published in peer-reviewed journals — but you have a right to know it when you weigh them.

The lesson here is not doubt about the procedure. It is that picking the right patient carries most of the weight. The trials enrolled patients whose SI joint had been confirmed as the pain source and whose conservative care had failed. Results in that group say little about a patient who has not passed through the same filter.

We implant SI-BONE devices. Which one we use depends on your anatomy and the surgical approach that fits it.

The iFuse Implant System uses triangular titanium implants placed from the side across the joint. The triangle shape resists twisting. Its porous surface is built for bone to grow onto and into. This is the implant used in both randomized trials described above. So the published results apply directly to this device, with no guesswork.

The Catamaran SI Joint Fusion System takes a different path across the joint. It places one larger implant along the line of the joint instead of several across it. It suits some pelvis shapes better than a side approach does.

Both are made by SI-BONE, Inc. and cleared for this use. We have no business ties to either brand — they are the tools. The choice between them is a surgical call about your pelvis, not a preference.

SI joint fusion is an outpatient procedure done under local anesthetic with mild sedation. An IV goes in, you get a light sedative, and the surgical site is numbed. The implants go in under live X-ray guidance through a small cut on the side. Most patients go home the same day.

Because mild sedation is used, arrange for someone to drive you home.

Keep the site clean and dry. Plan on a follow-up visit in the clinic within five to ten days so we can check the result in person. Do not lift anything over 20 pounds for two weeks.

Most patients are walking the same day. How much weight you put on the leg is guided by comfort, not a fixed schedule. Pain in the first several days is common and expected — it reflects the surgery itself, not a failure of it.

There is no national Medicare coverage determination for SI joint fusion. Coverage is set by region. In Missouri, the Medicare contractor publishes a local coverage determination covering percutaneous minimally invasive fusion of the sacroiliac joint, with specific criteria attached. Commercial policies vary, and we check each one.

Those criteria ask for the same things every time, and they match good practice no matter who pays. They want a documented stretch of failed conservative care, exam findings pointing at the joint, and proof by diagnostic block. This is one case where the payer’s rules and the medical rules point the same way.

We do not publish prices, because what each patient needs is set at the evaluation. Call (314) 481-5000 and we will check your coverage and tell you where you stand before anything is booked.

Fusion is not an early step. It is what is left when the joint has been pinned down, conservative care has truly been tried, and the relief from injection is real but short-lived.

Before it come changes to activity, physical therapy aimed at the pelvis instead of the lumbar spine, and SI joint injection to both diagnose and treat. For some patients, radiofrequency ablation of the nerves that serve the joint gives lasting relief without fusing anything.

Dr. Gurpreet Singh Padda, MD, MBA, MHP is a licensed physician and surgeon with surgical privileges, and this practice performs SI joint fusion. We lead with the least invasive option that can answer the question. We save fusion for when the joint has proven itself the source and nothing short of locking it down has held.