SI Joint Fusion
SI joint fusion is a minimally invasive procedure that permanently stabilizes the sacroiliac joint (where the sacrum meets the pelvis) by placing titanium implants across it. Bone grows in around the implants and fuses the joint over about a year. It is performed when SI joint dysfunction causes chronic lower back and buttock pain that has not responded to physical therapy and injections. Modern techniques use 2-3 small implants placed through a single lateral incision under fluoroscopic guidance.
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Who Needs SI Joint Fusion?
Patients with confirmed SI joint dysfunction, proven by significant temporary pain relief (75%+) from a diagnostic SI joint injection, who have failed at least 6 months of comprehensive conservative treatment. Also considered after lumbar spinal fusion, which shifts mechanical stress to the SI joint and can cause adjacent-level degeneration. Patient selection is the most critical variable: surgery should proceed only when the SI joint is definitively identified as the pain source.
What to Expect
Recovery Timeline
Walking with a walker. Weight bearing as tolerated. Surgical site pain is typically mild to moderate.
Transition to a cane. Light daily activity resumes. Most patients return to desk work within 2 weeks.
Physical therapy to restore gait, strength, and pelvic stability. Driving resumes once off narcotic medications, typically at 2-3 weeks.
Return to moderate activities: walking, cycling, non-impact exercise.
Bony fusion complete. Maximum pain relief and function. Most patients achieve 70-80% improvement in SI joint pain.
Risks & Complications
- Persistent or incomplete pain relief (roughly 20% of patients)
- Implant malpositioning
- Superior gluteal nerve injury with some approach angles
- Infection (less than 1%)
- Failed fusion requiring revision
- Adjacent joint stress over time
Frequently Asked Questions
How do I know if SI joint fusion is right for me?
The diagnostic injection is the deciding test. If a fluoroscopically guided injection into the SI joint drops your pain by 75% or more, that is strong evidence the SI joint is causing your symptoms. Combined with a documented 6-month trial of physical therapy and injections without lasting relief, you are a reasonable surgical candidate. If the injection does not relieve your pain, the SI joint is not the source and surgery will not help, regardless of how bad your MRI looks.
What is the success rate of SI joint fusion?
Clinical trials using the iFuse triangular titanium implant system (the most studied design) report 75-80% responder rates at 2 and 5 years, with most patients reducing or eliminating narcotic medication. Success rates are significantly higher in patients who had a clear positive diagnostic injection response. Patients with ambiguous pre-operative testing have much more variable outcomes.
Does SI joint fusion affect walking or hip movement?
The SI joint moves very little under normal conditions, roughly 2-4 degrees of rotation. Fusing it does not meaningfully change gait or hip mechanics. Most patients walk better after fusion because the pain limiting their mobility is gone. Adjacent joints like the hip and lumbar spine may see slightly more mechanical stress over years, but this is rarely a clinical problem.
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Search surgeonsEstimated Cost
$20,000 - $40,000 (before insurance). Medicare and most commercial insurers cover the procedure when criteria are met, including a documented positive diagnostic injection and failed conservative treatment.
Full cost breakdownRelated Specialty
Spine Specialists →Related Conditions
Other Procedures
This information is for educational purposes only. Costs are estimates and vary by location, surgeon, and insurance. Always consult a qualified healthcare provider.