Understanding the Sacroiliac Joint
The sacroiliac (SI) joint connects the sacrum (base of the spine) to the ileum (pelvic bone). It is a large, strong joint that transfers load from the spine to the legs. When the SI joint becomes painful due to arthritis, injury, or abnormal motion (SI joint dysfunction), it can cause debilitating lower back, buttock, and leg pain — often misdiagnosed as lumbar disc disease or sciatica.
Research suggests that the SI joint is responsible for up to 15–25% of chronic lower back pain cases. It is frequently missed as a diagnosis because its pain pattern closely mimics lumbar disc problems. Diagnosis is confirmed by a provocative SI joint injection — if pain is relieved by ≥75% after injection, the SI joint is confirmed as the pain source.
Symptoms of SI Joint Dysfunction
When is SI Joint Fusion Recommended?
- Confirmed SI joint pain on diagnostic injection (≥75% relief)
- Failed conservative management (physiotherapy, SI belt, NSAIDs) for 6+ months
- Failed SI joint steroid injections (temporary or no relief)
- Post-lumbar-fusion sacroiliac joint degeneration
The MIS SI Fusion Procedure
Positioning
Patient prone under general anaesthesia. Fluoroscopy positioned for real-time imaging. Small 2cm incision over the buttock.
Implant Placement
3–4 titanium threaded implants (or triangular titanium implants) placed across the SI joint under fluoroscopic guidance. Joint surface disrupted for fusion.
Recovery
Partial weight bearing for 4 weeks. Full weight bearing at week 6. Fusion confirmed on CT at 3 months. Most patients report significant pain relief within 1–3 months.