Sacroiliac Joint Fusion

Overview

Sacroiliac (SI) joint fusion is a surgical procedure that stabilizes the joint connecting the sacrum to the pelvis by placing implants or bone graft across it so the two bones grow together and stop moving against each other. The goal is to eliminate the abnormal motion and inflammation at the joint that is generating pain, when that joint (not the lumbar spine) has been identified as the true pain source.

This is not a first-line treatment. It is considered only for carefully selected patients whose SI joint pain has been confirmed with a diagnostic injection and who have not found lasting relief from months of conservative care. Most modern SI joint fusions in the United States are performed using a minimally invasive (MIS) technique with small titanium implants, though open approaches remain in use for specific situations.

When it's recommended

Before fusion is ever discussed, the SI joint must be confirmed as the source of your pain. The reference standard is an image-guided diagnostic injection of local anesthetic directly into the joint. If that injection reproducibly relieves your typical pain, it supports the SI joint as the generator and separates it from a lumbar spine problem, a distinction that changes the entire treatment plan.

Once the joint is confirmed, surgeons generally want to see that a real trial of nonoperative care has not worked: activity modification, a structured physical therapy program targeting the gluteal and core stabilizing muscles, anti-inflammatory medication, and often a therapeutic injection or radiofrequency ablation. Fusion is typically reserved for patients with persistent, functionally limiting pain despite this workup, and for select cases such as SI joint breakdown after a prior lumbar fusion that extends to the sacrum, or true traumatic instability of the joint.

How it works

Most patients today undergo a minimally invasive procedure in which the surgeon places a small number of implants, commonly three triangular titanium implants, across the SI joint through a one to two inch incision in the buttock, guided by X-ray or navigation imaging. The triangular cross-section is designed to resist rotation, and a porous coating on the implant surface allows bone to grow onto it over time, adding biological fixation to the initial mechanical stability. The procedure typically takes about an hour, involves minimal blood loss, and does not require removing the joint's cartilage.

An open approach, through either an anterior or posterior incision, directly exposes the joint so the surgeon can remove cartilage and pack bone graft across it, sometimes combined with screws or plates. This approach involves more tissue dissection and a longer recovery, and is generally reserved for cases with significant deformity, revision surgery after a failed prior fusion, or anatomy that does not lend itself to a percutaneous approach.

Preparing for the procedure

Your surgeon will confirm your diagnostic injection response, review imaging of your pelvis and lumbar spine, and go over your full list of medications, since blood thinners and certain supplements typically need to be paused beforehand. Optimizing bone health matters here just as it does for spine fusion, so smoking cessation, vitamin D and calcium status, and control of conditions like diabetes are often addressed before surgery to support bone healing around the implants.

Plan ahead for the early recovery period: arrange a ride home, set up your living space so frequently used items do not require excessive bending or stair climbing, and consider borrowing or renting a walker, cane, or crutches if you do not already have one, since a period of protected weight-bearing is standard after most MIS fusions.

Recovery and aftercare

Many patients go home the same day or after one night in the hospital, and most are walking with an assistive device within a day of surgery. Your surgeon will specify how much weight you can put on the operated side and for how long, a protected weight-bearing period that is tailored to your bone quality, the implant construct used, and whether one or both joints were fused. Most people gradually increase walking and light daily activity over the first few weeks, while avoiding excessive bending, lifting, and twisting until cleared.

Follow-up imaging and clinic visits track how well the implants are integrating with bone. Formal fusion and clearance for unrestricted lifting or high-impact activity generally take several months, and physical therapy is often introduced once initial healing allows to restore strength and normal movement patterns around the pelvis and low back.

Risks and considerations

As with any surgery, risks include bleeding, infection, blood clots in the legs or lungs, and anesthesia-related complications. Procedure-specific risks include implant malposition or loosening, nerve irritation or injury near the sacrum, incomplete pain relief, and, less commonly, the need for a revision procedure. Reported complication rates for the minimally invasive technique are low, and clinical trials have shown significant reductions in pain and disability along with a meaningful drop in opioid use among patients who respond to surgery.

Because SI joint fusion is only appropriate for a specific, confirmed presentation, the biggest overall risk is proceeding without adequate diagnostic confirmation. Outcomes are best in patients whose pain was clearly reproduced by a concordant diagnostic injection and who had a genuine trial of conservative care first; skipping that workup increases the chance that surgery will not resolve the pain because the SI joint was never the true source.