Sacroiliac Joint Dysfunction & Fusion Surgery​

Sacroiliac (SI) Joint Dysfunction occurs when the joint between the sacrum (the base of the spine) and the iliac bones of the pelvis becomes inflamed, unstable, or degenerative. The SI joint connects the spine to the pelvis and helps absorb the impact of walking, lifting, and twisting. Dysfunction in this joint can lead to lower back pain, buttock pain, or pain radiating down the legs.

In severe or chronic cases where conservative treatments fail, SI joint fusion surgery may be recommended to stabilize the joint and relieve pain.

How Common It Is and Who Gets It? (Epidemiology)

SI joint dysfunction is responsible for 15% to 30% of chronic lower back pain cases. It can affect people of all ages but is most common in adults over 40 and in women, particularly after pregnancy. Individuals who have had prior lumbar spinal fusion or pelvic trauma are also at higher risk.

Bilateral sacroiliac joints as seen on X-ray of the pelvis in anteroposterior view.

Why It Happens – Causes (Etiology and Pathophysiology)

The SI joint can become painful or unstable due to:

• Repetitive stress or trauma

• Degenerative arthritis or wear and tear with age

• Inflammatory diseases such as ankylosing spondylitis or Reiter’s disease

• Pregnancy or childbirth, which loosens pelvic ligaments

• Previous spine surgery, especially lumbar fusion, which alters biomechanics

• Infections or tumors (rare causes)

Over time, these factors can lead to inflammation, degeneration, and eventually restricted or painful movement in the joint.

How the Body Part Normally Works? (Relevant Anatomy)

The sacroiliac joint lies between the sacrum (a triangular bone at the base of the spine) and the iliac bones of the pelvis. Strong ligaments and muscles provide stability while allowing small gliding and rotating movements.
This limited motion helps distribute forces from the upper body to the legs and acts as a shock absorber during daily activities.

When the joint becomes inflamed or unstable, pain can develop in the lower back, buttocks, or legs.

What You Might Feel – Symptoms (Clinical Presentation)

Symptoms of SI joint dysfunction can mimic other spine or hip problems. Common signs include:

• Dull or aching pain in the lower back or buttocks

• Pain radiating down the thigh or leg (sometimes mistaken for sciatica)

• Increased discomfort when standing, climbing stairs, or sitting for long periods

• Relief with a tight belt or brace that supports the pelvis

• Stiffness or limited motion in the lower back

• Difficulty turning in bed or getting out of a car

Pain is usually felt on one side but can occur on both sides of the pelvis.

How Doctors Find the Problem? (Diagnosis and Imaging)

Diagnosis requires a careful combination of physical examination and imaging:

• Physical tests: Maneuvers such as the FABER test (Flexion, Abduction, External Rotation) and Gaenslen’s test reproduce SI joint pain.

• Imaging: X-rays, CT scans, or MRI may reveal degeneration or inflammation, though findings are often nonspecific.

• Diagnostic injection: A local anesthetic injected into the SI joint under imaging guidance can confirm the diagnosis if pain relief follows.

Classification

SI joint dysfunction can be classified based on its cause:

• Degenerative: Age-related or mechanical wear.

• Inflammatory: Related to systemic conditions like ankylosing spondylitis.

• Traumatic: Caused by injury or repetitive strain.

• Post-surgical: After lumbar fusion or pelvic surgery.
  It can also be described as hypermobility (too much motion) or hypomobility (too little motion).

Other Problems That Can Feel Similar (Differential Diagnosis)

SI joint dysfunction may be mistaken for:

• Lumbar disc herniation or spinal stenosis

• Hip arthritis

• Piriformis syndrome

• Facet joint arthritis

• Sciatica or nerve compression

Treatment Options

Non-Surgical Care

Most patients improve with conservative therapy.

• Physical therapy: Strengthens core, pelvic, and back muscles to stabilize the joint.

• Medications: NSAIDs reduce inflammation and pain.

• Injections: Corticosteroid injections provide temporary relief by reducing inflammation.

• Pelvic belts: Help stabilize hypermobile joints, particularly after pregnancy.

• Lifestyle modifications: Avoid prolonged sitting or uneven weight-bearing.

Interventional Care

If symptoms persist after conservative management, interventional procedures may be recommended:

• Radiofrequency ablation (RFA): Uses heat to destroy pain-transmitting nerves in the SI joint.

• SI joint fusion surgery: Fuses the sacrum and ilium to eliminate movement and stabilize the joint.

Understanding SI Joint Fusion Surgery

SI joint fusion is a surgical procedure designed to permanently stabilize the joint by fusing the sacrum and ilium.
Indications for surgery include:

• Persistent SI joint pain despite 6 months of conservative care

• Confirmed diagnosis via SI joint injection

• Significant joint instability or degeneration

Techniques:

• Open fusion: Larger incision, direct visualization of the joint.

• Minimally invasive fusion: Smaller incisions and specialized implants for faster recovery.

Recovery:
Most patients go home the same day or after one night. Full recovery takes several months, with physical therapy starting after initial healing. Fusion eliminates joint motion but significantly reduces pain in most cases.

Recovery and What to Expect After Treatment

• Early recovery: Patients may use crutches or a walker initially.

• Rehabilitation: Gradual return to activity with guided physical therapy.

• Long-term: Pain relief is typically achieved within 3–6 months as the bone fully fuses.

Minimally invasive techniques allow faster healing and reduced postoperative pain.

Bone tap

The bone is used for creating the path for the screw to engage in the bone. The bone tap has markings used to limit the depth of insertion during surgery.

Instruments used in posterior sacral fusion

Poly-axial sacral pedicle screws

The pedicle screws with the help of instruments shown above are used in sacral fusion and with the lumbar vertebra and the iliac bone to achieve stabilization at the sacroiliac and the L5-S1 joint.

Possible Risks or Side Effects (Complications)

Complications are rare but may include:

• Infection or bleeding

• Nerve irritation or numbness

• Implant loosening or failure

• Non-union (failure of bones to fuse)

• Persistent or recurrent pain

Proper patient selection and surgical technique minimize these risks.

Long-Term Outlook (Prognosis)

Most patients experience significant and lasting relief after SI joint fusion surgery. Studies report improvement in pain and function in over 80% of cases. Physical therapy and weight management help maintain long-term results.

Out-of-Pocket Costs

Medicare

CPT Code 27279 – Minimally Invasive SI Fusion: $190.37
CPT Code 27280 – Open SI Fusion: $332.18
CPT Code 27096 – Diagnostic/Therapeutic SI Joint Injection (if applicable): $37.59

Under Medicare, 80% of the approved amount for these procedures is covered once the annual deductible is met. Patients are responsible for the remaining 20%. Supplemental insurance plans—such as Medigap, AARP, or Blue Cross Blue Shield—typically cover this 20%, meaning most patients have little to no out-of-pocket cost for Medicare-approved SI joint procedures. These supplemental plans work directly with Medicare to ensure that patients undergoing minimally invasive or open SI fusion experience minimal financial burden.

If you have secondary insurance—such as Employer-Based Plans, TRICARE, or Veterans Health Administration (VHA)—it acts as a secondary payer after Medicare. Once your deductible is satisfied, these plans can cover the remaining coinsurance or balance. Secondary plans usually carry a small deductible ranging from $100 to $300, depending on your policy and provider network.

Workers’ Compensation
If your SI joint dysfunction or instability was caused by a work-related injury, Workers’ Compensation will pay for all treatment-related expenses, including injections, minimally invasive, or open fusion procedures. You will have no out-of-pocket costs for approved treatments under Workers’ Compensation coverage.

No-Fault Insurance
If your SI joint condition resulted from a motor vehicle accident, No-Fault Insurance will cover all necessary medical and surgical costs, including diagnostic injections and fusion surgery. The only potential charge may be a small deductible depending on your specific policy terms.

Example
Michelle, a 66-year-old patient, underwent minimally invasive sacroiliac fusion (CPT 27279) following persistent SI joint pain unresponsive to injections. Her Medicare out-of-pocket cost was $190.37. Because she carried supplemental insurance through AARP Medigap, the 20% that Medicare did not cover was fully paid, leaving her with no out-of-pocket expenses for the procedure.

Frequently Asked Questions (FAQ)

Q. What causes sacroiliac joint dysfunction?
A. The condition may result from wear and tear, previous back surgery, trauma, pregnancy, or inflammatory diseases like ankylosing spondylitis.

Q. How is SI joint dysfunction diagnosed?
A. Diagnosis involves physical tests, imaging studies, and a confirmatory SI joint injection that relieves pain.

Q. When is SI joint fusion surgery recommended?
A. Surgery is considered only after conservative treatments—like therapy, injections, and medication—fail to provide lasting relief.

Q. What is recovery like after SI joint fusion?
A. Most patients return to light activities within weeks and experience long-term pain relief once the joint fully fuses in 3–6 months.

Summary and Takeaway

Sacroiliac Joint Dysfunction is a common cause of lower back and pelvic pain, often misdiagnosed as a spinal problem. When conservative measures fail, SI joint fusion surgery offers a reliable solution by stabilizing the joint and relieving pain. With modern minimally invasive techniques, most patients experience fast recovery and durable results.

Clinical Insight & Recent Findings

A recent meta-analysis protocol outlined a systematic approach to evaluate the surgical and clinical efficacy of minimally invasive sacroiliac joint (SIJ) fusion compared with conservative treatment. The authors noted that SIJ dysfunction accounts for up to 30% of chronic low back pain cases, yet conservative therapies such as medications, physical therapy, and injections relieve symptoms in only about 50% of patients.

Advances in technology have made minimally invasive SIJ fusion a common procedure, offering shorter recovery times and fewer complications compared with traditional open surgery. The meta-analysis aims to synthesize recent data showing fusion rates ranging from 13% to 100% and assess patient-reported outcomes using measures such as the Visual Analogue Scale and Oswestry Disability Index.

The review emphasizes the need for standardized imaging criteria—preferably CT confirmation of trabecular bone bridging—to define true fusion success. Findings are expected to clarify the long-term benefits, fusion durability, and cost-effectiveness of minimally invasive SIJ fusion, providing evidence to guide surgical decision-making. (Study of minimally invasive sacroiliac joint fusion outcomes – See PubMed.)

Who Performs This Treatment? (Specialists and Team Involved)

Treatment is performed by orthopedic spine surgeons or neurosurgeons, often working with pain specialists, physical therapists, and rehabilitation teams.

When to See a Specialist?

You should consult a spine or orthopedic specialist if you experience:

• Chronic pain in the lower back or buttocks

• Pain radiating down the leg not caused by a herniated disc

• Worsening pain when standing or climbing stairs

When to Go to the Emergency Room?

Seek emergency care if you develop:

• Severe lower back pain with fever (possible infection)

• Sudden inability to walk or move your legs

• Loss of bladder or bowel control

What Recovery Really Looks Like?

Patients gradually return to normal activity over several months. Pain and stiffness decrease as fusion stabilizes the joint. Physical therapy enhances strength and flexibility for long-term stability.

What Happens If You Ignore It?

Untreated SI joint dysfunction may lead to chronic pain, pelvic instability, and reduced mobility. Long-term inflammation can also contribute to arthritis in nearby joints.

How to Prevent It?

• Maintain strong core and pelvic muscles.

• Practice good posture and proper lifting techniques.

• Avoid repetitive twisting or impact activities.

• Manage body weight and stay active.

Nutrition and Bone or Joint Health

A diet rich in calcium, vitamin D, and omega-3 fatty acids supports bone strength and reduces inflammation. Staying hydrated helps joint function and healing.

Activity and Lifestyle Modifications

Engage in low-impact activities such as walking, swimming, or yoga to keep joints mobile. Avoid prolonged sitting and use proper ergonomic support when standing or working.

Do you have more questions?