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Posterior Sacroiliac Joint Fusion

Your sacroiliac joints (the " SI" joints) are where your hips meet your spine. These joints don't have a lot of flexibility, but they do move slightly as you move your body, typically 2-3 degrees of movement. If SI joints become damaged or diseased, it can be painful, typically because of an increased load and movement of the affected joint. SI joint pain is commonly seen in patients who have had lumbar fusion operations, as the adjacent (inferior) segmental motion location involves the bilateral SI joints.

About Symptoms

SI joint pain starts in the lower back and buttock, and it can radiate to the hip, groin, and posterior thigh. Your leg may feel weak, and it may feel numb or tingly. You may notice SI joint pain when sitting or lying down, and you may also see it when you walk, climb stairs, or stand up after sitting.

How are SI Joint conditions diagnosed?

Often SI Joint conditions are diagnosed with a combination of an individual's pain pattern history and physical exam findings. History of lumbar to sacrum fusion, direct trauma to the SI joint, or childbirth may help with diagnosis also. The definitive diagnosis is to use an anesthetic and inject it into the joint and assess the patient's response. An alternative is an L4, L5 medial branch block with an S1-S3 lateral branch block; this would temporarily deinnervate the joint.


Treatment depends on the cause of your pain. You may benefit from physical therapy or intraarticular injections into the joint. Patients may benefit from a procedure called radiofrequency ablation as well. If the results from the injection or radiofrequency ablation diminish, or if a patient has a significantly painful, lax SI joint (Ehlers-Danlos), then a minimally invasive posterior SI Joint Fusion may

be an option to stabilize your joint.

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