The SI joint is one of the most commonly missed sources of low back and buttock pain — and one of the few that will not respond to anything aimed at the lumbar spine. When the diagnosis is confirmed and conservative care has failed, minimally invasive fusion stabilises the joint through a small lateral incision.
SI joint fusion construct
Suggested: posterior or lateral view of the pelvis showing triangular implants placed across the sacroiliac joint from the ilium into the sacrum.
The sacroiliac joint transmits the entire load of the spinal column into the pelvis. When it becomes a pain generator, the pattern is distinctive — pain below the belt line, over the buttock, sometimes referring into the groin or down the back of the thigh — and it is frequently mistaken for a lumbar disc or a hip problem.
It is a genuinely common cause. Published series attribute roughly 15 to 30 percent of chronic low back pain to the SI joint. It also becomes more likely after a lumbar fusion, because load that used to distribute across the lower spine is transferred into the pelvis instead.
Because a lumbar MRI will usually show something degenerative, patients often accumulate a long history of treatment aimed at the wrong structure. Diagnosing it depends on specific examination findings and injection testing.
This sequence matters. Fusing an SI joint that is not the pain generator will not help, so it has to be confirmed as the source first.
Pain centred below L5 over the joint itself, often pointed to with one finger just medial to the posterior superior iliac spine. Pain above the belt line points elsewhere.
A set of physical maneuvers that stress the joint — distraction, thigh thrust, compression, Gaenslen's, sacral thrust. Multiple positive tests substantially raise the likelihood the SI joint is responsible.
SI joint pain rarely shows up on a scan. X-rays and MRI are used here mainly to rule out the lumbar spine and the hip as the actual source.
An image-guided anesthetic injection into the joint. Meaningful, temporary relief is the confirmatory step, and most insurers require it before authorising fusion.
Physical therapy targeting the pelvic stabilisers, activity modification, bracing, and therapeutic injections come first. Fusion is considered when those have been genuinely tried and have not held.
The patient is positioned prone. Intraoperative imaging and CT-guided navigation establish the trajectory across the joint before anything is placed.
A small incision over the side of the buttock. The corridor passes through soft tissue rather than detaching muscle from the pelvis, which is the reason this is a same-day operation rather than an open one.
Guide pins are advanced across the joint under navigation, from the ilium through the SI joint and into the sacral body. Typically three implants are placed in a triangular configuration to resist rotation as well as shear.
Final imaging confirms position and that no implant has breached into the neural foramen or the pelvis. Closure is a few sutures.
Intraoperative CT with live instrument tracking. The sacrum has narrow safe corridors and the nerve roots sit close by — navigation is what makes the trajectory verifiable rather than estimated.
Where used, a robotic arm holds the planned trajectory rigidly so the guide pin follows the plan rather than drifting along the dense cortical bone of the ilium.
A press-fit triangular profile resists rotation, and the porous surface is designed for bone to grow into it over the months following surgery.
See navigation and robotics for how these systems are used across procedures.
Figures are general ranges from the published literature, not guarantees. Weight-bearing protocol in particular varies by implant, bone quality, and whether one or both joints were treated — follow the instructions you are given rather than these. Randomised trials of minimally invasive SI joint fusion have reported greater improvement in pain and function than continued non-surgical management in patients with a confirmed diagnosis; that is a group result and not a prediction for any individual.
SI joint fusion works well in correctly selected patients and poorly in incorrectly selected ones. The single biggest determinant of a good result is whether the SI joint was genuinely the source of pain to begin with. That is why the diagnostic sequence above matters, and why the answer is sometimes no.
Dr. Zaidi is an excellent surgeon. My back was an absolute mess. This is the best I have felt in 2 years. I can finally walk without any pain.Peggy C. · Google review
I saw Dr Zaidi to get options for treating my back pain. I have tried many different treatments but nothing worked. He explained what he might be able to do for me in great detail, and gave me reading material on my condition.Debi L. · Google review
Very personable. Very matter of fact. Not aggressive with treatment plan; starts slow in order to try all options to avoid surgery.Kaye M. · Google review
Verbatim from public Google reviews, shown with first name and last initial. These are general reviews of Dr. Zaidi's care, not accounts of SI joint fusion specifically. More patient reviews →