Lateral minimally invasive SI joint fusion following adult spinal deformity: a case-report and literature review

This case report describes lateral minimally invasive sacroiliac (SI) joint fusion for SI joint–mediated pain in a patient with a history of adult spinal deformity surgery. A 48-year-old woman with multiple medical comorbidities previously underwent long thoracolumbar fusion. She subsequently had L4-S1 anterior lumbar interbody fusion and posterior L4-pelvis instrumentation in 2010. Following a ground-level fall in 05/2021, she developed new left-sided hip and sacroiliac pain with intermittent left lower-extremity numbness. Radiographs demonstrated mild hip osteoarthritis and sacroiliac joint sclerosis; spine imaging revealed discontinuity of the right iliac fixation rod without acute fracture. MRI of the hip showed bilateral sacroiliitis in the setting of prior long segment thoracolumbar fusion. Three image-guided SI joint injections produced significant but transient pain relief, whereas medications and physical therapy did not provide durable improvement. Given the concordant clinical presentation, imaging, and positive diagnostic block response, the patient underwent left minimally invasive lateral SI joint fusion on 10/21/2021 without complications. She was discharged on postoperative day three with improved pain and resolution of radicular symptoms. At six-month follow-up, she reported sustained functional gains and improved mobility. This case highlights the importance of confirming SI joint–mediated pain after prior spinal fusion, the role of image-guided injections in diagnosis, and the potential effectiveness of lateral minimally invasive SI joint fusion in patients with limited response to nonoperative management.