Introduction: Sacral insufficiency fracture (SIF) is an uncommon but increasingly recognized complication following lumbosacral fusion, particularly in patients with compromised bone quality. The biomechanical vulnerability of the L5–S1 junction, combined with altered load transfer after anterior and posterior reconstruction, may predispose to early sacral failure. fusion, corticosteroid-associated bone fragility, cage subsidence, spinopelvic biomechanics, lytic spondylolisthesis, lumbosacral junction. Case Report: A 55-year-old male with lytic spondylolisthesis at L5–S1, repeated corticosteroid exposure, and neurogenic claudication underwent staged circumferential L4–S1 fusion (L5–S1 anterior lumbar interbody fusion, L4–L5 oblique lumbar interbody fusion, and percutaneous posterior fixation). Initial post-operative recovery was satisfactory. At 8 weeks, the patient developed recurrent lumbosciatica. Computed tomography (CT) demonstrated collapse of the S1 superior endplate with anterior cage subsidence and foraminal compromise. Revision surgery included bilateral L5–S1 foraminal decompression and posterior refixation. Persistent unilateral radiculopathy required re-exploration, revealing a mobile bone fragment causing dynamic nerve compression, which was resected. The patient subsequently experienced progressive pain relief and returned to functional activity. Radiographs at 8 months confirmed advanced fusion and fracture consolidation. Discussion: SIF after circumferential fusion may be precipitated by corticosteroid-associated bone fragility, preexisting pars defects, and increased shear forces across the lumbosacral junction. Early symptoms may mimic post-operative radiculopathy, contributing to delayed diagnosis. CT is the most sensitive modality for early detection. Revision strategies include posterior decompression and reinforcement of fixation; in higher-risk cases, pelvic fixation may be warranted. Conclusion: Sacral fracture after lumbosacral fusion requires a high index of suspicion in osteoporotic patients presenting with recurrent radicular pain. Comprehensive biomechanical planning and pre-operative bone density evaluation are essential to mitigate risk. Keywords: Sacral insufficiency fracture, circumferential fusion, anterior lumbar interbody fusion/oblique lumbar interbody
Barrientos et al. (Thu,) studied this question.