Abstract
BACKGROUND: Fibrous dysplasia (FD) is a rare, benign fibro-osseous disorder that can compromise structural integrity, particularly in weight-bearing bones like the sacrum. Managing sacral FD is challenging due to the need for both lesion control and biomechanical stabilization. OBSERVATIONS: A 34-year-old woman presented with chronic right sacral pain, functional impairment, and a large lytic lesion in the right sacral ala, later confirmed as FD. Conservative treatment, including physical therapy and epidural steroid injection, failed to provide relief. Imaging revealed an impending pathological fracture, prompting surgical intervention. A minimally invasive approach, including curettage, bone grafting, and iliosacral fixation with ingrowth screws, was performed. The patient experienced significant pain relief, functional improvement, and sustained stability, with 2-year follow-up confirming stable fixation and complete lesion filling. LESSONS: This case highlights the role of minimally invasive sacropelvic fixation in preventing structural failure in sacral FD. Integrating biomechanical stabilization with targeted lesion management optimizes outcomes. Long-term follow-up is essential to monitor implant stability and bone remodeling. https://thejns.org/doi/10.3171/CASE25159.