Recognizing Sacral Insufficiency Fractures Hidden in Plain Sight: An Illustrative Case Report

Sacral insufficiency fractures (SIFs) are stress fractures that occur when normal biomechanical forces act on weakened bone, most commonly in elderly patients with osteoporosis or other conditions that compromise bone integrity. Because symptoms are often nonspecific, typically presenting as low back, sacral, or pelvic pain, SIFs are frequently underdiagnosed or misinterpreted as other pathologies, including lumbar spine disorders or metastatic disease. Conventional radiographs have low sensitivity, and although computed tomography (CT) can help identify fracture lines and assist in surgical planning, magnetic resonance imaging (MRI) remains the most sensitive modality for early detection. We present two cases of SIFs with progressive pain and functional impairment. The first case involved an 86-year-old woman who developed severe low back pain following a fall, with imaging revealing bilateral sacral fractures involving Denis zones I and III. The second case involved a 61-year-old woman with a prior history of lumbar fusion who presented with worsening lumbar pain radiating to the lower extremities, saddle numbness, and fecal incontinence; imaging demonstrated bilateral sacral fractures with displacement. Both patients had persistent symptoms and fracture instability despite conservative measures and underwent minimally invasive bilateral sacroiliac fusion with trans-sacral screw fixation. Postoperatively, both patients experienced significant pain reduction and improved functional status. These cases highlight the importance of maintaining a high index of suspicion for SIF in patients with unexplained lumbosacral pain and risk factors for bone fragility. While conservative management remains the first-line treatment, surgical stabilization with trans-sacral screw fixation may provide effective mechanical stability, rapid pain relief, and improved functional recovery in patients with unstable fractures or failure of nonoperative therapy.