MRI findings consistent with sacrococcygeal osteomyelitis temporally associated with ultrasound-guided caudal epidural steroid injection: A case report

Caudal epidural steroid injection (CESI) is a widely used minimally invasive procedure for the management of chronic low back pain and radicular symptoms and is generally considered safe. However, rare but serious infectious complications such as epidural abscess, cellulitis, and osteomyelitis may occur. We report a case of MRI-consistent sacrococcygeal osteomyelitis temporally associated with ultrasound-guided CESI in a 65-year-old female patient with a history of diabetes mellitus, hypertension, coronary artery disease, and prior L4–S1 posterior spinal stabilization surgery. The patient underwent CESI due to persistent low back and bilateral leg pain despite conservative treatment. Although she initially experienced significant symptomatic relief, she developed malaise and a burning sensation at the injection site on the third post-procedural day. Laboratory investigations revealed elevated acute-phase reactants, and the patient was subsequently hospitalized for further evaluation and management. Contrast-enhanced magnetic resonance imaging demonstrated findings were suggestive of sacrococcygeal osteomyelitis involving S4–S5 and Co1 levels, accompanied by surrounding soft tissue infection (cellulitis). Following infectious diseases consultation, empirical intravenous antibiotic therapy was initiated, resulting in marked clinical and laboratory improvement. This case highlights sacrococcygeal osteomyelitis as an exceptionally rare but serious complication of CESI and emphasizes the role of risk factors such as diabetes mellitus and prior spinal instrumentation surgery in the development of post-procedural infection, as well as the importance of early recognition of new or worsening pain after the procedure.