Delayed Diagnosis of an Occult Femoral Neck Fracture Undetected by MRI and Dual-Energy CT: A Case Report

Although MRI and dual-energy CT (DECT) are considered highly sensitive tools for detecting bone marrow edema and subtle fractures, occult femoral neck fractures may still be missed. Here, we report a rare case in which an occult femoral neck fracture was not detected on MRI or DECT during the initial evaluation. A 64-year-old woman with myelodysplastic syndrome (MDS) and residual left hemiparesis presented with persistent left hip pain after a fall. Initial radiography, CT, MRI, and DECT revealed no evidence of fractures or bone marrow edema. Despite conservative management, the patient's symptoms persisted, and repeat imaging one month later revealed a non-displaced subcapital femoral neck fracture. The patient underwent internal fixation using the Femoral Neck System (DePuy Synthes, Johnson & Johnson, Raynham, MA, USA) combined with a cannulated cancellous screw and had an uneventful postoperative course. The absence of typical MRI findings was likely related to diffuse bone marrow alterations associated with MDS, which may have obscured fracture-related edema. DECT can also fail to detect early or subtle trabecular injuries, particularly when the imaging parameters are suboptimal. Occult femoral neck fractures may remain undetectable with MRI and DECT, particularly in patients with hematologic disorders affecting the bone marrow composition. Persistent hip pain, despite negative imaging findings, should prompt repeat or parameter-optimized imaging.