An<unk>  is a fracture that is not readily visible, generally in regard to projectional radiography ("X-ray"). Radiographically,<unk>  and subtle fractures are a diagnostic challenge. They may be divided into 1) high energy trauma fracture, 2) fatigue fracture from cyclical and sustained mechanical stress, and 3) insufficiency fracture occurring in weakened bone (e.g., in osteoporosis and postradiotherapy). Independently of the cause, the initial radiographic examination can be negative either because the findings seem normal or are too subtle. Advanced imaging tools such as computed tomography, magnetic resonance imaging (MRI), and scintigraphy are highly valuable in the early detection of these fractures. Fractures represent up to 80% of the missed diagnoses in the emergency department. Failure to recognize the subtle signs of osseous injury is one of the reasons behind this major diagnostic challenge. While<unk> s present no radiographic findings, radiographically subtle fractures are easily overlooked on initial radiographs. In both cases, a negative radiographic diagnosis with prominent clinical suspicion of osseous injury will prompt advanced imaging examination such as CT scan, magnetic resonance imaging, ultrasound, and nuclear medicine to confirm or exclude the clinically suspected diagnosis. The burden entailed in missing these fractures includes prolonged pain with a loss of function, and disability. Early detection, on the other hand, enables more effective treatment, a shorter hospitalization period if necessary, and decreased medical costs in the long run. It will also prevent inherent complications such as nonunion, malunion, premature osteoarthritis, and avascular osteonecrosis (as in scaphoid fracture). Of the three types of<unk> s mentioned above, the latter two, fatigue fracture secondary to repetitive and unusual stress being applied to bone with normal elastic resistance, and insufficiency fracture resulting from normal or minimal stress on a bone with decreased elastic resistance are also described as "stress fractures". These fractures are often a challenging diagnostic problem in daily clinical practice. Radiologists should be aware of the different situations and mechanisms of these injuries as well as the subtle radiographic signs that can be encountered in each situation. The knowledge of normal images and the consideration of the clinical context are of great value in improving the detection of these fractures either on conventional radiographs or with more advanced imaging tools.
Occult fracture
Stress fracture
Malunion
Nonunion
Pseudofracture
Vertebral compression fracture
Osteoradionecrosis
Spinal fracture