Imaging of insufficiency fractures.

This review article focuses on occurrence, imaging, and differential diagnosis of insufficiency fractures. Prevalence and the most common sites of insufficiency fractures and their clinical implications are discussed. Insufficiency fractures are due to normal stress exerted on weakened bone. Most commonly postmenopausal osteoporosis is the cause for insufficiency fractures. Additional conditions affecting bone turnover include osteomalacia, chronic renal failure, and high-dose corticosteroid therapy. It is a challenge for the radiologist to detect and diagnose insufficiency fractures as well as to differentiate them from malignant fractures. Radiographs are the basic modality used for screening of insufficiency fractures, yet depending on the location of the fractures, sensitivity is limited. Magnetic resonance imaging is a very sensitive tool to visualize bone marrow abnormalities associated with insufficiency fractures and allows differentiation of benign versus malignant fractures. Thin section multidetector computed tomography (CT) depicts subtle fracture lines allowing direct visualization of cortical and trabecular bone. Dedicated Mikro-CTs (Xtreme-CT) can detect subtle fractures reaching an in-plane resolution of 80 μm. Bone scintigraphy still plays a role in detecting fractures, with good sensitivity but unsatisfactory specificity. Positron emission tomography-CT with hybrid-scanners has been the upcoming modality for the differentiation of benign from malignant fractures. Bone densitometry and clinical fracture history may determine the future risk of possible insufficiency fractures.