Stress Reactions in Bone and Stress Fractures

The term "stress fracture" encompasses a spectrum of bone injuries resulting from repetitive submaximal loading that exceeds the bone's capacity for repair. This review explores the pathophysiology and clinical classifications of stress-related skeletal injuries, distinguishing between fatigue fractures-occurring when abnormal stress is applied to healthy bone-and insufficiency fractures, which arise from normal physiological stress on weakened bone. I discuss specific manifestations, including spondylolysis, distal clavicular osteolysis, atypical femur fractures, and pregnancy-associated vertebral compression fractures. Furthermore, the role of biomechanical alterations caused by conditions such as scoliosis and lumbosacral transitional vertebra in predisposing bone to stress reactions is addressed. Finally, I overview emerging future directions, specifically zero echo time MRI and deep learning-based synthetic CT, which generate CT-like images from MRI, and deep learning-based opportunistic CT screening for the early detection of osteoporosis, which provides a pathway to prevent catastrophic fracture through automated trabecular attenuation analysis.