What are the most common types of radiographically occult hip fractures?
Acute nondisplaced femoral neck fractures as well as insufficiency and stress fractures are usually not visible on radiographs or CT. Insufficiency fractures occur in osteoporotic bone with physiologic stresses, whereas stress (or fatigue) fractures occur in normal bone from increased abnormal or repetitive stress and are most common in young athletes.
Subcapital femoral fractures (those at the junction of the femoral head and neck) tend to occur in osteoporotic bone. Extracapsular fractures (intertrochanteric and subtrochanteric) affect older patients more often than intracapsular fractures do and are usually caused by direct injury.
MRI can also differentiate pathologic fractures from osteoporotic or insufficiency fractures, and fractures from bone contusions.