Imaging description

Radiographic studies of the pelvis may demonstrate insufficiency fractures of the pelvis. Pelvic insufficiency fractures most commonly occur in the sacrum, inferior pubic ramus, superior pubic ramus, ilium, and acetabulum. When insufficiency fractures of the pelvis are radiographically occult, they can be demonstrated by MRI. The MRI appearance of a fracture is that of a linear or curvilinear focus of hypointensity on T1-weighted images that is either hyper- or hypointense on T2-weighted or STIR images (Figure 50.1).

Importance

Pelvic insufficiency fractures can be a source of groin or pelvic pain in elderly women with underlying osteoporosis. In elderly women with a history of cancer, development of groin or pelvic pain can obviously raise concerns for recurrent or metastatic disease. Pelvic insufficiency fractures are frequently unrecognized on radiographs due to their subtle or occult appearance. When the radiograph is negative in this type of clinical scenario, MRI is helpful in differentiating tumor from an insufficiency fracture as the cause of the new pain. Finally, pelvic insufficiency fractures can also be seen in any patient that has an underlying condition that has caused secondary osteoporosis or altered normal bone metabolism.

Typical clinical scenario

An 80-year-old female with a history of breast cancer presents to the family care clinic with new onset of right groin pain. One of the concerns of her physician is that she might have recurrent breast cancer in the form of metastatic disease to the osseous pelvis. A pelvic radiograph was performed and demonstrated an osteopenic appearance to the bones, but it was negative for any focal bone lesions. An MRI was then performed to rule out radiographically occult metastatic disease to the osseous pelvis. The MRI demonstrated insufficiency fractures involving the right pubic rami.