MRI Area of Interest Without IV Contrast Given the importance of recognizing these high-risk fractures in the femoral head and neck, MRI is the preferred second-line study after initial negative radiographs to prevent delayed diagnosis. MRI does not use ionizing radiation, has excellent sensitivity, and allows for definitive diagnosis. MRI typically demonstrates linear T1 and T2 hypointense signal, representing fracture lines, and T1 hypointense and T2 hyperintense signal in the surrounding bone marrow, representing associated edema. MRI demonstrates stress abnormalities as early as bone scintigraphy and with as much sensitivity [25-28]. Stress (Fatigue-Insufficiency) Fracture In addition to confirming a suspected stress fracture, MRI may also demonstrate other reasons for occult pelvic pain, such as soft tissue abnormalities or the subchondral hip or supra-acetabular stress fractures described in some patients with osteoporosis [57]. Radiography Area of Interest Repeat In 10-14 Days A follow-up radiographic examination has increased sensitivity compared to initial radiographs [43] but is less sensitive than MRI. US Area of Interest There is increasing evidence of the usefulness of US in the early diagnosis of stress fractures of the distal extremities [44,45] and may allow visualization of posterior sacral fractures without the risk of ionizing radiation. However, definitive diagnosis of suspected hip or pelvic fractures should not be delayed by choosing US as the second-line study following negative or indeterminate radiographs, considering that additional imaging may be required following a negative or US indeterminate examination. Patients at high-risk for fracture completion include patients with osteoporosis, those on bisphosphonate therapy, and athletes.
Stress Fatigue Insufficiency Fracture Including Sacrum Excluding Other Vertebrae PCAs. MRI Area of Interest Without IV Contrast Given the importance of recognizing these high-risk fractures in the femoral head and neck, MRI is the preferred second-line study after initial negative radiographs to prevent delayed diagnosis. MRI does not use ionizing radiation, has excellent sensitivity, and allows for definitive diagnosis. MRI typically demonstrates linear T1 and T2 hypointense signal, representing fracture lines, and T1 hypointense and T2 hyperintense signal in the surrounding bone marrow, representing associated edema. MRI demonstrates stress abnormalities as early as bone scintigraphy and with as much sensitivity [25-28]. Stress (Fatigue-Insufficiency) Fracture In addition to confirming a suspected stress fracture, MRI may also demonstrate other reasons for occult pelvic pain, such as soft tissue abnormalities or the subchondral hip or supra-acetabular stress fractures described in some patients with osteoporosis [57]. Radiography Area of Interest Repeat In 10-14 Days A follow-up radiographic examination has increased sensitivity compared to initial radiographs [43] but is less sensitive than MRI. US Area of Interest There is increasing evidence of the usefulness of US in the early diagnosis of stress fractures of the distal extremities [44,45] and may allow visualization of posterior sacral fractures without the risk of ionizing radiation. However, definitive diagnosis of suspected hip or pelvic fractures should not be delayed by choosing US as the second-line study following negative or indeterminate radiographs, considering that additional imaging may be required following a negative or US indeterminate examination. Patients at high-risk for fracture completion include patients with osteoporosis, those on bisphosphonate therapy, and athletes.