Prevalence and patterns of occult hip fractures and mimics revealed by MRI

OBJECTIVE. The diagnosis of hip fractures can be difficult on radiography alone. MRI is frequently used to confirm or deny the presence of a minimally displaced hip fracture. This study evaluates the patterns of injury seen on MRI that are difficult to diagnose on radiography. MATERIALS AND METHODS. MRIs of 73 patients who were examined for possible hip fractures and whose radiographic findings were negative or equivocal for hip fracture were reviewed. Seventy-six studies were performed in 73 patients who were between 24 and 102 years old. MRIs were evaluated for the presence and location of bone or soft-tissue injury. Muscle injuries were categorized on the basis of location and type of injury. RESULTS. Forty-six percent (35/76) of the studies showed subtle fractures. Seventeen fractures were in the proximal femur and 18 in the innominate bone. Soft-tissue abnormalities were common, found in 65% of the studies. Twenty percent of the MRI findings were considered normal because there was no apparent finding on the images to explain the patients' symptoms. CONCLUSION. Soft-tissue abnormalities are commonly seen alone or in association with subtle fractures on MRI in the evaluation of patients with a clinical suspicion of hip fracture. MRI is recommended for all symptomatic patients whose radiographic findings are negative for hip fracture.