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.