The role of fat pad sign in diagnosing occult elbow fractures in the pediatric patient: a prospective magnetic resonance imaging study.

UNLABELLED: In 1954, Norell described the 'fat pad sign' for the first time. This refers to the radiological visualization of the elbow fatty tissue. This is a prospective study with the aim of clarifying the relation between the presence of a positive fat pad sign on the lateral radiograph and the type of injury verified on MRI. From January to December 2010, 31 children were diagnosed primarily with a positive fat pad sign. An above-the-elbow cast was applied and all patients were referred for an MRI within a few days. All patients were recommended a clinical follow-up and informed about the MRI results. After revision, five patients were found to have a negative fat pad sign and were excluded. This resulted in a total of 26 patients, 10 men and 16 women, mean age 10±2.62 years. The time between the injury and the initial radiological examination was 0.8±0.27 days and the MRI was obtained on an average of 6.6±3.84 days. A total of 12 patients had an injury of the left side and 14 of the right side. The MRI showed a posterior positive sign in all except five cases and six occult fractures, which accounts for 23%. Nineteen patients (73%) had a bone bruise. All patients except one had a normal range of movement with no pain on the last clinical examination after 2-3 weeks. The presence of a positive fad pad sign is not synonymous with occult fractures. Finding occult fractures on MRI does not alter the final treatment of these patients. On the basis of this study and review of other similar studies, pediatric patients who presented with elbow effusion verified on conventional radiographs could be treated with a cast for 2-3 weeks and extra clinical or radiological controls did not seem to be indicated. LEVEL OF EVIDENCE: Level III, development of diagnostic criteria on the basis of consecutive patients.