Measurement of femoral anteversion by magnetic resonance imaging--evaluation of a new technique in children and adolescents.

Anteversion of the femoral neck was measured by magnetic resonance imaging (MRI) in 19 children (37 hips) preoperatively before femoral rotation osteotomies. The results of this new technique were compared with values for anteversion obtained by computed-tomographic (CT) scanning and ultrasound. In order to determine the correlation between the three different methods and to assess their reliability, the measurements were performed independently by two observers at different times. There was a high correlation (Pearson's correlation coefficient) between MRI results and CT scan (r = 0.77) as well as MRI and sonography (r = 0.81), although the mean anteversion angles obtained by computerized tomography (34.0 degrees, range 5-82 degrees) and ultrasound (25.6 degrees, 10-40 degrees) were larger than the MRI values (23.2 degrees, 0-65 degrees), which can be explained by the different measurement techniques. Mean inter-rater as well as intra-rater reliability was high for MRI (r = 0.97 and r = 0.97) and CT (r = 0.99 and r = 0.96) but slightly less for sonography (r = 0.88 and r = 0.88). MRI is a novel method for evaluating femoral anteversion that does not require ionizing radiation, allows a precise anatomical measurement and reliable results. MRI is recommended for preoperative planning of pediatric femoral rotation osteotomy cases.