MR imaging measurement of the femoral antetorsional angle as a new technique: comparison with CT in children and adults.

Abstract

Our objective was to determine the accuracy, precision, and reliability of MR imaging as a technique for measurement of the femoral antetorsional angle. We used MR imaging to measure anteversion of the femoral neck in 44 patients: 19 children (range, 3-17 years old; mean, 11 years old) and 25 adults (range, 18-83 years old; mean, 29 years old). We found a high correlation between MR imaging and CT measurements (r = 77). On CT, the mean angle for children was 34 degrees and for adults it was 22.2 degrees. On MR imaging, the mean angle for children was 23.22 degrees and for adults it was 15.71 degrees. The mean anteversion angles obtained by CT exceeded those obtained by MR imaging. Mean interobserver and intraobserver agreements were high for MR imaging (r = .97 and r = .97, respectively) and for CT (r = .99 and r = .96, respectively). Compared with CT as the gold standard, MR imaging measurement of femoral anteversion allows precise anatomic measurements and produces reliable, reproducible results. MR imaging is recommended for preoperative planning in pediatric patients with femoral rotation osteotomies.