Three-dimensional measurement of femoral antetorsion: comparison to a conventional radiological method

The aim of our study was to produce a 3-D reconstruction of a CT dataset and compare it to the conventional method, with that same dataset, in terms of precision and the influence of femoral positioning. A mechanical support was developed to rigidly fix the femur in a designated position. After measuring the real AT, a CT scan with different femur positions was performed. Eight cadaveric specimens were utilized for this study. Each examination was performed twice and the mean value was recorded. The Jend method was chosen as the conventional mode for femoral antertorsion measurement. In the 3-D reconstruction, the angle between the femoral neck and trailing edge of the femoral condyles was measured. Measurement of the AT by 3-D reconstruction (0.8A degrees) was significantly better than the conventional method after (3.0A degrees; P = 0.016). The positioning of the femur influences measurement of the femoral AT angle by conventional method measurement whereas evaluation using the 3-D reconstruction was more independent of femoral positioning. 3-D reconstruction enables precise determination of the femoral AT angle, and is independent of femoral positioning as conventional methods seem to be. In clinical practice, 3-D reconstruction may allow a greater understanding of the femoral AT angle post fracture reduction and internal fixation. However, we believe the 3-D method of measuring the AT-angle can potentially optimize the patient's treatment outcome by allowing the orthopaedic surgeon to measure the femoral AT-angle more precisely after femoral fracture reduction.