Is the canal flare index a reliable means of estimation of canal shape? Measurement of proximal femoral geometry by use of 3D models of the femur

摘要

Background The canal flare index (CFI; the ratio of the diameter of the femoral canal at the isthmus in the anteroposterior (A-P) view to the diameter of the medullary canal 20 mm above the lesser trochanter) is often used as a canal characteristic. Clinically, however, CFI measurements are sometimes untrustworthy because of femoral rotation and, especially, greater anteversion among Japanese patients. Our objectives were to analyze femoral geometry, by use of 3D CAD models, to evaluate the effects of rotational error, and to seek an index less affected by rotation.