Aspects of femoral neck anteversion. Theoretical considerations and experimental results.

Although the general definition of femoral neck anteversion seems to be accepted, the details vary substantially and some measuring methods are based on anatomic prerequisites that are lacking. This may be a cause of inconsistent and incorrect determinations. An anatomic study was therefore performed. Only small differences were found between two neck axes and different methods for delineating the axes. Inconsistent use of the shaft axis gave substantial variations. The long axis of the femoral shaft was, however, not shown to be a source of substantial error. The variation between three different knee axes was substantial. The cross section of the femoral neck was found to be radially asymmetric. Therefore, a precise and unequivocal neck centre cannot be made by any combination of bi-plane projections of the neck.