[Preoperative planning and surgical technic in achieving stability and leg length equality in total hip joint...

One of the prerequisites for a good outcome of total hip arthroplasty is preoperative planning. Using a roentgenogram, the size of an implant, incision level on the femoral neck, depth required for fitting the cup, restoration of the center of hip rotation and, if necessary, correction of length descrepancy between the legs are determined. The preoperative planning based on an X-ray image was introduced by M. E. Müller and, in 1976, was modified by R. Schneider who used a transparent sheet for a template on which all relevant points guiding the surgical procedure are marked, i.e., the right position for implantation of the cup and stem, and incision lines. In uncomplicated cases, however, this approach is not necessary and the "planning principle of parallel lines" developed by L. Spotorno in 1988 can be used instead. The determination of length discrepancy between the legs is derived from a drawing of three reference lines on the roentgenogram. The lines parallel to each other indicace the same length for both legs. If the legs differ in length, the lines will diverge from each other in a way typical for this condition.