ANALYSIS OF LEG GEOMETRY - STANDARD TECHNIQUES AND NORMAL VALUES

The diagnosis of maralignments of the lower extremities includes analy sis of the geometry of the whole leg. The first step in the diagnostic process is a standardized physical examination. It provides valuable background information for an effective radiological diagnosis. Even w ith a thorough standardized physical examination it is not possible to define exactly the deformity or decide on an operative procedure. The diagnosis of axis deviations in the frontal plane can be measured on a conventional plain X-ray of the whole leg. In this view it is very i mportant that the knee joints are in a true a.p. view independent on t orsional deformities of the lower legs. Today the gold standard to mea sure the torsion and length of the lower extremities is the CT scan. H owever, the multitude of analytical methods for CT measurements descri bed in the literature do not lend themselves readily to comparison; th us, it is difficult to identify a clear method of choice. Not every CT measurement is better than a physical examination. Evidence of reprod ucibility and accuracy is a prerequisite for useful interpretation of the results. Up to this point in the literature there are only referen ce values for the Ulm CT Method. One alternative is the MR scan, which avoids radiological risks, but the reproducibility and accuracy of th e MRI method are not as good as for the CT method. Another alternative is ultrasound, where recent advances in the measurement of torsion an d length of the lower extremities have proven competitive with or supe rior to the accuracy of MRI. The three-dimensional determination of th e torsion and length of the lower extremities by ultrasound has now as sumed a leading role in the non-radiological diagnosis of malalignment s of the lower extremities in children and adolescents. This method fu rthermore is increasingly being used in preoperative planning of leg d eformities in adults.