[A new procedure for determining leg length and leg length inequality using ultrasound. II: Comparison of ultrasound, teleradiography and 2 clinical procedures in 50 patients].

The clinical methods still in common use for measuring leg length and leg length discrepancy (LLD) cannot always meet the demands of precision and accuracy. A method using ultrasound is presented and shown to be a standardized, non-invasive method allowing accurate determination of leg length and LLD. Once the validity had been proved experimentally, practical handling, precision and accuracy of this method were tested on 50 patients in whom teleradiography of the lower extremity was performed for different reasons. The sonographically determined measures of LLD were compared with the radiographic measurements and in addition clinical measurements were taken by direct (tape measure) and indirect methods ("lengthening" of the shorter leg by wooden blocks of known thickness). Adjustments to the ventral hip joint and to the medial knee joint served as standardized, easily reproducible sonographic reference points. The mean variance of repeated sonographic measurements as a reflection of precision amounted to 3.5 mm2 for leg length measurement, with a maximum of 13.5 mm2. In the case of LLD the mean divergence between sonographically and radiographically determined LLD was 0.9 +/- 2.7 mm, with a maximum of 6.4 mm. The clinical methods with mean divergence of -1.2 +/- 9.6 mm (direct method) and -1.0 +/- 6.1 mm (indirect method) proved to be less accurate. The method examined for measuring leg lengths and LLD by means of ultrasound is easy to manage and non-invasive. Its precision and accuracy make it superior to clinical measuring methods and could even make some radiographical examinations superfluous.