[Comparative study of echography and conventional radiology in the evaluation of the Insall-Salvati index].

For the study of painful patello-femoral syndromes, the authors suggest the use of US for the evaluation of the so-called Insall-Salvati ratio--i.e., length of patellar ligament/patellar length--whose alteration is suggestive of vertical patello-femoral malalignement (patella alta and patella infera). Ten normal volunteers (20 knees) were examined by means of both US and conventional radiology, and the Insall-Salvati ratio was calculated for each knee. US and radiologic measurements were statistically compared by the correlation-coefficient method: the result was 0.802. US measurements were repeated twice with 0.778 interobserver variability according to the Spearman correlation index. Based on their results, the authors conclude that, in the evaluation of the Insall-Salvati ratio, the diagnostic accuracy of US is almost the same as that of conventional radiology; the former method may even be preferred for it is a simple, quick and repeatable technique not needing ionizing radiations.