[Sonographic versus radiological assessment of chronic outer ligament instability of the upper ankle joint].

Chronic instability of the lateral upper ankle joint ligament is usually diagnosed by clinical and radiological examination. For the evaluation of an ultrasound method of testing lateral instability of the ankle joint we carried out a prospective study. We examined 23 adults who were actively engaged in some form of sport (21 male, 2 female, mean age 32 years) and had a preexisting lateral instability of the ankle. The instability was measured in the standard planes using Scheuba's stress apparatus with simultaneous ultrasound monitoring. The ultrasound examination was performed by positioning the 5-MHz applicator on the lateral side of the Achilles tendon, thus defining a plane from which the instability could be measured in both examination planes by observing the deviation between dorsal inferior edge of the tibia and the dorsal border of the talar roll. For the two examination planes, Spearman's rank-correlation coefficient between the radiological and ultrasound methods was 0.83 and 0.92. The sensitivity of the ultrasound method was 0.90, and the specificity was 0.85. Our study showed a good correlation between the two methods. A pathological talar tilt according to radiological criteria was also revealed by ultrasonography. Thus, all the advantages of ultrasound are now available for the evaluation of chronic lateral instability of the ankle joint.