Assessment of the ankle joint in clubfeet and normal feet to the age of four years by ultrasonography.

Purpose: To establish reproducible posterior ultrasonographic projections for evaluation of the movement in the talocrural joint in clubfeet and normal feet from the perinatal period up to the age of four years.

Methods: The feet in 105 healthy children and 46 patients (71 clubfeet and 21 normal feet) were examined. In all, 14 feet in seven patients were examined twice by two examiners independently to evaluate the repeatability of the ultrasonography scans. A posterior sagittal projection was used. The distance from the posterior aspect of the tibial physis to the posterior border of the talocalcaneal joint (Tib. phys - TCJ) was measured with the foot in neutral position and dorsiflexion. In plantar flexion the shortest distance between the tibial physis and the calcaneus was measured. The distance from the skin to the tibial epiphyses and the talus was measured in neutral position. The intraclass correlation coefficient (ICC) was calculated to evaluate the repeatability of the measurements.

Results: The interexaminer reliability was 0.71 to 0.89 ICC. The intra- and interobserver reliability measured as ICC was 0.68 to 0.99 for all measurements. The correlation between Tib. phys. - TCJ and clinical dorsiflexion varied much between the age groups.

Conclusion: Ultrasonography of the posterior aspect of the ankle joint can be done with high interexaminer reliability. The repeatability of image evaluation was high. Correlation to clinical measurements varied, therefore dynamic ultrasound in real time is clinically more useful than single measurements on frozen ultrasound images.