MR evaluation of talonavicular angle in congenital talipes equinovarus

A four-year clinical and sonographic longitudinal follow-up of clubfeet treated according to Ponseti with normal references

Purpose

To follow children with a clubfoot by ultrasonography during the entire treatment period up to 4 years and compare with controls.

Method

Thirty clubfeet in 20 children treated using the Ponseti method and 29 controls were followed by repeated ultrasonography investigations from neonates to the age of 4 years. The previously established coronal medial and lateral, sagittal dorsal and posterior projections were used. Changes over time, correlations to the Diméglio score, and the course of treatment were studied.

Results

The medial malleolus-navicular distance was shorter, while the talar tangent-navicular distance and the talo-navicular angle were larger in clubfeet than in controls even after the initial correction. The healthy feet in unilateral cases did not differ significantly from the controls. The range of motion in the talo-navicular joint was approximately 20° less in clubfeet than in controls during the first four years of life. The medial malleolus-navicular distance (r = -0.58) and the talo-navicular angle (r = 0.66) at the first ultrasonography showed the highest correlation to the number of casts needed to correct the deformities.

Conclusion

Ultrasonography can be used to evaluate the initial degree of deformities in clubfeet and to follow the progress of the treatment and growth. Ultrasonography showed a clear difference between clubfeet and controls during the first four years of life. Although it was not possible to define specific limit values as benchmarks in the treatment, dynamic ultrasonography can provide valuable support in the decision-making process when complementary treatment may be needed.

Level of evidence

III.

Statistical shape modelling to analyse the talus in paediatric clubfoot

One fifth of idiopathic clubfoot deformities cannot be fully corrected by Serial Ponseti casting and deformity recurs in 20%-30% of cases. To avoid x-ray exposure, the joints with largely unossified bones are diagnosed with magnetic resonance images (MRI). Typically, geometric measurements are made in the MRI planes; however, this method is inaccurate compared to measurements on three-dimensional (3D) models of the joint. More accurate measurements using the 3D bone shapes may be better at identifying differences between groups; and therefore, improve diagnosis. The entire set of shape features from MRI can be analysed simultaneously through statistical shape modelling (SSM) which assesses bone morphology of clubfoot in a more sensitive way. A method for SSM of the talus is developed in this study and the shape of the normal talus is compared with the one in clubfeet with residual deformity through both geometric measurements and SSM. Significant differences between two groups were found by both methods; and therefore, might contribute to improve diagnosis of clubfoot.

Assessment of talus deformity by three-dimensional MRI in congenital clubfoot

PURPOSE

To evaluate the morphological deformity of talus in congenital clubfoot by three-dimensional MRI.

MATERIAL AND METHOD

Subjects were five patients (two male, three female, mean age 5 months) with unilateral congenital clubfoot. Magnetic resonance imaging was performed of both feet using 1.5 T magnet. Based on the resulting magnetic resonance imaging volume data, a three-dimensional surface bone model was reconstructed by the Marching Cubes method. The long axis of the reconstructed model was determined, and in relation to the standard planes including this axis, the degree of talar head and neck deviation, and the relative positioning of the talus and navicular in the talonavicular joint were compared between normal foot and clubfoot.

RESULT

The talar head and neck angle in relation to the talus exhibited significant medial deviation in the clubfoot, but the degree of plantar deviation of the talar head and neck did not show significance. The navicular was located more medially in clubfoot than in normal foot. The volume of the total talar and of the ossific nucleus for the clubfoot was smaller than that for the normal foot.

CONCLUSION

The assessment technique presented herein was shown to be useful in ascertaining the various pathological characteristics associated with clubfoot.