Ponseti technique is a common non-surgical treatment based on serial manipulation and casting for idiopathic infant clubfoot. We have used three dimensional MRI throughout the treatment, to investigate the effect of the casts on the clubfoot of a one week old (at the beginning of treatment) male with unilateral right idiopathic congenital clubfoot deformity. A total of 21 MRI scans were obtained during weekly serial manipulation and corrective casting. Changes in shape, volume, ossification, and positional relationships of the hind foot anlagen were studied. We found that immediate shape changes occur following casting, particularly in the talus and the navicular, and when after one week the cast is removed the anlagen do not elastically return to their original shape and position prior to casting. Furthermore, the growth rate of some of the clubfoot anlagen, in particular the talus, was faster than normal. A faster ossification was observed in the calcaneus and cuboid. Results also showed correction in parallelism of calcaneus and talus in the anteroposterior plane, minor correction of this parallelism in the lateral view necessitating a heel cord tenotomy, and correction of the medial rotation of calcaneus. Under this treatment changes in talar neck angle yielded a decreasing trend. The navicular moved with respect to the head of the talus from a medial to a lateral position. Relative to the talar body it shifted laterally. Also the geometrical center of talus ossific nucleus was noted to move towards the center of the whole anlagen suggesting that the ossification extends in the opposite direction from the head of the talus. It was concluded that the mechanism of adaptation to the casting loads was quick deformation immediately upon cast application followed by adaptation to the new shape in the cast. These were qualitative findings. It was also concluded that most of the correction occurred during the initial treatment period, primarily during the first and second weeks (1). On the quantitative end, it was confirmed that MRI and computer techniques can be utilized to ascertain and quantify the abnormalities which were impossible to well identify otherwise. MRI based studies have powerful potential to provide helpful information on the choice of treatment as well as guidance throughout. For instance, it may therefore be possible in the present case to shorten the treatment time without adverse effects on the outcome.

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