The non-ossified tarsi of the neonatal foot can be imaged with modern high-resolution ultrasound. The aim of the study was to reconstruct in three dimensions the tarsal anatomy of the neonatal foot in both normal feet and in neonates affected by congenital talipes equinovarus, using high resolution 3D ultrasound.

A high resolution optically tracked freehand three-dimensional ultrasound system was used to obtain multiple data-sets from 22 normal neonatal feet and from two neonates with congenital talipes equinovarus. The neonates were examined whilst asleep or during feeding to ensure that the child remained immobile. 107 data-sets were recorded. Each data-set represented a single sweep of the probe over the antero-medial aspect of the lower calf, ankle and foot. Multiplanar reconstructions and manual segmentation of the non-ossifed tarsi were performed to produce three-dimensional surface rendered illustrations of both the normal and abnormal anatomy.

From 107 examinations of normal feet, there were 86 data-sets suitable for further three-dimensional analysis. The high-resolution B-scans clearly demonstrated the non-ossified tarsi. On average 5 successful identical data sets were recorded per foot. The reconstructions from each data-set were reproducible. From the talipes data-sets, the three-dimensional anatomical deformity was clearly demonstrated; the approximation of the medial pole of the navicular to the medial malleolus, the bare talar head, medial subluxation of the metarsals and the equinus deformity at the ankle joint.

It is possible to reconstruct the complex anatomy of the neonatal foot using three-dimensional ultrasound. The use of this technique in the abnormal foot may aid the clinician assess the severity of the deformity and the need for surgical intervention.