Radiography and sonography of clubfoot: A comparative study

Congenital talipes equinovarus is a common foot deformity afflicting children with reported incidence varying from 0.9/1000 to 7/1000 in various populations. The success reported with Ponseti method when started at an early age requires an imaging modality to quantitate the deformity. Sonography being a radiation free, easily available non-invasive imaging has been investigated for this purpose. Various studies have described the sonographic anatomy of normal neonatal foot and clubfoot and correlated the degree of severity with trends in sonographic measurements. However, none of these studies have correlated clinical, radiographic and sonographic parameters of all the component deformities in clubfoot. The present study aims to compare the radiographic and sonographic parameters in various grades of clubfoot.

Thirty-one children with unilateral clubfoot were examined clinically and graded according to the Demeglio system of classification of clubfoot severity. Antero-posterior (AP) and lateral radiographs of both normal and affected feet were obtained in maximum correction and AP talo-calcaneal (T-C), AP talo-first metatarsal (TMT) and lateral T-C angles were measured. Sonographic examination was done in medial, lateral, dorsal and posterior projections of both feet in static neutral position and after Ponseti manouever in the position of maximum correctability in dynamic sonography. Normal foot was taken as control in all cases. The sonographic parameters measured were as follows : Medial malleolar- navicular distance (MMN) and medial soft tissue thickness (STT) on medial projection, calcaneo-cuboid (C-C) distance, calcaneo-cuboid (C-C) angle and maximum length of calcaneus on lateral projection, length of talus on dorsal projection; and tibiocalcaneal (T-C) distance, posterior soft tissue thickness and length of tendoachilles on posterior projection. Also, medial displacement of navicular relative to talus, mobility of talonavicular joint (medial view); reducibility of C-C mal alignment (lateral view); talonavicular relation with respect to dorsal/ ventral displacement of navicular (dorsal view) and reduction of talus within the ankle mortise (posterior view) were subjectively assessed while performing dynamic sonography. Various radiographic and sonographic parameters were correlated with clinical grades.

MMN distance and STT measured on medial view, C-C distance and C-C angle measured on lateral view and tibiocalcaneal distance measured on posterior view showed statistically significant difference between cases and controls. A significant correlation was evident between sonographic parameters and clinical grades of relevant components of clubfoot. All radiographic angles except AP T-C angle were significantly different between cases and controls. However, they did not show correlation with clinical degree of severity.

All radiographic angles except AP T-C angle and sonographic parameters varied significantly between cases and controls. However, radiographic parameters did not correlate well with clubfoot severity. In contrast, sonography not only assessed all components of clubfoot comprehensively but also the sonographic parameters correlated well with the severity of these components. Thus, we conclude that sonography is a superior, radiation free imaging modality for clubfoot.