First trimester physiological development of the fetal foot position using three-dimensional ultrasound in virtual reality.

AIM: In anatomic studies of the embryo, it has been established that during the development of the lower limb, several changes in foot position can be observed defined as a temporary 'physiological clubfoot'. The aim of this study was to develop and test a measurement tool for objective documentation of the first trimester foot position in vivo and made an attempt to create a chart for first trimester foot position. METHODS: We developed a virtual orthopedic protractor for measuring foot positioning using three-dimensional virtual reality visualization. Three-dimensional ultrasound volumes of 112 pregnancies of women examined during the first trimester were studied in a BARCO I-Space. The frontal angle (plantar flexion) and the lateral angle (adduction) between the leg and foot were measured from 8 until 13 weeks gestational age. RESULTS: We observed that the frontal angle steadily decreases, whereas the lateral angle first increases, resulting in transient physiological clubfeet position at 10- to 11-week gestation, followed by a decrease to a normal foot position. CONCLUSION: A transient clubfoot position is present during the normal development of the lower limbs, and it has been measured in vivo for the first time. This study emphasizes that a diagnosis of congenital clubfoot should not be made in the first trimester of pregnancy.