Assessment of the three-dimensional relationship of the ossific nuclei and cartilaginous anlagen in congenital clubfoot by 3-D MRI

Abstract Purpose Radiographic measurement is the usual method used to objectively determine the extent of a congenital clubfoot deformity. Although radiographs have been used clinically to estimate the size and location of tarsal bones through measurements of the ossific nuclei, it is not clear to what extent these relationships are actually reflected in these measurements. So, we used a 3-D MRI system that could more objectively estimate sizes and positional relationships. Material and method We evaluated 5 patients with unilateral congenital clubfoot deformity. 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. We used this model to perform a comparative analysis of the volume and volume ratio of each cartilaginous anlage and ossific nucleus, the length of the talus and the calcaneus, and the position of the center of gravity of ossific nuclei within the cartilaginous anlagen. We measured the relationship between the ossific nuclei and cartilaginous anlagen in the talus and calcaneus of patients with unilateral clubfoot deformity. Result In clubfeet talus volume was reduced by 20.1% and calcaneal volume was reduced by 15.7%. Furthermore, the volume of the talar ossific nucleus was reduced by 42.6% and that of the calcaneal ossific nucleus was reduced by 12.1%. The length of the clubfoot talus was 8.2% shorter than normal, and that of the calcaneus was 4.8% shorter. Conclusion The assessment technique presented herein was shown to be useful in ascertaining the various pathological characteristics associated with clubfoot.