Six calcaneal fragments from patients aged 2, 3, 4, and 5 years with relapsed
talipes, and two normal feet from a 40-week-old stillborn fetus were studied. All tissue was sectioned in the sagittal or coronal plane and stained using
alcian blue and sirius red to distinguish cartilage and bone. Immunocytochemistry was performed to illustrate
collagen types I and II. Within the
clubfoot calcaneum, there were fewer chondrocytes and a diminished number of cartilage canals. Although a growth plate was present, the zones of differentiated chondrocytes were not apparent and the chondrocytes were smaller and flatter. The
alcian blue staining within the spherical physis was paler than normal, suggesting that the amount of extracellular
proteoglycans was reduced. Overall, the growth plate region of the
talipes calcaneum resembled that of a permanent cartilage, like articular cartilage. Abnormalities were also seen in the ossification center. Cartilage spicules were rare, and developing bone frequently abutted directly onto the growth plate cartilage. The relative absence of a primary spongiosa suggested that the physis was virtually inactive and endochondral bone formation was retarded. These findings are consistent with the hypothesis that an intrinsic primary
growth disorder causes the formation of a small hypoplastic bone and, subsequently, a smaller foot.