Ossification of the calcaneus in the normal fetal foot and in clubfoot.

The ossification of the fetal calcaneus was studied in a series of plastinated sections of 44 normal feet and three clubfeet. The results documented a precise sequence of perichondral and endochondral ossification in the normal calcaneus characterized by ossification grooves and associated cartilage canals. Within the clubfoot calcaneus, the coordination of perichondral and endochondral ossification is disturbed, ossification grooves and associated cartilage canals are not found in regular positions, and the process of endochondral ossification obviously is disturbed. The findings in the clubfoot specimens point to grave irregularities of the extracellular matrix within or outside the calcaneus.