PRENATAL GROWTH OF THE HUMAN MANDIBULAR CONDYLAR CARTILAGE

The question of whether the condylar cartilage possesses a growth pote ntial like that of the long bone growth plates has been the subject of contrasting viewpoints. We have recently established that the thickne ss of the human tibial growth plate progressively decreases during the second half of the fetal period, but that the changes in the total hu man condylar thickness do not correlate with fetal age or weight. The present study examined the change in the thickness of the human mandib ular condyle layers during the fetal growth of the mandible. Mandibles were obtained from autopsy of 19 human fetuses ranging in fetal age f rom 18 to 41 weeks. The total length of the mandible, the lengths of t he mandibular body and of the ramus were measured, as well as the geni al angles. The total thickness of the condyle, and the thicknesses of the articular, progenitor, cartilage, chondroblast, and hypertrophic c hondrocyte layers were measured on the central segment of central sagi ttal sections of the mandibular condylar cartilage. The total mandible , the corpus and the ramus lengths increased linearly with the age of the fetus and they all correlated strongly with fetal weight. However, changes in the total condylar thickness and in the thickness of the c artilage layer (chondroblast plus hypertrophic chondrocytes) did not c orrelate with fetal weight or mandibular length. The thickness of the articular layer increased with weight, but changes in the progenitor l ayer were independent of corporal and mandibular growth. These results suggest that changes in the structure of human mandibular cartilage d uring the prenatal period are more related to local mechanical factors and articular activity than to the general factors that are responsib le for bone lengthening at the epiphyseal growth plate.