Histomorphometric analysis of cartilage and subchondral bone in mandibular condyles of young human adults at autopsy.

After demineralization, sagittal sections were made from the lateral, the central and the medial parts of 33 mandibular condyles from people aged 20 to 36 years, and studied for undifferentiated mesenchymal (UM) cells, cartilage and subchondral bone, the thickness of which were measured. Two condyles showed a continuous layer of UM cells extending all over. In 13 condyles, UM cells were absent; 18 condyles showed variability in UM cell occurrence in one or more out of the nine standardized areas. In 14 condyles, non-hypertrophic cartilage was present, 10 condyles showed hypertrophic cartilage and in nine condyles hyperplastic cartilage. Hyperplastic cartilage was associated with minimal numbers of UM cells. In combination with hypertrophic cartilage the UM cell layer appeared less irregular. Of nine condyles with incongruence of the cartilage-bone interface and the articular surface, seven showed hyperplastic cartilage. Six out of these seven were free of bony changes. A negative correlation was found between the presence of UM cells and the condylar-cartilage thickness (p less than 0.05). These results suggest that condylar changes are initiated by alterations in the cartilage and that changes in the bone are secondary.