Developmental morphological and histological studies on structures of the human fetal elbow joint

In the present work, morphological changes in the developing human elbow jo int were studied at different prenatal ages (8, 12, 16, 20, 29 and 40 weeks ) and were compared with the same structures in the adult joint. The elbow joint had gone through its most important developmental changes during the 20th week of prenatal life, probably due to the direct dynamic effect of th e newly developed fetal movement. During later prenatal development, the ar ticular surfaces of the lower end of humerus and the upper ends of radius a nd ulna developed their characteristic congruencies, so that the highly cur ved convexities always articulate with the highly curved concavities. That process progressed postnatally and even till adult age. In full-term infant s it was found that the lower end of humerus had acquired its adult shape, while the shape of the upper ends of radius and ulna were still not fully d eveloped. They continued development in postnatal life even till adult age. In the present work, histological prenatal studies were done on longitudin al sections from the back of the capsule and synovial tissue, early (8 week s) and late in full term, and the results were also compared with the same structures in adults. It was found that at all ages, the capsules were form ed of cellular and fibrous elements, but at early prenatal age (8 weeks), t his cellular condensation was more massive and prominent while in full-term infants, it became generally more fibrous, but was still different compare d to adults. Basic cellular structures of the synovial tissue changed very little during the late prenatal developmental stage, as it did not become m ore fibrous than cellular during these periods, but differences in vascular ity became more obvious. The cartilaginous content of the articular surface at 8 weeks was highly cellular with very little intercellular matrix. In c ontrast to that of full term, this cartilage became fully chondrogenous wit h a notable decrease in cellular density and massive increase in matrix con tent. Copyright (C) 2000 S. Karger AG, Basel.