Vascularization of the fetal elbow joint.

Unlike the adult tissue, prenatal cartilage may be well vascularized. We studied the prenatal development of vascular channels within the epiphyses of the human elbow joint. Plastinated 200-1000 microns thick sections through the right and left arms of 12 fetuses with a crown-rump-length of 90-360 mm and of a newborn infant were investigated. Cartilage canals first develop within the distal humeral epiphysis, later on within the olecranon process and the radial head. With advancing age, the canals reveal an increasingly complex pattern of distribution. However, a constant basic pattern can be recognized at every developmental stage. The cartilage canals take their origin from the perichondrium. At their point of entrance into the cartilaginous tissue, their walls are often ill-defined and consist of several fibrous layers which gradually irradiate into the cartilage. At the opposite tip, the channel wall is more clearly demarcated. Many cartilage canals contain several vessels forming loops or branching into bunch-like structures at the tip of the canals. The vessels mostly lie adjacent to the canal walls, grouped around a core of loose connective tissue. As a rule different channels run towards the centre of the cartilage and do not form any anastomoses. The vascularization of the epiphyses of the human elbow joint takes place a long time before the secondary centres of ossification develop, which normally appear after birth. Thus, a direct causal relationship seems unlikely.