Figure 5.

Diagrammatic representation of the proximal head of the femur, depicting the formation of osteochondrotic clefts at the boundary between the epiphysis (e) and the growth plate (physis, p). Ascending metaphyseal vessels (mv) penetrate through canals between long columns of calcifying cells in the metaphysis (m). The metaphyseal vascular plexus (mvp) is formed by hairpin bends in fenestrated metaphyseal capillaries that return as venules coursing through the same canal (blue arrows). Translocated bacteria spread hematogenously and can exit the bloodstream through the fenestrated endothelium at the tips of the metaphyseal vascular plexus. The extravasated bacteria may adhere directly to the cartilage matrix, they colonize osteochondrotic clefts and zones of necrosis, and they form obstructive emboli in the metaphyseal vasculature. Similar hairpin bends and fenestrated capillary epithelia have been reported for the terminal epiphyseal vascular complex (evc), as well as for the terminus of penetrating epiphyseal vessels (pev) and the penetrating vascular plexus (pvp).