Analyses of the tidemark on human femoral heads. II. Tidemark changes in osteoarthrosis--a histological and histomorphometric study in non-decalcified preparations.

Histological and histomorphometric examinations were carried out on 88 human femoral heads, 63 from patients with osteoarthrosis and 25 controls. The changes of the tidemark were found to be multiform in the osteoarthrotic process and could be classified into three degrees of severity. Low-grade tidemark changes were characterized by reduplications of the tidemark and discontinuities of the tidemark line, occurring also in about one third of the controls. Vascular invasion into the tidemark as well as incipient calcification of basal hyaline cartilage were observed in middle-grade tidemark alterations. High-grade changes were distinguished by the disappearance of the tide-mark, advanced mineralization and ossification of basal hyaline and calcified cartilage and finally by the "tidemark and bone bald". Measuring the thickness of intact and osteoarthrotic hyaline cartilage, calcified layer and subchondral bone plate, it was possible to determine some correlations between the tidemark state and the structures measured. Variations in subchondral bone volume could also influence the tidemark and cartilage changes. The important role of the intercartilaginous junction in the pathogenesis and progress of osteoarthrosis is stressed.