Use of polarized light for quantitative determination of the adjustment of the tangential fibres in articular cartilage.

According to recent research the course of the tangential fibres is gaining increasing importance for the analysis of the first signs of pathological alterations in the articular cartilage. In a model-test, parallel-running synthetic double-refracting filaments, rotated between polarisator and analysator at right angles to each other effect an extinction curve which has two maxima at 45 degrees and the minimum at 0 degrees. Crossing filaments at different angles effects curves which are specific for the different angles in such a manner that with increasing angles to 45 degrees the curves approximate to a horizontal line. On the other hand the course of the different curves make it possible to determine corresponding angles. Then the same method is used to estimate the mean crossing-angles of tangential fibres in histological sections of articular cartilage with masked collagen fibres. The method is suitable for a quantitative calculation of the crossing-angles between 0 degrees and 45 degrees, which cannot be defined by the split-line method of Hultkrantz. In contrast to the conditions of the scanning electron microscope, the integrating nature of the polarized light is advantageous because it permits analysis of a more extensive visual field. From comparisons with the test model, a considerable variety of crossing angles of tangential fibres in the cartilage can be shown to exist.