[Calcinosis of the meniscus. Morphologic and roentgenographic findings for zonal classification]

Primary and secondary meniscal chondrocalcinoses lead to typical changes in X-ray pictures of isolated menisci. Combined X-ray, light and electron microscopic examination of the four menisci in 70 autopsy cases showed calcifications in 13 cases (18.6%). Three types of calcification could be discriminated with the help of topographical and morphological criteria: Type 1 A: disseminated calcification. All four menisci were affected equally. Crystals of calcium pyrophosphate dihydrate (CPPD) were found on light and electron microscopy. Energy-dispersive X-ray analysis (EDX) showed the crystal deposits to consist of 46.5% calcium and 53.5% phosphorus. Type 1 B: Calcification occurring in limited areas. A calcification was found which did affected neither a whole meniscus nor all four menisci of any "quartet" observed. Crystals were found next to areas of stronger meniscal degeneration. EDX showed the same results described for type 1 A. Type 2: Confluent calcification. A cloud-like diffuse calcification was discerned on the X-ray pictures. Light and electron microscopically pseudocystic structures appeared which contained a fine granular amorphous material. No crystals were found. The structures appeared in the neighbourhood of necrotic fibres. EDX showed 44% calcium, 51.2% phosphorus, 2.8% sulphur, 0.74% magnesium and 0.6% potassium. The findings lead to the conclusion that calcification type 1 A represents primary chondrocalcinosis, whereas type 1 B corresponds to secondary chondrocalcinosis. Type 2 was identified as postnecrotic, dystrophic calcification. Careful analysis of X-ray pictures of isolated menisci can yield useful information concerning pathogenetic factors of meniscal calcification.