To know the causative and growth factors of calcification of cervical yellow ligaments, we carried out a morphological investigation of 4 cases. This included CT scanning, histological, ultrastructural and crystallographical studies. The results were as follows: 1) The CT scan showed various kinds of calcified masses of spotty, nodular and mushroom shapes. The larger the mass a case had, the more serious the symptoms of myelopathy were. 2) The larger masses contained more hydroxyapatite (HA)

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... n calcium pyophosphate dihydrate (CPPD) or calcium phosphate. 3) In the non-alcified area of ligaments, a deposit of calcium crystals was observed inside the fibroblasts, which were surrounded by the proteoglycan (PG) layer, the collagen fiber layer and the layer of matrix vesicles. On the other hand, in the calcified area, many chondrocytes and matrix giant bodies (MGB) were observed.