The deposition of calcium pyrophosphate dihydrate (CPPD) and hydroxyapatite (HAP) crystals in human cervical ligamentum flavum is described. Specimens of the ligamenta flava were studied by scanning electron microscopy, energy dispersive X-ray microanalysis, and an X-ray diffraction study was carried out on the crystals. It was revealed that small foci of calcification were made of extremely small CPPD plate-shaped crystals. On the other hand, big foci were composed of two chemical species, CPPD and HAP, the latter being encased by the former. The X-ray diffraction pattern of CPPD crystal formed in ligamentum flavum coincided well with that of CPPD already reported (triclinic, P1, a=7.37A, b=8.29A, c=6.61A, a=102.96°, β=72.73°, γ=95.01°, Z=2).
