[Histological changes of the lumbar ligamentum flavum with age]

The present author investigated morphometrically the changes associated with age in 137 ligamenta flava of the lumbar spine obtained from 79 patients with lumbar diseases and obtained the following results. The predominant changes were decrease of elastic fibers and increase of collagen fibers. The area of type II collagen fibers increased with age in the dorsal and central portions. Those were followed by proliferation of cartilage cells and calcification. The proliferation of cartilage cells was marked in the cranial and caudal insertion portions, and the layer of cartilage cells widened with age. Two types of calcification, deposition of calcium pyrophosphate dihydrate (CPPD) and deposition of hydroxyapatite (HAP), were observed. HAP deposits were small and frequently found in the dorsal portion, while CPPD deposits were larger and widely distributed.