[Histological study on the ossification of the yellow ligament in the thoracolumbar spines of the cadavers. Especially on the early stage of the ossification].

The occurrence process of ossification of the yellow ligament (OYL) was studied radiographically and histologically by using the thoracolumbar spines of the cadavers taken out as en bloc. The subjects were from 44 to 89 years at age (average 66.1 years). After taking roentgenographs, the specimens were sectioned sagittally for histological observations with H-E stain, elastica.van-Gieson stain, safranin-O stain and alcian blue stain. The findings were as follows. 1. Roentgenographically, OYL was evidently found in 6 cases with average age of 71.5 years, while not found in 4 cases with average age of 58.0 years. OYL was more frequently recognized in elderly cadavers. This fact is presumed to be one of the physiological aging processes. 2. Histologically, ossification was found to start in the superior margin of the lamina. Ligament fibers of the yellow ligament attached to the bone tissue piercing through the uncalcified cartilage zone, tide mark and calcified cartilage zone in order. This structure is called enthesis. In the early stage of ossification, cartilage zone became wide being followed by endochondral ossification. Elastic fibers in the cartilage zone became sparse and fine granular calcification was focally found in the uncalcified cartilage zone. Then, these changes also occurred in the ligamentous attachment of the superior lamina, but they were more evident in the superior margin of the inferior lamina. 3. In the advanced stage of ossification, there were a widening of tide mark and an increase of chondrocytes in number. Linear calcified deposits were observed along the ligamentous fibers. Elastic fibers were reduced in the cartilage zone, enlarged and deranged.(ABSTRACT TRUNCATED AT 250 WORDS)