[Histopathological study of the aging process in the human sacroiliac joint].

It has not been well defined the morphologic characteristics of the aging process of the sacroiliac joints in man. We have, therefore, studied the sacroiliac joints of human subjects by light and scanning electron microscopy. The joints were collected from 55 Japanese fetuses and adult cadavers. The articular cartilages on both sacral and iliac sides were composed of hyaline cartilage in the fetuses and adults. In fetuses, loose fibrous strands were found in the articular space and appeared to represent a residue of the intermediate layer during formation of the articular space. In adults who were older than 30, the joints showed definite degeneration which was more severe on the cartilage at the iliac side than that of sacral side. Scanning electron microscopic observations supported the light microscopic findings. Fusion of the two articular surfaces was observed in 24% of the adult joints. These findings strongly suggest that the buffering capacity of the sacroiliac joints decreases with aging which appears to relate to the clinical symptom of low back pain.