Study of the Spinal Canal Stenosis with Special Reference to Its Bony Factors

An investigation was conducted to study the bony factors contributing to the narrowness of the spinal canal with the advance in age using 106 macerated vertebral columns of Japanese subjects. The following results were obtained : 1. Posterior osteophytes were classified according to three degrees of development. These were first found in the twenties, with the proportion of affected spines increasing thereafter. Osteophytes of higher degrees of development increased with the advance in age. As for localization, posterior osteophytes were frequently seen adjacent to the intervertebral discs where a high incidence of degeneration has been reported. The highest frequency of these was seen in the cervical region, and followed by the lumbar region. 2. Ossifications of the posterior longitudinal ligament at its vertebral attachment were classified according to four degrees of development. These were first seen in the twenties, with the incidence increasing thereafter. Ossifications of higher degrees of development increased with the advance in age. Localization resembled that of posterior osteophytes, the highest frequency of these being seen in the cervical region, followed by the lumbar region. 3. Ossifications of the ligamentum flavum at its vertebral attachment were classified according to three degrees of development. These were first seen in a single case of a 17-year-old boy. Their frequency increased by the thirties, and remained more or less constant thereafter. As for their degrees of development, ossifications of higher degrees did not increase of ter the third decade. Their highest frequency was seen in the thoracic region, and was rare in the cervical region. 4. The incidence of the co-existence of the three bony factors described above increased, especially in the lumbar region, and the degrees of narrowness became more intense with advance in age