[An experimental study on the influences of sex hormones on the posterior longitudinal ligament of the cervical spine and serum components].

In order to determine the origin of ossification of the posterior longitudinal ligament of the cervical spine, the author performed experiments using mature male rabbits raised under conditions designed to cause instability of the cervical vertebrae as a local factor and administered testosterone to the animals to produce an imbalance in the sex hormones as a systemic factor. The testosterone-estrogen ratios were high, and development of chondrocytes was noted at the part of attachment of the posterior longitudinal ligament to the vertebral body. Serum phosphate levels were significantly decreased. The imbalance of sex hormones not only affected the mechanism of calcium-phosphate regulation, but also contributed to an weakening of spinal ligaments. Furthermore, instability of cervical vertebrae acted on the spinal ligaments as a source of chronic minor trauma. Thus reactivity or reintegration will have a definite effect on ossification of the spinal ligaments.