Asymptomatic ossification of the posterior longitudinal ligament of the cervical spine

The cervical spines of 698 individuals without neurological symptoms, 20–80 years old, were studied roentgenographically and the incidence of ossification of the posterior longitudinal ligament of the cervical spine was determined. The incidence of asymptomatic ossification showed a roughly linear progression with advancing age. Eleven percent of the normal individuals in the sixth decade of life exhibited roentgenologic changes suggestive of ossification. There was no significant difference in incidence in the two sexes. Ossification of the posterior longitudinal ligament was seen to be widely distributed throughout the cervical vertebrae with the highest incidence at the level of C4. The sagittal diameters of the cervical bony spinal canal at the affected level were significantly smaller in the asymptomatic group of cases with ossification than in normal subjects without such changes. Sixty-seven percent of the ossified ligaments in this survey were independent of spondylotic changes such as posterior osteophytes or narrowing of the intervertebral disc spaces.