The role of calcium metabolism abnormalities in the development of ossification of the posterior longitudinal ligament of the cervical spine.

To study the role of calcium metabolism in the development of ossification of the posterior longitudinal ligament of the cervical spine, 39 patients with affected cervical spines were investigated using an oral calcium tolerance test and followed by cervical spinal radiography to evaluate disease progression. The average follow-up was 6 years. The patients were divided into two groups according to their responsiveness to an oral calcium load: a group of 14 patients with decreased calciuric responses and another group of 25 with normal responses. The incidence of the development of cervical ossification of the posterior longitudinal ligament in the decreased-response group was significantly higher than that in the normal group. Because these patients were managed operatively by laminoplasty, however, the incidence was low irrespective of their calciuric responses. These results suggest that the development of cervical ossification of the posterior longitudinal ligament is associated with decreased intestinal calcium absorption but that treatment with laminoplasty alters the mechanical environment of the cervical spine (eg, range of motion of the cervical spine is limited). The development of cervical ossification of the posterior longitudinal ligament may be controlled by this procedure.