Radiographical studies of ossification of the spinal ligaments.

Radiographical mesurement of the ossified area of the spinal ligaments was performed in 94 cases with cervical myelopathy due to ossification of the posterior longitudinal ligament. The cases were selected where lateral views of the radiogram were able to take in the entire spine.The ossified spinal ligaments measured, were the anterior longitudinal ligament (OALL), the posterior longitudinal ligament (OPLL), the yellow ligament (OYL) and the supraspinous ligament (OSSL). Ossified areas of the entire spine were plotted and analyzed on a computerized digitizer. The average ossified areas measured 1.78cm2 in OPLL, 4.73cm2 in OALL, 0.79cm2 in OYL and 2.63cm2 in OSSL. According to the volume and localization of the ossified area in the spinal ligaments, we classified them all into four types, that is, complete type, anterior type, posterior type and incomplete type. In the complete type and anterior type there tends to be a higher hyperostotic status. It was suggested that the formation of ossification of the spinal ligaments was influenced by many factors, such as genetic factors, continuous minor traumas to the ligaments and others.