Upper Cervical Instability of Ossification of Posterior Longitudinal Ligament

Abstract

Atlanto-axial subluxation is often associated with rheumatoid arthritis, Down syndrome, cerebral palsy, and the congenital fusion of the cervical spine.
However, there are few reports on the instability of the ossification of the posterior longitudinal ligament (OPLL).
Forty-one patients with OPLL were examined radiographically.
Atlanto-axial subluxation, occipito-atlanto instability (O/C1 instability) and atlanto-axial instability (C1/C2 instability) were examined using the parameters ADI and Bull's angle, and Fujiwara's C1/C2 angle.
Only one patient had atlanto-axial subluxation (ADI 6mm) among the 41 patients.
Thirty-three percent of the subjects showed O/C1 instability or C1/C2 instability.
No less than 50% of the cases of the continuous or mixed type showed upper cervical instability.
The authors believe that these data are important in the assessment of the instability of the upper cervical spine in OPLL.