Aim: Ossification of ligamentum flavum (OLF) mainly occurs in the thoracic spine, and rarely in the cervical spine. To clarify its etiology; the features of OLF in the cervical spine were reviewed in 50 reported cases.
Methods: Age, sex, location of OLF, classification of OLF, radiographic findings, computed tomography (CT) findings, magnetic resonance imaging findings, association of ossification of the posterior longitudinal ligament (OPLL), association of OLF in other spinal regions, and association of diffuse idiopathic skeletal hyperostosis (DISH) were analyzed in 23 detailed cases.
Results: Association of OPLL was observed in 7 of 20 cases and 4 of these 7 OPLL cases were at C2-4. Association of OLF in other spinal regions was recognized in 7 of 15 cases. DISH was also present in 3 of 7 cases. Local kyphosis was recognized in 10 of 12 cases by radiography. CT showed facet hypertrophy in 13 of 15 cases and lamina hypertrophy in 14 of 16 cases. Patients with OLF at C2-4 had high rates of local kyphosis and association of hyperostotic state, suggesting both local factors and systemic hyperostotic factors are involved in the formation of OLF of the upper cervical spine.
Conclusion: Local factors may be strongly related to the formation of OLF of the middle or lower cervical spine.