LAUSR

Ossification of the posterior longitudinal ligament (OPLL), ossification of the anterior longitudinal ligament (OALL), and ossification of the ligamentum flavum (OLF) sometimes are seen in the same patients, but the exact coexisting frequencies are not clear especially in the cervical region. The most frequent combination is OPLL and OALL. Cervical OPLL can coexist with thoracic OLF but is rarely associated with cervical OLF. All of these ossifying diseases of the cervical spinal ligaments are influenced by dynamic factors of the spinal column. The most frequent levels in the cervical spine affected by OPLL, OALL, and OLF are different because of anatomic differences inherent to each ligament.