title: Cervical ossification of the posterior longitudinal ligament: Biomechanical analysis of the influence of static and dynamic factors.
abstract: OBJECTIVE
  Cervical myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is induced by static factors, dynamic factors, or a combination of both. We used a three-dimensional finite element method (3D-FEM) to analyze the stress distributions in the cervical spinal cord under static compression, dynamic compression, or a combination of both in the context of OPLL.
  
  
  METHODS
  Experimental conditions were established for the 3D-FEM spinal cord, lamina, and hill-shaped OPLL. To simulate static compression of the spinal cord, anterior compression at 10, 20, and 30% of the anterior-posterior diameter of the spinal cord was applied by the OPLL. To simulate dynamic compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction. To simulate combined static and dynamic compression under 10 and 20% anterior static compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction.
  
  
  RESULTS
  The stress distribution in the spinal cord increased following static and dynamic compression by cervical OPLL. However, the stress distribution did not increase throughout the entire spinal cord. For combined static and dynamic compression, the stress distribution increased as the static compression increased, even for a mild range of motion (ROM).
  
  
  CONCLUSIONS
  Symptoms may appear under static or dynamic compression only. However, under static compression, the stress distribution increases with the ROM of the responsible level and this makes it very likely that symptoms will worsen. We conclude that cervical OPLL myelopathy is induced by static factors, dynamic factors, and a combination of both.
authors: Norihiro
authors: N
authors: Nishida
authors: Tsukasa
authors: T
authors: Kanchiku
authors: Yoshihiko
authors: Y
authors: Kato
authors: Yasuaki
authors: Y
authors: Imajo
authors: Yuichiro
authors: Y
authors: Yoshida
authors: Syunichi
authors: S
authors: Kawano
authors: Toshihiko
authors: T
authors: Taguchi
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology*; D002574:Cervical Vertebrae / Q000473:pathology; D006801:Humans; D008959:Models, Neurological; D017887:Ossification of Posterior Longitudinal Ligament / Q000150:complications*; D013116:Spinal Cord; D013118:Spinal Cord Diseases / Q000209:etiology*
keywords: Cervical myelopathy; Dynamic factor; Finite element method; Ossification of the posterior longitudinal ligament; Static factor