title: Biomechanical study of the effect of degree of static compression of the spinal cord in ossification of the posterior longitudinal ligament.
abstract: OBJECTIVE
  The authors evaluated the biomechanical effect of 3 different degrees of static compression in a model of the spinal cord in order to investigate the effect of cord compression in patients with ossification of the posterior longitudinal ligament (OPLL).
  
  
  METHODS
  A 3D finite element spinal cord model consisting of gray matter, white matter, and pia mater was established. As a simulation of OPLL-induced compression, a rigid plate compressed the anterior surface of the cord. The degrees of compression were 10, 20, and 40% of the anteroposterior (AP) diameter of the cord. The cord was supported from behind by the rigid body along its the posterior border, simulating the lamina. Stress distributions inside of the cord were evaluated.
  
  
  RESULTS
  The stresses on the cord were very low under 10% compression. At 20% compression, the stresses on the cord increased very slightly. At 40% compression, the stresses on the cord became much higher than with 20% compression, and high stress distributions were observed in gray matter and the lateral and posterior funiculus. The stresses on the compressed layers were much higher than those on the uncompressed layer.
  
  
  CONCLUSIONS
  The stress distributions at 10 and 20% compression of the AP diameter of the spinal cord were very low. The stress distribution at 40% compression was much higher. The authors conclude that a critical point may exist between 20 and 40% compression of the AP diameter of the cord such that when the degree of the compression exceeds this point, the stress distribution becomes much higher, and that this may contribute to myelopathy.
authors.affiliation: Department of Orthopedic Surgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan. kato-yo@yamaguchi-u.ac.jp
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kato
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Kanchiku
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Imajo
authors.forename: Kotaro
authors.initials: K
authors.lastname: Kimura
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ichihara
authors.forename: Syunichi
authors.initials: S
authors.lastname: Kawano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hamanaka
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yaji
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Taguchi
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D017846:Longitudinal Ligaments / Q000503:physiopathology*; D008959:Models, Neurological; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology; D017887:Ossification of Posterior Longitudinal Ligament / Q000503:physiopathology*; D010841:Pia Mater / Q000502:physiology; D013116:Spinal Cord / Q000503:physiopathology*; D013117:Spinal Cord Compression / Q000503:physiopathology*; D013314:Stress, Mechanical