title: Mechanical analysis of the lumbar vertebrae in a three-dimensional finite element method model in which intradiscal pressure in the nucleus pulposus was used to establish the model.
abstract: We established a three-dimensional finite element method (FEM) model of the 4th and 5th vertebrae, using computed tomography (CT) images (2-mm slice thickness) of a healthy 29-year-old man. Because of the lack of specific data regarding the material characteristics of the nucleus pulposus of intervertebral discs, we used intradiscal pressure in the nucleus pulposus to establish the model. We referred to data from Nachemson and from Sato et al. regarding intradiscal pressure and to the methods of Shirazi-Adl for data for other material characteristics (see text for these references). The mid-position model bears a load of 294 N in the vertical direction, while the models of the flexed and extended positions bear loads of 15 N-m. In addition, a degenerative disc model without intradiscal pressure was created for the standing model. The use of these models allowed the investigation of von Mises stress on the vertebral endplates and the annulus fibrosus. We also examined von Mises stress on the facet joint in normal and degenerative disc models. There was increased von Mises stress on the vertebral endplate in the anterior, center portions. von Mises stress on the annulus fibrosus increased in the posterior portion, the entrance to the neural foramen, and the exit of the neural foramen. von Mises stress was greater during flexion in the posterior portion; in particular, increasing to about 1.6 times the level seen with other postures. No changes were observed in von Mises stress on the vertebral endplates or annulus fibrosus in the degenerative disc model, but von Mises stress on the facet joints was about 2.5 times that seen in the normal disc model.
authors.affiliation: Department of Orthopaedic Surgery, Miyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Goto
authors.forename: Naoya
authors.initials: N
authors.lastname: Tajima
authors.forename: Etsuo
authors.initials: E
authors.lastname: Chosa
authors.forename: Koji
authors.initials: K
authors.lastname: Totoribe
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kuroki
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Arizumi
authors.forename: Takashi
authors.initials: T
authors.lastname: Arai
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology*; D007405:Intervertebral Disc Displacement / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D008961:Models, Structural; D011312:Pressure; D013314:Stress, Mechanical