Vibration characteristics of the human spine under axial cyclic loads: effect of frequency and damping.

Study Design: A nonlinear finite element model of lumbar spine segment L3-L5 was developed. The effects of upper body mass, nucleus injury, damping, and different vibration frequency loads were analyzed for the whole body vibration.

Objectives: To analyze the influence of whole body vibration on facets of lumbar spine and to analyze the influence of nucleus injury, upper body mass, and damping on the dynamic characteristics of lumbar spine.

Effect of facetectomy on lumbar spinal stability under sagittal plane loadings.

Study Design: A study using an anatomically accurate finite-element model of a L2-L3 motion segment to investigate the biomechanical effects of graded bilateral and unilateral facetectomies of L3 under flexion and extension loadings.

Objective: To predict the amount of facetectomy on lumbar motion segment that would cause segmental instability, therefore enhancing the understanding concerning the role of the facet under sagittal loadings.

Summary Of Background Data: This study provides a quantitative study on the role of facets in preserving segmental lumbar stability.

Kinematics of the thoracic T10-T11 motion segment: locus of instantaneous axes of rotation in flexion and extension.

The purpose of this study was to determine the locations and loci of instantaneous axes of rotation (IARs) of the T10-T11 motion segment in flexion and extension. An anatomically accurate three-dimensional model of thoracic T10-T11 functional spinal unit (FSU) was developed and validated against published experimental data under flexion, extension, lateral bending, and axial rotation loading configurations. The validated model was exercised under six load configurations that produced motions only in the sagittal plane to characterize the loci of IARs for flexion and extension.

Effects of cervical cages on load distribution of cancellous core: a finite element analysis.

Methods: The study was designed to analyze the load distribution of the cancellous core after implantation of vertical ring cages made of titanium, cortical bone, and tantalum using the finite element (FE) method. The intact FE model of C5-C6 motion segment was validated with experimental results.

Results: The percentage of load distribution in cancellous core dropped by about one-third of the level for the intact model after the cage implantation.

Validation of T10-T11 finite element model and determination of instantaneous axes of rotations in three anatomical planes.

Study Design: A finite element (FE) model of thoracic spine (T10-T11) was constructed and used to determine instantaneous axes of rotation (IARs).

Objectives: To characterize the locations and loci of IARs in three anatomic planes.

Summary Of Background Data: The center of rotation is a part of a precise method of documenting the kinematics of a spinal segment for spinal stability and deformity assessments and for implant devices study.

Finite element analysis of cervical spinal instability under physiologic loading.

The definition of cervical spinal instability has been a subject of considerable debate and has not been clearly established. Stability of the motion segment is provided by ligaments, facet joints, and disc, which restrict range of movement. Moreover, permanent damage to one of the stabilizing structures alters the roles of the other two.