FINITE ELEMENT ANALYSIS (FEA) OF SPINAL IMPLANT DISC

Keywords: Spinal Implant FEA, Spinal Disc, Implant Analysis, Abaqus, Ansys

Abstract:

A implant development and manufacturing organization is interested in carrying out FEA on a spinal implant design.The implant will be made from Polyurethane material. The disc is of symmetrical design with screwable attachments on its top and bottom surface. The disc is thus sandwiched between rigid plates. The goal of the analysis was accurate simulation of flexion, extension, torsion and bending deformation modes.

Methodology:

Multi-step analysis was carried out by first simulating the pre-compression and then simulating the extension, flexion etc. in the second step.

  1. Non-linear material property of the Polyurethane material had to be included.
  2. Large expansion deformation along with multi-step analysis procedure had to be carried out.
Figure 1: Deformation modes, FEA Model and Deformed Shape in Flexion/Extension

Results and Discussion:

The FEA model and the deformation plots are shown in the Figure 1. The Polyurethane disc was modeled in Abaqus using 3-dimensional continuum elements. High stresses were noted at the different locations in the design. An iterative design optimization procedure was carried out to lower stresses along the bond area and interiors. The large deformation elastic analysis allowed the materials to be adequately defined. The stress-concentration locations were identified as ‘hot-spots’ and are fatigue-critical locations.

References:

  1. Dassault Systemes, Abaqus theory and reference manuals.
  2. Coombs, D. et al. Simulation of Lumbar Spine Biomechanics Using Abaqus, Simulia Abaqus Users Conference, 2011.
  3. Mummaneni, P. and Heid, R.W., The Future in the Care of the Cervical Spine: Interbody Fusion and Arthroplasty, Journal of Neurosurgery (Spine 1), 2004.